Graduate Student to Discuss Effects of Pesticide Exposure and Diet on Mason Bees

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Olivia Kline is a graduate student in Dr. Neel Joshi's lab in the Department of Entomology and Plant Pathology.

The Department of Entomology and Plant Pathology is hosting seminar speaker Olivia Kline, a graduate student in Neel Joshi's lab, today. The seminar is titled, "The Effects of Pesticide Exposure and Diet on the Health, Reproduction, and Behavior of Mason Bees (Osmia spp.)."

The seminar takes place at 9 a.m. via Zoom link:

• Zoom Link.

• Meeting ID: 854 8763 0877

• Passcode: email enpl@uark.edu

The seminar is open to everyone.

Kline describes the research:

Several mason bee species, including Osmia lignaria and Osmia cornifrons, are efficient and valuable pollinators in orchards. They can be used to supplement honey bee (Apis mellifera) pollination, to improve yields and reduce costs compared to A. mellifera alone. Mason bees can encounter many stressors in their environment, which can negatively impact their health and pollination ability. These stressors include pesticide use and habitat loss due to agricultural expansion. Honey bees are often used as surrogates for other bee species when assessing the risks of pesticides and other stressors on bee health, but different bee species can vary widely in their response to stressors. Because of this, research into the impact of stressors on solitary bees is needed to create mitigation strategies and better protect the health of bee pollinator communities. This study assessed the lethal and sublethal impacts of pesticides on mason bee health, physiology and ability, and the effects of floral diversity on bee activity and fecundity.

As pest insects become more resistant to commonly applied pesticides, new active ingredients and formulations are produced to provide effective pest control. Two recently released systemic insecticides, flupyradifurone and sulfoxaflor, can be used to combat neonicotinoid-resistant pests, but may pose a risk to Osmia spp. We exposed four bee species, A. mellifera, O. lignaria, O. cornifrons and O. californica, to field realistic doses of both insecticides and measured toxicity, as LD50 values, and survival over 96 hours. Apis mellifera was the least sensitive to both insecticides, followed by O. cornifrons, and with O. lignaria and O. californica as the most sensitive. Female Osmia bees were more sensitive than males of the same species.

The sublethal impacts of flupyradifurone and sulfoxaflor on Osmia spp. health were measured using their detoxification enzyme expression, feeding preferences, flight and foraging ability, and gut microbial communities after exposure. Additionally, O. cornifrons were exposed to the commonly used garden pesticides glyphosate, chlorothalonil and spinosad, and their gut bacterial communities were compared. Flupyradifurone, but not sulfoxaflor, increased the expression of P450 enzymes in O. lignaria females. Flupyradifurone also caused impaired mobility and foraging activity of O. lignaria females at 24 hours following exposure. Osmia lignaria females showed some avoidance of food contaminated with higher concentrations of flupyradifurone, but overall O. lignaria seemed unable to detect sulfoxaflor or flupyradifurone. The effects of the tested pesticides on O. cornifrons gut bacterial community composition and diversity were minimal.

Finally, we raised O. lignaria in field cages planted with either a wildflower mix or a buckwheat monoculture and measured the effects on bee activity and fecundity and on soil health. The different planting types had little impact on soil nutrient content and the soil microbiome. Bees, however, were more active and were successfully able to reproduce in the wildflower mix groups, whereas bees in the buckwheat groups had lower activity and produced no offspring. This work demonstrates the risk of insecticides to mason bee health and pollination ability and the importance of an adequate and varied diet for bee fecundity.

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