Water revisited: a powerful attractant for certain stored‐product moths

Pheromone-baited traps have shown promise in monitoring infestations of stored products in storage facilities. Mass trapping has had limited success (Phillips, 1997; Trematerra, 1997) in reducing pest insect damage in stored products. Identification of minor components emitted by female moths that are attractive and can be released in effective amounts from the traps may increase the efficacy of traps but may still not result in population reduction, due the high mating ability of the remaining males. In order to de facto reduce populations, traps that catch females are needed. Investigations of pheromones combined with food odours as attractants for males and ovipositing females have met with limited success (Chambers, 1990; Phillips, 1997; Liang et al., 1998). Chow et al. (1977) trapped large numbers of female and male pyralid moths with water traps. Both Ephestia (Cadra) cautella Walker and Plodia interpunctella Hübner (Lepidoptera: Pyralidae) infested the storage facility in which the trapping was conducted, but as the trapped insects were submerged in water, easy identification of the two species was not possible. Therefore, the authors could not investigate differential attraction of the two species. The interesting and overlooked results of Chow et al. (1977) raises the question whether water alone attracts pyralid males and females. In the present study we investigate if attraction to water differs between the sexes and between two species of pyralids, the Mediterranean flour moth, Ephestia kuehniella Zeller, and the almond moth, E. cautella (Lepidoptera: Pyralidae). Both species are serious cosmopolitan pest insects on stored products, e.g., wheat, grain, fruit, chocolate, and nuts (Phillips, 1994) and cause large economic losses for the food industry (Reichmuth, 1999). Our objectives were to compare the attraction to water with the attraction to commercial pheromone baits. As both species are stored-product moths and live under water-deprived conditions, we hypothesised that the water would attract both males and females, whereas the pheromones would attract males only. Subsequently, a mass trapping trial was conducted in the chocolate factory in an attempt to determine the possibility of decreasing the population of moths by using traps baited with water.