First report on voracity and feeding preference of predatory beetle, Thalassa montezumae (Coleoptera:Coccinellidae)on croton scale, Phalacrococcus howertoni (Hemiptera: Coccidae)

Authors: FRANCIS, NETALIE - Florida A & M University; KANGA, LAMBERT - Florida A & M University; MANNION, CATHARINE - University Of Florida; HASEEB, MUHAMMAD - Florida A & M University; ANANGA, ANTHONY - Florida A & M University; Legaspi, Jesusa

Submitted to: Journal of Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/6/2022
Publication Date: 7/9/2022
Citation: Francis, N., Kanga, L.H., Mannion, C., Haseeb, M., Ananga, A., Legaspi, J.C. 2022. First report on voracity and feeding preference of predatory beetle, Thalassa montezumae (Coleoptera:Coccinellidae) on croton scale, Phalacrococcus howertoni (Hemiptera: Coccidae). Journal of Agriculture. 12(7):990. https://doi.org/10.3390/agriculture12070990.
DOI: https://doi.org/10.3390/agriculture12070990

Interpretive Summary: The green croton scale, Phalacrococcus howertoni, was first detected in the United States in Florida in 2008 on ornamental croton and designated a new species in 2010. The scale was recognized as a potential pest because of its high rate of reproduction and its production of destructive sooty mold. A predatory beetle, Thalassa montezumae was identified as a potential biological control agent against the green croton scale. Because the beetle has potential for use in an integrated pest management system, researchers from Florida A&M University, University of Florida and USDA-ARS-CMAVE in Tallahassee, FL evaluated its compatibility with foliar and drench formulations of the chemical insecticides, imidacloprid and bifenthrin. These effects were studied by exposing beetles to insecticide-treated scales (P. howertoni) and leaves. Both systemic and contact insecticides caused mortality to adult and immature stages of the predatory beetle with no difference in mortality between the imidacloprid foliar treatment and bifenthrin. However, less mortality was recorded when imidacloprid was applied systemically as a drench. The susceptibility of the predatory beetles to insecticides suggests that chemical control measures will have to be applied judiciously with this insect predator in an IPM program against the green croton scale. However differences in application method and pesticide may provide a window of compatibility of the two approaches for scale control.

Technical Abstract: The green croton scale, Phalacrococcus howertoni Hodges & Hodgson gen. nov., sp. nov. (Hemiptera: Coccidae), was first detected in the United States in Florida in 2008 on croton (Codiaeum variegatum (L.). The green croton scale was recognized as a potential pest because of its high reproductive rate and production of sooty mold. The predatory beetle, Thalassa montezumae Mulsant (Coleoptera: Coccinellidae) is being evaluated as a potential biological control agent. Because the beetle may be used in an integrated pest management system, we evaluated the survival and behavior of T. montezumae after exposure to plants (direct contact) and host scales (indirect contact) treated with foliar imidacloprid, systemic imidacloprid applied as a drench and a foliar applied pyrethroid insecticide (bifenthrin). Direct contact foliar applications of imidacloprid and bifenthrin resulted in 50% and 40% adult beetle mortality on day 1, in contrast to imidacloprid drench which caused 20% mortality after day 3. There was no mortality in untreated controls. Mortality of 2nd and 3rd instar beetles peaked on day 3 at 55% in foliar applications of bifenthrin. In experiments evaluating exposure to treated P. howertoni scales, there was no adult beetle mortality until 48 hours after exposure to foliar formulations of imidacloprid and bifenthrin. The imidacloprid drench caused 10% mortality after 24 hours. In 2nd and 3rd instar beetles, mortality was highest after 24 hours for both foliar treatments. In tests of time to death after exposure, 77% of adult beetles died in the first 24 hours and 87% of larvae died within the first 24 hours after exposure. Susceptibility to insecticides suggests that chemical control measures will have to be applied judiciously with T. montezumae in an IPM program.