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The germination of oil-formulated conidia of the insect pathogen, Metarhizium anisopliae

Published online by Cambridge University Press:  01 July 1999

L. IBRAHIM
Affiliation:
IACR-Rothamsted, Harpenden, Herts, AL5 2JQ, U.K.
A. BECKETT
Affiliation:
School of Biological Sciences, University of Bristol, Woodland Road, Bristol BS8 1UG, U.K.
S. J. CLARK
Affiliation:
IACR-Rothamsted, Harpenden, Herts, AL5 2JQ, U.K.
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Abstract

Conidia of Metarhizium anisopliae need water activity (Aw)>0·98 for germination irrespective of whether they are formulated in an aqueous or oil carrier. The presence of nutrients in the carriers or culture medium accelerated germination but did not increase the range of Aw (or humidities) over which conidia could germinate. Insect extract stimulated more conidia to germinate than yeast extract. Oils appeared to extract fungistatic and stimulatory compounds from the insect cuticle. The ratio of these compounds depends on both the insect species and the carrier. Conidia of M. anisopliae formulated in oils were observed with SEM to flow over the surface of insect and plant cuticles. The conidia were probably deposited at sites which are conducive for germination and infection and consequently increased the overall mortality of insects. In contrast, aqueous formulations of conidia remain as drops on the leaf surface immediately after application with a pipetteman or sprayer.

Type
Research Article
Copyright
© The British Mycological Society 1999

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