VQ97084 IntegratBd management of Sderotinia disease in beans

Transcription

1 VQ97084 IntegratBd management of Sderotinia disease in beans Hoong Pung and Rob O'Brien Serve-Ag Research and Queensland Department of Primary Industries

2 VG97084 This report is published by the Horticulture Australia Ltd to pass on information concerning horticultural research and development undertaken for the vegetable industry. The research contained in this report was funded by Horticulture Australia Ltd with the financial support of the vegetable industry and Serve-Ag Pty Ltd. All expressions of opinion are not to be regarded as expressing the opinion of Horticulture Australia Ltd or any authority of the Australian Government. The Corporation and the Australian Government accept no responsibility for any of the opinions or the accuracy of the information contained in this report and readers should rely upon their own enquiries in making decisions concerning their own interests. Cover price: $22.00 (GST Inclusive) ISBN Published and distributed by: Horticultural Australia Ltd Level 1 50 Carrington Street Sydney NSW 2000 Telephone: (02) Fax: (02) horticulture@horticulture.com.au Copyright 2001 orticuttur Austrs

3 SERVE-AG RESEARC1 Registered Research Agency No Integrated management of Sclerotinia disease in beans FINAL REPORT Horticultural Research & Development Corporation Project VG97084 (completion date 30/06/00) by Dr. Hoong Pung (Serve-Ag Research) and Dr. Rob O'Brien (Queensland Department of Primary Industry) 29 November 2000 Telephone (03) Facsimile (03) (Int ) P.O. Box 690, Devonport, Tasmania Hillcrest Road, Devonport sar@serve-ag.com.au Website:

4 Sclerotinia disease on green beans

5 Table of Contents INDUSTRY SUMMARY 1 TECHNICAL SUMMARY 2 RECOMMENDATIONS 4 INTRODUCTION 5 PRODUCT FORMULATIONS 6 SECTION 1: LITERATURE REVffiW 8 SECTION 2: GROWER SURVEY AND FIELD INSPECTIONS : GROWER SURVEY : FIELD INSPECTIONS 21 SECTION 3: FUNGICIDE RESISTANCE 24 SECTION 4: FUNGICIDE APPLICATION METHODS SPRAY COVERAGE : FIELD TRIALS CONDUCTED IN 1998/ : THE EFFECTS OF WATER VOLUME ON SUMISCLEX EFFICACY : THE EFFECTS OF SPRAY ADJUVANTS ON THE SYSTEMIC ACTIVITY OF FUNGICIDES 47 SECTION 5: ALTERNATIVE PRODUCTS 51 SUMMARY 51 INTRODUCTION : FIELD TRIAL CONDUCTED IN 1997/ : FIELD TRIALS CONDUCTED IN 1998/99 55 SECTION 6: REFINING FUNGICIDE APPLICATION METHODS AND EFFICACY OF ALTERNATIVE PRODUCTS 64 SUMMARY 64 INTRODUCTION : FIELD TRIALS CONDUCTED IN 1999/ TECHNOLOGY TRANSFER 78 REFERENCES 79 ACKNOWLEDGMENTS 80 APPENDICES 81 GROWER SURVEY FORM APPENDIX i CRITICAL CONCENTRATIONS OF SPIN FLO AND SWITCH FOREC50 TESTING AVCARE FUNGICIDE GROUPING APPENDIX II APPENDIX HI

6 Industry Summary White mould, caused by Sclerotinia sclerotiorum, is a major disease problem of both green and navy beans, causing yield losses by premature plant death through lower stem infection, and/or infection of beans. Green bean crops with greater than 8% Sclerotinia are rejected due to difficulties in processing. This 3-year HRDC funded project aimed to identify the cause of poor Sclerotinia control in the field, to review new developments in Sclerotinia control on other crops, to identify alternative control products, and to improve methods for Sclerotinia control. Fungicide application methods and timing A survey of bean growers showed that application methods are highly variable between growers, and that, along with different weather conditions, location and cultural practices, can influence the level of Sclerotinia control. Field studies showed that the timing of the first spray application of Sumisclex or Fortress (procymidone) is the most important factor in determining the level of Sclerotinia control. Application methods such as spray nozzle types, droplet size, and water volume, were shown to have less influence. Fungal resistance to fungicide None of the 37 isolates of Sclerotinia sclerotiorum collected from different areas of Queensland and Tasmania and screened for sensitivity to the fungicides Benlate, Sumisclex, Switch and Spin Flo, were found to be resistant to any of the fungicides. Alternative products In field trials conducted over three seasons, Sumisclex or Fortress, applied at the rate of 1.5L/ha, often resulted in the most effective disease control. Among the alternative fungicide and biological products evaluated in field trials, two new products, Switch and Spin Flo (also sold as Bavistin), were identified as having potential for Sclerotinia control. Spin Flo gave better disease control than Benlate or Switch, and may be a suitable alternative to Benlate, for use in alternation with procymidone. A field trial conducted in Queensland from March to May 2000, showed that Spin Flo performed as well as procymidone. Note that at the time of the publication of this report, Spin Flo is still not registered for use in bean crops. Extension of results Project findings were presented through newsletters, field days, Tasmanian vegetable extension days and conferences, throughout the life of the project, and at the QFVG Growing for Profit Day, 15 th November 2000, at Gympie, Queensland. SERVE-AG RESEARCH 1

7 Technical Summary White mould, caused by Sclerotinia sclerotiorum, is a major disease problem of both green and navy beans, causing yield losses by premature plant death through lower stem infection, and/or infection of beans. Green bean crops with greater than 8% Sclerotinia are rejected due to difficulties in processing. This 3-year HRDC funded project aimed to identify the cause of poor Sclerotinia control in the field, to review new developments in Sclerotinia control on other crops, to identify alternative control products, and to improve methods for Sclerotinia control. Literature review/field inspections Control of white mould on beans caused by S. sclerotiorum requires an integrated approach in crop management. The disease management strategy is based on knowledge of the fungal disease cycle, effectiveness of fungicides, application methods, and the importance of field hygiene and crop rotations. The use of cultural practices such as reduced plant density, row spacing and orientation, and irrigation to reduce microclimatic conditions that favour the disease, has been researched and recommended. A literature review was conducted to cover research studies in these areas, with particular emphasis on knowledge that may assist in improving current disease control practices and future requirements. Field observations indicated that the most important factors that influence the level of Sclerotinia disease are location, paddock terrain, weather, variety, plant litter on the ground, mechanical damage and poor water drainage. These factors need to be taken into consideration in deciding plant density, row spacing, and the timing and number of fungicide sprays to be used. Fungal resistance to fungicides None of the 37 isolates of Sclerotinia sclerotiorum and one isolate of Sclerotinia minor, collected from different areas of Queensland and Tasmania and screened for sensitivity to the fungicides benomyl (Benlate), procymidone (Sumisclex or Fortress), cyprodinil + fludioxonil (Switch), and carbendazim (Spin Flo), were found to be resistant to any of the fungicides. Fungicide application methods A survey of bean growers showed that application methods are highly variable, and along with different weather conditions, location and cultural practices, can influence the level of Sclerotinia control. Field studies showed that the timing of the first spray application of procymidone is the most important factor in determining the level of Sclerotinia control. Application methods such as spray nozzle types, droplet size, and water volume, were shown to have less influence. Fungicides / alternative products In field trials conducted over three seasons, procymidone at the rate of 1.5L/ha often gave the greatest disease reduction compared to other products evaluated. Two new products, Switch and Spin Flo, were also identified as having potential for Sclerotinia control. Spin Flo gave better disease control than Benlate or Switch, and may be a suitable alternative to Benlate, for use in alternation with Sumisclex. A field trial conducted in Queensland in early 2000, showed that Spin Flo performed as well as Sumisclex. Note that at the time of the publication of this report, Spin Flo is not registered for use in bean crops. The economic feasibility of registering Spin Flo is being evaluated by Aventis CropScience Pty Ltd (formerly Rhone-Poulenc Rural Australia Pty Ltd). SERVE-AG RESEARCH 2

8 Technical Summary (Cont.) Although Switch significantly reduced disease incidence and severity when compared to the untreated control, the level of control was much lower than with the currently registered products Sumisclex and Benlate. As a result, Novartis Crop Protection Pty Ltd has indicated that the company would not be interested in further studies, or in registering this product for Sclerotinia control in beans. ABG8001 and ABG8013, biocontrol products based on Trichoderma harzianum produced in Israel, were also evaluated in this project. ABG8001 is a registered biocontrol agent for disease control and is sold commercially. Unfortunately, samples of the product supplied for field testing over a two-year period had low viability. Therefore, the resulting poor efficacy in Sclerotinia disease control may not be representative of the product's potential if the required biocontrol population is attainable. Laboratory tests showed that Trichoderma was tolerant to Sumisclex. The application of ABG8001 with Sumisclex appeared to cause a slight reduction in Sclerotinia incidence and severity compared to Sumisclex alone. Little or no disease control was recorded when ABG8001 was applied alone. This raised the possibility of enhancing the performance of the biocontrol agent when applied with a suitable fungicide. The biocontrol product PRP01, which is based on Coniothyrum minitan, is a fungal parasite of S. sclerotiorum that is sold in Europe as pre-plant product application for Sclerotinia disease control. In a field trial evaluation, this biocontrol agent did not reduce disease incidence when applied alone. This could be due to infections from airborne ascospores produced in adjacent untreated areas. Unlike ABG8001, PRP01 was found to have a good viability and shelf life. There was, however, a significant interaction between pre-plant PRP01 soil applications and post-plant Fortress foliar sprays. The soil treatment with PRP01, followed by Fortress spray applications with 500L/ha water, gave better disease control than Fortress spray applications alone. This indicates that this biocontrol product has the potential of improving Sclerotinia control if used in conjunction with a regular fungicide spray program. It is recommended that biocontrol agents be evaluated in long-term studies to properly determine their potential for Sclerotinia disease control, especially for reducing the level of sclerotia in soil. SERVE-AG RESEARCH 3

