Chemical control of olive fruit fly in olives, 2024

This study evaluated the efficacy of conventional and organic insecticides for the control of olive fruit flies. The study was conducted in Napa, CA at a commercial olive orchard. The orchard was planted with 10 ft × 15 ft trees by row spacing. Seven experimental treatments and 2 treated checks were replicated 5 times in an RCB design. Each replicate was 3 trees long, and the outer 2 trees served as unsampled-treated buffers. All experimental treatments and 1 treated check received a high bait (750 g white sugar, 281.3 ml Nu-Lure Insect Bait, and 187.7 ml Brandt Insect Bait per 75 gallons/acre) and 1 experimental treatment (MBI-306 at 20.0 fluid ounces per acre) and 1 treated check received a low bait (100 g white sugar, 37.5 ml Nu-Lure Insect Bait, and 25 ml Brandt Insect Bait per 75 gallons/acre). Treatments were applied at pit hardening (2 Aug), at OLFF population increase (29 Aug), and again 4 weeks later (25 Sept) approximately 1 month before harvest (Oct 29). Treatments were applied with a handheld sprayer operating at 150 psi with a finished spray volume of 75 GPA. To determine when to apply the population increase spray, the OLFF population was monitored weekly from 2 Aug to 29 Oct with Trécé AM-NB yellow panel traps baited with ammonium carbonate lures. One trap was placed in the center tree of each treated check. The traps were checked weekly and replaced as needed, and the ammonium carbonate lures were replaced every 5 weeks. A week after harvest on 4 Nov, damage assessments were conducted with 250 olives per replicate (1,250 olives total per treatment). Olives were inspected for OLFF stings and olives with stings were dissected for larval tunneling. The mean percent olives with OLFF stings, tunneling, and total infestation (olives with stings plus olives with tunneling) for each treatment were analyzed by one-way ANOVA. Means were separated using Fisher’s LSD (P ≤ 0.05).

The high-bait-treated check was significantly more attractive than the low-bait-treated check (Table 1). All experimental treatments except for Sequoia significantly reduced the mean percent stings and total infestation compared to the high-bait-treated check. There was no significant difference among the experimental treatments and the low-bait-treated check. None of the treatments significantly reduced tunneling compared to either the low- or high-bait-treated checks.¹

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