Volume 49, Issue 1 pp. 47-55
Research Article
Full Access

Persistence of Metarhizium flavoviride and Consequences for Biological Control of Grasshoppers and Locusts

Matthew B. Thomas

Corresponding Author

Matthew B. Thomas

Leverhulme Unit for Population Biology and Biological Control, Natural Environment Research Council Centre for Population Biology, Imperial College, Silwood Park, Ascot, Berks SL5 7PY, UK

Leverhulme Unit for Population Biology and Biological Control, Natural Environment Research Council Centre for Population Biology, Imperial College, Silwood Park, Ascot, Berks SL5 7PY, UKSearch for more papers by this author
Simon N. Wood

Simon N. Wood

Leverhulme Unit for Population Biology and Biological Control, Natural Environment Research Council Centre for Population Biology, Imperial College, Silwood Park, Ascot, Berks SL5 7PY, UK

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Juergen Langewald

Juergen Langewald

IITA Plant Health Management Division Biological Control Centre for Africa, BP 08-0932, Cotonou, Benin

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Chris J. Lomer

Chris J. Lomer

IITA Plant Health Management Division Biological Control Centre for Africa, BP 08-0932, Cotonou, Benin

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Abstract

The residual infectivity of an oil formulation of the fungal entomopathogen Metarhizium flavoviride was measured during a field trial against the rice grasshopper, Hieroglyphus daganensis, in north Benin.

The pattern of infectivity was shown to decline exponentially following application, with a half-life of 6·8 days. In this environment, infections due to residual spores from the spray were identified as a key route of infection and accounted for 40–50% of the total infection measured 12 days after application.

To examine the within- and between-season consequences of such residual infection, a simple host–pathogen model was developed. The model revealed that even very small increases in residual activity could provide large increases in total mortality and that under certain conditions, residual infection was essential for effective pest control. This aspect of the activity of mycopesticides is rarely considered.

The implications of these results are discussed in the context of developing optimum spray strategies for locust and grasshopper control under different ecological conditions. © 1997 SCI.

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