Evaluation of new fungicides and a mixture of captan and mancozeb to control apple scab, 2012

摘要

The objectives of this trial were to compare the efficacy of fungicide programs that were comprised of: site-specific fungicides, formulations of captan and mancozeb, and a tank mixture of captan and mancozeb referred to as captozeb by apple growers.Treatments were prior to rains or during rain breaks roughly at weekly interval during the ascospore ejection season starting at budbreak until early June. Products within a program were applied for every application, except where noted. Product rates were expressed with concentration of formulation (g/100 ml or ppm). The products were: Captan Supra 80WDG (United agri products Canada, 80% captan) at 2 rates (750 ppm, 0,15%), Allegro 500F (Syngenta, 40% fluazinam) (470 ppm), Inspire Super (Syngenta, 8,4%difenoconazole + 24,1% cyprodinil) (312 ppm), Fontelis (Dupont, 20% penthiopyrad) (535 ppm), Aprovia (Syngenta, Solatenol (benzovindiflupyr)) (143ppm), Penncozeb 75DF (United agri products Canada, 75% Mancozeb) (0,16%), and a tank mix of the low rate ofCaptan (750 ppm) and Penncozeb (0,16%) called Captozeb. Treatments were replicated on 4-5 trees in a randomized design in an 8-yr-old McIntosh orchard on M.9 rootstock with a spacing of 1,25m x 3,65m. Buffer trees separated treated trees and drift to adjacent rows was prevented with a portable plastic shield. All treatment applications were made to drip using a high-pressure handgun sprayer. A volume equivalent to 1600L per ha was required to wet the trees during this period. Tree bud phenology in thisplot on the spray dates were 15 Apr. - green tip, 19 Apr. - half inch green, 25 Apr. - tight cluster, 3 May -pink, 11 May -king bloom, 21 May - late petal fall, 28 May - fruit set, 1 Jun - first cover. Sprays were applied on dry foliage and had time todry before subsequent rain. Maintenance sprays common to all plots including Captan during summer were applied with a standard airblast sprayer according to standard grower practice. Apple scab was rated on cluster leaves (22 June) and on extension shoots (29 June) by counting the number of scabbed leaves on 15 flower clusters, or on 15 shoots per tree. Fruits were harvested and rated on 30 August. Marketable yield and scab incidence were recorded for each tree. Because of overdispersion, scab incidencewas best modeled with a mixed effect model using tree row as a random effect and a negative binomial error distribution. Statistical analysis was done using count data models in the open source software "R".