Evaluation of SDHI fungicides for apple scab control on Rome Beauty, 2012

摘要

Fungicide programs were evaluated in a mature apple orchard at the Penn State Fruit Research & Extension Center to evaluate the efficacy of succinate dehydrogenase inhibition (SDHI) fungicides applied alone or in combination with other fungicides forcontrol of apple scab. The test was conducted in a randomized complete block design with four replications per treatment. Treatments were applied dilute to both sides of the trees with a boom sprayer at 400 psi, which delivered 100 gal/A. Treatment applications were made on 8 to 15-day intervals beginning at half-inch green (1/2" GT, 22 Mar); tight cluster/pink (TC/P, 30 Mar); pink/bloom (P/B, 10 Apr); full bloom (FB, 19 Apr); petal fall (PF, 27 Apr); 1st cover (1C, 12 May) and 2nd cover (2C, 25 May). Summer cover sprays were applied from 3rd through 7th cover with a boom sprayer. A standard program of insecticide sprays was applied separately to all the treatments. Weather data was recorded with electronic monitoring systems (Davis ProVantage WeatherSystem), and scab infection periods calculated using a modified Mills apple scab infection model. Rainfall for Apr, May, Jun, Jul, and Aug was 2.4 in., 5.41 in., 3.21 in., 5.11 in., and 3.86 in., respectively. Apple scab pressure was severe at the test site. There were 45 infection periods during the primary season from 15 Mar to 15 Jun. The incidence of apple scab symptoms on Rome Beauty was determined for spur leaf clusters (16 May) and shoot leaves and fruit on 1 Jun and 28 Jun by examining 25 randomly selected spur clusters, shoots and fruit. Data was analyzed by analysis of variance and significance between means was determined using Fisher’s Protected LSD test (P < 0.05) (SaS Institute Inc., Cary, NC).