1993 Summary of Apple Fungicide Trials and Related Extension Information from the Hudson Valley

Transcription

1 NOT FOR PUBLICATION 1993 Summary of Apple Fungicide Trials and Related Extension Information from the Hudson Valley David A. Rosenberger, Plant Pathologist Cornell University's Hudson Valley Laboratory* PO Box 727, Highland, NY, Tel: Fax: *Part of the N. Y. State (Geneva) Agricultural Experiment Station Technical Assistant for Fungicide Trials...Fritz Meyer Technical Assistant for IPM/SARE Trials...Cathy Engle Summer Assistants/Data Collectors...Leah Christiana Kristin Mesic Secretary/ Administrative Assistant...Donna Clark Orchard/Building Maintenance Persons...Larry Mesic Albert Woelfersheim REPORT FOR STOWE, VT MEETINGS October 19, 1993

2 1993 Growing Season Rosenberger, Meyer and Engle Weather and Infection Periods Page Summary of Rainfall, McIntosh Phenology, Apple Scab Infection Periods, and Scab Ascospore Maturity and Discharge at the Hudson Valley Laboratory Scab ascospore information * Wetting periods ** M.26 block % cumm. % avg. rain- Mill's McIntosh mature dis- start dura- temp fall rating Date growth stage spores charged date time tion (F) (in.) 1 2 Apr 6 Dormant Apr Apr H Apr 12 Green Tip Apr Apr Apr M Apr Apr 19 Half-in. green Apr ? Apr 24 Tight cluster Apr Apr May 1 Pink May 3 King bloom First active scab lesion found on cluster leaves May H + May 6 Bloom May 10 Petal fall May May M + May May May H + May May L + May M + * Ascospore maturity and cumulative percent Jun of ascospores discharged were determined by Jun H + performing pseudothecial squash mounts using Jun H + leaves collected from an abandoned apple End of Primary scab season orchard near the Hudson Valley Lab on the Jun dates indicated. ** Wetting periods were Jun determined using a DeWit Leaf Wetness meter. Jun Rainfall was measuredwith a tipping bucket Jun rain gauge and mean temperatures were Jun calculated using data from a CR 21 micrologger. Jul Jul Jul Jul Aug Aug Aug Aug Aug Aug Aug Aug

3 Max/Min Temperatures ( F) and Rainfall (inches) All readings were taken at 0800 EST on the dates indicated for preceeding 24 hour period. Rosenberger, Meyer and Engle Page 2 APRIL MAY JUNE JULY AUGUST SEPTEMBER Date Max Min Precip Max Min Precip Max Min Precip Max Min Precip Max Min Precip Max Min Precip Avg/Tot

4 Cross Protection Block Copper Experiment 1993 Rosenberger, Meyer and Engle Page 3 BACKGROUND: Some growers in Michigan reportedly are using high rates of copper sulfate alone (up to 50 lb/a) in a dormant spray to control fireblight. They reported exceptional results (unreplicated trials, of course). OBJECTIVES: To determine the effects of using copper sulfate alone, in Bordeaux mix, and with or without an oil sticker by evaluating activity against apple scab, incidence of fruit russetting, and levels of fixed and soluble copper residues sprayed trees. The information could be useful for improving fireblight control strategies while minimizing potential phytotoxicity to fruit. TREATMENTS APPLIED: Trt Material and rate/100 1 Trt Material and rate/ Tribasic Copper Sulfate 8 lb 5. Bordeaux mix Tribasic Copper Sulfate 8 lb & Spray oil 6E 1% 6. Bordeaux mix & Spray oil 6E 1% 3. Tribasic Copper Sulfate 16 lb 7. Bordeaux mix Tribasic Copper Sulfate 16 lb & Spray oil 6E 1% 8. Bordeaux mix & Spray oil 6E 1% 9. Control 1 Materials were applied 9 April to plots arranged in a 2x2x2 factorial design with four replicates plus an untreated control also replicated four times Table 1. Grand means for effects of copper sulfate, lime and oil spray combinations on early apple scab infection and on russet on Delicous fruit at harvest. % infection with apple scab 2 Mean ruset Cluster Terminal rating for % fruit leaves leaves Fruitlets Fruit fruit at with russet Treatment 1 26 May 10 Jun 10 Jun 27 Aug harvest 3 rated 3 Copper sulfate Eight lb/100 gal Sixteen lb/100 gal Lime None Eight lb/100 gal Spray oil 6E None One per cent Unsprayed controls There were no significant effects of treatments on incidence of apple scab or on incidence and severity of russetting in the factorial experiment. Incidence of apple scab in unsprayed controls was significantly different (P = 0.05) from other treatments when treatment means were compared using a standard analysis of variance, but there were no differences between controls and treatments in the incidence and severity of russetting. 1 Treatments were applied 9 Apr. Subsequent fungicide sprays were Dithane DF 1 lb 8, 14 May; Dithane DF 3 lb + Captan 50W 3 lb 21 May; Dithane DF 3 lb 3 June; Captan 50W 1 lb 21 June; 12 July; 9 Aug. 2 Data were collected from all leaves on 25 clusters or terminals per plot on dates indicated, 50 fruitlets per plot in June, and 100 fruit per plot in August. 3 Fruit russeting was evaluated at harvest by rating 100 fruit per plot on a scale of 1-5 (1 = no russet, 2 = rough or enlarged lenticels, 3 = slight russetting between lenticels, 4 = moderate russet, 5 = severe russet). Fruit rated in category 3, 4, or 5 could not be sold as US Extra Fancy.

