Interspecific competition between endo- and ectoparasitoids attacking Tuta absoluta

Abstract

Tuta absoluta is a major pest threatening tomato crops worldwide. In the Mediterranean basin, biological control mainly relies on zoophytophagous predators which coexist with larval parasitoids, the native ectoparasitoid Necremnus tutae and the recently established South American endoparasitoid Dolichogenidea gelechiidivoris. Although both are effective natural enemies of T. absoluta, their interactions remain poorly understood. Here, we explored the potential competitive outcomes between these two parasitoids through no-choice, choice, and behavior experiments. In single-species assays, D. gelechiidivoris exhibited high larval parasitism (92%) and effectively reduced T. absoluta densities, whereas N. tutae relied more on host-feeding and host-killing behaviors with lower parasitism (48%). When the parasitoids co-occurred, T. absoluta mortality increased to ~ 80% while parasitism for each species decreased by well over 50%. Necremnus tutae also showed a preference for host-feeding or killing larvae previously exposed to D. gelechiidivoris. This elevated larval mortality was likely driven by high probing activity from D. gelechiidivoris in combination with continued host-feeding and host-killing by N. tutae. Our findings demonstrated interspecific competition between the two larval parasitoids, emphasizing the importance of considering such dynamics when integrating them into biological control programs against T. absoluta.