Lethal and sublethal effects of contact insecticides and horticultural oils on the hibiscus bud weevil, anthonomus testaceosquamosus linell (Coeloptera: Curculionidae)

Authors: GREENE, DANIEL - University Of Florida; Yang, Xiangbing; VELAZQUEZ-HERNANDEZ, YISELL - University Of Florida; VARGAS, GERMAN - University Of Florida; Kendra, Paul; MANNION, CATHARINE - University Of Florida; REVYNTHI, ALEXANDRA - University Of Florida

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/9/2023
Publication Date: 6/11/2023
Citation: Greene, D.A., Yang, X., Velazquez-Hernandez, Y., Vargas, G., Kendra, P.E., Mannion, C., Revynthi, A.M. 2023. Lethal and sublethal effects of contact insecticides and horticultural oils on the hibiscus bud weevil, anthonomus testaceosquamosus linell (Coeloptera: Curculionidae). Insects. 14(6):544. https://doi.org/10.3390/insects14060544.
DOI: https://doi.org/10.3390/insects14060544

Interpretive Summary: The hibiscus bud weevil (HBW), which is native to Mexico and southern Texas, was first detected in south Florida in 2017 where it has become a serious pest of ornamental hibiscus plants. HBW damages the hibiscus by feeding and ovipositing on developing flower buds, causing damage and bud drop that makes this flowering plant unsuitable for market. To develop a management program for HBW, scientists from the University of Florida (Homestead, FL) and USDA-ARS (Miami, FL) investigated the effects of 21 contact insecticides and horticultural oils on reproduction, feeding, and oviposition of HBW under both laboratory and greenhouse conditions. The results showed that insecticides including diflubenzuron, pyrethrin, spinetoram plus sulfoxaflor, and spirotetramat demonstrated efficacy against HBW as compared to the control, with significantly lower oviposition rates, fewer larvae, and feeding holes per bud on insecticide treated plants. This study identified effective control options for HBW, providing growers with useful information for developing management program for this destructive pest in South Florida.

Technical Abstract: In 2017, the hibiscus bud weevil (HBW), Anthonomus testaceosquamosus Linell (Coeloptera: Curculionidae) was found outside of its native range of Mexico and Texas infesting hibiscus plants in Miami-Dade County in Florida. Although regular insecticide applications are required in hibiscus nurseries within the state, the effects of commercially available products on the HBW have yet to be documented. Therefore, we selected 21 different insecticide and horticultural oil products to evaluate their effects on the reproductive rate and feeding and oviposition behavior of the HBW. In laboratory experiments, the estimated marginal mean (EMM) proportion of mortality in adult weevils exposed to diflubenzuron-treated hibiscus leaves and buds reached 0.87 and 0.69, respectively, and hibiscus buds treated with diflubenzuron contained the fewest number of eggs and feeding/oviposition holes. Among horticultural oil products, significant mortality was only observed in experiments in which adult weevils were directly sprayed (direct experiments). Pyrethrins and spinetoram plus sulfoxaflor reduced the oviposition rate and caused significant mortality in direct experiments. Diflubenzuron, pyrethrins, spinetoram plus sulfoxaflor, and spirotetramat were further tested via contact toxicity experiments and greenhouse experiments. Contact toxicity experiments demonstrated that the tested insecticides, with the exception of diflubenzuron, were highly toxic to HBW adults. In greenhouse experiments, only those hibiscus plants treated with pyrethrins had significantly fewer feeding/oviposition holes and larvae within their flower buds when compared to control (water-treated) plants. These results constitute an important first step in the identification of effective chemical control options for the HBW.