Fungicide resistance in Botrytis on strawberries and other soft-fruits

Transcription

1 Fungicide resistance in Botrytis on strawberries and other soft-fruits Roland W. S. Weber Esteburg Obstbauzentrum Jork Dept. of Food Science, Aarhus University Jordbær og bringebærseminar, Drammen (15 March 17) Obstbauversuchsanstalt Jork

2 1. Biology of Botrytis 2. Detection and relevance of fungicide resistance 3. Fungicide resistance in space and time 4. Results from Norway 5. Recommendations

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4 Botrytis on strawberries Primary infection at flowering State of latency in receptacle of flower Fruit rot (primary infection) at onset of fruit ripening Secondary infections of further ripening fruits Uncontrollable epidemic

5 Secondary infections: fruit-to-fruit spread

6 Fungicides with Botrytis activity in Norway Rovral 75 WG: Iprodione Teldor: Fenhexamid Switch: Cyprodinil + Fludioxonil Amistar: Azoxystrobin Signum: Pyraclostrobin + Boscalid Luna Sensation*: Trifloxystrobin + Fluopyram * Pending registration Strawberries 3x 2x 2x [2x] 3x 1x Raspberries?x 2x 2x - 2x - All of these are specific fungicides risk of resistance development! Type of resistance Hydroxyanilid target mutation Strobilurin / QoI target mutation Carboxamide / SDHI target mutation Anilino-Pyrimidine target mutation and multi-drug resistance Phenylpyrrole multi-drug resistance only Dicarboximide target mutation

7 1. Biology of Botrytis 2. Detection and relevance of fungicide resistance 3. Fungicide resistance in space and time 4. Results from Norway 5. Recommendations

8 Germ-tube growth [%] Definition: Baseline sensitivity 1 1 Strains within our strawberry fields showing the highest possible sensitivity to a given fungicide EC 5 [ppm],1,1, Fungicide concentration [µg/ml]

9 Germ-tube growth [%] Definition: resistance factor 1 1 Baseline Partial (moderate) resistance.3 ppm RF = = 3.1 ppm EC 5 [ppm] Resistance factor (RF) A 3-fold increase in fungicide concentration is needed to reach EC 5,1,1, Fungicide concentration [µg/ml]

10 Germ-tube growth [%] Definition: moderate and high resistance 1 1 Baseline Moderate resistance (RF <5) High resistance (RF >1) EC 5 [ppm] Colour codes for this lecture Moderate resistance (MR) High resistance (HR),1,1, Fungicide concentration [µg/ml]

11 Fruit infestation by Botrytis [%] How relevant is the laboratory test? Inoculation of green fruits on potted strawberry plants with strains with sensitivity (S3) or multiple resistance (MR4) to all fungicides; determination of fruit rot at harvest (14) Sensitive strain (S3) 5-fold resistant strain (MR4) 78% 68% Efficacy 97% 1% Flint Teldor Signum Switch Untreated Untreated Flint Teldor Signum Switch

12 Routine assay of Botrytis Spores on fruits suspension Place on assay plates Evaluate after 14 h (3 samples, 8 fungicides) No fungicide.1 ppm 1 ppm

13 Fungicide resistance in a raspberry field W N S O baseline reduced sensit. moderate res. high res. Thio.-Methyl Iprodione Fenhexamid Trifloxystrobin Boscalid Cyprodinil Fludioxonil Resistance is identical within a lesion Resistance may vary within a field 15 samples per field are necessary for a clear result 25 m

14 Properties of fungicide resistance in Botrytis 1. Identical resistance pattern of all spores within a single grey mould lesion each lesion must be due to a single-spore infection 2. Different resistance spectra between different lesions a population comprises many different strains 3. Analysis of 15 grey mould lesions is sufficient to assess fungicide resistance status of the local Botrytis population

15 1. Biology of Botrytis 2. Detection and relevance of fungicide resistance 3. Fungicide resistance in space and time 4. Results from Norway 5. Recommendations

16 Fenhexamid 11 and 12 (strawberries) Kiel Rostock Hamburg Oldenburg Bremen Osnabrück Hannover Braunschweig Magdeburg Münster

17 Share of resistant strains [%] Single resistances on strawberries in Northern Germany 8 6 4

18 Share of total population [%] Strains with 5-fold resistance on strawberries in Northern Germany 35 Simultaneous resistance to all 5 fungicide groups

19 Where do multi-resistant strains come from? 1. They arise de novo in fields 2. They are introduced (e.g. by contaminated nursery material) 3. They exist in the vicinity and immigrate into fields (selected by intensive fungicide use)

20 Share of total population [%] Multiple resistance in strawberry nursery material: Netherlands versus Germany Dutch material German material 1 x 1x 2x 3x 4x 5x Number of fungicide rsistances per strain

