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Detecting the titer in forest soils of spores of the gypsy moth (Lepidoptera: Lymantriidae) fungal pathogen, Entomophaga maimaiga (Zygomycetes: Entomophthorales)

Published online by Cambridge University Press:  31 May 2012

Ronald M. Weseloh  and
Theodore G. Andreadis
Ronald M. Weseloh*
Affiliation:
Department of Entomology, Connecticut Agricultural Experiment Station, 123 Huntington Street, New Haven, Connecticut, United States 06511
Theodore G. Andreadis
Affiliation:
Department of Soils and Water, Connecticut Agricultural Experiment Station, 123 Huntington Street, New Haven, Connecticut, United States 06511
*
1Corresponding author (e-mail: Ronald.Weseloh@po.state.ct.us).
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Abstract

Bioassays and direct counts were used to assess the abundance of resting spores of the gypsy moth, Lymantria dispar (L.), fungal pathogen, Entomophaga maimaiga Humber, Shimazu and Soper in forest soils. Resting spores in soil collected in October, January, and March and held under refrigeration germinated as readily as spores collected in April, but those collected in April germinated faster. Bioassays of resting spores in soils from different sites in Connecticut were directly related to results obtained from physically counting spores in the soil, and weakly correlated with a previously developed forest-based bioassay. The number of resting spores in a site was inversely related to the number of years since the site had last been defoliated by the gypsy moth, resulting in an implied maximum viability of resting spores of about 10 years. This maximum longevity was similar to a direct measure of long-term resting-spore viability. The study implies that resting-spore load in the soil may be an important determinant of the ability of the pathogen to control the gypsy moth.

Résumé

Des tests et des dénombrements directs ont permis d’estimer l’abondance des spores de réserve du champignon Entomophaga maimaiga Humber, Shimazu et Soper, un pathogène de la Spongieuse Lymantria dispar (L.), dans des sols forestiers. Les spores de réserve récoltées en octobre, janvier et mars et réfrigérées ont germé aussi facilement que les spores récoltées en avril, mais la germination était plus rapide chez ces derniers. Des tests biologiques sur les spores de réserve de plusieurs sites du Connecticut étaient fortement reliés aux résultats de dénombrements directs des sols et en corrélation faible avec un test antérieur à l’échelle de la forêt. Le nombre de spores de réserve à un site était inversement proportionnel au nombre d’années écoulé depuis la dernière défoliation par la Spongieuse, ce qui semble devoir établir implicitement à approximativement 10 ans la viabilité maximale des spores de réserve. Cette estimation de la longévité maximale correspond à la valeur obtenue par mesure directe de la viabilité à long terme des spores de réserve. Les résultats indiquent que la quantité de spores de réserve contenue dans le sol peut être un facteur déterminant important de l’efficacité du pathogène dans la lutte contre la Spongieuse.

[Traduit par la Rédaction]

Type
Articles
Information
The Canadian Entomologist , Volume 134 , Issue 2 , April 2002 , pp. 269 - 279
Copyright
Copyright © Entomological Society of Canada 2002

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