DEVELOPMENT OF METARHIZIUM SPP. FOR THE CONTROL OF GRASSHOPPERS AND LOCUSTS

Four research programmes are investigating the entomopathogenic fungal genera Metarhizium and Beauveria for locust and grasshopper control i n Africa. In the LUBILOSA programme, surveys for pathogen isolates rev ealed a morphologically distinctive Metarhizium flavoviride Gams and R ozsypal attacking acridoids in West Africa, Madagascar, and elsewhere. Metarhizium anisopliae (Metschnikoff) Sorokin isolates with virulence to acridoids were also obtained, including several from non-orthopter an hosts. Natural epizootics of both genera are rare in acridoid popul ations, but do occur. A standardized screening method discriminated vi rulent from non-virulent isolates. The great majority of the most viru lent isolates were from the acridoid group of M. flavoviride. A Niger isolate chosen for development from this group had low Virulence to ho ney bees and parasitic Hymenoptera and was not infective to insects in several other orders. Field tests were carried out on formulations of oil mixtures, using ULV application rates of 1-2 L/ha and 2-5 x 10(12 ) conidia per hectare. In preliminary tests, target insects were spray ed successfully in small field arenas and in large cages. Trials in 19 93 on variegated grasshopper gave an approx. 90% reduction in field po pulations after 15 days. Trials on various acridids, predominantly Hie roglyphus daganensis Krauss, in dense grass in northern Benin showed s lower mortality, although up to 70% population reduction was achieved. Trials using a vehicle-mounted ULV sprayer (the Ulva-Mast) in open gr assland in Niger gave >90% mortality in samples of mixed acridids. In Mall, a Malian isolate of M. flavoviride was shown to be slightly more virulent than the standard Niger isolate; both isolates gave signific ant population reductions against nymphs of Oedaleus sengalensis Kraus s and Kraussella amabile (Krauss) in 1-ha plots. Successful small-scal e field trials have also been carried out using the standard M. flavov iride isolate in South Africa against brown locust and in Australia us ing an Australian isolate against wingless grasshopper. In Mauritania, a trial using the Niger isolate against desert locust nymph bands gav e up to 90% mortality in caged samples by day 9 after spraying. The un caged treated bands were completely destroyed by predators while untre ated bands fledged. Oil-based ULV formulations of M. flavoviride are c apable of causing high mortality in the field populations of all acrid oids against which they have been field tested and show great promise for development as components of IPM strategies for these pests.