Within‑host competition between Cotesia flavipes and Heterorhabditis bacteriophora in Diatraea saccharalis

Abstract

The larval parasitoid Cotesia flavipes (Cameron, 1891) (Hymenoptera: Braconidae) has been widely used for biological control of the sugarcane borer Diatraea saccharalis (Fabricius, 1974) (Lepidoptera: Crambidae) in Brazil. The entomopathogenic nematode (EPN) Heterorhabditis bacteriophora Poinar, 1976 (Rhabditida: Heterorhabditidae) also has shown to be a promising agent for controlling the pest. However, in some cases, EPNs can negatively affect non-target organisms, such as parasitoids. Thus, this work evaluated the within-host interaction between C. flavipes and H. bacteriophora. Caterpillars of D. saccharalis were offered to adult females of C. flavipes for parasitism and then inoculated with H. bacteriophora in intervals of three days until the 12th day. After death, caterpillars were kept for four days and dissected to verify the agent that caused death. We observed an intraguild competition between both control agents. When the EPN was applied until the 12th day after parasitism, it developed and killed the parasitoid, even colonizing its larvae and pupae inside the caterpillar body. On the other hand, when the EPN was applied after 12 days from the parasitism, the parasitoid could develop, but not the EPN. We could conclude that the parasitoid C. flavipes and the EPN H. bacteriophora are not compatible for controlling D. saccharalis. If combined in a single control strategy, it must be considered a safe interval of more than 12 days between applications of each of them.