Neonicotinoids, honeydew, and insect mortality

Researchers report a previously unexplored route of insect exposure to neonicotinoid insecticides. Neonicotinoids are among the most widely used insecticides and can harm beneficial insects that feed on contaminated nectar and pollen. Alejandro Tena and colleagues examined whether beneficial insects could also be exposed to neonicotinoids through contaminated honeydew. Honeydew is a sugar-rich substance excreted by phloem-feeding insects and an important nutrient source for many beneficial insects, such as pollinators and natural enemies of insect pests. The authors collected honeydew produced by citrus mealybugs (Planococcus citri) that fed on citrus trees treated with either water or the neonicotinoids thiamethoxam and imidacloprid, applied either via the soil or as a foliar spray. The honeydew was fed to two beneficial insect species: a hoverfly (Sphaerophoria rueppellii) and a parasitic wasp (Anagyrus pseudococci). A majority of hoverflies and wasps that fed on mealybug-produced honeydew from thiamethoxam-treated trees died within 3 days, as did approximately half of the hoverflies that fed on honeydew from foliar imidacloprid-treated trees, compared with 6-15% of beneficial insects fed on control honeydew. Honeydew from a significant fraction of insecticide-treated trees contained detectable levels of neonicotinoids. No neonicotinoids were detected in honeydew from control trees. The results suggest that beneficial insects could be exposed to neonicotinoids via contaminated honeydew, which is likely to affect a wider range of insects than contaminated nectar, according to the authors.

Article #19-04298: "Neonicotinoids in excretion product of phloem-feeding insects kill beneficial insects," by Miguel Calvo-Agudo et al.

MEDIA CONTACT: Alejandro Tena, Instituto Valenciano de Investigaciones Agrarias, Valencia, SPAIN; tel: +34-96-342-41-51; e-mail: atena@ivia.es

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