9 Recommendations When using a boom sprayer, spray water volumes ranging from about 150 to 400L/ha appear to be adequate, when applied at the early flowering period. Early fungicide applications, at 5 to 10% plants with first flowers and before canopy becomes dense, give optimum disease control. The recommendations on the labels of Benlate and Sumisclex, to spray when 75% plants first show open flowers, need to be reviewed. In areas prone to severe Sclerotinia disease, cultural practices, such as low planting density, wider row spacing, and bean varieties, that can assist in reducing conditions conducive to disease development, should be considered. In areas that are not prone to severe Sclerotinia infections, an increase in planting density in conjunction with the use of appropriate fungicide and spray methods, could significantly increase yield per hectare. Fungicides based on procymidone, Sumisclex and Fortress, are still the most effective products for control of Sclerotinia in bean crops. Carbendazim (Spin Flo and Bavistin) appears to give better disease control than benomyl (Benlate), and may be a suitable alternative to benomyl for use in alternation with procymidone. Biocontrol agents need to be evaluated in long-term studies to properly determine their potential for Sclerotinia disease control, especially for reducing the level of sclerotia in soil. SERVE-AG RESEARCH 4

10 Introduction Target Disease Sclerotinia rot or white mould disease caused by Sclerotinia sclerotiorum. Background White mould, caused by Sclerotinia sclerotiorum, is a major disease problem of both green and navy beans. It can cause yield losses by premature plant death through lower stem infection, and/or infection of beans. Green bean crops with greater than 8% Sclerotinia are rejected due to difficulties in processing. High yields are essential to enable the Australian processing bean industry to be competitive against imported products. Unfortunately, increasing yield per hectare is often hampered by an increase in Sclerotinia. Conditions that promote crop growth and yield also promote Sclerotinia disease severity. As a result of this interaction, many crops are intentionally grown under less than ideal conditions for maximum yield, limiting growth in order to reduce disease severity. This means that many bean crops are losing up to 50% of potential yield. The potential of narrow row spacing to double yield is also hampered by unreliable control of Sclerotinia. Benomyl (Benlate) and procymidone (Sumisclex or Fortress) are the only two fungicide products currently registered for use against Sclerotinia disease on beans. There have been concerns that the regular use of these control products may result in Sclerotinia resistance to the fungicides. The withdrawal of one registered product would further limit the choice of available fungicides for the control of Sclerotinia. Hence, many growers consider the evaluation and development of new products for Sclerotinia control to be essential. In recent years, field officers and growers have noted poor control of Sclerotinia on beans. It is not clear whether this relates to the fungicides used, spray methods, crop density, spray timing or other factors. This is of great concern to growers, in view of the high cost of chemical control programs. This project, therefore, aimed to identify the cause of poor Sclerotinia control in the field, to review new developments in Sclerotinia control on other crops, to identify alternative control products, and to improve methods for Sclerotinia control. Bean plants tend to be most susceptible to white mould disease close to maturity, when crops become very dense. Flowers are produced from about six weeks after sowing until harvest, and most of them are located beneath the plant canopy. High humidity, prolonged plant wetness, and flowering beneath the crop canopy create an ideal environment for disease infection. Unfortunately, with canopy closure, spray penetration of fungicide sprays can be very poor. Under such conditions, a competitive non-pathogenic fungus such as Trichoderma may prevent late Sclerotinia disease development. Trichoderma based biocontrol products for disease control are now available commercially and are to be evaluated in this project. SERVE-AG RESEARCH 5

11 Product Formulations Fungicides Product Active ingredient (a.i.) Rate of a.i. Formulation Chemical Group Amistar azoxystrobin 500g/kg Wettable granules Strobilurin Benlate benomyl 500g/kg Wettable powder Benzimidazole Bravo chlorothalonil 720g/L Suspension concentrate Multi-site activity SS01 chitosan 4% Suspension liquid Unspecified Folicur tebuconazole 430g/L Suspension concentrate Fortress procymidone 500g/L Suspension concentrate DMI Dicarboximide Rovral iprodione 250ml/L Suspension liquid Dicarboximide Saprol triforine 200g/L Suspension liquid DMI Spin Flo carbendazim 500g/L Suspension concentrate Sumisclex procymidone 500g/L Suspension concentrate Switch cyprodinil + fludioxonil 375g/kg + 250g/kg Wettable powder Benzimidazole Dicarboximide Anilinopyrimidine * The chemical group, used for resistance management, was developed by Avcare (Appendix iii). Biocontrol products Product Active ingredient (a.i.) Rate of a.i. Formulation ABG8001 Trichoderma harzianum 10 8 colony forming units/g Wettable powder ABG8013 Trichoderma harzianum 10 8 colony forming units/g Wettable powder PRP01 Coniothyrum minitans 10 8 colony forming units/g Soluble granules SERVE-AG RESEARCH 6

12 Product Formulations (Cont.) Spray Adjuvants Product Active ingredient (a.i.) Rate of a.i. Agral Nonyl ethlene oxide 600g/L Agridex Paraffin based petroleum oil + polyol fatty acid esters 714g/L + 155g/L Bond Synthetic latex + nonylphenolethoxylate 450g/L+100g/L DCTron Plus Spray Oil Petroleum oil 839g/L NuFilm Di-1-p menthene 96% SprayTech Codacide Oil Organic vegetable oil N/a X-77 Nonyl ethlene oxide 370g/L SERVE-AG RESEARCH 7

13 Section 1: Literature Review The successful control of white mould on beans, caused by Sclerotinia sclerotiorum, requires an integrated approach in crop management. The disease management strategy is based on knowledge of the fungal disease cycle, effectiveness of fungicides, application methods, and the importance of field hygiene and crop rotations. The use of cultural practices such as reduced plant density, row spacing and orientation, and irrigation to reduce microclimatic conditions that favour the disease, has been researched and recommended. However, bean growers in Australia are under increasing pressure to increase production by means of increasing plant densities in order to remain competitive internationally. High yield is essential to enable the Australian processing bean industry to be competitive against imported products. A review has therefore been conducted in this project to cover research studies on the areas mentioned above, with particular emphasis on knowledge that may assist in improving current disease control practices and future requirements. A literature search of published articles was conducted on the CAB Abstracts and Agricola. S. sclerotiorum has a wide host range, with infection recorded on over 360 types of plants. The fungus can survive as sclerotia in soil or in infected seeds for 3-5 years (Hall & Steadman 1991). Direct mycelial infection from sclerotia can occur particularly on the stem base and foliage that are in contact with the ground. However, the predominant form of primary infection by S. sclerotiorum on bean plants is through ascospore infection of senescent plant material such as spent blossoms or damaged plant tissues (Hall & Steadman 1991). Ascospores are sensitive to UV light, desiccation and high temperatures (25 C & above) (Caesar & Pearson 1983, Phillips 1994). As a result, ascospore survival on shaded leaves within a dense canopy is about 20% higher than on exposed leaves (Caesar & Pearson 1983). Sclerotinia infection by ascospores, mycelial growth and disease spread is optimum at C, while no infection occurs at 5 C or 30 C (Phillips 1994, Abawi & Grogan 1975). Isolates of S. sclerotiorum collected from 28 locations, and screened for sensitivity to Benlate (benomyl, benzimidazole group) and Rovral (iprodione, dicarboximide group), showed no resistance to either of the fungicide products or groups (O'Brien, 1996). Sumisclex (procymidone), which belongs to the dicarboximide group of fungicides, was not tested. There has been no published record of fungal resistance to Sumisclex. To prevent resistance from developing, only two consecutive sprays of Sumisclex are recommended. For additional sprays, it should either be alternated with a product from another fungicide group or mixed with a protectant fungicide. Resistance of bean cultivars to the disease has been recorded. Reduced disease infections may be associated either with physiological resistance such as cultivar tolerance to oxalic acid secreted by the pathogen (Tu 1989) or with canopy architectural avoidance such as upright and open bushes, which makes the microclimate less conducive to infection (Schwartz et al. 1978). In Australia, a diverse germplasm of bush types have been screened for both types of resistance to S. sclerotiorum in a Queensland navy bean breeding program (Middleton et al. 1995). Many fungicide products have been evaluated and registered for use to control S. sclerotiorum on beans and other crops. A review has been conducted on products registered for use on other crops in Australia, New Zealand, Britain, and North America. Many of the products, like thiram, copper, chlorothalonil, dicloran, mancozeb, iprodione, and sulphur, have been shown in efficacy trials to be less effective than relatively new products like Sumisclex and Benlate. Others, such as Amistar, Folicur, and Saprol, will be evaluated in this project. SERVE-AG RESEARCH 8

14 1: Literature Review (Cont.) The effectiveness of fungicide applications may be affected not only by the type of fungicide used, but also by factors such as application methods and timing. Disease control was found to be less effective when the spray volume was reduced from 550 to 243L/ha (Morton & Hall 1989). Hunter et al. (1978) recommended a volume of 440L/ha, while a volume of 1000L/ha was used in other studies (unpublished efficacy trial studies). Crop Care recommends that Sumisclex be applied at 1000L/ha to ensure good coverage (Crop Care Technotes). In practice, however, a spray volume of 10OOL/ha was found to be impractical by many bean growers. As for spray timing, fungicides must be applied during the flowering period to prevent infection of bean blossoms (Hunter et al. 1978). Steadman (1983) noted that protective fungicide applications gave good disease control on bean varieties that have a short flowering habit, such as snap bean. Erratic control was obtained on bean types like green beans that have a long and indeterminate flowering habit. SERVE-AG RESEARCH 9

15 Section 2: Grower survey and field inspections 2.1: Grower survey Introduction This survey study was conducted with 10 growers in Queensland and 21 growers in northern Tasmania, to help identify different fungicide application methods used by growers for Sclerotinia control on beans, and their level of satisfaction with these control methods. Materials & Methods The survey was conducted in the 1998/99 season as a one-to-one interview with each grower, using a questionnaire that was developed for this study (Appendix i). The responses were entered onto a database, and where possible, the percentage of growers responding to a particular practice was tabulated and expressed in charts, which are included in the following pages. Results & Discussion A total of 31 growers responded to the survey questionnaire. In summary, control practices are as follows: Types of fungicide used are Benlate and Sumisclex (Sumisclex is most commonly used). Rates of Sumisclex used range from 1.0 to 2.5L/ha (1.5L/ha most common). Types of spray unit used are standard boom, air-assisted boom, air blast sprayer, and shoulder spray pack blower/mister (82% of growers surveyed use standard boom). Spray nozzles used are cone jet (48%) and fan jet (52%). Water volume ranges from 130 to 700L/ha (22% at 400L/ha most common, followed by 14% at160l/ha). Number of spray applications ranges from 1 to 3 (depending on location of growers). Timing of the first spray, or the only spray applied, ranges from early flowering to small bean pods. Satisfied with current control program: 44% Yes, 48% No, 4% Average, 4% Not sure. In comparing the practices between the two main bean production regions in Tasmania and Queensland, there are some obvious differences: In Tasmania, beans are usually sown at a much higher plant density (16-20 plants/row in Tas. vs 8-14 plants per row in Qld.) and narrower row spacing (average of 60cm in Tas. vs average of 70cm in Qld.). Queensland growers usually apply one to two fungicide sprays, compared with two to three sprays in Tasmania. In Queensland, the disease tends to vary from year to year depending on the rainfall and prolonged wet periods, especially between May to June. In drier periods, the disease incidence is either very low or not significant. Weather conditions are cooler and wetter in Tasmania. Even in seasons where lower than usual rainfall is recorded, irrigation and dense planting can still create ideal conditions beneath the crop canopy for the disease. SERVE-AG RESEARCH 10

