Improving Natural Enemy Selection in Biological Control through Greater Attention to Chemical Ecology and Host-Associated Differentiation of Target Arthropod Pests

Abstract

Host-associated differentiation (HAD) refers to cases in which genetically distinct populations of a species (e.g., herbivores or natural enemies) preferentially reproduce or feed on different host species. In agroecosystems, HAD often results in unique strains or biotypes of pest species, each attacking different species of crops. However, HAD is not restricted to pest populations, and may cascade to the third trophic level, affecting host selection by natural enemies, and ultimately leading to HAD within natural enemy species. Natural enemy HAD may affect the outcomes of biological control efforts, whether classical, conservation, or augmentative. Here, we explore the potential effects of pest and natural enemy HAD on biological control in agroecosystems, with emphases on current knowledge gaps and implications of HAD for selection of biological control agents. Additionally, given the importance of semiochemicals in mediating interactions between trophic levels, we emphasize the role of chemical ecology in interactions between pests and natural enemies, and suggest areas of consideration for biological control. Overall, we aim to jump-start a conversation concerning the relevance of HAD in biological control by reviewing currently available information on natural enemy HAD, identifying challenges to incorporating HAD considerations into biological control efforts, and proposing future research directions on natural enemy selection and HAD.

Undercover operation: Belowground insect herbivory modifies systemic plant defense and repels aboveground foraging insect herbivores

“…Although (E)-β-ocimene emissions did not solely determine aboveground herbivore foraging decisions, it is worth noting that (E)-β-ocimene plays important roles in other ecological interactions involving cucurbit plants. When damaged by herbivores, plants emit characteristic blends of volatiles, which can attract insect predators and parasitoids (i.e., natural enemies) to kill herbivores and thereby serve as an indirect defense (Turlings and Erb, 2018;Thompson et al, 2022). Cucumber (Cucumis sativus) plants damaged by spider mites emit greater quantities of (E)-β-ocimene, as well as other volatile compounds (Kappers et al, 2010(Kappers et al, , 2011, which play important roles in the attraction of natural enemies for indirect defense (Agrawal et al, 2002).…”