Efficacy of Captan /Thiophanate-methyl combinations for summer disease control in apples, 2007

摘要

Fungicide treatments were evaluated for summer disease control in an 8-yr-old research orchard of Golden Delicious trees spaced 4.9 m x 7.4 m. The test was conducted in a randomized block design with four single-tree replications per treatment. Sprayswere applied to both sides of the row with a Swanson model DA-500 airblastsprayer (935 L/ha, 100 gal/A). Cover spray dates (3C through 7C) were 19 Jun, 3 Jul, 17 Jul, 31 Jul and 14 Aug. Control of early and mid-season diseases was accomplished on the following dates with the listed materials (product per acre rates): 2 Apr, Cuprofix Disperss 6 lb; 10 Apr, Captan 80 WDG 2.5 lb, Manzate 75 DF 3 lb; 18 Apr, Scala 5 SC 5 oz, Manzate 75 DF 3 lb; 25 Apr, BacMaster 1.25 lb, Captan 80 WDG 2.5 lb, Manzate 75 DF 3 lb; 3 May, Manzate 75 DF 3 lb, Flint 2 oz, BacMaster 1.25 lb; 10 May, Manzate 75 DF 3 lb, Indar 75WSP 2.7 oz, BacMaster 1.25 lb; 24 May, Manzate 75 DF 3 lb, Flint 2 oz; and 7 Jun, Captan 80WDG 2.5 lb, Manzate 75 DF 3 lb. Eight early-season apple scab infection periods (prior to 1 Jun) were followed by 17 additional scab infection periods from the period 1 Jun through 30 Aug. Fourteen infection periods occurred during the test period. Total precipitation inApr, May, Jun, Jul, and Aug was 2.5, 0.9, 2.8, 1.8 and 4.4 inches, respectively. Maintenance insecticide sprays were applied separately with the same equipment. Generally warm temperatures were adequate for summer disease development; however, limited wetting in July slowed the development of summer diseases. Hail on 25 Augresulted in physical injury to the majority of fruit in the trial; however, there were enough non-injured fruit to evaluate at harvest. Only fruit without injuries were utilized in the harvest and postharvest assessments. Incidence of diseases on fruit was determined from 25 fruit from each treatment and block (100 total fruit per treatment). Fruitwere harvested and evaluated on 17 Sep, then placed in refrigerated storage at 34deg F for 3 months. Fruit were rated a second time on 17 Dec, then were left at ambient temperature (65 – 68deg F) for 2 weeks and examined a third time for additional rotdevelopment. Percent data were transformed (arcsin transformation) and subjected to analysis ofvariance and means separation with the Waller-Duncan k-ratio t-test (SAS Institute, Cary, NC).