Risk and toxicity assessment of a potential natural insecticide, methyl benzoate, in honey bees (Apis mellifera L.)

Authors: Zhu, Yu Cheng; WANG, YANHUA - Zhejiang Academy Of Agricultural Sciences; Portilla, Maribel; Parys, Katherine; LI, WENHONG - Guizhou Academy Of Agricultural Sciences

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/27/2019
Publication Date: 11/1/2019
Citation: Zhu, Y., Wang, Y., Portilla, M., Parys, K.A., Li, W. 2019. Risk and toxicity assessment of a potential natural insecticide, methyl benzoate, in honey bees (Apis mellifera L.). Insects. 10:382. https://doi.org/10.3390/insects10110382.
DOI: https://doi.org/10.3390/insects10110382

Interpretive Summary: Methyl benzoate (MB) is a component of bee semiochemicals for communication. Recent discovery of insecticidal activity of MB against insect pests provides a potential alternative to chemical insecticides. The aim of this study was to examine any potential adverse impact of MB on honey bees. By using two different methods, a spray for contact and feeding for stomach toxicity, LC50s were 236,610 and 824,990 mg per liter, respectively 2,002-fold and 173,163-fold lower contact toxicity than imidacloprid and abamectin. Piperonyl butoxide (PBO, inhibiting P450 oxidases [P450]) significantly synergized MB toxicity in honey bees, indicating P450s are the major MB-detoxification enzymes for bees. Assessing additive/synergistic interactions indicated that MB aggravated the toxicity of all four insecticides (representing four different classes) in honey bees. Another adverse effect of MB in honey bees was the significant decrease of orientation and flight ability by approximately 53%. Other influences of MB included minor decrease of sucrose consumption, minor increase of P450 enzymatic activity, and little to no effect on esterase and glutathione S-transferase (GST) activities. By providing data from multiple experiments, we have substantially better understanding how important the P450s are in detoxifying MB in honey bees. MB could adversely affect feeding and flight in honey bees, and may interact with many conventional insecticides to aggravate toxicity to bees. However, MB is a relatively safe chemical to bees. Proper formulation and optimizing proportion of MB in mixtures may be achievable to enhance efficacy against pests and minimize adverse impact of MB on honey bees.

Technical Abstract: Methyl benzoate (MB) is a component of bee semiochemicals. Recent discovery of insecticidal activity of MB against insect pests provides a potential alternative to chemical insecticides. The aim of this study was to examine any potential adverse impact of MB on honey bees. By using two different methods, a spray for contact and feeding for stomach toxicity, LC50s were 236,610 and 824,990 mg a.i. L-1, respectively 2,002-fold and 173,163-fold lower contact toxicity than imidacloprid and abamectin. Piperonyl butoxide (PBO, inhibiting P450 oxidases [P450]) significantly synergized MB toxicity in honey bees, indicating P450s are the major MB-detoxification enzymes for bees. Assessing additive/synergistic interactions indicated that MB aggravated the toxicity of all four insecticides (representing four different classes) in honey bees. Another adverse effect of MB in honey bees was the significant decrease of orientation and flight ability by approximately 53%. Other influences of MB included minor decrease of sucrose consumption, minor increase of P450 enzymatic activity, and little to no effect on esterase and glutathione S-transferase (GST) activities. By providing data from multiple experiments, we have substantially better understanding how important the P450s are in detoxifying MB in honey bees. MB could adversely affect feeding and flight in honey bees, and may interact with many conventional insecticides to aggravate toxicity to bees. However, MB is a relatively safe chemical to bees. Proper formulation and optimizing proportion of MB in mixtures may be achievable to enhance efficacy against pests and minimize adverse impact of MB on honey bees.