Effects of chronic dietary thiamethoxam and prothioconazole exposure onApis melliferaworker adults and brood

Abstract

BACKGROUND Chronic exposure of honey bees (Apis mellifera Linnaeus) to the neonicotinoid thiamethoxam and the fungicide prothioconazole is common during foraging in agricultural landscapes. We evaluated the survival and hypopharyngeal gland development of adult worker honey bees, and the survival of the worker brood when chronically exposed to thiamethoxam or thiamethoxam and prothioconazole in combination. RESULTS We found that 30 days of exposure to 40 μg kg–1 of thiamethoxam significantly (P < 0.001) increased the frequency of death in worker adults by four times relative to solvent control. The worker brood required 23 times higher doses of thiamethoxam (1 mg L–1 or 909 μg kg–1) before a significant (P = 0.04), 3.9 times increase in frequency of death was observed relative to solvent control. No additive effects of simultaneous exposure of worker adults or brood to thiamethoxam and prothioconazole were observed. At day 8 and day 12, the hypopharyngeal gland acinar diameter was not significantly different (P > 0.05) between controls and adult workers exposed to thiamethoxam and/or prothioconazole. CONCLUSION These results indicate that chronic exposure to field‐realistic doses of thiamethoxam and/or prothioconazole are unlikely to affect the survival of adult workers and brood. © 2019 Society of Chemical Industry

Chronic High-Dose Neonicotinoid Exposure Decreases Overwinter Survival of Apis mellifera L.

“…Compared to the literature on chronic laboratory neonicotinoid exposure of summer workers, our study demonstrates that winter workers are more sensitive to THI under conditions of chronic exposure in the laboratory. In our study, significant decreases in winter worker survival were observed after chronic exposure to 5, 10, and 20 ng/g of THI, while, in our previous work [37], we found no significant effect of chronic 10 and 20 ng/g of THI exposure on summer worker survival. Similarly, Overmyer et al (2018) [20] found no effect of chronic, 117 ng/g of THI exposure on summer adult worker survival, while, in our study, chronic, 100 ng/g of THI exposure resulted in over 70% decreases in survival time of winter workers compared to controls (Table S2).…”

In Vitro Effects of Pesticides on European Foulbrood in Honeybee Larvae

“…The THI concentrations selected (Table 2) were based on previously tested THI concentrations which did not significantly impact larval survival [16], and the total dose of THI provided in the diet represented 84.2-842 times the calculated, worst-case, field-relevant exposure of a worker larva to THI (1.9 ng), which was calculated based on estimated worker larval consumption of 5.4 mg pollen and 180 mg nectar during development [47], and reported maximal environmental concentrations of THI in pollen (86 ng/g) and nectar (13.3 ng/g) [21]. Thus, the concentrations of THI tested were not intended to be field-realistic; but instead, high concentrations with the potential for observable, sublethal effects.…”

“…Increased numbers of pesticide residues in wax, particularly fungicides, which inhibit sterol biosynthesis [15], have been significantly associated with colony mortality [13]. There is also a concern for the negative effects of chronic, in-hive pesticide exposure on the developing worker brood [16], although the transfer of pesticides from pollen and honey to royal jelly is considered to be low, ranging from 0.001%-0.016% [17].…”

Within‐Body Distributions and Feeding Effects of the Neonicotinoid Insecticide Clothianidin in Bumblebees (Bombus terrestris)

“…Mortality among Bombus and non‐ Bombus bee species due to chronic neonicotinoid exposure is found at concentrations starting from 20 μg/kg and higher (Alkassab and Kirchner 2016; Wood et al 2020). Lower and field‐realistic concentrations, which often do not lead to increased mortality, lead to sublethal responses like impaired learning and memory (Stanley et al 2015; Phelps et al 2018), and reduced consumption of food (Laycock et al 2012; Cresswell et al 2014; Thompson et al 2015).…”