We investigated the direct pathogenicity of different plant-associated fungal isolates towards cotton aphid, Aphis gossypii Glover. Spores’ suspensions of one presumably non-pathogenic species of fungus originally isolated as endophytes from cotton Chaetomium globosum, as well as spores from the commercially available entomopathogen Beauveria bassiana, were diluted with sterile water to final concentrations of 1x107, 106,105, 104, 103, and 102 spores/ml. Second instar aphids were dipped in spore suspensions for 5 seconds. Controls were dipped in sterile water only. Ten aphids per treatment were placed on cotton leaf squares (2cm2) in 100 mm diameter Petri dishes on moistened filter paper and sealed with parafilm. There were three replicates per treatment. Plates were kept in an incubator with a 14L:10D photoperiod, 25 °C ± 1 °C and 60-70% RH. The number of surviving aphids was recorded daily for 14 days. We performed Kaplan-Meier survival analysis and pairwise comparisons using the Log-Rank test with FDR p-value adjustment to compare the survival probability between the treatments. Overall, we observed lower survival in cotton aphids dipped in all fungal treatments compared to the control. Effects were present at all fungal spore treatment concentrations when we combined the replicates with C. globosum strains showing a higher mycosis confirmation compared to B. bassiana. Our results indicate novel insect pathogenicity of these strains of plant-associated C. glosobosum.
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