Evaluation of Insecticides to Control Navel Orangeworm in Fig, 2021

We assessed the efficacy of three insecticides to control navel orangeworm (NOW) on figs near Chowchilla and Firebaugh, CA in 2021. At each location, applications were initiated after second fig harvest (there are usually 4–5 harvests per year, starting in July). The Chowchilla site had ‘Tena’ variety figs with 10 ft tree × 24 ft row spacing. Plots contained three trees and there was one untreated tree between each plot for a buffer. Treatments were arranged in a RCBD with five replications. The Firebaugh site had ‘Black Mission’ variety figs with 15 ft tree × 24 ft row spacing. Treatments were arranged in a RCBD with eight replicates of single-tree plots. Plots were sprayed 3–4 times from late Aug to early Oct using a single nozzle boom equipped with D3 spray tips and 45 cores powered by CO₂ at 40 psi with a spray volume of 50 gpa. Application dates were 25 Aug and 1, 7, and 15 Sep near Chowchilla and 13, 22, 29 Sep and 4 Oct near Firebaugh.

Infestation levels were evaluated on 20 Aug, 15 Sep, and 8 Nov at Chowchilla and on 22 Sep and 8 Nov at Firebaugh by collecting 50 figs per plot that were later processed in a commercial laboratory (Safe Food Alliance, Kingsburg, CA) to determine percent infestation by NOW. Data were analyzed using a logistic regression in R Statistical Software with ‘Treatment’ as a fixed effect. Infestation data for each site and date were evaluated separately, so no random effects were included in the model. For the 8 Nov evaluation at Chowchilla, 32% of data points were excluded from analysis after the quality of data was compromised due to infestation by driedfruit beetle [Coleoptera: Nitidulidae, Carpophilus hemipterus].

Control plots had substantial levels of NOW infestation on 8 Nov at both locations (Table 1. Chowchilla, 44%; Firebaugh, 19%). In the final fig assessment from both orchards, NOW infestation levels in all treatments were numerically lower than in the control plots (Chowchilla, NS; Firebaugh, P < 0.01). In the final fig assessment at Firebaugh, Altacor and Verdepryn significantly lowered the percentages of NOW infestation by 10.2% and 11.6%, respectively. In final fig assessment at Chowchilla, plots treated with Intrepid three times had the numerically lowest percent NOW infestation while at Firebaugh, plots treated with Verdepryn had the lowest infestation. Prior to trial initiation, there were significant differences in NOW infestation levels ranging from 1.0% to 6.6% at Chowchilla and 8.6% to 13.2% at Firebaugh.¹

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