Egg parasitoids of stink bugs: Research status and potential for biological control

Egg parasitoids are among the most important natural enemies associated with herbivorous stink bugs, and they show remarkable potential as biological control agents. On the other side, some egg parasitoid species also attack predaceous bugs, thus affecting the efficacy of these important entomophagous insects. Most studied stink bug egg parasitoids belong to Platygastridae (=Scelionidae) and Encyrtidae, the main research topics concerning behavior, chemical ecology, behavioural ecology and field efficacy. Some species have been used for biological control programs. However, some constraints may prevent egg parasitoids from becoming effective agents in inundative biocontrol projects, the most important being incomplete behavioral and ecological knowledge for most species and inefficient mass production. Thus, understanding the host selection strategies of egg parasitoids and the chemical stimuli involved would lead to enhanced biological control through behavioral manipulation of egg parasitoids in the field, and to the development of better rearing methods. Egg parasitoids of herbivorous stink bugs may adopt differing host selection strategies, the most important being the exploitation of kairomones from non-target instars in combination with host-induced plant synomones (indirect resistance), and associative learning. The chemically mediated behavior of these wasps may be exploited, e.g., through the development of plants with elevated expression of indirect induced resistance, or spraying fields with resistance elicitors. Important elements toward implementation include procedures for selection of egg parasitoids, evaluation of their specificity, risk assessment of new introductions, release methods, and quality control. Implementation of knowledge acquired from laboratory studies must finally be scaled up and transferred to growers