Interaction of Insecticides and Fungicides in Bees

Abstract

Honeybees and wild bees are among the most important pollinators of both wild and cultivated landscapes. In recent years, however, a significant decline in these pollinators has been recorded. This decrease can have many causes including the heavy use of biocidal plant protection products in agriculture. The most frequent residues in bee products originate from fungicides, while neonicotinoids and, to a lesser extent, pyrethroids are among the most popular insecticides detected in bee products. There is abundant evidence of toxic side effects on honeybees and wild bees produced by neonicotinoids, but only few studies have investigated side effects of fungicides, because they are generally regarded as not being harmful for bees. In the field, a variety of substances are taken up by bees including mixtures of insecticides and fungicides, and their combinations can be lethal for these pollinators, depending on the specific group of insecticide or fungicide. This review discusses the different combinations of major insecticide and fungicide classes and their effects on honeybees and wild bees. Fungicides inhibiting the sterol biosynthesis pathway can strongly increase the toxicity of neonicotinoids and pyrethroids. Other fungicides, in contrast, do not appear to enhance toxicity when combined with neonicotinoid or pyrethroid insecticides. But the knowledge on possible interactions of fungicides not inhibiting the sterol biosynthesis pathway and insecticides is poor, particularly in wild bees, emphasizing the need for further studies on possible effects of insecticide-fungicide interactions in bees.

Sublethal Effects of Four Insecticides Targeting Cholinergic Neurons on Partner and Host Finding in the Parasitic Wasp Nasonia vitripennis

“…Thus, multiple ingestions of very low doses could ultimately lead to measurable sublethal effects. Insecticides are often used in multicomponent blends (Yu & Ting, 2019), and the simultaneous use of pesticides from other classes (fungicides, herbicides; Schuhmann et al, 2022) may result in exposure of parasitic wasps to multiple active substances, which may cause additive or synergistic adverse effects (Tosi et al, 2022; Wang et al, 2020; Willow et al, 2019). Guttation water from plants grown from coated seeds may contain significant amounts of insecticides (e.g., up to ~100 ng/µL thiacloprid, 150 ng/µL thiamethoxam, and up to 200 ng/µL imidacloprid; Girolami et al, 2009), although no literature data are available for the insecticides tested in the present study.…”

Chronic exposure of mosquito larvae to pesticide residues endangers a new generation of agrochemicals repurposed for malaria prevention

“…Some neonicotinoid insecticides act slowly and are also known to have a wide range of sublethal effects in addition to acute toxicity on non-target species [23,40]. Thus, beside lethal toxicity in 24 h, we used life table analysis to monitor some of the sublethal effects of neonicotinoids on Anopheles larvae, starting with L4 transformation rate.…”

Unraveling the Impact of Pesticide Exposure on Apis Honey Bees: An Investigation on Succinate Dehydrogenase Subunit A (SDHA) Inhibition Mechanisms

“…Insecticides and fungicide mixtures are among the substances that bees take up in the field and these combinations can be one of the reasons for the lethality of these pollinators. [3] Various studies show that a handful number of pesticides are the succinate dehydrogenase inhibitors. The dysfunction of the succinate dehydrogenase enzyme disrupts energy production and mitochondrial reproduction, thereby leading to death.…”

“…However, a notable decrease in these pollinators has been observed in recent years. Insecticides and fungicide mixtures are among the substances that bees take up in the field and these combinations can be one of the reasons for the lethality of these pollinators [3] . Various studies show that a handful number of pesticides are the succinate dehydrogenase inhibitors.…”