Evaluation of Ranman and Phostrol programs for control of downy mildew on wine grapes, 2012

摘要

Fungicide programs were evaluated for control of downy mildew on Vidal grapes in a research vineyard at the Penn State Fruit Research & Extension Center, Biglerville, PA. Vines were spaced at 6 x 9 ft. and were cordon-trained and hand-pruned. The treatments were arranged in a randomized complete block design with four replications. The vineyard received an insecticide maintenance program throughout the season using an air-blast sprayer (100 gal/A at 400 psi). All treatment plots received a fungicidemaintenance program applied at 10-14 day intervals to control powdery mildew and other diseases. Treatment applications were made using a Bean covered-boom dilute sprayer delivering 50-100 gal/A at 100 psi, depending on canopy growth and development 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-selectedleaves and clusters per plot. Severity (percent infection within a leaf 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).