Neonicotinoids and other systemic insecticides can contaminate honeydew, which is an important food source for beneficial insects in the agroecosystems, according to an international team of researchers.
John Tooker, professor of entomology in Penn State's College of Agricultural Sciences, was part of the multidisciplinary team that conducted a review of the scientific literature, concluding that systemic insecticides in honeydew are a serious concern, particularly in large-acreage crops that commonly are treated with these products.
Honeydew is the excretion product of sap-sucking insects such as aphids, mealybugs, whiteflies, and psyllids, Tooker explained.
“This rich carbohydrate source is a common food for many beneficial insects, including pollinators, such as bees and flies, and some natural enemies of pests, such as ants, wasps, and beetles,” he said. “Honeydew often is more abundant than nectar in agroecosystems.”
In their review, the researchers cited a 2019 study published in the Proceedings of the National Academy of Sciences by some of the co-authors, who found that honeydew represents a novel route of exposure to neonicotinoids, the most widely used group of systemic insecticides in the world. These insecticides often are applied in the form of seed coatings, and as a plant germinates and grows, the insecticide in its sap kills pest insects that feed on it.