Disruption of Sex Pheromone Communication in Cylas formicarius (Coleoptera: Apionidae) as a Potential Means of Control

Abstract

Sweetpotato weevil, Cylas formicarius (Fabricius), is the most limiting factor of sweet potato, Ipomoea batatas (L.) Lam., production worldwide (Jansson & Raman 1991). Feeding and oviposition damage in roots and vines can cause severe cosmetic and economic damage. In response to tissue damage, sweet potato roots produce foul tasting terpenoids (Uritani et al. 1975) rendering them unpalatable for human consumption. Thus, commercial growers can tolerate very little sweetpotato weevil damage. Historically, weevil management has relied heavily on cultural and chemical control (Sutherland 1986, Chalfant et al. 1990). However, chemical control provides little protection once an egg is laid because immatures develop within roots and vines (Chalfant et al. 1990). Cultural controls, such as sanitation, crop rotation, planting away from weevilinfested fields, removal of alternate hosts, hilling plants, etc., can help to reduce damage (Talekar 1991); however, they require considerable labor and have not been universally adopted. Recent studies indicate that entomopathogenic nematodes and sex pheromones may provide new means to control the sweetpotato weevil (Jansson 1991, Jansson et al. 1991). Pheromones have typically been used three ways: (1) monitoring insect populations using pheromone-baited traps; (2) mass-trapping, where large numbers of traps are used to reduce the insect population; and (3) mating disruption, in which the pheromone is used at high dosages to permeate the atmosphere so as to disrupt communication between the sexes, thus reducing mating (Kydonieus & Beroza 1982, Campion 1984). Mating disruption has been examined in many insect systems (McLaughlin et al. 1972, Shorey et al. 1972, Landolt et al. 1982, Sower 1982, Schwalbe & Mastro 1988, for reviews see Kydonieus & Beroza 1982, Campion 1984), and in general, some success has been achieved. The objective of our study was to examine the potential of sweetpotato weevil synthetic sex pheromone as a mating disruptant by examining male confusion (i.e. communication disruption) in a large commercial field plot.