16 2: Grower survey and field inspections (Cont.) All except one grower surveyed in Tasmania use travelling gun irrigators, compared to mainly overhead sprinklers used by the Queensland growers. The average bean yield expected by Tasmanian growers is 10,000kg, compared to 6,500kg by Queensland growers. Apart from planting density, different varieties can also influence yield. Survey findings Crop rotation - previous bean crop (years none given I never i 10 8 en 4 i 3 i 2 i 1 i C ) % growers Sclerotinia disease in grower's area always often sometimes - unknown WM C ) % growers SERVE-AG RESEARCH 11

17 2: Grower survey and field inspections (Cont.) Average heights of mature bean plants (cm) none given!,'ziu IIZ i I I % growers Bean planting density (Plants / metre row) n 8-9 n I i i I C ) % growers SERVE-AG RESEARCH 12

18 2: Grower survey and field inspections (Cont.) Spacing between plant rows (cm) none given ~ I I I I I " J % growers SERVE-AG RESEARCH 13

19 2: Grower survey and field inspections (Cont.) Sclerotinia control programs used by bean growers Type of fungicide used Sumisclex & Benlate _j Benlate Sumisclex J C ) % growers Rate of Sumisclex used (L/ha) 1.5 & 2.5 =] & ,., % growers i 1 Satisfied with current control measures not given I don't know average n No Yes - i i % growers SERVE-AG RESEARCH 14

20 2: Grower survey and field inspections (Cont.) Comments on improvements for Sclerotinia control on bean crops 1. Increased row spacing from 46 to 53cm should be an advantage in controlling Sclerotinia. 2. This is only our second year growing beans; therefore have a lot to learn. 3. Less overlap when drilling beans. 4. Would like to see better bean varieties with resistance to Sclerotinia. 5. Label recommendations do not give all the relevant information, eg. how long before rain to apply. Also, a variety of chemicals in the same coloured containers lends itself to errors, and chemicals can be hard to pour. 6. Other chemicals and improved timing. 7. Fungicide to control Sclerotinia at low water volume. 8. Better control, earlier application of sprays and perhaps granular application rather than sprays. 9. Cheaper chemicals. 10. Field day on better application. 11. Fungicide as good as Ronilan or better. 12. Better spray than Sumisclex, preferred Ronilan. 13. Go back to using Ronilan. 14. Would prefer not to be reliant on only one chemical for disease control. 15. Want something that works, and a range of products to choose from. 16. Can't get much better. SERVE-AG RESEARCH 15

21 2: Grower survey and field inspections (Cont.) Spray methods used by growers Type of spray unit used shoulder spray pack blower - mister air blast 1 1 air assist boom standard boom % growers Type of spray nozzle used fan cone % growers Number of fungicide sprays applied 5 ' ' J i. i % growers SERVE-AG RESEARCH 16

22 2: Grower survey and field inspections (Cont.) Days between spray applications 7 to 14 I 7 to 10 I 7 to to I 8 I 7 I only one spray I % growers 35 Spray water volume/hectare "i::,,: i.zzi,"!,,':,:,','p,'..' i i p i i i i i C ) % growers 3 0 SERVE-AG RESEARCH 17

23 2: Grower survey and field inspections (Cont.) Method of determining when to apply fungicide sprays weather & disease presence weather & small beans weather & flowering weather [ flowering time ofyearwithdisease problems crop stage & lable rec. 1st. petal drop 70%flower & disease presence 10%flower & label rec. small beans lateflowering70-75% midflowering30% [ earlyflowering10% [ first flower % growers SERVE-AG RESEARCH 18

24 2: Grower survey and field inspections (Cont.) If the label recommends high water volume spray of 1000L/ha, are you able to do so? none given 1 No Yes i n i i % growers Who apply fungicide sprays? spray contractor self () % growers 7C 8 0 Who gives advice on when to apply fungicide sprays? Agronomic Processing field officer Self I "T I I I % growers SERVE-AG RESEARCH 19

25 2: Grower survey and field inspections (Cont.) What is the best way for information to be provided to growers? not given chemical representative agronomist ZII I 1 on 1 exchange I internet QFV news magazine letter booklet newsletter I I I I field officer I field day I % growers SERVE-AG RESEARCH 20

26 2. Grower survey and field inspections (Cont.) 2.2: Field inspections In 1999, field inspections were conducted on 10 bean crops in Tasmania that had severe disease problems, to determine the cause of poor disease control. Field observations indicated that the most important factors are location, paddock terrain, weather, plant litter on the ground, mechanical damage and poor water drainage. These factors need to be taken into consideration in deciding plant density, row spacing, and the timing and number of fungicide sprays to be used. Some of these crops were sprayed with Sumisdex or Benlate, using an air-assisted sprayer at a high water volume of 1000L/ha, indicating that severe disease can still develop under disease favourable conditions, even with the appropriate fungicide application methods. However, when compared to areas that were not sprayed, the fungicide treatments did cause a large reduction in disease incidence and severity. Crops sown in sheltered areas such as Merseylea, or high rainfall areas like Forest, are more prone to high disease incidence and severity, compared to exposed areas such as Sassafras and Forth. The main bean variety examined in this study was Rapier, a whole bean grown for processing, which has a long flowering period. Field observations showed that once flowering commenced on plants, flowers continued to be produced until harvest (Figure 2.2.1). As a result of the indeterminate and long flowering period, the plants are susceptible to infection by Sclerotinia ascospores from the first flower production until harvest. Fungicides applied early, at about 5 to 20% plants with first flowers, before the plant canopy becomes too dense, provide good protection from Sclerotinia infection. However, good spray penetration into the plant canopy to prevent infection of late flowers is difficult to achieve on larger plants with a dense canopy. Most of the paddocks inspected have undulating ground, and disease pressure was always worse in low-lying areas where the ground tends to stay wet longer after rainfall or irrigation. As a result, plants in poor drainage areas (Figure 2.2.2), dips or low lying areas (Figures & 2.2.4), are prone to high disease incidence, even after fungicide applications. Persistent rainfall close to harvest can be devastating for the spread of Sclerotinia disease. Large and heavy plants, which are heavily laden with maturing or matured bean pods, tend to collapse or lean against one another, facilitating the rapid spread of the disease. The efficacy of fungicide sprays can be influenced by plant size and canopy, whereby poor spray coverage beneath the canopy of larger plants increases the risk of Sclerotinia infections (Figure 2.2.5). Mechanically damaged plants, especially in travelling irrigator runs or wheel tracks, are highly susceptible to Sclerotinia infections, which can then spread to adjacent areas (Figure 2.2.6). SERVE-AG RESEARCH 21

27 2. Grower survey and field inspections (Cont.) Figure 2.2.1: Bean plants at close to harvest, producing both pods and flowers. Figure 2.2.2: Beans not harvested in a large section of a field with poor drainage due to severe Sclerotica infections. Figure 2.2.3: Obvious low-lying areas across plant rows at the initial bean crop stage. Figure 2.2.4: Yellowing areas caused by severe Sclerotinia infections in low-lying areas across the plant rows. Figure 2.2.5: Uneven plant growth in a crop. Larger plants usually have poor spray coverage beneath the canopy due to dense plant canopy. Figure 2.2.6: Damaged plants in spray or irrigation tracks are highly susceptible to Sclerotinia infections. SERVE-AG RESEARCH 22

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29 Section 3: Fungicide resistance Summary Thirty-seven isolates of S. sclerotiorum from various host crops, and from a wide geographic range, were screened for sensitivity to the fungicides Switch, Spin Flo and Sumisclex. None of the isolates were found to be resistant to any of the fungicides. No resistance to Benlate was found on isolates of S. sclerotiorum collected from 28 locations, in a sensitivity test by O'Brien (1996). Introduction Fungicides are used to control Sclerotinia in beans. Some, such as the benzimidazoles (Benlate and Spin Flo) and dicarboximides (Ronilan and Sumisclex) have been used for many years. Additional fungicides (e.g. Switch) from other chemical groups are being sought to lessen the chances of fungicide resistance developing. Isolates of S. sclerotiorum were collected from Tasmania and Queensland, and screened for sensitivity to three fungicides to determine whether any showed resistance, and to establish base line data for future tests. Materials & Methods The sensitivity test consisted of measuring fungal growth rates on culture plates amended with a range of concentrations of the fungicides. The test fungicides were Switch, Spin Flo, and Sumisclex. A preliminary test (Appendix ii) showed that for Spin Flo, the sensitivity (EC50) lay between 0.1 and 1, while for Switch it was <0.1. Previous experience with Sumisclex has indicated that the EC50 should be between 0.1 and 1. Molten potato dextrose agar (50 C) was amended with fungicide solutions to give concentration ranges(ppm, a.i.)of0, 0.01,0.1,0.3, 0.6,1 and 10 for Spin Flo and Sumisclex, and 0, 0.001, 0.003, 0.01, 0.03, 0.1, 0.3 and 1.0 for Switch. Plates were poured (20ml_ per plate), allowed to stand overnight, then inoculated at two sites, directly opposite one another on the margin of the plate, with cores taken from the margin of a 72 hour colony. Cores were 4mm diameter and were placed inverted on the test plate to bring mycelium in direct contact with the agar. Growth of the 37 isolates of S. sclerotiorum and one isolate of S. minor were marked after 23 hours and again after a further 25.5 hours. The length of growth between the two marks was measured (two per inoculation site) and an average hourly growth rate deduced for each isolate on each fungicide concentration. From these, EC50 and minimum inhibitory concentration vajues (MIC) were deduced as ppm, a.i. SERVE-AG RESEARCH 24

