Insecticide Trial for a Mealybug in Grapes, 2019

The efficacy of buprofezin was evaluated as a delayed dormant application on grapes to control a mealybug, Planococcus ficus. Applaud formulated product was applied at 12 and 24 oz/a and compared with an industry standard Lorsban Advanced at 32 fl oz/a and water-only control. Treatment plots were established in a ~35-yr-old vineyard of ‘Thompson Seedless’ managed for juice production near Dinuba, CA. Treatments were applied on 27 March (~2 wk after budbreak) diluted in 100-gal water per acre using R. L. Flomaster Standard 2-Gallon Sprayers. Five-vine plots were set in an RBC design, with a single vine buffer between plots and four replicates. Prior to applications, plots were rated using a 0–3 rating system for the presence of mealybugs on the vine trunk and no significant plot differences were found. Applaud and Lorsban sprays included a nonionic adjuvant at 0.25% VV. Mealybugs were recorded every 1–2 wk, from May through July, on five leaves on each of the three middle vines per plot. Treatments were compared by ANOVA and means were separated using Tukey’s HSD test. Vine damage was evaluated near harvest-time 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. Buprofezin residue on 500 g fruit samples per vine, collected 30 July, was tested by a private laboratory (PrimusLabs, Santa María, CA).

There were no treatment differences until mealybugs began moving in larger numbers from the trunk and cordon to the leaves, thereafter mealybug densities were higher (91–114 DAT) on the control than the Applaud or the Lorsban treatments (Table 1). In pairwise comparisons, Applaud 12 and 24 g/acre had lower damage ratings than the control (Table 2). No residues of buprofezin were found on any fruit clusters, collected 125 DAT. Data show that Applaud applied near bud break may be an alternative to Lorsban applied as a delayed dormant.

This research was supported by a grant from the California Table Grape Commission and industry gifts of pesticides.