Evaluation of fungicide programs for control of fungal diseases of four wine grape cultivars, 2007

摘要

A trial of four spray programs for control of fungal diseases of wine grapes was conducted in a research vineyard of 6-year-old, Vertical Shoot Position-trained grapevines at the University of Maryland’s Lower Eastern Shore Research and Education Center (LESREC), Salisbury. The trial was a split-block design with four replicates. The five main plot (row) treatments comprised an optimal program incorporating newer fungicides and frequent rotations among fungicide classes, two programs adapted from 2006 grower programs that successfully controlled grape diseases in eastern Maryland (Grower 1) and the Piedmont region (Grower 2), a “soft” program using only one application of a conventional fungicide, and an unsprayed control. Treatments, which weretimed to the phenology of ‘Chardonnay’, the earliest cultivar, were applied as follows: 1 = 27 Apr (0–1 in. shoot), 2 = 4 May (3–5 in. shoot), 3 = 10 May (10–12 in. shoot), 4 = 17 May (12–17 in. shoot), 5 = 24 May (pre-bloom), 6 = 31 May (bloom), 7= 7 Jun (post-bloom), 8 = 14 Jun (1st cover), 9 = 25 Jun (2nd cover), 10 = 5 Jul (3rd cover/bunch closing), 11 = 16 Jul (4th cover), 12 = 26 Jul (5th cover/veraison), 13 = 7 Aug (6th cover), 14 = 21 August (pre-harvest). Two border rows and an unused row in the trial area received a complete fungicide program to manage all diseases. Fungicide treatments were applied with an over-the-row shielded boom sprayer using six TeeJet Twin Flat Spray 60-8004VS tips delivering 40 gpa at 45 psi. Subplots consistedof 3-vine panels of four standard wine grape cultivars—‘Cabernet Franc’, ‘Cabernet Sauvignon’, ‘Chardonnay’, and ‘Merlot’—arranged in a randomized complete block design. The entire vineyard received a season-long maintenance program for weed control and was treated with Sevin XLR (1qt/A) on 3 Jul and 25 Jul for Japanese beetle control. Disease severity ratings were made on 5 Sep for ‘Chardonnay’ and ‘Merlot’ and on 19 Sep for ‘Cabernet Franc’ and ‘Cabernet Sauvignon’, approximately one week before fruit matured. In each plot, a visual evaluation was made of the percentage of the area infected on each of three shoots and the percentage of fruit infected on each of three clusters. Rainfall amounts at LESREC were 5.60, 0.97, 2.44, 2.03, 4.10, and 0.91 inches for Apr, May, Jun, Jul, Aug, and Sep, respectively.