5 Cross Protection Block Copper Experiment 1993 Rosenberger, Meyer and Engle Page 4 Table 2. Grand means for effects of copper sulfate, lime and oil spray combinations on copper residues on bark and cluster tissue 12 days and 18 days after treatments were applied. Bark samples 2 Cluster samples 3 ppm copper Copper removed by ppm copper Copper removed by on/in bark rinsing expressed as on/in tissue rinsing expressed as µg/g after washing µg/sq cm bark surface after washing dry cluster weight Factor 1 21 Apr 27 Apr 21 Apr 27 Apr 4 21 Apr 27 Apr 21 Apr 27 Apr 5 Copper sulfate Eight lb/100 gal * * * 58.3 * Sixteen lb/100 gal Lime None ** 55.8 ** 0.09 ** 0.04 ** 80.7 ** 54.0 ** 2.25 ** 0.45 ** Eight lb/100 gal Spray oil 6E None One per cent Untreated control trees a a 32.3 a * Treatments were significantly different (P = 0.05) as determined by factorial analysis of treatments. ** Treatments were significantly different (P = 0.01) as determined by factorial analysis of treatments. 1 Treatments were applied on 9 Apr. Five wetting periods with a total of 1.41 inches of rain occurred between application and the first sample collection on 21 Apr. Two wetting periods occurred between 21 Apr and the second sample date, 27 Apr, with a total of 1.96 inches of rain. 2 On each sampling date, three bark patches were collected from random locations on the lower trunk of each of three trees in each plot by removing bark samples with a Jones patch budder. Samples were shaken for 30 seconds in 100 ml of deionized water. Bark patches were then dried and analyzed for copper content, and copper content of the wash water was also determined and used to calculate the amount of copper removed from bark surface. The background level of copper in bark from untreated trees was 27.7 ppm and 27.2 ppm on 21 & 27 Apr, and in wash water from control trees was 0.02 µg and 0.02 µg on 21 & 27 Apr. 3 On each sampling date, a total of 25 clusters was collected at random from the three trees in each plot. Samples were shaken for 30 seconds in 100 ml deionized water on 21 Apr and 250 ml of deionized water on 27 Apr. Clusters ere then dried and analyzed for copper content and copper content of the wash water was also determined and used to calculate e amount of copper removed from the clusters. The background level of copper in the clusters was 39.1 ppm and 32.3 ppm on 21 & 27 Apr, and in wash water from control trees was 0.41 µg and 0.09 µg on 21 & 27 Apr. The mean dry weight of the clusters was 1.9 g on 21 Apr and 3.7 g on 27 Apr. 4 There was a significant interaction between effects of copper and the effects of oil on the amount of copper that washed off the bark samples. 5 There was a significant interaction between effects of copper and the effects of lime on the amount of copper that washed off the clusters.