30 3: Fungicide resistance (Cont.) Results The sensitivity of isolates to Spin Flo and Sumisclex were similar, with mean EC50 values of 0.78 and 0.80 respectively, and values of 1 ppm (Tables 1 and 2). Isolates were more sensitive to Switch (EC50, 0.02; MIC, 0.1). The variation from the mean was low. Discussion Isolates of S. sclerotiorum came from widely differing geographical areas, different hosts and different histories. Sumisclex is unregistered and would not have been used on the broccoli isolates, while collections from beans in the Gympie area in Queensland, and the north-west coast of Tasmania, were from farms where dicarboximide fungicides have been used regularly for about 15 years. Despite this, all isolates were similar in their sensitivities to the three fungicides. This suggests that Sclerotinia sclerotiorum is not a variable organism and does not readily produce fungicide resistant strains. Related fungi, e.g. S. fructicola and Botrytis cinerea, on the other hand, very quickly developed strains resistant to the benzimidazole and dicarboximide fungicides. The test also highlighted that Switch should be a useful fungicide for control of Sclerotinia since the mean EC50 for this fungicide is lower than that of the other two by a factor of 35. This would depend on the fungicide having a field performance that matches its in vitro activity. If field performance were satisfactory, registration of Switch would provide a range of fungicides from three different chemical groups for control of the disease. Isolates from future outbreaks of Sclerotinia sclerotiorum can now be evaluated for fungicide sensitivity using the figures in Tables 1 and 2 as base sensitivity data. In this way, resistant strains will be detected. SERVE-AG RESEARCH 25

31 3: Fungicide resistance (Cont.) Table 1: Sensitivity (EC50) of 37 Sclerotinia isolates to three fungicides Location / EC50 (ppm) Isolate crop Switch Spin Flo Sumisclex Tasmania - Bean HP1 HP 2 HP 3 HP 4 HP 5 HP 7 HP 9 HP 10 HP 11 HP 12 HP 13 HP 14 HP 15 HP 16 HP Gympie, Qld - Bean JHB2 JHB4 JHB 4-2 JHB7 JHB 8 JHB 8-3 JHB 9 JHB 13 JHB 13-1 JHB 14 JHB Downs, Qld - Broccoli R R S S Caboolture, Qld - Bean BpS Average Qld - Bean S. minor SERVE-AG RESEARCH 26

32 3: Fungicide resistance (Cont.) Table 2: Sensitivity (minimum inhibitory concentration [MIC]) of 37 Sclerotinia isolates to three fungicides Location / crod Tasmania - Bean Gympie, Qld - Bean Downs, Qld - Broccoli Caboolture, Qld - Bean Isolate HP1 HP 2 HP 3 HP 4 HP 5 HP 7 HP 9 HP 10 HP 11 HP 12 HP 13 HP 14 HP 15 HP 16 HP 17 JHB 2 JHB4 JHB 4-2 JHB7 JHB 8 JHB 8-3 JHB 9 JHB 13 JHB 13-1 JHB 14 JHB R R S S BpS MIC (ppm) Switch Spin Flo Sumisclex Average Qld - Bean S. minor 1 SERVE-AG RESEARCH 27

33 Section 4: Fungicide application methods Summary Tests on spray coverage and penetration through the plant canopy were conducted using different spray water volumes and spray equipment (Section 4.1). Spray volume of 1000L/ha gave the best coverage and penetration through the plant canopy in the two tests conducted. At 300L/ha, as used by many green bean growers, the spray coverage was variable and appeared to be dependent on the type of spray equipment and speed used. Spray coverage tests conducted in 1999 (Section 4.1.2), using a standard boom sprayer, showed that by increasing the spray volume, most of the spray droplets were deposited on the upper parts of the plants. This causes many overlaps of the spray droplets, while increased coverage of the middle to lower parts of the plants was minimal. A higher spray volume was also generally applied with larger aperture spray nozzles, which create larger size droplets, which again tend to be deposited on the upper parts of the plants. A field trial was conducted to evaluate the effects of different fungicide application methods, with the use of different spray timings, water volumes and spray nozzle types. From the different fungicide application methods examined, different spray timing caused the greatest difference in disease incidence and disease severity (Trial 4.2.1). An early Sumisclex spray, where the first spray was applied at the 5% with first flower stage, greatly reduced disease incidence and severity compared to those where the first spray was applied 10 days later, at 90% plants with first flowers. This showed that early fungicide application is critical under field conditions that are conducive to high Sclerotinia disease. In comparing other application methods, when hollow cone nozzles were used, lower spray volume of 250L/ha caused a greater reduction in disease incidence and severity compared to the higher water volume of 590L/ha (Trial 4.2.1). This finding showed that even though there was greater spray coverage with the higher water volume (Section 4.1.1), there were many overlaps in the coverage (Section 4.1.2). An increased water volume, at 500L/ha or more, also caused a dilution effect, which could reduce the fungicide efficacy in the resulting spray mixture (Section 4.3). In the spray with low water volume, the number and distribution of droplets to different parts of the foliage appeared to be adequate (Section 4.1.2). This may explain the lack of difference between the different spray volumes. In a field trial conducted in an area prone to only low disease pressure, there was no difference between the different application methods on the disease incidence and severity (Section 4.2.2). This indicates that applications methods are not as critical under conditions with low disease pressure. It is interesting to note that with each of the spray nozzle types used, the higher water volume tended to cause a slightly higher disease severity index compared to the lower volume. Only one treatment, which used air inducted fanjet spray nozzles (Spray System Al 05), gave very poor disease control, due to poor spray coverage and penetration into the plant canopy as a result of its large and heavy spray droplets. SERVE-AG RESEARCH 28

34 4: Fungicide application methods (Cont.) Laboratory and glassshouse studies were conducted to determine whether the systemic activity of Sumisclex and Spin Flo could be enhanced by spray adjuvants (Section 4.4). The oil based adjuvants, Agridex and DC Tron consistently improved the systemic activity of both Sumisclex and Spin Flo against S. sclerotiorum. NuFilm was an effective adjuvant for Sumisclex but not Spin Flo. The non-ionic surfactant X-77 did not improve the systemic activity of either fungicide. Introduction Laboratory tests conducted in Section 3 showed that none of the Sclerotinia isolates were resistant to the two registered fungicide products for Sclerotinia control in beans. The other factors that may influence the control of Sclerotinia disease on beans, are fungicide application methods, the efficacy of the fungicide used, and disease pressure and field conditions. One area of fungicide application method that has often been queried is the spray water volume. Some field advisors recommend that a high water volume of 1000L/ha is essential for maximum disease control, while other field advisers recommend a low water volume of 250L/ha. Many growers find that the application of a high water volume rate, eg 1000L/ha, is impractical, timeconsuming and hence costly. The time required to apply a high water volume can be double or more than that required for low volume spray. Fungicide application methods were examined in this section, with the following studies: Section 4.1: spray coverage and penetration through the plant canopy. Section 4.2: evaluation of the effects of fungicide application methods in the control Sclerotinia disease in field trials. Section 4.3: a laboratory study to determine the effects of Sumisclex concentration on its efficacy for Sclerotinia control. Section 4.4: the effects of spray adjuvants on the performance of Sumisclex and Spin Flo in laboratory and glasshouse studies. SERVE-AG RESEARCH 29

35 4.1 Spray coverage 4: Fungicide application methods (Cont.) 4.1.1: Spray coverage as affected by water volume and pressure Introduction The aim of these tests was to determine the effects of different spray pressures and water volumes on spray coverage. Materials & Methods Two field tests were conducted in 1997 on the green bean variety, Rapier, at Moriarty and Merseylea, NW Tasmania, using water sensitive paper strips placed on leaves located at the top, middle, and bottom parts of bean plants. Note that flowers are produced throughout the different plant parts. Both tests were conducted on plants when about 10% plants showed first blossoms. The test at Moriarty was conducted using the grower's spray equipment, while a Serve-Ag Research air-pressurised hand sprayer was used for the Merseylea test (nozzle TX12 for 400kPa & TX26 for 700kPa). Hollow cone nozzles were used in both tests. Spray droplet coverage on the water sensitive paper strip was measured and tabulated using image-processing analysis with SigmaScan Plus. Results & Discussions Figure : Effects of spray pressure & water volume on bean plant coverage 7har/moni - 7bar/300L - 4bar/300L - 4bar/160L ^...J ^wmipw _ ( 1 1 above: using grower's air-assisted sprayer ntop H middle U bottom - below: using Serve-Ag's air-assisted hand sprayer 7bar/1000L - 7bar/300L 11!^ ill.. ( 4bar/300L - o.o i r %coverage as measured by water sensitive paper SERVE-AG RESEARCH 30

36 4: Fungicide application methods (Cont.) A spray volume of 10OOL/ha gave the best coverage and penetration through the plant canopy in the two tests conducted (Figure ). At 300L/ha, as used by many green bean growers, spray coverage appeared to be dependent on the type of spray equipment used. Excellent coverage and penetration, similar to 1000L/ha was achieved at the Merseylea site, with a high pressure of 700kPa at 300L/ha, using a precision air-pressurised hand sprayer. In contrast, poor coverage and penetration was obtained with both 400 and 700kPa at 300L/ha at the Moriarty site, using the grower's air-assisted sprayer. The findings above indicate that spray coverage is likely to be highly variable between growers even when similar volume and pressure is used : Spray coverage as affected by spray type and water volume Introduction The aim of this study was to determine the effects of different types of nozzle, and water volumes, on spray coverage. Materials & Methods Tests were conducted in 1999 in commercial green bean crops at Merseylea and Forth, NW Tasmania, using water sensitive paper strips placed on leaves located at the top, middle, and bottom parts of bean plants. The tests were conducted using grower's spray equipment, fitted with different hollow cone and fan nozzles. The tests were conducted on plants when about 5-20% plants showed first blossoms. Results & Discussions Representative samples of the spray pattern by different spray nozzles and water volumes on water sensitive paper are shown in figures The spray droplet patterns on the water sensitive papers indicate that by increasing the spray volume, most of the spray droplets were deposited on the upper parts of the plants (Figures & ). This caused many overlaps of the spray droplets, while increases in the spray droplets to the middle to lower parts of the plants were minimal. Higher spray volumes were also generally applied with larger aperture spray nozzles, creating larger size droplets, which again tended to be deposited on the upper parts of the plant. Even at a low water volume, the number and distribution of droplets to different parts of the foliage appeared to be adequate. In sprays applied with the commonly used boom sprayer, plant size appeared to have a much greater effect in reducing the spray penetration to the lower parts of the plants than spray water volume (Figures & ). However, when sprays were applied with an air-assisted boom sprayer, the spray coverage and penetration was more even, irrespective of plant size (Figure ), when compared to the standard boom sprayer (Figure ). SERVE-AG RESEARCH 31

