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Conidial discharge in the aphid pathogen Erynia neoaphidis

Published online by Cambridge University Press:  12 July 2001

Farhad HEMMATI
Affiliation:
Entomology and Nematology DepartmentIACR-Rothamsted, Harpenden, Herts AL5 2JQ, UK E-mail: judith.pell@bbsrc.ac.uk Department of Agriculture, University of Reading, Reading RG6 2AT, UK. Present address: Bureau of International Scientific Research and Communications, AREEO, PO Box 19835-111, Tabnak Avenue, Tehran, Iran.
Judith K. PELL
Affiliation:
Entomology and Nematology DepartmentIACR-Rothamsted, Harpenden, Herts AL5 2JQ, UK E-mail: judith.pell@bbsrc.ac.uk
H. Alastair McCARTNEY
Affiliation:
Plant Pathology DepartmentIACR-Rothamsted, Harpenden, Herts AL5 2JQ, UK
Suzanne J. CLARK
Affiliation:
Statistics DepartmentIACR-Rothamsted, Harpenden, Herts AL5 2JQ, UK
Michael L. DEADMAN
Affiliation:
Department of Agriculture, University of Reading, Reading RG6 2AT, UK. Present address: Department of Agronomy, Horticulture, Entomology and Plant Pathology, Sultan Qaboos University, PO Box 34, Al Khod 123, Sultanate of Oman.
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Abstract

The patterns of conidial discharge of Erynia neoaphidis were measured from three species of aphids: nettle aphid (Microlophium carnosum), grain aphid (Sitobion avenae) and pea aphid (Acyrthosiphon pisum). The effects of release height, morph of aphid and temperature on the horizontal and vertical discharge of conidia were studied. Numbers of conidia deposited in the dorsal and lateral directions were distributed with distance in truncated bell shaped patterns. Discharge distances ranged from 2 to 11 mm and half the conidia caught travelled further than 5 mm. There was little difference in the horizontal dispersal patterns of conidia when ejected from cadavers of different morphs of the same species, or from different species. The weight of infected aphids showed little correlation with discharge patterns. Values of maximum discharge distance, Dm, were generally between 6 and 9 mm. Temperature had a significant effect on conidia discharged from the dorsal surface of apterous A. pisum cadavers. Dm was greater at 18 °C than at 10 or 25 °. Vertical discharge distances for conidia released from A. pisum cadavers ranged between about 2 and 8 mm. The maximum height to which conidia were projected vertically was not affected by temperature. However, the average height tended to be greater at 18 °. Half of the conidia reached heights of about 3.5 mm while the maximum heights reached were about 8 mm. The initial speeds of conidia were estimated from measured discharge distances. The results suggest that conidia of E. neoaphidis may be ejected at speeds of about 8 ms−1.

Type
Research Article
Copyright
© The British Mycological Society 2001

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