Evaluation of Allorhogas pyralophagus Marsh (Hymenoptera: Braconidae) for the biological control of Diatraea spp. (Lepidoptera: Pyralidae) in sugar-cane in Guyana

In 1989, a mass production and field release programme of Allorhogas pyralophagus Marsh (Hymenoptera: Braconidae) for the control of the Diatraea spp., particularly D. centrella (Moschler) (Lepidoptera: Pyralidae) in sugar-cane, was initiated by the Guyana Sugar Corporation. The programme was terminated in 1995 after the release of approximately two million adult parasites resulted in a mean field parasitism in Diatraea spp. larvae of only 0.22%. In contrast, 62% of Diatraea spp. larvae were parasitised in vitro as were 32% of larvae in young cane shoots exposed to A. pyralophagus in the laboratory. Neither Diatraea larvae in young cane plants caged in the field nor those recovered from Echinochloa polystachya (Kunth) Hitchc. and Paspalum virgatum L. around release fields showed any parasitism by A. pyralophagus. The reasons for the low rate of host acquisition outside the laboratory are not known, but it is clear that A. pyralophagus offers little prospect for significant control of Diatraea spp., particularly D. centrella in sugar-cane in Guyana. (C) 1997 Elsevier Science Ltd.