6 M.9 Block Fungicide Trial Rosenberger, Meyer and Engle Apple Scab Infection Page 5 % Infection with apple scab 1 Material and rate % cluster leaves % terminal leaves % fruitlets of formulated product Jersymac Redcort Jerseymac Redcort Jerseymac Redcort Jerseymac Redcort per 100 gal ( 100 liter) 2 2 Jun 7 Jun 15 Jun 15 Jun 3 Aug 3 Aug 15 Jun 16 Jun 1) Control d 44.7 d 86.1 e 70.3 f 89.5 e 99.5 e g 83.8 d 2) Captan 50W 2 lb (239.7 g) c 11.8 bc 3.7 c 2.8 bc 3.8 bc 3.6 c 11.6 cd 2.8 b 3) Captan 75WG 1.33 lb (159.4 g) c 11.5 bc 4.6 c 1.8 abc 1.4 ab 3.0 bc 11.8 cd 0.8 ab 4) Nova 40W 1.33 oz (10.0 g) [to 8 Jun] Topsin M 85WDG 3 oz (22.5 g) a 1.2 a 0.0 a 2.8 bc 0.1 a <0.1 a 0.5 a 0.0 a 5) Nova 40W 1.33 oz (10.0 g) [to 8 Jun] Topsin M 85WDG 3 oz (22.5 g) a 0.2 a <0.1 a 0.1 a 1.0 ab <0.1 a 1.5 ab 0.1 ab 6) Ziram 76WG 2 lb (239.7 g) c 18.9 c 14.5 d 11.9 e 19.1 d 21.5 d 37.4 ef 11.4 c 7) TD lb (119.8 g) c 19.0 c 12.1 d 9.0 de 15.7 d 15.7 d 21.7 d 0.9 ab 8) Nova 40W 1.5 oz (11.2 g) [to 12 May] Nova 40W 1.25 oz (9.4 g) & Dithane DF 1 lb (119.8 g) [24 May - 8 Jun] Topsin M 85WDG 3 oz (22.5 g) a 0.4 a 1.0 b 0.4 ab 0.3 a 0.5 ab 23.0 de 0.0 a 9) Nova 40W 1.25 oz (9.4 g) & Dithane DF 1 lb (119.8 g) [24 Apr to 8 Jun] Topsin M 85WDG 3 oz (22.5 g) a 0.6 a 1.0 b 1.0 ab 1.4 ab 0.1 a 6.8 bc 0.9 ab 10) Fluazinam 0.8 pt ( 100 ml) b 1.7 a 5.3 c 5.2 cd 5.5 c 5.4 c 18.1 d 0.9 ab 11) Fluazinam 0.4 pt (50 ml) c 9.6 b 13.2 d 8.3 de 15.3 d 17.5 d 49.6 f 10.6 c Mean separations were determined using Fisher's Protected LSD (P = 0.05). The arcsin transformation was used for statistical analyses. 1 Data collected from all leaves on 25 clusters or terminals per tree or from 50 fruitlets per tree on dates indicated. 2 Treatments were applied 24 Apr; 3, 12, 24 May; 8, 25 Jun; 15 Jul; 6 Aug

7 M.9 Block Fungicide Trial Rosenberger, Meyer and Engle Powdery Mildew, Cedar Apple Rust and Early Fruit Ratings Page 6 % Terminal leaves % Harvested fruit Material and rate % Terminal leaves with powdery mildew 1 with cedar apple rust 2 infected with scab 3 of formulated product Redcort Redcort Redcort Smoothee Jerseymac per 100 gal ( 100 liter) 4 16 Jun 24 Jun 21 Jul 14 Jul 2 Aug 1) Control f 7.1 c 33.9 e 42.3 d g 2) Captan 50W 2 lb (239.7 g) cd 4.8 b 7.7 d 19.1 c 10.8 bc 3) Captan 75WG 1.33 lb (159.4 g) cd 3.2 b 3.6 abcd 13.1 bc 12.0 c 4) Nova 40W 1.33 oz (10.0 g) [to 8 Jun] Topsin M 85WDG 3 oz (22.5 g) a 0.1 a 0.8 abc 3.6 a 4.7 ab 5) Nova 40W 1.33 oz (10.0 g) [to 8 Jun] Topsin M 85WDG 3 oz (22.5 g) ab 0.0 a <0.1 a 3.1 a 4.0 a 6) Ziram 76WG 2 lb (239.7 g) e 1.9 b 7.9 d 2.5 a 39.5 ef 7) TD lb (119.8 g) bc 2.8 b 6.3 cd 5.6 ab 28.1 de 8) Nova 40W 1.5 oz (11.2 g) [to 12 May] Nova 40W 1.25 oz (9.4 g) & Dithane DF 1 lb (119.8 g) [24 May - 8 Jun] Topsin M 85WDG 3 oz (22.5 g) a 0.0 a 0.2 a 2.4 a 21.7 d 9) Nova 40W 1.25 oz (9.4 g) & Dithane DF 1 lb (119.8 g) [to 8 Jun] Topsin M 85WDG 3 oz (22.5 g) a 0.0 a 0.5 ab 1.9 a 11.6 bc 10) Fluazinam 0.8 pt ( 100 ml) de 4.6 b 8.3 d 1.8 a 18.4 cd 11) Fluazinam 0.4 pt (50 ml) cd 2.0 b 5.3 bcd 1.9 a 47.1 f Mean separations were determined using Fisher's Protected LSD (P = 0.05). The arcsin transformation was used for statistical analyses. 1 Data collected from 8 youngest leaves on 25 terminals per tree. 2 Data collected from all leaves on 25 terminal per tree. 3 Data collecteed from 100 fruit per tree. 4 Treatments were applied 24 Apr; 3, 12, 24 May; 8, 25 Jun; 15 Jul; 6 Aug

