Honey bee survival and pathogen prevalence: from the perspective of landscape and exposure to pesticides

Authors: ALBURAKI, MOHAMED - University Of Tennessee; CHEN, DENIZ - North Carolina State University; DKINNRT, JOHN - University Of Tennessee; Meikle, William; TARPY, DAVID - North Carolina State University; Adamczyk, John; STEWART, SCOTT - University Of Tennessee

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/11/2018
Publication Date: 6/13/2018
Citation: Alburaki, M., Chen, D., Dkinnrt, J.A., Meikle, W.G., Tarpy, D.R., Adamczyk Jr, J.J., Stewart, S.D. 2018. Honey bee survival and pathogen prevalence: from the perspective of landscape and exposure to pesticides. Insects. 9(2):65.
DOI: https://doi.org/10.3390/insects9020065

Interpretive Summary: Honey bees are unique in their role as our most important pollinators, as well as in their close link to the immediate environment, which they depend on for pollen and nectar. Because of their foraging, they are exposed not just to agrochemicals used to treat crops, but to diseases and pests as well. Given this dependence on, and threats from, the environment, how important are the effects of apiary site when considering common measures of bee colony health? In this study sixteen bee colonies were established across 4 different areas, two with intensive agriculture and two without it. The presence and severity of important diseases and pests were noted, and samples of honey, wax, foraging bees and bees that died outside the hive were analyzed for pesticide residues. The study showed that while pesticide levels found in bee hives in agricultural areas were sometimes high, and there were bee kills, the quality of bee forage in those areas was also high. Some differences were observed in the incidence of some viral diseases was observed, but it did not appear linked to exposure to agriculture.

Technical Abstract: 1. The honeybee (Apis mellifera L.) is one of the most economically important insects for humans. Besides providing six different products, the honeybee plays a significant role in the ecosystem as a highly efficient pollinator and environmental sentinel. 2. In order to study the in situ effects of the agricultural and pesticide exposure on honeybee health, sixteen honeybee colonies were placed in four different agricultural landscapes. Those landscapes were three agricultural areas with varying levels of agricultural intensity (AG areas) and one non-agricultural area (NAG area). Colonies were monitored for different pathogen prevalence and pesticide residues over a period of one year. 3. RT-qPCR was used to study the prevalence of seven different honeybee viruses as well as Nosema apis in colonies located in a NAG system and agricultural systems with various intensities of soybean, corn, sorghum and cotton production. Populations of the parasitic mite Varroa destructor were also extensively monitored. 4. Comprehensive MS-LC pesticide residue analyses were performed on samples of wax, honey, foragers, winter bees, dead bees and crop flowers for each apiary and location. 5. Our results indicated that both cotton and sorghum flowers contained potentially lethal doses of insecticide including neonicotinoids, while soybean and corn posed less to no toxicity risk for bees. Several events where foraging bees were found dead in front of hives was observed in the AG areas, and high concentrations of neonicotinoid insecticides were detected in dead bees. 6. Significantly higher level of varroa loads were recorded in colonies of the AG areas, but this at least partly correlated with increased colony size and did not necessarily result from pesticide exposure. None of the other studied pathogens differed significantly between AG and NAG areas. 7. Our data suggests that agricultural crops provided bees with better and more sustainable forages, but there was an increased risk of pesticide exposure and significantly higher pathogen loads.