Pesticides and Bee Health

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Are pesticides reducing honey bee populations?


There has been a growing concern over the role of pesticides and their potential contribution to honey bee decline in the United States. In the past decade, there has been agreement among scientists and beekeepers alike that honey bee populations are declining, and seem to be accelerating. There are several hypotheses about why, but there appears to be at least three or four primary factors including the varroa mite and the newly identified Israeli acute paralysis virus (IAPV). Another recent study published last year, suggested that a species of parasitic fly is a potential culprit for the decline in honey bee populations. While there is no one explanation for colony collapse disorder (CCD), it is likely that a combination of all these factors is possible for such dramatic decline in honey bee populations.

Could pesticides be responsible?

For a long time, the exposure of honey bees to chemical insecticides has been a major concern for beekeepers, growers, and scientists alike and for good reason. Over 90 different types of fruit and vegetable crops are pollinated solely by bees and a recent report estimated that the economic value of commercial bee pollinators is around $15 billion annually. And that’s just from the European non-native species, Apis mellifera. It was also estimated that native bee pollination attributes up to $2.5 billion annually…that’s a lot of money and thus it is understandable that there is a concern from commercial growers and commercial beekeepers. Around 2.4 million colonies are utilized for crop pollination and many of these colonies are used more than once per season. Now figure that a field is being treated with herbicides, insecticides, to control pests and you get a lot of exposure to chemicals, which have been shown to reduce the overall health of honey bees. This long-term, sublethal exposure to pesticides could potentially be a contributing, if not, major factor in the overall decline of honey bee colonies, although there is much research that still needs to be conducted.

While there is no clear consensus as to what exactly is responsible for the decline in honey bee populations, it is likely that prolonged exposure to pesticides can reduce the health of honey bee colonies and the reduction in colony health can make them more vulnerable to attack from things like varroa mites or viruses. So while pesticides may play a part in reducing honey bee populations it is unclear at this point if they are solely responsible for honey bee decline. Most likely, multiple factors are contributing to the decline in honey bee health and at least for now, scientists are in general agreement on this.

What role can a gardener play?

            Homeowners have a major role in protecting honey bee populations. Studies have shown that increasing plant diversity in your will increase the abundance and diversity of insects in your lawn. This enhanced diversity increases pest suppression by natural enemies and also increases the diversity of other wildlife, including songbirds. For example, white clover, while considered to be a weed by some, is actually an excellent and highly nutritious pollen and nectar source for honey bees.

If you actively manage your weeds, you can also do your part. We often stress reading the label when applying any pesticide and here’s why. Studies have shown that an application of a granular insecticide did not harm foraging bee populations as long as it was followed immediately by an irrigation event. When granular applications were made and NOT followed by irrigation, bee populations declined drastically. Liquid applications of a particular insecticide further did not reduce foraging bee populations. So you can still help to conserve as long as you read, and properly mix and apply your pesticides. By also making sure that you are monitoring and applying pesticides only when it is necessary, you can reduce the amount of exposure that bees have to pesticides.

To learn more about other consumer horticultural programs contact Sam Marshall, Horticultural Agent,  at You can call the Cooperative Extension office at 910-253-2610. Visit the Extension website at

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