8 M.9 Block Fungicide Trial Rosenberger, Meyer and Engle Mite Counts Page 7 Material and rate of formulated product Mean number of mites per leaf (Jerseymac) 1 per 100 gal ( 100 liter) 2 ERM 3 ERME 3 ARM 3 1) Control c 3.7 a c 2) Captan 50W 2 lb (239.7 g) bc 5.4 a 60.8 c 3) Captan 75WG 1.33 lb (159.4 g) bc 6.6 a 66.6 c 4) Nova 40W 1.33 oz (10.0 g) Topsin M 85WDG 3 oz (22.5 g) c 5.7 a <71.5 c 5) Nova 40W 1.33 oz (10.0 g) Topsin M 85WDG 3 oz (22.5 g) c 3.8 a 47.8 abc 6) Ziram 76WG 2 lb (239.7 g) bc 9.0 a 58.4 c 7) TD lb (119.8 g) ) Nova 40W 1.5 oz (11.2 g) Nova 40W 1.25 oz (9.4 g) & Dithane DF 1 lb (119.8 g) Topsin M 85WDG 3 oz (22.5 g) ) Nova 40W 1.25 oz (9.4 g) & Dithane DF 1 lb (119.8 g) Topsin M 85WDG 3 oz (22.5 g) bc 6.0 a 51.5 bc 10) Fluazinam 0.8 pt ( 100 ml) ab 1.0 a 29.9 ab 11) Fluazinam 0.4 pt (50 ml) a 0.9 a 29.6 a Mean separations were determined using Fisher's Protected LSD (P = 0.05). The log 10 transformation was used for statistical analyses of mite data. 1 Mite counts were performed by brushing 25 leaves per tree from Jerseymac cultivar in each plot on 28 Jul. Treatments 7 and 8 were not sampled. 2 Treatments were applied 24 Apr; 3, 12, 24 May; 8, 25 Jun; 15 Jul; 6 Aug. Treatments (and rate per 100 gallons) which may have impacted mite populations included 2% oil applied 19 April; Asana XL 5.8 fl oz applied 29 April (early pink) for aphids; Carbaryl 50WP 12 oz applied with NAA 18 May for fruit thinning, 1.5 lb applied 20 June for leafhopper; Vydate L 1.5 pt applied 17 July for leafminer. Samples for mite counts were collected 28 July. Omite 30W 2.5 lb was applied 5 August. Trees treated with fluazinam showed less bronzing in September than did trees receiving other treatments. 3 ERM - European red mite (Panonychus ulmi Koch); ERME - European red mite eggs; ARM - apple rust mite (Aculus schlechtendali Nalepa)