21 Multi-resistant strains in raspberry longcanes Origin Batches x res. 1x res. 2x res. 3x res. 4x res. 1 3 (n=37) (n=45) (n=37) (n=15) x res. Total 1 (n=134) 3.7% 3.% 29.9% 9.% 1.4% 44.% Longcane nursery plants may be heavily contaminated with Botrytis strains possessing multiple resistance caution when planting a long-term field

22 Percent of isolates Spread of fenhexamid resistance from nursery material to an adjacent established field 1 Nursery plants planted 5 planted Assay: c. 15 overwintered cane lesions each spring Weber & Entrop (17) Eur. J. Plant Pathol Year of sampling 14 15

23 Percent of isolates Spread of multi-resistant strains from nursery material to an adjacent established field 6 planted 5 planted Nursery plants Assay: c. 15 overwintered cane lesions each spring 3 Weber & Entrop (17) Eur. J. Plant Pathol Year of sampling 14 15

24 Share of resistant strains [%] Immigration of resistant strains into a cherry orchard ESTEBURG experimental orchard Share of moderate and high resistance 1, 11, 12 and 13 No use of benzimidazoles or iprodione during the sampling period evidence of immigration and selection of strains with multiple fungicide resistance

25 The role of advisors Trifloxystrobin 14 and 15 Kiel Rostock Advisor 1 Intensive fungicide use Hamburg Oldenburg Bremen Advisor 2 Moderate fungicide use Hannover Osnabrück Braunschweig Magdeburg Münster

26 Share of resistant strains [%] Intensive versus moderate fungicide use 14 1 Advisor 1 Intensive use (5-6x) 46.1% of strains with 5x resistance 1 Advisor 2 Moderate use (3-4x) 6.7% of strains with 5x resistance

27 Share of resistant strains [%] Intensive versus moderate fungicide use 15 1 Advisor 1 Moderate use (4x) 36.7% of strains with 5x resistance 1 Advisor 2 Moderate use (3-4x) 6.7% of strains with 5x resistance

28 The situation in Northern Germany 1. Resistance against all currently used fungicides is widespread threat to fungicide efficacy 2. Strains with multiple (5x) resistance are common 3. Resistant strains may be introduced with nursery material, or may immigrate into a field 4. Intensive fungicide use causes enrichment of resistant strains

29 1. Biology of Botrytis 2. Detection and relevance of fungicide resistance 3. Fungicide resistance in space and time 4. Results from Norway 5. Recommendations

30 Share of resistant isolates [%] Overall results: Norway in a North European context 1 N. Germany 14 (474 isolates) 1 Denmark 15 (14 isolates) 1 Norway 16 (511 isolates)

31 Share of resistant isolates [%] Overall results: Norway in a Norwegian context 1 Eastern Norway (35 isolates) 1 Western Norway (128 isolates) 1 Northern Norway (78 isolates)

32 Share of resistant isolates [%] Effect of spray intensity: Norway 16 1 Thio.-Methyl 1 Iprodione 1 Fenhexamid Spray schedule 16 (total number of Botrytis sprays)

33 Share of resistant isolates [%] Effect of spray intensity: Norway 16 1 Strobilurins 1 Boscalid 1 Fluopyram Spray schedule 16 (total number of Botrytis sprays)

34 Share of resistant isolates [%] Effect of spray intensity: Norway 16 1 Fludioxonil 1 Cyprodinil 1 5-fold resistant (excl. Thio-Met and Fpm) Spray schedule 16 (total number of Botrytis sprays)

35 The situation in Norway Higher resistance levels in Norway than in the rest of Northern Europe 2. >5% multi-resistant isolates! 3. High levels of resistance even in unsprayed (first-year) plants influence of nursery material? 4. Direct correlation between spray intensity and resistance enrichment

36 General spray recommendations for Norway 1. De-intensify your spray schedules: 3 or max. 4 sprays 2. No sprays with Botrytis fungicides after flowering 3. Strobilurins (e.g. Amistar) have no effect against Botrytis 4. All current fungicides equally strongly affected by resistance development 5. Luna Sensation so far exempt from resistance development if registered, use only once per season! 6. If Luna Sens. gets registration, use either Luna Sens. or Signum

37 Resistant isolates [%] QoI and SDHI resistance in N. Germany QoI Boscalid Fluopyram Registration for 15 season

38 Combination of Fpm resistance with others Strawb. Raspb. FH Flu Cyp Strob Bos isolates isolates sens sens sens sens sens 5 2 sens sens sens sens R 3 sens sens sens R sens 2 sens sens sens R R 2 sens sens R R s 3 sens sens R R R 1 sens R R sens sens 1 sens R R sens R 2 sens R R R R 2 1 R R R sens R 1 R R R R sens 1 R R R R R 27 5

