Fungicide sensitivity of honey bee associated fungi
Abstract - Honey bees are exposed to a wide range of pesticides while pollinating agricultural crops. These pesticides residues are found in beeswax, nectar and pollen in the hive. Some of the pesticides found are fungicides which are not generally considered harmful to insects. However, these fungicides may negatively impact mutualistic fungi associated with honey bees causing indirect harm to colony health. Fungi are implicated for helping break down complex protein molecules and therefore allowing the honey bees to attain more nutrients from the food source. The objective of this experiment was to identify if honey bee associated fungi were affected by fungicides that honey bees are exposed to. In order to achieve this objective, a number of fungi were isolated from bee bread and the honey bee digestive tract. Five of these isolates were genetically identified by sequencing of the internal transcriber spacer regions 1 and 4 and selected for fungicide sensitivity testing. Each fungal isolate was subject to five treatments with replications. With the exception of Mucor hiemalis, all fungal species growth was significantly reduced (p ≤ 0.05) by the fungicides chlorothalonil, iprodione, and boscalid at day 2 of exposure.
This research suggests that while fungicides may not directly affect the honey, they may disrupt the normal balance of fungal associates in the hive. This imbalance may result in decreased nutritional attainment from bee bread thus indirectly affecting the health or behavior of the honey bee. More research is needed to identify the functional roles of fungi in honey bees.
Tylosin & Fumagillin - Impacts on honey bee midgut bacterial symbionts
Abstract- Concern for the managed honey bee population has been developing after drastic
losses in the past decade. Suspected causes include new pests, pathogens, pesticides, migratory beekeeping, and nutritional deficiencies from a monoculture diet. To avoid the increasing threat of microbial pathogens, some beekeepers treat hives annually with tylosin and fumagillin, antibiotic compounds. Emerging research has identified the honey bee microbiome as an important aspect of colony health. It is unclear whether annual prophylactic treatments of tylosin and fumagillin applications deplete symbiotic microorganisms in the honey bee digestive tract.
The purpose of this research was to gain an initial understanding if tylosin and fumagillin
treatments significantly alter composition of Lactobacillus species in the honey bee midgut
microbiome. Using a laboratory based, in vitro well-diffusion test and a caged in
vivo experiment, four treatment groups consisting of 1) tylosin application, 2) fumagillin
application, 3) tylosin with fumagillin application and 4) no chemical application as the control, were each replicated four times. Honey bees were sampled before treatment application, 5 days after treatment and 12 days after treatment. Midgut contents were then homogenized and concentration of Lactobacilli spp. in each midgut was assessed with a plate dilation series on MRS selective media. Colony Formation Units (CFU) were counted after plate inoculation and 72 hours of incubation. Proportions of high, medium and low CFU data were compared between treatment groups. Results suggest a need to further investigate the impact of annual antibiotic treatments and for a better understanding of the honey bee microbiome.