Habitat and plant specificity of Trichogramma egg parasitoids—underlying mechanisms and implications

Abstract

Egg parasitoids of the genus Trichogramma are among the most important and best-studied natural enemies worldwide. Parasitism levels by Trichogramma vary greatly among different habitats, plants or plant structures on which the host eggs are located. Here we summarise the published evidence on mechanisms that may underlie the observed variation in parasitism rates. These mechanisms include plant spacing, plant structure, plant surface structure and chemistry, plant volatiles and plant colour. In addition, plants can affect parasitoid behaviour and activity by providing carbohydrate food sources such as nectar to the adult wasps, and by affecting the nutritional quality of the host eggs for progeny development. Knowledge of plant and habitat factors that affect Trichogramma spp. efficacy has important implications for biological control, and for assessing the risks that mass-released Trichogramma spp. may pose to non-target insects. [KEYWORDS: Biological control ; Conservation biological control ; Food ecology ; Multi-trophic interactions ; Non-target effects ; Plant volatiles ; Trichomes]