Efficacy of topical application, leaf residue or soil drench of Blastopores of Isaria fumosorosea for citrus root weevil management: Laboratory and greenhouse investigations

Authors: AVERY, PASCO - UNIVERSITY OF FLORIDA; Hunter, Wayne; HALL, DAVID; JACKSON, MARK; POWELL, CHARLES - UNIVERSITY OF FLORIDA

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/11/2016
Publication Date: 11/22/2016
Citation: Avery, P.B., Hunter, W.B., Hall, D.G., Jackson, M.A., Powell, C.A. 2016. Efficacy of topical application, leaf residue or soil drench of Blastospores of Isaria fumosorosea for citrus root weevil management: Laboratory and greenhouse investigations. Insects. 7(4):E66. https://doi.org/10.3390/insects7040066.
DOI: https://doi.org/10.3390/insects7040066

Interpretive Summary: Evaluation of an entomopathogenic fungi, Isaria fumosorosea, showed significant infection and potential for use as a biological control agent against the citrus weevil, Diaprepes abbreviatus. The fungus applied topically on larvae and adults caused 13% and 19% mortality after 7 days, respectively. Infected adults fed less than untreated weevils. Treatment on leaves which were ingested by the weevils resulted in 100% mortality 35 days post-treatment compared to 33% in the control. Soil drench applications of the fungus resulted in only 2-4% larval mortality. Biological control measures using the fungus may provide an additional treatment against D. abbreviatus, particularly adults.

Technical Abstract: Different treatment applications with Isaria fumosorosea blastospore formulation (Ifr strain 3581) were assessed for efficacy in the management of the citrus weevil Diaprepes abbreviatus. Ifr when applied topically on larvae and adults at a rate of 107 blastospores/ml and incubated in original rearing cups in the dark at 25°C for 2 – 3 weeks. Larval mortality due to the infection of Ifr was assessed after 2 weeks as compared to the control. Topical spray applications caused 13% and 19% mortality in larvae and adults after 7 days, respectively. Weevil adults given a single exposure Ifr-treated leaf for 24 h consumed less than the control, and resulted in 100% mortality 35 days post-treatment compared to 33% in the control. Soil drench applications of 100 ml of Ifr spores with the addition of 1400 mL of water reached 9-11 cm below the sand surface per potted citrus seedling, resulted in only 2-4% larval mortality. Biological control measures using Ifr may provide an additional treatment against D. abbreviatus larvae and adults, although benefits from soil drenching may not significantly increase larval mortality.