Using pheromones to monitor Lygus populations in fruit crops in the UK

Abstract: Capsid bugs (Miridae) cause serious economic damage to numerous crops throughoutthe world. Among these, species of Lygus and closely-related genera are intractable pests on soft,bush- and top-fruit, alfalfa and cotton in Europe and the US. In several of these species thefemales have been shown to produce a sex pheromone that attracts conspecific males. Wherechemical studies of these pheromones have been undertaken, three compounds; hexyl butyrate,(E)-2-hexenyl butyrate and (E)-4-oxo-2-hexenal have invariably been found (e.g. Drijfhout et al.,2002; Innocenzi et al., 2004). However, it has proved extremely difficult to demonstrateattraction of male bugs to blends of the synthetic chemicals, at least in part because thesechemicals are also known as alarm compounds produced by both males and females of many bugspecies. Innocenzi et al. (2005) reported attraction of males of L. pratensis to a mixture of allthree chemicals and attraction of L. rugulipennis to a blend of hexyl butyrate and (E)-4-oxo-2-hexenal. However, the blends were not well-defined and the dispensers extremely short-lived.We have been studying the female sex pheromones of L. rugulipennis. Collections ofvolatiles from individuals have shown that females produce all three of the above compounds butmales do not. These results suggest the three compounds are indeed components of the femalesex pheromones of this species. This was further substantiated by the observation that thesecompounds are produced only during a well-defined period immediately after dawn, coincidingwith the time virgin females were most attractive to males in field tests. Detailed studies havebeen carried out to determine the exact compositions of the blend produced and then to devisedispensing systems for the synthetic chemicals that mimic these. So far we have been able to trapmales of L. rugulipennis with a particular blend in a novel, practical dispenser.