37 Figure : The effects of different spray nozzle types and water volumes, applied using spray coverage and penetration of different parts of bean plants (as indicated by the yellow Conejet(TX26) Spray volume L/ha Spray pressure kpa Cone jet (TX 10) Spray volume L/ha Spray pressure kpa Fan jet (XR 1100 Spray volume L Spray pressure Top Middle Bottom SERVE-AG RESEARCH

38 Figure : The effects of two different spray volumes, applied using fan jets on commercial spray units, on spray coverage and penetration. Figure : The commercial crop, o when applied with jets, with a water v High volume spray with 400L/ha Average plant heights was 30cm Low volume spray with 160Uha Average plant heights was 32cm Small plan Average plant height..:_._! W8& # &L mfm*\ '.- SERVE-AG RESEARCH

39 Figure : The effects of different plant sizes in a commercial crop, on spray coverag penetration of a fungicide spray, applied with a commercial air-assisted boom sprayer us 300L/ha volume and 600kPa pressure. Big size plants Average height 40cm Medium size plants Average height 25cm Small size plants Average height 14cm Top Middle Bottom SERVE-AG RESEARCH

40 4: Fungicide application methods (Cont.) 4.2: Field trials conducted in 1998/99 Trial Details SITE1 SITE 2 CROP Green bean Green bean LOCATION Merseylea (GH) Forth, Tasmania VARIETY Rapier Rapier SOIL TYPE Ferrosol Ferrosol REPLICATES 5 5 SOWING DATE 22 December December 1998 HARVEST DATE 26 February March 1999 PLOT SIZE 1.6m x 8m 1.2m x 6m TRIAL DESIGN Randomised complete block Randomised complete block 4.2.1: Site 1, Merseylea Introduction This trial, which was located in an area that is prone to severe Sclerotinia disease at Merseylea in NW Tasmania, was designed to evaluate the effects of different methods of applying 1.5L/ha Sumisclex, on Sclerotinia disease incidence and severity. Materials & Methods Spray Applications The fungicide Sumisclex was applied at the rate of 1.5L/ha, using a hand-pressurised sprayer. The specified spray nozzle type, volume and pressure were used according to the treatments given in Table In Treatments 1-4, the first spray was applied at 5% plants with first opened flowers, on 1 st February 1999, followed by another two sprays applied at 7 days intervals. In Treatments 5-8, the first spray was applied at 90% plants with first flowers (10 days after the 1 st spray for Treatments 1-4), followed by another two sprays applied at 7 days intervals. SERVE-AG RESEARCH 35

41 4: Fungicide application methods (Cont.) Table : Treatment list No Treatment * Spray nozzle Water volume (L/ha) Spray pressure (kpa) First spray timing ** 1 ConejetTX10-250L-5% Conejet TX % 2 Conejet TX26-590L-5% Conejet TX % 3 Teejet TP L-5% Teejet TP % 4 Teejet XR L-5% Teejet XR % 5 Conejet TX10-250L-90% Conejet TX % 6 Conejet TX26-590L-90% Conejet TX % 7 Twinjet L-90% Twinjet % 8 Twinjet L-90% Twinjet % 9 Untreated Control N/a N/a N/a N/a * Treatments L/ha Sumisclex applied. ** First spray based on percentage of plants with flowers. Disease assessments Plants from a 5m length of the middle row of each treatment plot were assessed for disease incidence and severity. The disease incidence was tabulated as a percentage of the total number of plants per plot infected by Sclerotinia. The disease assessment was conducted one week prior to commercial harvest. The disease severity was assessed according to the following severity rating: 1 = mild disease - infection of single stem, leaf or bean; 2 = moderate disease - infection of multiple stem branches; 3 = severe disease - infection affecting the whole plant. The disease severity index was calculated from these ratings, as the sum of the total number of diseased loci multiplied by their respective rating values, and divided by 3. Results & Discussion This trial, located in an area that is prone to severe Sclerotinia disease, has very high disease incidence and severity. With the exception of Treatment 6, all fungicide applications resulted in significant reduction in disease incidence compared to the untreated control (Table , Figure ). All fungicide treatments reduced the disease severity compared to the untreated control SERVE-AG RESEARCH 36

42 4: Fungicide application methods (Cont.) Table : The effects of different methods of applying 1.5L/ha Sumisclex, on Sclerotinia disease incidence and severity No Treatment First spray - flowers opened % Disease incidence % Plants with severe infections Disease severity index 1 ConejetTX10-250L-5% 10% 31.5ab 2.8 a 14.3 a 2 Conejet TX26-590L-5% 10% 32.0 ab 5.3 ab 17.9 ab 3 Teejet TP L-5% 10% 28.4 a 1.3 a 12.3 a 4 Teejet XR L-5% 10% 23.8 a 1.9 a 12.2 a 5 Conejet TX10-250L-90% 90% 59.1 cd 14.1 c 32.4 c 6 Conejet TX26-590L-90% 90% 70.5 de 24.2 c j 40.3 c 7 Twinjet L-90% 90% 47.5 be 13.6 be 30.6 be 8 Twinjet L-90% 90% 49.4 be 12.5 be 28.7 be 9 Untreated Control N/a 81.2 e 42.4 d 58.9 d Within the same column, means followed by a same letter are not significantly different at the 5% level according to Duncan's Multiple Range Test. Figure : % Disease incidence Untreated Control Conejet TX26-590L-90% Conejet TX10-250L-90% Twinjet L-90% Twinjet L-90% Conejet TX26-590L-5% Conejet TX10-250L-5% Teejet TP L-5% Teejet XR L-5% SERVE-AG RESEARCH 37

43 4: Fungicide application methods (Cont.) Table : The effects of i spray timing on Sclerotinia disease incidence and severity No. Treatments based on application timing % Disease incidence % Plants with severe infections Disease severity index 1-4 5% 28.9 a 2.8 a 14.2 a % 56.0 b 16.2 b 33.0 b 9 Untreated control 81.2 c 42.4 c 58.9 c Within the same column, means followed by a same letter are not significantly different at the 5% level according to Duncan's Multiple Range Test. Figure : Effects of timing of first spray, on disease incidence and severity Untreated control 90% - 5% H%Disease incidence %Plants with severe infections Of the different fungicide application methods evaluated, different spray timing caused the greatest difference in disease incidence and disease severity (Table , Figure ). Plants treated with Sumisclex when 5% plants had first flowers, had a significantly lower disease incidence and severity compared to those treated 10 days later, when 90% plants had first flowers. This showed that the fungicide applied at an early flowering period is critical under field conditions that are conducive to high Sclerotinia disease pressure. The percentage of plants with first flowers increases rapidly from 5% to 100% within a very short period of about 2 weeks. Plant size also increases rapidly during the flowering period, covering the gaps between plants and plant rows. Hence, in an area prone to severe disease, it is better to spray early, as any delay in fungicide application due to rainfall or other factors, is likely to result in poorer disease control. SERVE-AG RESEARCH 38

44 4: Fungicide application methods (Cont.) Table : The effects of spray water volume on Sclerotinia disease incidence and severity No. Treatments based on spray water volume* % Disease incidence % Plants with severe infections Disease severity index 1,5 250L/ha 42.8 a 7.8 a 22.3 a 2,6 590L/ha 51.3 b 14.8 b 29.1 b 9 Untreated control 81.2 c 42.4 c 58.9 c * Analysis based only on treatments using cone jet nozzles TX10 and TX26 (ie. Treatments 1, 2, 5, and 6) and the untreated control (Treatment 9). Within the same column, means followed by a same letter are not significantly different at the 5% level according to Duncan's Multiple Range Test Figure Effects of spray water volume on disease incidence and severity (hollow cone jet nozzle used) Untreated control 590L/ha H%Disease incidence 250Uha %Plants with severe infections In treatments where cone jet nozzles were used, plants sprayed with the lower spray volume of 250L/ha had significantly lower disease incidence and severity than when sprayed with the higher water volume of 590L/ha (Table ). It is possible that this phenomenon is caused by a combination of two factors. Firstly, the dilution effect with a higher water volume may reduce the efficacy of the resulting fungicide spray mixture. Secondly, the use of high water volume with a standard boom sprayer, did not increase the spray coverage beneath the plant canopy, but instead caused an increase in the overlap of spray droplets on the upper leaves (Section 4.1). Effects of the dilution factor and fungicide concentrations in spray mixtures are further discussed in Section 4.3. SERVE-AG RESEARCH 39

45 4: Fungicide application methods (Cont.) 4.2.2: Site 2, Forth Introduction This trial was conducted in an area that is not prone to severe Sclerotinia disease, at Forth in NW Tasmania. Sclerotinia mycelial inoculum was, therefore, applied to the trial site to ensure development of the disease. The trial was designed to evaluate the effects of different methods of applying fungicides, on the control of Sclerotinia sclerotiorum in beans. Two relatively low cost fungicides, Saprol and Rovral, were also examined in alternation with Sumisclex, to determine the feasibility of applying low cost products at the early flowering stage, for disease control. Materials & Methods Trial site The trial was located on level ground at the Forthside Vegetable Research Station. The bean crop (cv. Rapier) was sown at a high density of six rows per 1.2m bed, with a narrow spacing of 20cm between rows. There were 14 plants/m in a single row. Sclerotinia inoculum Sclerotes of S. sclerotiorum, collected from an infected cabbage crop in the previous season, were pre-conditioned by storing in a fridge for five months before use. They were then applied along the middle of each treatment plot after seeching emergence on 18 th January 1999 (26 days after sowing). The trial plots were later sprayed with Sclerotinia mycelial inoculum, on 13 th February 1999 (5 days after the first fungicide application), at 90% plants with flowers. The inoculum was applied at a rate of 252L/ha and 500 kpa pressure, using a knapsack precision sprayer fitted with a 1.5- meter boom, and Spray Systems TX10 hollow cone nozzle. The weather conditions were cloudy and humid. Sclerotinia mycelial inoculum, consisting of fragments of fungal hyphae, was prepared by inoculating agar blocks of S. sclerotiorum culture onto autoclaved barley grains (150g barley and 175ml distilled water) and incubating it at room temperature (15-25 C) for 4 weeks. The colonised grains were then macerated in a blender. Sclerotes and big particles were removed using a 425-um stainless steel sieve. The Sclerotinia mycelial inoculum was diluted with tap water to 50 colony-forming units/ml of inoculum suspension prior to spraying. SERVE-AG RESEARCH 40

