In-season drip and foliar insecticides for a mealybug in grapes, 2023

The efficacy of flonicamid (Beleaf 50SC), imidacloprid (Admire Pro), spirotetramat (Movento), 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. There were 6 treatments: Beleaf 50SG (applied via chemigation or foliar), Sivanto Prime, Admire Pro, Movento, and an untreated check. Treatment plots were established in a 25-year-old vineyard of ‘Selma Pete cultivar’ managed for raisin grapes near Sanger, California. Five-vine plots were set in an RCB design, with a 2-vine buffer between plots and 4 replicates. Initial insecticide treatments were applied on 2 June (budbreak to 18” of cane growth), with Beleaf 50SC (5.6 oz/a) and Admire Pro (14 oz/a) were applied through the drip system, with water run through the system 2 h before and after product application. Two weeks later (15 June) Beleaf 50SC (5.6 oz/a), Movento (8 oz/a), and Sivanto Prime (14 oz/a) were applied as a foliar using R. L. Flomaster Standard 2-Gallon Sprayers (Root-Lowell Manufacturing Co.) at a rate of 100 gallons per acre; treatments had a non-ionic adjuvant (Dyne-Amic) at a rate of 0.5% V/V. Vine infestation was evaluated pretreatment, 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. Pretreatment ratings showed no difference among treatment plots (χ² = 16.673, df = 15, P = 0.339). Posttreatment, mealybugs were recorded on 3 leaves per vine (60 leaves per treatment) on 27 July, and on every vine trunk during a 3-min timed count on both 7 and 27 July (data were combined). Treatments were compared by ANOVA and means were separated using Tukey’s HSD test; data from trunk counts were transformed (sqrt (X + 0.5)) to normalize the variance.

Trunk counts showed a relatively low population density that was highly clumped in distribution, reducing overall treatment comparison because of a high variance for each treatment mean. Beleaf 50SC applied in the drip system had lower mealybug counts than the control or Beleaf 50SC applied as a foliar (Table 1). Leaf counts showed low mealybug populations across all treatments; Admire and Movento had higher counts than Beleaf (drip or foliar) or Sivanto (Table 1).¹

Footnotes