Evaluation of semiochemical based push-pull strategy for population suppression of ambrosia beetle vectors of laurel wilt disease in avocado

Abstract

Ambrosia beetles (Coleoptera: Curculionidae: Scolytinae and Platypodinae) bore into tree xylem to complete their life cycle, feeding on symbiotic fungi. Ambrosia beetles are a threat to avocado where they have been found to vector a symbiotic fungus, Raffaelea lauricola, the causal agent of the laurel wilt disease. We assessed the repellency of methyl salicylate and verbenone to two putative laurel wilt vectors in avocado, Xyleborus volvulus (Fabricius) and Xyleborus bispinatus (Eichhoff), under laboratory conditions. Then, we tested the same two chemicals released from SPLAT flowable matrix with and without low-dose ethanol dispensers for manipulation of ambrosia beetle populations occurring in commercial avocado. the potential active space of repellents was assessed by quantifying beetle catch on traps placed 'close' (~5-10 cm) and 'far' (~1-1.5 m) away from repellent dispensers. Ambrosia beetles collected on traps associated with all in-field treatments were identified to species to assess beetle diversity and community variation. Xyleborus volvulus was not repelled by methyl salicylate (MeSA) or verbenone in laboratory assays, while X. bispinatus was repelled by MeSA but not verbenone. Ambrosia beetle trap catches were reduced in the field more when plots were treated with verbenone dispensers (SPLAT) co-deployed with low-dose ethanol dispensers than when treated with verbenone alone. Beetle diversity was highest on traps deployed with low-dose ethanol lures. the repellent treatments and ethanol lures significantly altered the species composition of beetles captured in experiment plots. our results indicate that verbenone co-deployed with ethanol lures holds potential for manipulating ambrosia beetle vectors via push-pull management in avocado. this tactic could discourage immigration and/or population establishment of ambrosia beetles in commercial avocado and function as an additional tool for management programs of laurel wilt. Ambrosia beetles (Coleoptera: Curculionidae: Scolytinae and Platypodinae) bore into trees to complete their life cycle within xylem galleries. However, while ambrosia beetles damage the tree during entry, they do not directly feed on the plant tissue; they have obligate nutritional relationships with symbiotic fungi 1. The fungi are introduced to the tree during initial tree colonization and then, the beetles feed and reproduce while consuming them. Although neither ambrosia fungi nor beetles are monophyletic, both groups are named so because of their close association 2. Once the fungi are established in the tree, the beetles begin to deposit eggs. Their mating systems vary greatly from haplodiploid scolytine species of the tribe Xyleborini to harem polygyny in Pityophthorus lautus (Eichhoff; tribe Corthylini) 3. Economically, ambrosia beetles do the most damage when their symbiotic fungus

Quercetin and Rutin as Modifiers of Aphid Probing Behavior

“…As a consequence, alternative methods of aphid management are in high demand. One of the routes explored is the manipulation of aphid behavior so the insect is either disoriented or discouraged from feeding [11][12][13][14]. This is often achieved by the use of antifeedants or attractants, especially in the 'push-pull' strategies [15][16][17][18].…”

Recent advances toward the sustainable management of invasive Xylosandrus ambrosia beetles

“…Similarly, Addesso et al (2019) did not find ethanol-injected trap trees reduced attacks on adjacent, less attractive trees; varying densities of perimeter ethanolbaited traps also failed to protect ethanol-injected trap trees. However, Rivera et al (2020) observed a significant reduction in Xyleborus spp. ambrosia beetle captures (vectors of laurel wilt [Raffaelea lauricola T. C.…”

“…This management strategy, known as push-pull, manipulates the behavior of insects by combining the two forces: (1) a repellent to 'push' them away from the cultivated host and (2) an attractant to 'pull' them into a trap crop or artificial trap (Cook et al 2007). However, efforts to use ethanol lures or trap trees (i.e., ethanol-injected or flood-stressed plants) as a 'pull' attractant and synthetic repellents as a 'push' component has had inconsistent results (Ranger et al 2013b;Addesso et al 2019;Werle et al 2019;Rivera et al 2020).…”

“…The main challenge facing recent attempts to develop push-pull against ambrosia beetle species has been relatively weak activity of the repellents tested to date. In cases where efforts were made to understand mechanisms of efficacy, the effective repellent radius of verbenone-releasing dispensers has been quantified as less than 1 m (Byers et al 2018;Rivera et al 2020). Accordingly, it would need a high density of these repellent dispensers per treated area for effective management, which would likely be impractical and not economically sustainable.…”

Use of Semiochemicals for the Management of the Redbay Ambrosia Beetle

“…However, a push-pull strategy using ethanol traps and verbenone as attractants and repellents, respectively, failed to reduce non-native ambrosia beetle attacks on potted dogwoods [ 64 ]. In avocado, where R. lauricola is likely transmitted by beetles other than X. glabratus [ 65 ], a push-pull strategy using ethanol (that attracts most beetles found in avocado groves) and verbenone showed promising results [ 66 ]: the addition of attractive lures had a significant interaction with verbenone, and no ambrosia beetles were captured within the push-pull treatment on traps situated less than 1 m from the treated trees during the duration of the experiment (30 days).…”