Honeybee colonies are dying, about one-third of all hives globally each year, an enormous tragedy for bees and beekeepers alike. There’s not a single cause, but rather a congruence of interacting issues including pesticides, diseases and pests, among others.
But not everywhere; a recent study from Africa indicates that Kenyan honeybees are not so seriously afflicted, due to diminished presence or impact from three of the major components causing colonies to collapse elsewhere on our planet.
Kenyan colonies were found to have a low exposure to pesticides, with only four pesticides found in colonies, and those at low levels. In comparison, over 129 pesticides are commonly found in North American honeybee hives, often at concentrations high enough to harm bees. Pesticide interactions with each other and with bee diseases and pests are one of the most significant factors contributing to colony demise, so these low numbers were good news for Kenyan beekeepers.
The Penn State researchers also found low incidences of Nosema, a fungal disease that has reached outbreak proportions in many parts of the world. Nosema was only recently introduced to Kenya, which may account for it’s low levels in colonies. But pesticides are known to reduce bees’ capacity to combat Nosema, so a more intriguing possibility is that Nosema is low in Kenya is because the low pesticide presence in Kenyan colonies reduces the disease’s virulence.
Another factor in the relatively good health of Kenyan colonies is that the varroa mite is not as deadly as its been elsewhere in the world, because African bees may be less susceptible. For one thing, African bees have higher levels of hygienic behavior, removing mites from cells in which they feed on larvae and grooming adult mites off of adult bees. The African bees also may be less attractive to varroa, perhaps due to having a different odor than European bees, or stiffer external hairs that make bee cuticle less hospitable to the mites.
The life cycle of African bees also contributes to diminished varroa impact. Colonies abscond (abandoning hives) and swarm (reproducing) frequently, which causes breaks in brood rearing that limit the ability of varroa to reproduce. Also, brood of African bees take about 2 days less to develop from egg to adult than in the European-derived bees found elsewhere in the world’s beekeeping regions, which isn’t quite enough time for the varroa mites to mature inside the African brood cells.
One beneficial side effect of reduced levels of varroa and nosema is reduced chemical use by beekeepers, saving money but most significantly reducing the pesticide load that bees are exposed to. While any one factor does not explain the relative health of Kenyan honeybees, it seems that reduced exposure to pesticides has contributed to healthier bees and a viable beekeeping industry.
If I was the czar of global agriculture, I would command reduced pesticide use by both farmers and beekeepers. That’s a key element for bee health, because in addition to directly toxic effects and subtle sublethal impacts on bee behavior, many pesticides diminish bees’ immune responses and thereby increase susceptibility to diseases and pests.
The Kenyan and many other studies have made it clear that a dramatic change in global agricultural practices is part of the solution for the current malaise afflicting honeybee colonies, and also the many species of wild bees equally susceptible to death by agriculture.
We know that reduced pesticide use will benefit bees; it’s lack of political and social will that keeps colonies dying. Until that changes, bees will continue to be challenged by our increasingly toxic planet.
For more information, see:
Muli E, Patch H, Frazier M, Frazier J, Torto B, et al. (2014). Evaluation of the Distribution and Impacts of Parasites, Pathogens, and Pesticides on Honey Bee (Apis mellifera) Populations in East Africa. PLoS ONE 9(4): e94459. doi:10.1371/journal.pone.0094459