Field Infection of Zonocerus variegatus following application of an oil‐based formulation of Metarhizium flavoviride conidia

Conidia of Metarhizium flavoviride grown in diphasic culture with sporulation on rice, were extracted in kerosene and formulated with peanut oil. The formulation led to high mortality when applied to field populations of Zonocerus variegatus; between 70 and 95% of insects in samples collected from the field 0, 3 or 7 days after spraying died. Sporulation of M. flavoviride was observed in 70–80% of the dead‐treated insects, which compares favourably with results obtained in laboratory bioassays. Many dead Z. variegatus, some with internal sporulation, were found in shaded niches and oviposition sites in the treated plots. No sporulation was observed in samples collected prior to application, and both sporulation and mortality differed significantly between control and treated plots. Some infections were observed in insects collected 16 and 23 days after treatment; these late infections may be a consequence of contact with spores surviving in the environment.     

Effet de l'application d'un mélange lambda-cyhalothrin (pesticide chimique) et de spores de Metarhizium anisopliae (flavoviride) var. acridum Driver and Milner (biopesticide) appliqué sur les larves de sauteriaux au Mali

A mixture of lambda-cyhalothrin (lambda-cyhalothrin: chemical insecticide) and Metarhizium anisopliae ( flavoviride ) var. acridum Driver and Milner, an entomopathogenic fungus (bioinsecticide) was used for grasshopper control in Mali. An oil-based formulation of Metarhizium anisopliae ( flavoviride ) var. acridum Driver and Milner has been developed by LUBILOSA a collaborative project for locust and grasshoppers control. It takes 6 to 10 days for the biopesticide to kill the hosts, which is not a problem for larvae in fallows because they will die before reaching the farmers' fields. However, if crops are infested by adults, the farmers can not wait for 6 to 10 days. An experiment was conducted in Mali using a mixture of a biopesticide and chemical pesticide. The mixture of lambda-cyhalothrin (chemical insecticide) and Metarhizium anisopliae ( flavoviride ) var. acridum (biopesticide: oil-based entomopathogenic fungus spore suspension) was applied to nymphs of Sahelian grasshoppers, using ultra low volume (ULV) sprayers. Both the mixture and lambda-cyhalothrin alone gave quick mortality, with slightly higher mortality for the mixture. Mortality due to the Metarhizium treatments began 2 days after application and subsequently reached similar levels of mortality to the lambda-cyhalothrin mixture treatments. The efficacy of the mixture was greater than Metarhizium alone. The efficacy of lambda-cyhalothrin reached 80% on the day following application, but declined after 10 days, due probably to immigration of untreated grasshoppers.