Growers follow the label: An analysis of bee-toxic pesticide use in almond orchards during bloom

Abstract

California almond orchards are most U.S. beekeepers' first stop on their pollination and honey production circuit, so the agrochemicals bees are exposed to in almonds can shape the vitality of their colony for the rest of the year. We explored the potential for honey bee exposure to bee-toxic agrochemicals during almond bloom by utilizing the California Department of Pesticide Regulations' Pesticide Use Report database from 1990 to 2016. We found that overall, growers are observing the pesticide labels and reducing their use of labeled bee-toxic pesticides during almond bloom. However, we also found that insect growth regulators, fungicides and organosilicone surfactants — agrochemicals often not labeled as toxic to bees — are commonly applied during almond bloom. These agrochemicals can be sublethally or synergistically toxic to adult honey bees and bee larvae, presenting potential harm to colonies during almond pollination. Our findings demonstrate the need for a shift in the U.S. Environmental Protection Agency's labeling requirements, as well as continued communication between almond growers, pesticide applicators and beekeepers to keep colonies at a low risk of bee-toxic agrochemical exposure.

Inert agricultural spray adjuvants may increase the adverse effects of selected insecticides on honey bees (Apis mellifera L.) under laboratory conditions

“…Agricultural spray adjuvants improve the ability of PPP to spread or better adhere to the leaves of the crop or the surface of the target insect. These adjuvants are currently not regulated in Europe, the United States, or Canada (Durant et al 2021). That is, they can be mixed with any insecticide class without prior risk assessment.…”

A selected organosilicone spray adjuvant does not enhance lethal effects of a pyrethroid and carbamate insecticide on honey bees

“…At present (January 2023), 278 adjuvants are approved for field use in Germany ( BVL, 2023b ), allowing for countless possible mixing combinations with PPP. They are often used as mixing partners in weed control ( BVL, 2023b ), but can also be combined with insecticides ( Ciarlo et al, 2012 ) and applied to bee-attractive crops ( Durant et al, 2021 ). Unlike PPP, such as insecticides or fungicides, adjuvants do not contain active substances and therefore are subject to less strict testing requirements ( EPRS (European Parliamentary Research Service), 2018 ).…”

Toxicity of spray adjuvants and tank mix combinations used in almond orchards to adult honey bees (Apis mellifera)

“…Almond growers often apply a variety of agrochemicals during bloom to which honey bees may be exposed ( State of California – California Pesticide Information Portal 2023 ). These applications may contain multiple agrochemicals combined into a “tank mix” and usually include a fungicide, sometimes include an insecticide, and often include one or more spray adjuvants that are intended to improve spray performance ( Mullin et al 2015 , Durant et al 2020 ). Insecticides applied to almonds during bloom ( Fig.…”