Low-density Pyemotes zhonghuajia effectively controls the eggs and early instar larvae of Megabruchidius dorsalis

Abstract

Megabruchidius dorsalis (Coleoptera: Bruchinae) is an oligophagous storage pest that damages the seeds of Gleditsia L. in Asia and Europe. Pyemotes zhonghuajia Yu, Zhang & He (Acari: Pyemotidae), an endemic natural enemy of wood-boring pests, is characterized by its preference for dark environments and strong search capabilities. This study investigated the efficiency of P. zhonghuajia to parasitize M. dorsalis based on three parameters as follows: mortality rate, parasitic preference, and functional response. We found that P. zhonghuajia exhibited high mortality rates against the eggs, early instar larvae, and pupae of M. dorsalis, particularly achieving 100% mortality for eggs and 1st–2nd instar larvae within 6 h of treatment. P. zhonghuajia showed a greater inclination to parasitize 3rd–4th instar larvae and pupae of M. dorsalis. The parasitic behavior of P. zhonghuajia toward M. dorsalis eggs and 1st instar larvae conformed to a type III functional response, indicating that parasitism rate increased with host density and then decreased at higher host densities. Increased density of P. zhonghuajia negatively impacted its searching efficiency. In conclusion, P. zhonghuajia was highly efficient in parasitizing various developmental stages of M. dorsalis (especially eggs and early larvae) and could be used for biological control.