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Title: Larval pollen stress increases adult susceptibility to clothianidin in honey bees

item MOGREN, CHRISTINA - Louisiana State University Agcenter
item Danka, Robert
item HEALY, KRISTEN - Louisiana State University Agcenter

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/23/2018
Publication Date: 1/8/2019
Citation: Mogren, C.L., Danka, R.G., Healy, K.B. 2019. Larval pollen stress increases adult susceptibility to clothianidin in honey bees. Insects. 01-10. https://10.3390/insects10010021.

Interpretive Summary: Honey bees face a variety of factors that threaten their health and survival. Two major environmental influences that potentially impact bee health are inadequate availability of food and exposure to insecticides. We tested how larval bees that are stressed by a lack of pollen (the source of all protein for bees) respond during adulthood when they are exposed to a neonicitinoid insecticide. In laboratory tests, pollen-deprived bees had poorer survival in after feeding on insecticide-treated sugar syrup containing relatively low doses of the insecticide. In pollen-deprived field colonies, levels of both a detoxification enzyme and lipids varied between trials. In addition, the test showed that supplementing bees with a protein source helped colonies respond better to stress from insecticide exposure. These results suggest that beekeepers can improve colony health during times of poor pollen availability by feeding locally collected pollen.

Technical Abstract: Neonicotinoid insecticides have come under scrutiny for their potential role in honey bee declines. Additionally, reduced access to forage in agricultural areas creates the potential risk for interactions with these pesticides in regions critical for honey production. In this study, we sought to determine whether sufficient access to pollen during larval development could mitigate stress associated with oral clothianidin exposure in honey bee adults. An apiary was established where pollen traps deprived half of the colonies of pollen, which was then supplemented to the others. Adults were fed 0, 10, 40, 200, or 400 µg/L clothianidin in the laboratory, and larval and adult lipids and superoxide dismutase (SOD) activities were compared between feeding treatments. Survival at sublethal concentrations of clothianidin was significantly reduced for adult bees reared in pollen deprived colonies. Adult SOD activity was affected by clothianidin dose but not larval feeding treatment, though within the pollen-deprived cohort, SOD was greater in controls than those fed clothianidin. Larval SOD differed between field replicates, with supplemented colonies having slightly higher activity levels during a period of pollen dearth, indicating that supplementation during these periods is particularly important for mitigating oxidative stress within the hive. Larval lipids were significantly higher in supplemented colonies during a substantial pollen flow, though adult lipids were unaffected by feeding treatment. These results suggest that during periods of pollen dearth, oxidative stress and adult worker longevity will be improved by supplementing colonies with locally collected pollen.