Development of practical pheromone lures for Lygus hesperus and Lygus elisus (Heteroptera: Miridae).

Abstract

The mirid bugs Lygus hesperus (Knight) and L. elisus (van Duzee) are key pests of forage, fiber, and fruit crops. Our goals were to identify pheromone components produced by females of both species and to develop practical pheromone dispensers for use in monitoring these pests. Volatiles collected from virgin female L. elisus contained (E)-2-hexenyl butyrate (E2HB) as the major component with lesser amounts of hexyl butyrate (HB) and (E)-4-oxo-2-hexenal (E4OH) (ratio 117.2:100:17.1, respectively), whereas volatiles and solvent extracts from L. hesperus contained HB and E4OH as major components, with only small amounts of E2HB (100:23.6:3.4, respectively in volatiles). Dispensers fabricated from pipette tips released the components at ~10 µg/d in a ratio similar to the loading ratio. These lures were used to optimize the pheromone blends in field studies from 2012 to 2017. Blends of E2HB and E4OH attracted L. elisus, and a 100:60 blend was optimal. Blends of HB and E4OH attracted L. hesperus, and a 100:60 blend was adopted as a base blend. The additions of possible minor components such as (Z)-3-hexenyl butyrate, (E)-2-hexenal, or 1-hexanol did not improve the attraction of L. hesperus. In trials in alfalfa and strawberry, traps baited with blends of HB:E4OH (100:60) were equally or more effective for monitoring L. hesperus than sweep or vacuum samples, with pipette tip dispensers lasting 2-3 weeks under field conditions. The numbers of L. hesperus captured were lower than expected as compared with reports of pheromone trapping for other Lygus spp. Some possible reasons were investigated.