46 4: Fungicide application methods (Cont.) Table : Treatment list No Treatment Product & Rate (L/ha) Spray nozzle Water volume (L/ha) Spray pressure (kpa) First spray timing* 1 Conejet TX10-250L-10% 2 Conejet TX26-590L-10% 3 Teejet AH 5-180L-10% 4 Teejet AI05-511L-10% 5 Twinjet TJ08-730L-10% 6 Twinjet TJ03-260L-10% 7 Conejet TX10-250L-90% 8 Twinjet TJ08-730L-90% Sumisclex 1.5 Conejet TX % Sumisclex 1.5 Conejet TX % Sumisclex 1.5 Teejet AM % Sumisclex 1.5 Teejet AI % Sumisclex 1.5 Twinjet TJ % Sumisclex 1.5 Twinjet TJ % Sumisclex 1.5 Conejet TX % Sumisclex 1.5 Twinjet TJ % 9 Saprol f/b Sumisclex-10%** Saprol 2.0 Sumisclex 1.5 Conejet TX10 Twinjet TJ % 10 Rovral f/b Sumisclex-10%** Rovral 2.0 Sumisclex 1.5 Conejet TX10 Twinjet TJ % 11 Untreated control N/a N/a N/a N/a N/a *First spray based on percentage of opened flowers on plants ** f/b denotes followed by 2 sprays of Sumisclex Spray Applications A hand-pressurised sprayer was used for all treatments. The spray nozzle, volume and pressure applied is specified in the treatment list (Table ). In Treatments 1-4, a first spray of 1.5L/ha Sumisclex was applied at 10% opened flowers, followed by another two sprays at 7 days intervals. For Treatments 9-10, 2.0L/ha Saprol and 2.0L/ha Rovral respectively were applied in the first spray (Table ), followed at 7-day intervals by 1.5L/ha Sumisclex alone, for the second and third sprays. In Treatments 7-8, a first spray of 1.5L/ha Sumisclex was applied at 90% opened flowers, followed by another spray 7 days after. A third spray scheduled for Treatments 7-8 was not applied as some bean pods were half full at the second spray. SERVE-AG RESEARCH 41

47 4: Fungicide application methods (Cont.) Disease assessments Plants from a 5m length of the middle row of each treatment plot were assessed for disease incidence and severity. The disease incidence was tabulated as the percentage of the total number of plants per plot infected by Sclerotinia. The disease severity was assessed according to the following severity rating: 1 = mild disease - infection of single stem, leaf or bean; 2 = moderate disease - infection of multiple stem branches; 3 = severe disease - infection affecting the whole plant. The disease severity index was calculated from these ratings as the sum of the total number of diseased loci multiplied by their respective rating values, and divided by 3. The data was analysed using StatGraphic Plus, and if significantly different, the mean data was separated using Duncan's Multiple Range Test. Results & Discussion Table : The effects of different application methods and/or fungicide treatments on Sclerotinia disease incidence and severity No. Treatment % Disease incidence # % Plants with severe infections # Disease severity index * 1 Conejet TX10-250L-10% a 2 Conejet TX26-590L-10% ab 3 TeejetAI15-180L-10% a 4 TeejetAI05-511L-10% be 6 TwinjetTJ03-260L-10% a 5 TwinjetTJ08-730L-10% a 7 Conejet TX10-250L-90% 12.5 " a 8 Twinjet TJ08-730L-90% a 9 Saprol f/b Sumisclex-10% d 10 Rovral f/b Sumisclex-10% ab 11 Untreated control cd * Means followed by a same letter are not significantly different at the 5% level according to Duncan's Multiple Range Test # No significant difference between the treatments. The area is exposed to windy conditions, which rapidly dry the crop, and hence the location is less prone to severe infection compared to the location for Site 1 (Section 4.2.1). Therefore, bean seeds were planted at double the commercial density in order to create an environment that is conducive to Sclerotinia infection. Sclerotinia disease developed late in the trial area, at close to harvest, when the crop canopy become denser. SERVE-AG RESEARCH 42

48 4: Fungicide application methods (Cont.) Figure : % Disease incidence Untreated control Saprol & Sumisclex-10% TeejetAI05-511L-10% Rovral & Sumisclex-10% Conejet TX26-590L-10% TeejetAI15-180L-10% Conejet TX10-250L-10% TwinjetTJ08-730L-10% TwinjetTJ03-260L-10% Twinjet TJ08-730L-90% Conejet TX10-250L-90% Figure : Disease severity index Untreated control Saprol & Sumisclex-10% TeejetAI05-511L-10% Rovral & Sumisclex-10% Conejet TX26-590L-10% TeejetAI15-180L-10% Conejet TX10-250L-10% Twinjet TJ08-730L-10% Twinjet TJ03-260L-10% Twinjet TJ08-730L-90% Conejet TX10-250L-90% I -. I ZZZZ i I, I SERVE-AG RESEARCH 43

49 4: Fungicide application methods (Cont.) There was no significant difference between treatments in the disease incidence and percentage of severely infected plants in this trial (Table , Figure ). Although not significant, plants treated with Sumisclex tended to have a lower disease incidence compared to plants in the untreated control. Except for Treatment 4, the disease severity index was lower in the fungicide treatments, when compared to the untreated control. Treatment 4, which used air inducted fanjet spray nozzles (Al 05), gave very poor coverage and penetration into the plant canopy due to its large and heavy spray droplets. Apart from Treatment 4, the lack of difference between the fungicide treatments with different spray nozzles and volumes indicates that under low disease pressure conditions, application methods are not critical. It is interesting to note that within each of the spray nozzle types used, the higher spray water volume tended to result in a slightly higher disease severity index than that of the lower water volume (Table ). This trend of increase in disease severity with the higher water volume, is consistent to similar observations in the trial at Site 1 (Section 4.2.1). The spray timing did not influence disease control in this study. Two sprays of Sumisclex applied with late sprays (Treatments 7-8) appeared to result in similar disease incidence as when 3 sprays were applied with early applications (Treatments 1-5). This indicates that in areas where the local climatic conditions do not favour the disease, late spray timing, just before the plant canopy becomes too dense, may be more appropriate. In the grower survey (Section 2.1), some Queensland bean growers applied only 1 to 2 fungicide sprays, at late growth stage when pods are forming. Fungicide sprays of Saprol followed by Sumisclex appeared to give poor disease control, and the disease severity index was higher than the untreated control (Table , Figure ). Although not significantly different, Rovral followed by Sumisclex, appeared to had a higher disease severity index compared to Sumisclex only sprays. SERVE-AG RESEARCH 44

50 4: Fungicide application methods (Cont.) 4.3: The effects of water volume on Sumisclex efficacy Introduction Sumisclex is applied with different water volumes on bean crops, resulting in different concentration of the product in spray mixtures. The effect of low Sumisclex concentrations in spray mixtures with high water volumes is not known. Therefore, an in-vitro study was conducted to test the inhibitory activity of different concentrations of Sumisclex (at dilution rates regularly used by growers) on Sclerotinia. Materials & Methods The different Sumisclex concentrations investigated in this study were equivalent to the product concentrations when 1.5L Sumisclex was diluted with water volumes ranging from 150 to 1000L/ha, as are used by growers in fungicide sprays on bean crops. Half strength potato dextrose agar (HPDA) was amended with Sumisclex at the concentrations shown in the treatment list (Table 4.3.1). Plates were poured, cooled and inoculated by placing a 10mm diameter disc of the S. sclerotiorum mycelium colony on the centre of each plate. Colony margins were marked and measurements of the growth from the fungal disc were recorded after 7,10 and 13 days. The test was repeated three times, and the means of the three tests are shown in Table S. sclerotiorum culture was prepared by inoculating the fungus on HPDA and incubating it for 10 days at 23 C. The fungal mycelium covered the whole HPDA plate after incubation. Fungal discs were cut from the fungal culture on HPDA using a 10mm diameter cork borer that had been heat sterilised. Results & Discussions Table 4.3.1: The effects of different concentrations of Sumisclex on the inhibition of S. sclerotiorum growth No. Sumisclex concentration on agar (ml/l agar) Equivalent to concentration of 1.5L/ha Sumisclex applied at the water volume (L/Ha) % inhibition 7 days 10 days 13 days control SERVE-AG RESEARCH 45

51 4: Fungicide application methods (Cont.) When Sumisclex is used at 1.5L/ha, an increase in the spray water volume will decrease the concentration of the product in the resulting spray mixture. This study showed that the reduction in the fungicide concentration to 3.0ml/L or less, which is equivalent to that caused by an increase in the water volume from 500L to 1000L/ha, also reduced its efficacy in inhibiting Sclerotinia growth (Table & Figure 4.3.1). Figure 4.3.1: Effects of dilution by different water volumes, on Sumisclex efficacy 100 S~ f! W days - 10 days -«,- 13 days Water Volume (L/ha) 100 SERVE-AG RESEARCH 46

