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Document Type

Peer-Review Article

Abstract

Laboratory bioassays were conducted to assess the virulence of two entomopathogenic fungi, Beauveria bassiana, and Metarhizium anisopliae to 5th instars of the banded sunflower moth, Cochylis hospes,(Lepidoptera: Cochylidae). Temperature conditions of 20 and 25°C and high humidity, (near saturation) were nearly optimal for development of both fungi. Concentrations of 10(7) to 10(8) conidia/ml produced 100% mortality in 10 days or less and 106 conidia/ml produced 90% mortality at 21 to 26 days. Median lethal concentrations of conidia (LC50) from M. anisopliae were 3.6 x 103 at 25°C and 4.1 x 103 at 20°C. The LC50 for B. bassiana was 14.9 x 104 conidia/ml at 20°C and 6.7 x 103 conidia/ml at 25°C. Although B. bassiana tended to be less virulent at 20°C, these differences were not significant. The high humidities required for germination and growth may reduce the usefulness of these fungi as con­trol agents of C. hospes in the northern Great Plains. Further studies and field evaluations are needed to determine if there are microhabitats in the soil or on the sunflower head where the humidity is high enough for germination and growth of B. bassiana or M. anisopliae. Targeting of C. hospes stages in the soil to avoid contaminating the seed or oil with saprophytic fungal spores may be preferred to targeting the sunflower plant for reasons of preserving seed quality, marketing, and consumption.

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Entomology Commons

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