Quasi-Double-Blind Screening of Semiochemicals for Reducing Navel Orangeworm Oviposition on Almonds

A three-step, quasi-double-bind approach was used as a proof-of-concept study to screen twenty compounds for their ability to reduce oviposition of gravid female navel orangeworm(NOW), Ameylois transitella (Lepidoptera: Pyralidae). First, the panel of compounds, whose identity was unknown to the experimenters, was tested by electroantennogram (EAG) using antennae of two-day old gravid females as the sensing element. Of the twenty compounds tested three showed significant EAG responses. These three EAG-active compounds and a negative control were then analyzed for their ability to reduce oviposition via small-cage, two-choice laboratory assays. Two of the three compounds significantly reduced oviposition under laboratory conditions. Lastly, these two compounds were deployed in a field setting in an organic almond orchard in Arbuckle, CA using black egg traps to monitor NOW oviposition. One of these two compounds significantly reduced oviposition on black egg traps under these field conditions. Compound 9 (later identified as isophorone) showed a significant reduction in oviposition in field assays and thus has a potential as a tool to control the navel orangeworm as a pest of almonds.