52 4: Fungicide application methods (Cont.) 4.4: The effects of spray adjuvants on the systemic activity of fungicides Introduction The effects adjuvants have on assisting the fungicides Sumisclex and Spin Flo to enter leaf tissue and exert systemic activity against S. sclerotiorum, were examined in laboratory and glasshouse studies. Adjuvants examined included X-77, Agridex, DCTron Plus Spray Oil, NuFilm, SprayTech Codacide Oil and Bond. Materials & Methods Standard procedures in all tests The fungicides, Sumisclex and Spin Flo, were both applied at the rate of 0.5ml/L to all leaf surfaces by Preval compressed gas sprayer. Initial tests showed that, at normal rates (1ml/L), both fungicides were very effective in limiting the invasion of discs by S. sclerotioum. In order to differentiate between adjuvants, a sub-optimal rate (0.5 ml/l) is used. Bean plants (cv. Labrador) were raised singly in 12.5cm diameter pots in a glasshouse. Leaves were cut from the bean plants, washed in a solution containing 2ml/L liquid chlorine + 5 drops/l Tween 80 for 1 minute, rinsed thoroughly in running tap water, rinsed in sterile distilled water for 30 seconds and blotted dry. Leaf discs were cut from leaves using an 18mm diameter cork borer and placed dorsal side up on petri dishes containing water agar. A pathogenic isolate of S. sclerotiorum was maintained by transferring to fresh potato dextrose agar plates every three days. Fungal inoculum was from rapidly growing 2-day-old cultures of S. sclerotiorum. Culture discs (4mm diameter) were cut from the zone just behind the advancing colony margin and placed inverted in the centre of the leaf discs. The invaded area of the leaf disc turned brown and the maximum diameter was measured 48 hours after inoculation. Control leaf discs that were not treated were usually completely invaded after 30 hours. Experiments 1,2,3 and 4(a) were conducted using the leaf disc technique, on different adjuvants, position and number of test leaves per plant, and the number of leaf discs taken from each leaf, and are described below. Experiment 1 Treatments: Spin Flo and Sumisclex alone and combined with X-77, Agridex, DC Tron and NuFilm in unreplicated single plant plots. Five leaf discs per treatment were taken from a young mature trifolate leaf. Experiment 2 Treatments: As for Experiment 1, except that ten leaf discs per treatment were taken from five leaves (2/leaf). SERVE-AG RESEARCH 47

53 4: Fungicide application methods (Cont.) Experiment 3 Treatments: Spin Flo and Sumisclex alone and combined with X-77, Agridex, DC Tron (2 rates), NuFilm, Spraytech and Bond, in unreplicated single plant treatment plots. Ten leaf discs per treatment were taken from five leaves (2/leaf). Experiment 4(a) Treatments: Sumisclex alone and combined with X-77, DC Tron and NuFilm in single plant plots with five replications. Five leaf discs per plot were taken from the central trifolate leaf at the base of a flower stalk. Experiment 4(b) glasshouse study Plants from 4(a) were inoculated by spraying with macerated cultures of S. sclerotiorum (5 cultures/l) and incubating in a moist chamber in the glasshouse for 48 hours. Three days after inoculation, the 10 most severely affected leaves on each plant were rated on a 0-5 scale of severity, where 0 = no disease symptoms and 5 = >50% leaf area affected. Results The results of the leaf disc inoculation experiments are shown in Table The trends in Experiments 1-3 are that: - Sumisclex is more effective than Spin Flo; Oil-based products (DC Tron and Agridex) are the most effective adjuvants for Spin Flo; DC Tron, Agridex and NuFilm are the most effective adjuvants for Sumisclex. In the replicated experiment 4(a) DC Tron and NuFilm improved the performance of Sumisclex, while X-77 decreased the performance of this fungicide (P = 0.05). In the glasshouse inoculation experiment, the only treatment to sustain infection was the untreated control. Sumisclex, with or without adjuvants, was very effective in preventing infection from the macerated culture inoculum (Table 4.4.2). There appeared to be little or no difference between the Sumisclex treatments, with or without adjuvants. SERVE-AG RESEARCH 48

54 4: Fungicide application methods (Cont.) Tabl e :The effects of Sumisclex and Spin Flo combined with various spray adjuvants on t he susceptibility of bean leaf discs, to infection by S. sclerotiorum Lesion diameter (mm) No Treatment Man = 18 Exptl Expt2 Expt3 Expt 4a* 1 Untreated control d 2 Spin Flo 0.5mL/L Spin Flo 0.5ml_/L + X ml_/L Spin Flo 0.5mL/L + Agridex 2mL/L Spin Flo 0.5ml_/L + D C Tron 2mL/L Spin Flo 0.5mL/L + D C Tron 5mL/L Spin Flo 0.5mL/L + NuFilm 2mL/L Spin Flo 0.5mL/L + Spraytech 2mL/L Spin Flo 0.5mL/L + Bond 1mL/L Sumisclex 0.5ml_/L b 11 Sumisclex 0.5mL/L + X mL/L c 12 Sumisclex 0.5ml_/L + Agridex 2mL/L Sumisclex 0.5ml_/L + D C Tron 2mL/L a 14 Sumisclex 0.5mL/L + D C Tron 5mL/L Sumisclex 0.5ml_/L + NuFilm 2mL/L a 16 Sumisclex 0.5ml_/L + Spraytech 2ml_/L Sumisclex 0.5ml_/L + Bond 1 ml/l 13.7 * Within the same column, means followed by the same letter are not significantly different at the 5% according to Least Significant Difference Test. level, SERVE-AG RESEARCH 49

55 4: Fungicide application methods (Cont.) Table 4.4.2: The effects of spray adjuvants on the ability of Sumisclex to protect bean leaves from infection by S. sclerotiorum No Treatment Disease severity rating (0-5)** 1 Sumisclex 0.5ml_/L + NuFilm 2ml_/L 0 2 Sumisclex 0.5ml_/L + D C Tron 2ml_/L Sumisclex 0.5mL/L + X ml_/L Sumisclex 0.5mL/L Untreated control 3.6 * Results are the means of five replications in a glasshouse trial *Severity rating based on the five most severely affected leaves on each plant rated on a 0-5 scale where 0 = no symptoms; 5 = >50% leaf area destroyed. Discussion Experiments in this study were designed to simulate severe weathering of surface fungicide deposits followed by inoculation challenge. They indicated that oil-based adjuvants would be more effective than non-ionic adjuvants for use with Spin Flo, and oil-based products and NuFilm should improve the performance of Sumisclex. The improvement by these adjuvants may be due to greater movement into the leaf of the fungicide, or improved surface retention. It is suspected that for Spin Flo, the main effect is improved penetration, while for Sumisclex both modes of action may be important. It is interesting that NuFilm improved the performance of Sumisclex but not Spin Flo. NuFilm produces a tenacious deposit, which is not easily eroded. For this reason it is suspected that it assists Sumisclex by improved surface activity. For benzimidazole fungicides, which exert their main effect from within leaf tissues, this type of deposit does not improve performance. The glasshouse inoculation of whole plants showed that without the simulated weathering given to the leaf discs, all Sumisclex treatments, with or without adjuvants, were effective. A field study was conducted as part of this project (Section 6.1.3) with the most appropriate adjuvants identified in the laboratory studies, to determine whether the adjuvants can enhance fungicide efficacy under field conditions. SERVE-AG RESEARCH 50

56 Section 5: Alternative products Summary In trials conducted to evaluate alternative products for the control of Sclerotinia in beans, Sumisclex has often given the greatest disease reduction compared to other products evaluated. From alternative products evaluated, only Switch and Spin Flo (also sold as Bavistin) gave significant Sclerotinia control compared to untreated controls. Although Switch gave significant disease control compared to the untreated control, the level of control was much lower than with currently registered products, Sumisclex and Benlate. As a result, Novartis Crop Protection Pty Ltd has indicated that the company would not be interested in further studies or in registering this product for Sclerotinia control in beans. Spin Flo gave better control than Benlate and Switch, and may be a suitable alternative to Benlate for use in alternation with Sumisclex. A field trial conducted in Queensland from March to May 2000, showed that Spin Flo performed as well as Sumisclex. At the time of publication of this report, the economic feasibility of registering Spin Flo for Sclerotinia control in beans was being evaluated by Aventis CropScience Pty Ltd (formerly Rhone-Poulenc Rural Australia Pty Ltd). ABG8001 and ABG8013, biocontrol products based on Trichoderma harzianum and produced in Israel, were also evaluated in this project. Only ABG8001 is a registered biocontrol agent for disease control and is sold commercially. Unfortunately, samples of the product supplied for field testing over a two-year period had low viability. Therefore, the resulting poor efficacy in Sclerotinia disease control in these trials may not be representative of the capability of the agent if the required biocontrol population is attainable. Laboratory tests showed that Trichoderma was tolerant to Sumisclex. The application of ABG8001 with Sumisclex appeared to cause a slightly higher reduction in Sclerotinia incidence and severity compared to Sumisclex alone. Little or no disease control was recorded when ABG8001 was applied alone. Introduction Benomyl (Benlate) and procymidone (Fortress and Sumisclex) are the only products currently registered for use against Sclerotinia disease on beans. The withdrawal of one of these products would further limit the choice of available fungicides for the control of Sclerotinia. Another fungicide product, vinclozolin (Ronilan), which was considered by some growers to be highly effective against Sclerotinia on beans, has recently been withdrawn from the market. Field trials were therefore conducted to identify and evaluate a range of alternative products for the control of Sclerotinia disease in beans. SERVE-AG RESEARCH 51

57 5.1: Field trial conducted in 1997/98 5: Alternative products (Cont.) 5.1.2: Site 1, Forth, Tasmania Trial Details CROP LOCATION VARIETY SOIL TYPE Green bean Forth, Tasmania Rapier Ferrosol REPLICATES 5 SOWING DATE 3 December 1997 HARVEST DATE 27 February 1998 PLOT SIZE TRIAL DESIGN 1.2m x 6m Randomised complete block Introduction This trial was conducted on a green bean crop at Forth, Tasmania to evaluate the efficacy of different types of chemical and biocontrol products for Sclerotinia control. Materials & Methods S. sclerotiorum sclerotes, collected from an infected cabbage crop in September 1997, were broadcast evenly onto bean rows in trial plots at 2 weeks after sowing and prior to seedling emergence. All products except for ABG8001 and ABG8013, are chemical based fungicide products. ABG8001 and ABG8013 are biocontrol products based on Trichoderma, a fungal biocontrol agent. Field conditions throughout the crop growth were warm, windy and very dry. SERVE-AG RESEARCH 52

58 5: Alternative products (Cont.) In the absence of rainfall, irrigation was applied twice a week starting from 7 weeks after sowing, and three times a week from 10 weeks after sowing. Sprays were applied at 7 (75% plants with first opened flower blossoms), 8 & 9 weeks after sowing. The chemical and biocontrol products were applied using an air-pressurised knapsack precision sprayer, fitted with TX26 cone jet nozzles at 400kPa pressure, and 10OOL/ha spray water volume. Table : Treatment list No. Product Product Rate/ha Spray timing 1 Folicur 350ml 2 Benlate 1.5kg 3 Sumisclex 1.5kg 4 Saprol 250ml 3 sprays: 5 Amistar 600ml 1 st spray at 75% plants with first flowers, then at 7 day 6 ABG kg intervals 7 ABG kg 8 ABG kg 9 ABG8001 f/b 2 x Sumisclex** 10 ABG8001 f/b Sumisclex f/b ABG8001** 2.0kg & 1.5kg 2.0kg & 1.5kg 11 Sumisclex f/b2xabg8001** 1.5kg & 2.0kg 12 Untreated N/a N/a f/b denotes followed by Assessments The numbers of plants infected by Sclerotinia in each plot were counted, and disease incidence was tabulated as the percentage of the total number of plants per plot infected. The first disease assessment was conducted at 10 weeks after sowing (1 week after the final spray). The final assessment was conducted at 12 weeks after sowing (3 weeks after final spray). The data could not be normalised because of very high standard deviations of mean values; therefore the analysis was conducted using Kruskal-Wallis test on the median values of disease incidence. SERVE-AG RESEARCH 53

