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United States Department of Agriculture

Agricultural Research Service

Title: Soil -- a Natural Source of Entomophthoralean Fungi Infecting Aphids

Authors
item Nielsen, Charlotte - UNIVERSITY OF COPENHAGEN
item Hajek, Ann - CORNELL UNIVERSITY
item Humber, Richard
item Eilenberg, Jorgen - UNIVERSITY OF COPENHAGEN

Submitted to: International Organization for Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 8, 1999
Publication Date: N/A

Interpretive Summary: Fungal pathogens of insects must have means available to survive periods when their hosts are not present in the environment. Nearly all insect-pathogenic fungi in the order Entomophthorales survive these periods as thick-walled resting spores but a few fungi in this group (including some species such as PANDORA NEOAPHIDIS, a globally distributed, very important pathogen of aphids) cannot form such resting spores. This study confirmed that this fungus and other aphid pathogens in the Entomophthorales may survive winter in the soil in special forms such as the 'normal' spores of the fungus with highly thickened walls rather than as the resting spores that are more typical of these fungi. This finding provides methods to test for the presence in soil of fungal inoculum that can survive the winter (or other host-free periods) and suggests forms of the fungus to be looked for in soil in which the fungus might survive.

Technical Abstract: The aim of the project was to investigate whether soil is a natural source of inoculum of entomophthoralean fungi infecting aphids, particularly with reference to winter survival of PANDORA NEOAPHIDIS (= ERYNIA NEOAPHIDIS). Soil was sampled during spring 1997 from different ecosystems including organically grown fields and underneath birdcherry, the winter host for the ebirdcherry aphid, RHOPALOSIPHUM PADI. It was documented that inoculum of P NEOAPHIDIS, CONIDIOBOLUS OBSCURUS, CONIDIOBOLUS sp., and BASIDIOBOLUS sp. was present in the soil, since grain aphids (SITOBION AVENAE) got infected with these species after 18 hours of contact with the soil. Additional laboratory studies indicate so far that the winter survival structure for P. NEOAPHIDIS may be thick-walled conidia.

Last Modified: 10/23/2014
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