Laboratory evaluation of the pathogenicity of Beauveria bassiana and Metarhizium anisopliae to larvae of the banded sunflower moth, Cochylis hospes (Lepidoptera : Cochylidae).

Laboratory bioassays were conducted to assess the virulence of two entomopa thogenic fungi, Beauveria bassiana, and Metarhizium anisopliae to 5th insta rs of the banded sunflower moth, Cochylis hospes, (Lepidoptera: Cochylidae) . Temperature conditions of 20 and 25 degrees C and high humidity, (near sa turation) 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 an d 10(6) conidia/ml produced 90% mortality at 21 to 26 days. Median lethal c oncentrations of conidia (LC50) from M, anisopliae were 3.6 x 10(3) at 25 d egrees C and 4.1 x 10(3) at 20 degrees C. The LC50 for B. bassiana was 14.9 x 10(4) conidia/ml at 20 degrees C and 6.7 x 10(3) conidia/ml at 25 degree s C. Although B. bassiana tended to be less virulent at 20 degrees C, these differences were not significant. The high humidities required for germina tion and growth may reduce the usefulness of these fungi as control agents of C. hospes in the northern Great Plains. Further studies and field evalua tions 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 gr owth 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.