Control of Vine Mealybug in Wine Grapes, 2020 Open Access

This study evaluated the efficacy of Sequoia, Sivanto, and Assail, as replacements of Lorsban Advanced for the delayed dormant application for VMB control. The study was conducted in a ‘Chardonnay’ vineyard near Manteca, CA. Eleven experimental treatment programs and an untreated check were replicated four times in an RCB design. Each replicate was five vines long. The two outside vines in each replicate were considered treated buffer and not sampled. The orchard was planted on 5 ft. vine by 9 ft. row spacing. Foliar treatments were applied with a hand-held sprayer operating with a finished spray volume of 150 gal/ac. VMB infestation was evaluated in a 1-min search of the trunk. On 4 May, this search was conducted on one central vine per replicate. Afterwards, the evaluation was conducted on two central vines and the average value was used for analysis. All evaluations conducted on and after 29 June included both the trunk and cordon during the 1-min search. Damage assessment was categorized as follows: 0 = no VMB or honeydew, 1 = honeydew but not visible VMB, 2 = honeydew and visible VMB, and 3 = honeydew and greater than 10 VMB. On and after 29 June, the number of VMB feeding sites was counted on both the trunk and cordon. One feeding site was defined as a ca. 2 cm in diameter moist spot. Prior to commercial harvest on 20 and 21 August, 25 fruit clusters per center vines in each replicate were evaluated for VMB damage using the same scoring system as the trunk and cordon evaluation. Fruit clusters with a score of 2 or 3 were considered unmarketable. Trunk and cordon evaluation score data were analyzed using Kruskal–Wallis test with means separation using Wilcoxon rank sum test with the Bonferroni correction at P ≤ 0.05. The fruit infestation data were analyzed with an ANOVA with means separation using Fisher’s Protected LSD test at P ≤ 0.05.

The delayed dormant application of Lorsban Advanced had significantly lower season mean VMB score on trunk and cordon compared with the delayed dormant application of Sivanto HL, Sequoia 2SC, or Assail 30SG (Table 1). The delayed dormant application of Sivanto HL, Sequoia 2SC, or Assail 30SG did not significantly reduce the season mean VMB score on trunk and cordon compared with similar experimental control programs without the delayed dormant applications. All experimental control programs had significantly lower season mean VMB scores compared to the untreated check, Movento 2SC alone or Movento 2SC followed by two applications of Assail 30SG. All experimental control programs had significantly lower mean VMB feeding sites when compared with the untreated check (Table 2). There was no significant difference in mean percent unmarketable fruit clusters among the delayed dormant application of Lorsban Advanced, Sivanto HL, Sequoia 2SC, or Assail 30SG control programs. Also, there was no significant difference in mean percent unmarketable fruit clusters among the delayed dormant application of Lorsban Advanced, Sivanto HL, Sequoia 2SC, or Assail 30SG control programs and similar control programs without the delayed dormant application. These treatments had significantly higher mean percent unmarketable fruit clusters compared with the Sequoia 2C followed by Movento 2SC and two applications of the low rate of Venerate XC, Movento alone, and untreated check. All experimental control programs had significantly lower mean VMB feeding sites when compared with the untreated check.¹

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