Evaluation of dormant sprays and fungicide programs for control of black rot and Phomopsis in juice grapes, 2014.

摘要

The experiment was conducted in a mature 'Niagara' vineyard at the Trevor Nichols Research Center in Fennville, MI. Vines were spaced at 6 x 10 ft and were cordon trained and hand pruned. Treatments were applied to 7-vine plots and were replicated four times in a randomized complete block design. Sprays were applied using a research sprayer equipped with six 5-gal tanks, a 12-volt 3.8-gpm high-flow electric pump set at 55 psi, and an XR TeeJet 8002VS nozzle on a 5-ft spray boom. Spray volume was 75 gpa. Spray dates and approximate phenological stages were as follows: 30 Apr (dormant), 7 May, 16 June (10 -16 in. shoot), 25 June (immediate prebloom and bloom), 10 Jul (1st post-bloom, pre-bunch closure), 22 Jul (2nd post-bloom, bunch closure), 5 Aug (Quintec application to control powdery mildew), 14 Aug (3rd post-bloom), and 20 Aug (4th post-bloom). Rainfall between spray dates was 0.11, 3.62, 1.14, 1.75, 0.55, 0.55, 1.13 and 2.08 in., respectively. Diseases were visually rated on 25 randomly selected leaves and clusters from the center vines in each plot. Black rot on leaves and clusters was rated on 7 Aug. Phomopsis was rated on clusters (rachis and fruit) on 6 Sep. Incidence was calculated as % leaves or clusters with disease, and severity was calculated as % area symptomatic on diseased plant parts only. Overall severity was calculated as (incidence x severity)/100. On 2 Sep, twenty five individual canes per plot were rated for Phomopsis cane and leaf spot by starting at the first node from thecordon and extending along 3 feet of growth. Phomopsis was rated on these canes using a 1 to 5 scale where 1 = 0 - 20%, 2 = 21- 41%, 3 = 42-60%, 4 = 61-80% and 5 = 81-100% of internodes covered with lesions. Vines were monitored for phytotoxicity throughout the season.