Evaluating a new aphid biocontrol agent: The role of aphid density in modulating oviposition behaviour in the American hoverfly, Eupeodes americanus, and the aphid midge, Aphidoletes aphidimyza

Abstract

AbstractHoverfly larvae are voracious predators of aphids but have limited dispersal capacity, so their survival depends critically on female selection of oviposition sites. For aphid control purposes, the ability of females to find small aphid colonies is especially valuable. In this study, the oviposition strategy and minimum aphid density triggering the oviposition of the American hoverfly, Eupeodes americanus (Wiedemann, 1830) (Diptera: Syrphidae), was compared with that of the aphid midge, Aphidoletes aphidimyza (Rondani, 1847) (Diptera: Cecidomyiidae), a predator commercially available in Canada as a reference. Oviposition behaviour was evaluated at densities of 0, 2, 5, 10, and 50 aphids per plant. This was tested on two economically significant plant/aphid systems: pepper plants infested by the green peach aphid, Myzus persicae (Sulzer 1776) (Hemiptera: Aphididae), and cucumber plants infested with the melon aphid, Aphis gossypii Glover 1877. Results showed that both predators lay their eggs in proportion to the size of the colony of aphids. Oviposition by E. americanus required a minimum density of 5 aphids on cucumber but only 2 on pepper, whereas for A. aphidimyza, it was also 5 aphids on cucumber, but 10 on pepper. The hoverfly laid more than twice as many eggs as A. aphidimyza on pepper. It also laid more eggs on pepper than on cucumber and the pattern is the opposite for A. aphidimyza. Therefore, the identity of the aphid‐host plant complex appears to modulate the oviposition of these predators. This study demonstrates the ability of E. americanus to respond to lower densities of aphids than A. aphidimyza early in the infestation on sweet pepper plants and shows that its oviposition rate is at least as effective as A. aphidimyza on cucumber. Consequently, these attributes of its oviposition behaviour indicate that E. americanus has great potential for use as an aphid biocontrol agent in these crops.