Evaluation of table grape cultivars for susceptibility to downy mildew in Biglerville, PA, 2012

摘要

Commercial table grape cultivars were evaluated for resistance to downy mildew at the Penn State Fruit Research & Extension Center, Biglerville, PA. Vines were trained to a single top wire. Vines were spaced 6 x 9 ft. All cultivars were arranged in arandomized complete block design with 4 replications, 4 - vines per plot. The vineyard received a maintenance insecticide program throughout the season using an air-blast sprayer (100 gal/A at 400 psi). To control seasonal diseases, one half of the vineyard received conventional rotational program 1 (Ranman, Quintec, Rally, Revus, Vivando, Presidio, and Pristine) and the other half of the vineyard received alternative low fungicides resistance program 2 (Micro Sulf, Manzate Pro-Stick, Sulforix, and Phostrol) that were applied at 7-14 day intervals. On 20 Jun, the susceptibility of the different cultivars to downy mildew was evaluated on leaves and fruit by visually determining the percent infected among 40 arbitrarily-selected leaves and fruit per cultivar - plot. 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).