59 5: Alternative products (Cont.) Results & Discussions A very low level of white mould was found in the first disease assessment at week 10. Most infections developed between weeks 10 and 12, due to wet conditions caused by increased irrigation. At week 10, Treatments 2, 3, 7,10 and 11 showed significant reduction of Sclerotinia infected plants compared to the untreated control (Table ). At week 12, only Treatments 2, 3, 4 and 9 significantly reduced disease incidence compared to the untreated control plants. Among the alternative products evaluated in this study, only Amistar and Saprol showed potential in reducing Sclerotinia disease. Table : Treatment effects on Sclerotinia disease incidence % Sclerotinia incidence No. Treatments 10 weeks after sowing median (%) 12 weeks after sowing median (%) 1 Folicur SC ab a 2 Benlate WP 0.00 b 1.60 c 3 Sumisclex WP 0.00 b 3.59 be 4 Saprol 1.09 a 5.34 be 5 Amistar 0.32 ab 5.86 abc 6 ABG8001 (2kg) 0.94 ab a 7 ABG8001 (4kg) 0.00 b 7.56 ab 8 ABG a 6.45 ab 9 ABG8001 f/b 2 Sumisclex 0.66 ab 3.87 be 10 ABG8001 f/b Sumisclex f/b ABG b 7.04 ab 11 Sumisclex f/b 2 ABG b ab 12 Untreated control 1.28 a a Within the same column median values means followed by a same letter are not significantly different at the 5% level according to Kruskall-Wallis Test. At 12 weeks after sowing, the biocontrol products ABG8001 and ABG8013 had not caused any significant reduction in Sclerotinia infections compared to the untreated plants (Table ). The biocontrol product mode of operation relies on maintaining a high population of the biocontrol agents on plant surfaces to prevent other organisms from establishing. The lack of control noted by the biocontrol agents is likely to be caused by low population and unsuitable environmental conditions. Unlike chemical products, biocontrol agents' efficacies are dependent on environmental factors for Sclerotinia control (Hannusch & Boland 1995). SERVE-AG RESEARCH 54

60 5.2: Field trials conducted in 1998/99 5: Alternative products (Cont.) Trial Details SITE1 SITE 2 SITES 3 & 4 LOCATION Gympie, Queensland Merseylea, Tasmania Forth, Tasmania GROWER Mr Joe Harrison Mr Jeremy Rockcliff Forthside Vegetable Research Station BEAN VARIETY Redlands Greenleaf Rapier Rapier REPLICATES PLANTING DATE 1 June December December 1998 PLOT SIZE 1 plant row x 6m 1.6m x 8m 1.2m x 8m TRIAL DESIGN Complete randomised block Complete randomised block Complete randomised block PLANT DENSITY 10 plants/m in single row 16 plants/m in a single row 14 plants/m in single row : Site 1, Gympie, Queensland Introduction This trial was conducted to evaluate alternative chemical and biocontrol products for Sclerotinia control. Materials & Methods The trial was in an area where Sclerotinia blight occurs regularly. The trial area was on a moderately sloping, north facing block. A bean isolate of S. sclerotiorum was grown in liquid V8 culture for 7 days before being macerated and sprayed evenly over all plots on 27 th July and 5 th August Liquid medium (200ml Campbells V8 juice and 3g CaCO s in 1L distilled water) was autoclaved in lots of 100ml in 250ml flasks, and then inoculated with S. sclerotiorum. After 5-7 days incubation, the contents of 10 flasks were macerated and diluted with distilled water to make up a volume of 4L, which was sprayed over the trial area. Except for Treatment 10, 2 sprays were applied on all product treatments (Table ). The weather conditions at both application times were considered suitable for Sclerotinia development. In particular, the second application was followed by 2 days of showery weather. A gas pressurised (600 kpa) hand lance with double nozzles (Hardi , hollow cone pattern) applied sprays at L/ha. Agridex 1 ml/l was used a spray adjuvant for all treatments except ABG8001, which had no wetting agent. SERVE-AG RESEARCH 55

61 5: Alternative products (Cont.) The trial was assessed twice (11 th and 21 st August 1998) by examining each plant for signs of Sclerotinia infection. This was converted to a percentage of plants infected (Table ). Plant populations per plot varied from Table : Treatment list No. Treatment Product Rate Application schedule 1 Benlate 1.5kg/ha 2 Sumisclex 1.5L/ha 2 sprays applied: 3 Saprol(1L) 1.OL/ha the 1 st spray at early flowering on 17 th July 98, then 2nd spray applied 4 Saprol(1.5L) 1.5L/ha 10 days later 5 Folicur (0.35 L) 0.35L/ha 6 Folicur (0.45L) 0.45L/ha 7 ABG8001 (2kg) 2.0kg/ha 8 ABG8001 (4kg) 4.0kg/ha 9 ABG8001 (6kg) 6.0kg/ha 10 ABG8001 (2kg) - regular 2.0kg/ha 4 sprays applied: 1 st spray as above, then at 10 day intervals until close to harvest. 11 Untreated control N/a N/a Results & Discussion The inoculation of plots with Sclerotinia mycelial inoculum did not lead to high disease levels. Sclerotinia infection was very low at the first disease assessment but increased to 5.5% infected plants in the unsprayed plots at the second assessment (Table ). However, no significant difference could be found between the treatments, due to uneven disease distribution and high variability between replicate plots. The consistent absence of disease from all of the replicate plots of Benlate and Sumisclex treatments suggests, however, that these fungicides still gave the most reliable control of Sclerotinia compared to all other products in this study (Table ). No improvement in disease control was recorded with the higher rates of Folicur and Saprol. Similarly, increases in the rates of ABG8001, from 2kg/ha to 6kg/ha, did not increase the level of disease control. There were concerns regarding the poor viability of Trichoderma in the batch of ABG8001 supplied. SERVE-AG RESEARCH 56

62 5: Alternative products (Cont.) Table : Percentage of plants infected by S. sclerotiorum at the 2 nd disease assessment, 82 days after planting No. Treatment Replicate Mean* 1 Benlate Sumisclex Saprol(1L) Saprol(1.5L) Folicur (0.35 L) Folicur (0.45L) ABG8001 (2kg) ABG8001 (4kg) ABG8001 (6kg) ABG8001 (2kg) - regular Untreated control * Not significant at the 5 % level according to analysis of variance : Site 2, Merseylea, Tasmania Introduction This trial was conducted within a commercial bean crop at Merseylea, which is located in a sheltered valley in NW Tasmania, where conditions tend to stay humid and warm longer. Green bean crops grown in this area are known to be prone to high incidence and severity of Sclerotinia disease. Materials & Methods Sclerotinia inoculation Sclerotinia mycelial inoculum consisting of fragments of fungal hyphae, was prepared by inoculating agar blocks of S. sclerotiorum culture onto autoclaved barley grains (150g barley and 175ml distilled water) and incubating it at room temperature (15-25 C) for 4 weeks. The colonised grains were then macerated in a blender. Sclerotes and big particles were removed using a 425-um stainless steel sieve. The Sclerotinia mycelial inoculum was diluted with tap water to 50 colony-forming units/ml of inoculum suspension prior to spraying. SERVE-AG RESEARCH 57

63 5: Alternative products (Cont.) The Sclerotinia mycelial inoculum was sprayed onto the trial area two days after the first fungicide spray application (20% plants with open flowers). The inoculum was applied at a rate of 252L/ha and 500 kpa pressure, using a knapsack precision sprayer fitted with a 1.5-meter boom, and Spray Systems TX10 hollow cone nozzle. The weather conditions at the time of fungal application were warm, cloudy and humid, which was considered to be optimal for Sclerotinia infection. Fungicide Applications Three sprays applied at 7-day intervals, with first spray at early flowering (10% plants with first flowers). The sprays were applied using a knapsack precision sprayer fitted with a 1.5-meter boom, and Spray Systems TX26 hollow cone nozzle at 450 kpa, and 590L/ha water, in all product applications. No spray adjuvant was used. Table : Treatment list No Fungicide Rate (a.i./ha) Product Rate/ha Application Schedule 1 Sumisclex 0.75kg 1.5L 2 Benlate 0.75kg 1.5kg 3 Bravo 1.12kg 1.6L 3 sprays: 4 SS01* 0.2 % 1.2L 1 st spray applied when 10% plants 5 Switch 375g + 250g 1.0kg have first flowers 6 Rovral 500ml 2.0L 7 Saprol 380g 2.0L 8 Spin Flo 0.75kg 1.5L 9 SS01 0.2% 1.2L 10 Control N/a N/a * SS01 is believed to work by enhancing plant defence against disease. Disease assessment The disease assessment was conducted one week prior to commercial harvest. Plants in a 5 metre single row were removed from the centre of each plot to assess for disease incidence and severity. The disease incidence was then tabulated as the percentage of the total number of plants per plot infected by Sclerotinia. The disease severity was assessed according to the following severity rating: 1 = mild disease - infection of single stem, leaf or bean; 2 = moderate disease - infection of multiple stem branches; 3 = severe disease - infection affecting the whole plant, with plant dying or dead. SERVE-AG RESEARCH 58

64 5: Alternative products (Cont.) Results & Discussions The Sclerotinia mycelium inoculum generated a high disease level, ranging from 6% to 99% of plants in the treated plots with Sclerotinia infections (Table ), as well as even disease distribution. Plants in the trial area also had more severe Sclerotinia infection than plants outside the trial area (Figure ). The inoculum was applied one day after the first fungicide treatment, under conditions suitable to fungal infection. Figure : Healthy plants in plant row outside the trial area (A), adjacent to diseased plants in Sclerotinia inoculated plant row (B) SERVE-AG RESEARCH 59