18
Jun
Registered Pesticides Toxic to Honey Bee Larvae, Study Finds
(Beyond Pesticides, June 18, 2026) In a study comparing pesticide active ingredients (isolated single chemicals) with full pesticide product formulations containing added ingredients (the packaged products that can contain carriers, sticking agents, emulsifiers, etc.), researchers find the full formulation to be generally more toxic. The research evaluates acute and chronic exposures of four mosquito adulticide active ingredients (AIs), three product formulations, and one biological larvicide pesticide formulation containing Bacillus thuringiensis israelensis (Bti) on honey bee larvae in vitro and finds that three of the four exceed levels of concern (LOCs) set by the U.S. Environmental Protection Agency (EPA). EPA publishes Guidance for Assessing Pesticide Risks to Bees in which it identifies levels of harm. The scientists who conducted the study, published in Environmental Challenges, are based at the University of Florida and Auburn University. This study references Bti (Vectobac12AS) as the least toxic product, since the acute LD50 (lethal dose that kills 50% of the test population) is well below EPA-set LOCs. However, the study only focused on whether Bti harms honey bees. In contrast, there are some indications of its potential adverse effects on other beneficial insects, moths, and butterflies (see fact sheet here) and aquatic life, including studies […]
