In Season Drip and Foliar Insecticides for a Mealybug in Grapes, 2019

The efficacy of imidacloprid, spirotetramat, and flupyradifurone were evaluated as in-season applications on grapes, applied through the drip system or as a foliar, to control a mealybug, Planococcus ficus. There were six treatments: Admire Pro, Movento, Sivanto HL (drip), Sivanto HL (foliar), Movento + Sivanto (foliar), and a water-only Control. Treatment plots were established in a 12-yr-old vineyard of ‘Pinot Gris cultivar’ managed for wine grapes near Huron, CA. Ten vine plots were set in an RBC design, with a ten-vine buffer between plots and five replicates. Initial treatments were applied on 3 May (budbreak to 18” of cane growth), with Admire Pro and Sivanto HL applied through the drip system, each at 14 oz/a. The following week (10 May) Movento (8 fl oz/a) was applied as a foliar using a Stihl SR 450 sprayer/duster at 100 gal/a. On 18 June, Sivanto was applied as a foliar at 6 oz/ac in a stand-alone treatment and with an earlier Movento treatment, using the Stihl sprayer at 100 gal/ac. All foliar sprays included Dyne-Amic adjuvant (0.25% VV).

Vine infestation was evaluated pre-treatment, when the mealybugs were hidden under the trunk bark or on the roots, based on the previous year’s infestation using a 0–3 rating system, where 0 = no mealybug damage, 1 = honeydew (indicating the presence of mealybugs), 2 = mealybugs and/or damage on trunk, leaves and/or fruit, and 3 = severe mealybug damage to trunk, leaves, and fruit. Ratings were compared in a 2 × 2 contingency table with treatments separated using Pearson’s chi-square. Pre-treatment ratings showed higher infestation in the Admire Pro, Sivanto HL (drip) and control treatments (χ ² = 146.96, df = 18, P < 0.001). Post-treatment, mealybugs were recorded on five leaves on each of the six middle vines per plot (30 leaves per plot per treatment), every 2–3 weeks, from May through September; data are presented for monthly counts until July, when mealybugs began moving in larger numbers from the trunk and cordon to the leaves. Treatments were compared by ANOVA and means were separated using Tukey’s HSD test.

There were no treatment differences from May to mid-June (not all data not shown) as mealybugs were primarily on the trunk. All insecticide treatments had lower mealybug densities than the control and by 27 June, and this pattern was relatively consistent through mid-August (Table 1). After harvest (16 August), mealybug densities increased and treatment differences were more apparent, with Control and Admire higher than Sivanto (drip and foliar), and Sivanto higher than Movento (alone and applied with Sivanto) (Table 1). Post-harvest, Sivanto foliar often performed better than Sivanto drip (Table 1). Data show that, in this trial, Movento and Movento plus Sivanto provided season long control, whereas Admire did not provide season-long control; Sivanto applied as a mid- or late-season foliar can be used to lower mealybug densities.¹

Footnotes