Efficacy of fungicide programs to control downy mildew on Chancellor and Traminette, 2012

摘要

This test was conducted to evaluate the efficacy of registered and experimental fungicides for management of grape powdery mildew. Fungicide applications were made to Chancellor and Traminette grape vines located at the Penn State Fruit Research & Extension Center vineyard, Biglerville, PA. The plot consisted of 4 Vitis interspecific hybrids Chancellor, Chambourcin, Traminette, and Vidal Blanc that were randomly planted in each post length, spaced at 6 x 9 ft. The treatments were applied to a 4-vineplot arranged in a randomized complete block design with four replications. All cultivars received treatments but only Chancellor and Traminette were evaluated for downy mildew. A standard insecticide maintenance program was separately applied using an airblast sprayer delivering 100 gal/A at 400 psi. A standard fungicide maintenance program provided season-long control of the common grapevine diseases other than downy mildew. Treatments were applied using a Bean covered-boom dilute sprayer delivering 50-100 gal/A at 100 psi, depending on the stage of canopy development. Treatment applications were made from 30 Apr (timing 3=4-8” shoot growth) to 11 Jul (timing 9=5th Postbloom stage). 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. Incidence of downy mildew was rated on leaves and fruit clusters by visually determining the percent infected among 25 arbitrarily-selected leaves and fruit clusters per plot. Severity (percent infection within a shoot or cluster) was rated using the Barratt-Horsfall scale and was converted to percent area infected using Elanco conversion tables. Data was analyzed using analysis of variance and mean separation was determined by the Fisher’s Protected LSD test (P < 0.05) (SAS Institute Inc., Cary, NC).