Infection of sentinel cotton aphids (Homoptera: Aphididae) by aerial conidia of Neozygites fresenii (Entomophthorales: Neozygitaceae)

Uninfected adult Aphis gossypii (Homoptera: Aphididae) apterae (sentinel aphids) on cotton leaves were exposed for 8 h to the air over a commercial cotton field in Louisiana during the night of 1-2 July 1995. At 0015 h there were 90,437 primary conidia/m3 air of the fungus Neozygites fresenii (Entomophthorales: Neozygitaceae) at the midfield position as determined from Rotorod samples. Forty-eight percent (n = 106) of the sentinel aphids exposed for 8 h at midfield were infected by aerial conidia of N. fresenii. Exposure of sentinel aphids outside the cotton field, at 10 and 100 m downwind and 10 m upwind, resulted in 34.8% (n = 131), 24.0% (n = 129), and 17.4% (n = 146) infected aphids, respectively. These data demonstrate that wind-dispersed aerial conidia of N. fresenii are infective and rapidly and efficiently disperse the pathogen throughout aphid populations within and between fields.