Review: The risks of spray adjuvants to honey bees

Authors: SHANNON, BRANDON - The Ohio State University; Jeon, Hongyoung; JOHNSON, REED - The Ohio State University

Submitted to: Journal of Insect Science
Publication Type: Review Article
Publication Acceptance Date: 9/27/2023
Publication Date: 12/6/2023
Citation: Shannon, B., Jeon, H., Johnson, R. 2023. Review: The risks of spray adjuvants to honey bees. Journal of Insect Science. 23(6). Article 20. https://doi.org/10.1093/jisesa/iead100.
DOI: https://doi.org/10.1093/jisesa/iead100

Interpretive Summary: Protecting honeybees and other beneficial insects from pesticide applications is important to have healthy pollinator population for agricultural production in the US. However, only active ingredients of pesticides are generally evaluated for their toxicity to honeybees and beneficial insects although spray adjuvants are commonly tank mixed with pesticides because spray adjuvants are not regulated as strict as pesticides. Therefore, the impacts of common key ingredients of spray adjuvants to honeybees and other beneficial insects are generally unknown. In this study, comprehensive literature review has been conducted to analyze their toxicities and effects to honeybees and other beneficial insects. The learning from the review was also used to provide guidelines to the regulators, manufacturers, applicators and researchers to minimize the influences of pesticide applications to honeybees and other beneficial insects.

Technical Abstract: Pesticide applications are often made as “tank mixes” of multiple pesticide products to broaden control spectrum and may include spray adjuvants to enhance pesticide activities. The adjuvant products primarily aim to increase the spreading and sticking of droplets and increase the penetration of active ingredients through the surface of leaves or targeted pests. The “principal functioning agents” that provide the desired function of adjuvants are classified by EPA as “inert ingredients.” Therefore, they do not undergo the same testing and risk assessment that is required of pesticide active ingredients and generally have no mitigation measures that prevent application onto crops during bloom at times of day when bees are foraging. Honey bees are at an increased risk of exposure to these pesticide-adjuvant tank mixtures while providing agricultural pollination services. Colony losses attributed to applications of pesticides thought to have low risk to honey bees have been reported by beekeepers providing pollination services to almonds in California, highlighting the need to focus on the toxicity of the adjuvants present in pesticide tank mixtures. This review summarizes the current literature on the risks posed to honey bees by agricultural adjuvants and tank mix combinations of adjuvants with pesticides. Based on the current state of knowledge, we make recommendations to pesticide applicators, product manufacturers, regulatory agencies, and researchers regarding adjuvant toxicity to honey bees with the goal of reducing risks that the “not so inert ingredients” in adjuvants pose to honey bees and other beneficial insects.