Field evaluation of two entomopathogenic fungi; Beauveria bassiana and Metarhizium anisopliae as a biocontrol agent against the spiny bollworm, Earias insulana Boisduval (Lepidoptera: Noctuidae) on cotton plants

Abstract

Abstract Background The Earias spp. are devastating pests which reduce cotton yield up to 40% as seed cotton. Efficacy of Metarhizium anisopliae and Beauveria bassiana as bio-insecticides were investigated against the spiny bollworm, Earias insulana Boisduval (Lepidoptera: Noctuidae), under field conditions in Egypt throughout two successive seasons 2018 and 2019. Results Results showed E. insulana population reduction during both seasons after bio-insecticidal applications. M. anisopliae strains (S1, S2) treatments showed significant reductions in the mean numbers of infested bolls with E. insulana after 14 days from the 1st spray. Reduction percentages of E. insulana infestation reached to 77.74 and 76.51% respectively, after application of M. anisopliae strains (S1, S2) treatments; then, the infestation reduction percentages increased to 88.48 and 85.41% after the 2nd spray by the same fungal strains; then, the infestation reduction percentages increased to 90.16 and 90.84% after 3rd spray of the same fungal strains in season 2018. In 2019 season, the infestation reduction percentages of E. insulana was 85.48 and 80.75%, after the 1st spray of M. anisopliae strains (S1, S2), respectively, which increased to 92.40 and 89.87%, after 14 days from the 2nd spray by the two fungal strains respectively, and then increased to 94.12 and 93.73%, after 14 days from the 3rd spray of M. anisopliae (S1 and S2) respectively. In season 2018, the infestation reduction percentage of E. insulana by B. bassiana strains (S1, S2) recorded 73.09 and 71.89%, respectively and 81.04 and 82.89% respectively, in season 2019, after 14 days of the 1st spray. While after the 2nd spray of the two tested B. bassiana strains, the infestation reduction percentage of E. insulana was 85.41 and 85.41% respectively, in season 2018, whereas it was 89.16 and 89.16% respectively, in season 2019. Then after 14 days of the 3rd spray by the same fungus strains, the reduction percentage of E. insulana increased to 86.56 and 85.35%, respectively, in season 2018, and 90.83 and 90.83% in season 2019. Conclusions Tested strains of B. bassiana and M. anisopliae fungi proved their potential for decreasing E. insulana infestation percentages through 2–3 spray treatments under field conditions.

Keywords

• Earias insulana
• Biopesticides
• Metarhizium anisopliae
• Beauveria bassiana
• Field application
• Cotton