Larry J. Gut

General principles of attraction and competitive attraction as revealed by large-cage studies of moths responding to sex pheromone

Knowledge of how insects are actually affected by sex pheromones deployed throughout a crop so as to disrupt mating has lacked a mechanistic framework sufficient for guiding optimization of this environmentally friendly pest-control tactic. Major hypotheses are competitive attraction, desensitization, and camouflage. Working with codling moths, Cydia pomonella, in field cages millions of times larger than laboratory test tubes and at substrate concentrations trillions of times less than those typical for enzymes, we nevertheless demonstrate that mating disruption sufficiently parallels enzyme (ligand) –substrate interactions so as to justify adoption of conceptual and analytical tools of biochemical kinetics. By doing so, we prove that commercial dispensers of codling moth pheromone first competitively attract and then deactivate males probably for the remainder of a night. No evidence was found for camouflage. We generated and now validate simple algebraic equations for attraction and competitive attraction that will guide optimization and broaden implementation of behavioral manipulations of pests. This analysis system also offers a unique approach to quantifying animal foraging behaviors and could find applications across the natural and social sciences.

Mechanized applicator for large-scale field deployment of paraffin-wax dispensers of pheromone for mating disruption in tree fruit

A tractor-mounted mechanized applicator was developed for large-scale deployment of paraffin-wax dispensers of pheromone for mating disruption of oriental fruit moth, Grapholita molesta (Busck). The wax formulation was mostly water and emulsified paraffin wax containing 5% (by weight) pheromone [93:6:1 blend of (Z)-8-dodecen-1-yl-acetate:(E)-8-dodecen-1-yl-acetate: (Z)-8-dodecen-1-ol]. Ten milliliters of wax was applied per tree as approximately 160 deposits (0.04 ml of wax per drop). An average of 23 min was required to treat 1 ha of crop. Disruption efficacy of mechanically applied wax was measured relative to an untreated control in replicated 0.4-ha blocks within a recently abandoned apple orchard. From 6 May to 27 June, 100% disruption of tethered virgin females and 97% inhibition of pheromone traps was achieved for 52 d with two applications of wax. However, during mid- to late summer (July-August), this level of efficacy was maintained for only approximately 1 wk after each of two applications. Higher temperatures later in the season may have accounted for abbreviated efficacy of the applied small drops. Mechanically applied paraffin-wax technology may increase adoption of mating disruption given that a higher level of efficacy was achieved despite deploying less active ingredient per hectare relative to that used with reservoir dispensers. The savings in labor by not requiring hand application of reservoir dispensers could be directed toward cost of machinery. However, the short duration of efficacy obtained with the current wax formulation and mechanical applicator is judged uneconomical given the eight or more applications that would have been required for high-performance disruption over the full season. Larger drops with lower surface area-to-volume ratios are expected to prolong pheromone release for extended efficacy and desirable overall economics.

Efficacy and mode of action of female‐equivalent dispensers of pheromone for mating disruption of codling moth

1 We evaluated the efficacy and mode of action of commercially available female‐equivalent dispensers of pheromone for mating disruption of codling moth Cydia pomonella (L.) (Lepidoptera Tortricidae).