Parasitism Behavior of Tetrastichus howardi (Hymenoptera: Eulophidae) on Larvae and Pupae of Sugarcane Borers

Abstract

Control of the sugarcane borers, Diatraea saccharalis and Diatraea impersonatella (= D. flavipennella) (Lepidoptera: Crambidae), in Brazil, is based on mass release of the larval parasitoid Cotesia flavipes (Hymenoptera: Braconidae). However, this method does not prevent some pupae of these borers from completing development and recolonizing the crop. Thus, additional control is required. This study investigated the parasitoid Tetrastichus howardi (Hymenoptera: Eulophidae) to control pupae of sugarcane borers, especially D. impersonatella. Regardless of larval instar and species, no larval parasitism occurred within 24 h of exposure. Nevertheless, a longer exposure period (ca. 96 h) resulted in parasitism of older larvae. Approximately 90% of pupae of both borers were parasitized by T. howardi within 24 h of exposure, and the parasitoid produced a similar number of offspring with >90% females. The developmental time of T. howardi parasitizing D. impersonatella pupae was delayed ~2 days from that of in D. saccharalis. No-choice trails revealed that parasitoid females took longer to start probing larvae compared to pupae. Likewise, when larvae and pupae were offered simultaneously (choice test), the latter represented the first choice of about 92% T. howardi females. The elapsed time to first attack was less on pupae than on larvae, whereas the number of attacks and probing time was greater on pupae. In addition, parasitism on D. impersonatella pupae was higher than on larvae feeding on artificially infested sugarcane seedlings. These results suggest that T. howardi prefers to parasitize the pupal stage and has the potential to be used as a biological control agent to complement the control of sugarcane bores.