Direct and Indirect Competitive Interactions between Ooencyrtus nezarae and Paratelenomus saccharalis Parasitizing Megacopta cribraria Egg Patches

SIMPLE SUMMARY: This article studied the interaction between two egg parasitoids, Paratelenomus saccharalis and Ooencyrtus nezarae, of the kudzu bug (Megacopta cribraria). In the laboratory, we focused on how the timing of arrival to host eggs influences egg parasitism, competition, aggressive behaviors of wasps, and intraguild predation of wasp larvae in host eggs. Results showed that interspecific interactions reduced P. saccharalis emergence in the presence of O. nezarae; however, the degree of this effect altered when wasps were released sequentially versus simultaneously and over time. Adults P. saccharalis competed aggressively for the shared host, although O. nezarae larvae outcompeted in multiparasitized eggs. Our results suggest that O. nezarae has the potential to negatively impact the population dynamics of P. saccharalis, which could influence the success of biological control programs targeting the kudzu bug. ABSTRACT: The present study investigated egg parasitoid interspecific interactions between a generalist, Ooencyrtus nezarae Ishii (Hymenoptera: Encyrtidae) and a specialist, Paratelenomus saccharalis Dodd (Hymenoptera: Platygastridae) in a laboratory setting using kudzu bug (Megacopta cribraria Fabricius, (Hemiptera: Plataspidae)) eggs as their shared host. Three experiments were conducted to evaluate the emergence of wasps from parasitized hosts after the simultaneous and sequential release of wasps, monitor aggressive behavior of P. saccharalis, and quantify intraguild predation of O. nezarae larvae on heterospecific P. saccharalis larvae. Results showed that total host egg parasitism was higher when both wasps were released simultaneously than if wasps were released sequentially. Ooencyrtus nezarae produced more total offspring than P. saccharalis in all sequential/simultaneous treatments but produced male offspring in most cases. In the aggressive behavioral experiment, specialist, P. saccharalis used head butting to fight O. nezarae, but no other aggressions were observed. In an experiment examining intraguild predation, O. nezarae was able to develop in host eggs parasitized by P. saccharalis four days earlier, acting as a superior larval competitor. These findings shed light on the potential interspecific interactions between O. nezarae and P. saccharalis, which may determine their relative abundance and influence their compatibility in kudzu bug biological control programs.