Push–pull strategy that combines olfactory and visual cues for management of ambrosia beetles (Coleoptera: Curculionidae: Scolytinae and Platypodinae) in avocado

Ambrosia beetles (Coleoptera: Curculionidae: Scolytinae and Platypodinae) pose a significant threat to avocado production primarily because they serve as vectors for Harringtonia lauricola (T.C. Harr., Fraedrich & Aghayeva) Z.W. de Beer & M. Procter, the fungal pathogen responsible for laurel wilt disease. Unfortunately, effective strategies for managing either the pathogen or its beetle vectors remain limited. To address this challenge, we investigated behavioral manipulation as a potential tool for managing vector populations. First, we assessed the effectiveness of combining visual and olfactory cues in developing an attractive bait station in the form of a tree (later designated as "tree-mimic"). Next, we incorporated known ambrosia beetle repellents (a verbenone: methyl salicylate blend) into a push-pull strategy targeting natural ambrosia beetle populations. Our results indicated that tree-mimics (cardboard tubes wrapped in UV-reflecting mulch and baited with slow-release ethanol dispensers) were highly attractive to ambrosia beetles. They outperformed other tested combinations of visual and olfactory lures. In replicated small-plot trials under commercial avocado grove conditions, plots treated with verbenone and methyl salicylate wax matrix had significantly fewer beetle captures compared to untreated controls. This reduction occurred regardless of whether tree-mimics were deployed 3 m beyond the plot boundaries. Overall, our results suggest that using verbenone and methyl salicylate blend alone as a repellent may, in some cases, be sufficient to reduce beetle landings on avocado trees. While tree-mimics proved effective in attracting beetles, their impact on reducing beetle presence was only marginal on trees with direct repellent application.