EVALUATION OF ALLORHOGAS-PYRALOPHAGUS MARSH (HYMENOPTERA, BRACONIDAE)FOR THE BIOLOGICAL-CONTROL OF DIATRAEA SPP. (LEPIDOPTERA, PYRALIDAE) IN SUGARCANE IN GUYANA

In 1989, a mass production and field release programme of Allorhogas p yralophagus Marsh (Hymenoptera: Braconidae) for the control of the Dia traea spp., particularly D. centrella (Moschler) (Lepidoptera: Pyralid ae) in sugar-cane, was initiated by the Guyana Sugar Corporation. The programme was terminated in 1995 after the release of approximately tw o million adult parasites resulted in a mean field parasitism in Diatr aea spp. larvae of only 0.22%. In contrast, 62% of Diatraea spp. larva e 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 Echi nochloa polystachya (Kunth) Hitchc. and Paspalum virgatum L. around re lease 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 sign ificant control of Diatraea spp., particularly D. centrella in sugar-c ane in Guyana. (C) 1997 Elsevier Science Ltd.