39 Prospects for Luna Sensation Most Fpm-resistant strains are of the MR type but: the expected quick rise of Fpm resistance has not yet occurred in Germany Recommendation: 1. Use only 1x Signum or Luna Sensation per season 2. Use them early (beginning of flowering)

40 1. Biology of Botrytis 2. Detection and relevance of fungicide resistance 3. Fungicide resistance in space and time 4. Results from Norway 5. Recommendations

41 Multiplication, overwintering The connection between enrichment of fungicide resistance and reduced fungicide efficacy Assumption: 9% efficacy against sensitive strains, % against resistant strains 1 st year 2 nd year 1% resistance share: 3 of 3 spores Fungicide use in 1 st year 5% resistance share: 3 of 6 spores 5% resistance share: 15 of 3 spores Fungicide use in 2 nd year 88% resistance share: 15 of 17 spores 6 of 3 spores infect flowers (efficacy = 8%) 17 of 3 spores infect flowers (efficacy = 43%)

42 Share of resistant strains [%] Resistance enrichment in raspberries by 4x fenhexamid at blossom Thioph.-Methyl Iprodione Fenhexamid Trifloxystrobin Boscalid Fludioxonil Cyprodinil Enrichment of fenhexamid resistance by 4x Teldor at blossom Enrichment gives rise to lower efficacies from the second year onwards Data from 1 season (Weber & Entrop, 11) untreated (18.8% fruit rot) 4x Teldor (8.2% fruit rot) 56.4% effic.

43 Effects of single-sided or excessive spray sequences Enrichment of strains with fungicide resistance in the first season Reduction of fungicide efficacy in the second (or third) season A less frequent fungicide use reduces the danger of resistance spread and means more fungicide efficacy in the long-term

44 The fungus/host balance The weather Aim: Shifting the balance between fungus and host as far as possible to the plant in order to support the weakening fungicides Botrytis Fungicides Fertilisation Ventilation Hygiene

45 Non-chemical control of Botrytis Picking and removal of infected fruits (especially at beginning of harvest!) Moderate fertilisation Sufficient planting distance Ventilation (tunnel, protective coverings) Drip irrigation instead of overhead irrigation

46 Moderate use of fungicides 1. Preferably 3 applications (max. 4) at blossom: Less (fungicides) = more (efficacy) 2. Focus of fungicide applications on first half of flowering 3. No botryticides after flowering! 4. Resistance tests can avoid redundant fungicide applications 5. Possible spray sequence for strawberries: Beginning of flowering Signum or Luna Sens. % flowers open Switch 5% flowers open Teldor (>5% flowers open Switch)

47 Losses to Botrytis [%] Securing yields by fungicides and fruit picking 5 4 Infected fruits not removed 3 Fungicide effects Effects of infected fruit removal Fruit picking number Main harvest Infected fruits removed Weber & Entrop (15) Undgå resistens mod gråskimmel. GartnerTidendeRoland 8/15: Weber 8-9.

48 Modest use of fungicides + removal of rotted fruits = high yield security

49 Key statements (1) 1. The fungicide resistance test is highly relevant to fruit production 2. Botrytis strains with resistance to all currently used fungicides are common in Norway 3. The efficacy of all fungicides has declined in recent years due to fungicide resistance 4. Resistant strains can be introduced with nursery plant material 5. Strains with multiple resistance pose a particular threat to strawberry production

50 Key statements (2) 6. An enrichment of resistance occurs in the first spray season, but loss of efficacy may be felt only from second season onwards 7. Enrichment of fungicide resistance is strongly influenced by local spray schedules: The more sprays, the more resistance 8. We do not know how competitive multi-resistant strains are outside sprayed strawberry fields 9. Picking of rotten fruit especially at the beginning of harvest is a critical measure to secure the yield 1. A modest use of fungicides can retard or avoid enrichment of resistant strains

51 Efficacy against sensitive strains Share of sensitive strains Real efficacy in the field How many sprays to give the optimum efficacy? 1 Optimum longterm strategy Number of sprays with a given fungicide at flowering

52 Literature 1. Weber, R.W.S. (15). Masser af resistens i gråskimmel på jordbær. Gartner Tidende 7/15: Weber, R.W.S. & Entrop, A.-P. (15). Undgå resistens mod gråskimmel. Gartner Tidende 8/15: Weber, R.W.S. (16). Resistent gråskimmel i danske jordbær. Gartner Tidende 132 (5): -21. Roland.Weber@lwk-niedersachsen.de

53 Thank you for your interest!