In-Season Drip and Foliar Insecticides for a Mealybug in Grapes, 2021

The efficacy of imidacloprid (Admire Pro), spirotetramat (Movento), spirotetramat–pyriproxyfen (Senstar), sulfoxaflor (Sequoia), acetamiprid (Assail), and flupyradifurone (Sivanto Prime) were evaluated as in-season applications on grapes, applied through the drip system or as a foliar, to control a mealybug, Planococcus ficus (Hemiptera: Pseudococcidae). Treatment plots were established in a 12-yr-old vineyard of ‘Pinot Gris cultivar’ managed for wine grapes near Kerman, CA. Ten-vine plots were set in an RCB design, with a two-vine buffer between plots in each row and eight replicates in a randomized block design. Single application treatments were 1) Admire Pro (14 oz/a) and 2) Sivanto (28 oz/a) applied at shoot elongation (30 Apr) through the drip system, 3) Movento (8 oz/a) and 4) Senstar (16 oz/a) applied at bloom as a foliar (12 May), and 5) Sequoia (5.75 oz/a), 6) Sivanto (14 oz/a), and 7) Assail 70W (2.3 oz/a) applied as a foliar to coincide with the movement of mealybugs from the trunk to the leaves (1 Jul). Double application treatments were 8) Sequoia (5.75 oz/a) applied 17 Jun followed by Movento (8 oz/a) on 1 Jul, 9) Movento (8 oz/a) applied 17 Jun followed by Sequoia (5.75 oz/a) on 1 Jul, and 10) a water-only control. Foliar applications were made with two-gallon hand-pump sprayers at 100 gal/a and included Dyne-Amic adjuvant (0.5% VV). All of these materials have been shown to reduce P. ficus densities on grape leaves and in grape clusters; the goal here was to determine their impact on the P. ficus population under bark on the grape trunk.

Vine infestation was evaluated pretreatment during plot establishment (19–23 Apr) by looking for honeydew on the trunk and ant movement to make sure that all plots contained mealybugs. Posttreatment (10–18 Aug), trunk infestation was compared among treatments by recording all second instar to adult (including ovisacs) mealybugs found on the trunk and cordon during a 3-min search per vine for the six inner vines of each plot. Treatments were compared by ANOVA and means were separated using Tukey’s HSD test.

Treatments of Assail, Senstar, Sivanto (foliar application), Movento followed by Sequoia, and Sequoia followed by Movento had lower mealybug densities than the control, the systemic-only applications (Admire Pro, Movento, Sivanto via drip) and a foliar application of Sequoia were not lower than the control (Table 1). Movento or Sequoia alone did not suppress mealybug densities, but in combination were lower than the control. Similarly, Senstar (with two modes of action) reduced mealybug density, suggesting that two modes of action may be needed to control P. ficus in protected locations of the vine.¹

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