9 Postharvest Study Rosenberger, Meyer and Engle Control of Penicillium with Various Formulations of Rovral Page 8 Objectives: 1. Determine effects of using one application of Rovral versus repeat applications as might occur on the west coast where fruit may be treated at harvest and again when fruit are pre-sized. 2. Compare various formulations of Rovral. 3. Compare Topsin M, Mertect, and Rovral Methods: Empire fruit were harvested 30 September 1992 and held in cold storage at 37 F until the experiment was initiated on 14 December. All fruit were wounded on a single face using three nails mounted in a cork so as to produce wounds approximately 2-mm diameter by 3 mm deep and spaced 10 mm apart in a triangular pattern. Wounded fruit were held at 55 F until treatments were applied the following day. Fruit were inoculated by submersing them for 30 sec in a spore suspensions containing 0.01% Tween 80 and 5x10 3 conidia/ml of a benzimidazole-sensitive isolate of Penicillium expansum. Fruit were treated by submersing them for 30 seconds in fungicide solutions or in a water control. Treatments were applied to four replicates of 50 fruit each, using separate tanks of inoculum for each replication. After treatments were completed, 25 of the fruit from each replicate were placed on spring cushion trays, packed into wooden crates, and stored at 37 F until they were evaluated for decay 45 days later (29 January). The other 25 fruit in each replicate were stored in baskets at 37 F and were re-treated with the same fungicides (or water control) 29 days after the first treatment. Following the second treatment, these fruit were packed and stored like the fruit which received only a single treatment. Both groups of fruit were evaluated for decay 45 days after the first treatments had been applied. All fruit was then stored at 65 F and evaluated again for incidence of decay after 3, 7, and 10 days. Fruit showing decay at any one of the three nail wounds were considered decayed. Mean fruit firmness as determined from random samples of 25 fruit was 16.3 at harvest and 13.1 at the time treatments were initiated in December. By the end of the trial, fruit were considerable over-mature and would not have met minimum market standards. Overmature fruit is generally considered more susceptible to decay, so fruit condition in this trial contributed to a severe test. Results: All treatments provided excellent control of decay throughout the 45-days of cold storage following inoculations. However, differences between treatments developed during the 10 days that fruit were held at 65 F. Rovral 50W at 1 lb/100 gal failed to control Penicillium even in fruit which were treated twice. At the end of the trial, a single application of Topsin M was more effective than either Mertect or most of the Rovral treatments. The combination of Rovral at 1 lb plus Mertect at 8 oz was just as effective as Topsin M alone at 12 oz, and this treatment would probably have out-performed Topsin M if inoculum had included benzimidazole-resistant isolates of Penicillium. There were less treatment differences in fruit which were treated twice. No significant differences were detected between the three formulations of Rovral. Conclusions: Rovral 50W at 1 lb/100 gallons has proven inadequate for controlling Penicillium in apples. Even when used at higher rates, Rovral does not provide the long-term control afforded by Topsin M, but it did appear comparable to Mertect in this trial. Combinations of Rovral plus a benzimidazole fungicides have performed well in this and other trials. These combinations should be tested against mixed populations of benzimidazole-resistant and benzimidazole-sensitive Penicillium to gain a better understanding of how these combinations might perform in packing houses where benzimidazole-resistance is common in Penicillim expansum.

10 Postharvest Study Rosenberger, Meyer and Engle Control of Penicillium with Various Formulations of Rovral (continued) Page 9 Table 1. Incidence of Penicillium blue mold in wounded Empire fruit at several intervals following fungicide treatment on 15 December % fruit with blue mold decay after: Materials and rate 45 days at 45 days at 37 F plus shelf-life test at 65 F for: of formulated material at 37 F 3 days 7 days 10 days per 100 gal (29 Jan) (1 Feb) (5 Feb) (8 Feb ) Control b 60.8 c 91.4 d 92.3 d Mertect 340F 16 fl oz a 0.2 ab 6.9 ab 7.4 b Topsin M 85WDG 12 oz a 0.0 a 0.2 a 0.2 a Rovral 50WP 1 lb a 2.9 b 30.5 c 47.2 c Rovral 50WP 2 lb a 0.0 a 10.6 b 14.8 b Rovral 50WG 2 lb a 0.0 a 8.1 b 15.9 b Rovral 4F 2 qt a 0.2 ab 2.9 ab 5.6 ab Rovral 50WP 1 lb + Mertect 340F 8 fl oz a 0.0 a 2.9 ab 3.7 a Means within columns followed by the same letter are not significantly different as determined by Fisher's Protected LSD (P = 0.05). The arcsine transformation was used for statistical analyses. Means are from four replicates of 25 fruit each. Table 2. Incidence of Penicillium blue mold in wounded Empire fruit at several intervals following fungicide treatments applied on 15 December 1992 and repeated again on 13 January % fruit with blue mold decay after: Materials and rate 45 days at 45 days at 37 F plus shelf-life test at 65 F for: of formulated material at 37 F 3 days 7 days 10 days per 100 gal (29 Jan) (1 Feb) (5 Feb) (8 Feb ) Control b 77.1 b 96.8 c 98.9 d Mertect 340F 16 fl oz a 1.5 a 2.9 a 6.9 ab Topsin M 85WDG 12 oz a 0.2 a 0.2 a 0.2 a Rovral 50WP 1 lb a 0.2 a 22.4 b 35.4 c Rovral 50WP 2 lb a 0.0 a 1.0 a 9.5 b Rovral 50WG 2 lb a 0.0 a 1.9 a 5.7 ab Rovral 4F 2 qt a 0.0 a 1.9 a 5.1 ab Rovral 50WP 1 lb + Mertect 340F 8 fl oz a 0.0 a 0.5 a 1.5 ab Means within columns followed by the same letter are not significantly different as determined by Fisher's Protected LSD (P = 0.05). The arcsine transformation was used for statistical analyses. Means are from four replicates of 25 fruit each.