Evaluation of chemical controls for navel orangeworm in almonds, 2024

The efficacy of various insecticides against NOW in almonds was evaluated at the UC Kearney Agricultural Research and Extension Center in Parlier, CA in 2024. The almond block was planted in 2016 and consisted of Nonpareil (50%), Monterey (25%), and Carmel (25%) varieties with 9 ft tree × 20 ft row spacing. Only the Nonpareil variety trees were used for this experiment, which followed an RCB design with double-tree replicates. There were 6 replicates for each of the 10 treatments. Treatments were applied using a mounted 100-gallon air-blast sprayer to deliver 200 gpa at 260 psi at 1% hull-split on 15 Jul, with a follow-up application 2 weeks later on 29 Jul. To determine the efficacy of the insecticides on NOW management, 250 nuts were collected from each plot on 19 Aug, and nuts were evaluated in the laboratory for NOW infestation. In the laboratory, nuts were cracked open and rated as either “clean,” “blank,” “shrivel,” or “infested with NOW.” Nuts classified as “blank” or “shrivel” were excluded from subsequent analysis, as they did not provide an opportunity for NOW infestation. The proportion of almonds infested in different insecticide treatments was compared using a generalized linear mixed model with a binomial distribution and a logit link function (PROC GLIMMIX) in SAS. The model included “insecticide treatment” as a fixed effect and “replicate” as a random effect to account for variability among replicates. A significant fixed effect was followed by Tukey’s post hoc test to determine significant differences among treatments.

Across all treatments, NOW infestation ranged from 3.8% to 8.0% (Table 1). The low and medium Pyrone treatments were the only treatments to significantly lower NOW damage compared to the water-only check. However, the low and medium Pyrone treatments did not show significant differences in control compared to the industry standard treatment (Intrepid 2F/Altacor), its variant with OR-009-E as an adjuvant (Intrepid 2F/Altacor + OR-009-E), and Altacor eVo. In addition, although these 3 treatments (Intrepid 2F/Altacor, Intrepid 2F/Altacor + OR-009-E, and Altacor eVo) showed lower NOW damage than the water-only check, the reductions were not statistically significant. The findings from this study suggest that low and medium concentrations of Pyrone may provide effective alternatives to Intrepid 2F and Altacor. However, it is worth noting that the high concentration of Pyrone did not achieve the same level of control as the low and medium concentrations.¹

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