Pesticides and Honeybees

August 28, 2004

By Sandy Woods, Master Gardener

While gardening barefoot in my yard the other day, a sharp pain shot through my toe. Thinking that I had stepped on a sharp sticker, I was surprised to see that I had stepped on a honeybee. Grumbling, I needed to remind myself about the important role the honeybee plays in our gardens, and how their existence is being threatened – not by the barefooted gardener, but by the overuse of pesticides.

Honeybees are some of our most beneficial insects, yet most of us probably take them for granted. Not only do they produce a surplus of honey and beeswax, they are almost indispensable in the pollination of many fruit and vegetable crops. While pollination can take place via wind and other insects, only the honeybee is available for this purpose on such a large-scale basis.

Many in the agricultural field are concerned about the decline in honeybee populations. While parasitic mites and infectious diseases are responsible for some of this decline, honeybee colonies are also being adversely affected by direct effects of pesticide contamination. Honeybees can be exposed to pesticides in several ways. Worker bees gathering nectar and pollen may be directly exposed to pesticides, or they may carry pesticide-contaminated pollen back to the hive and expose other honeybees.

We can all do our part to avoid or minimize such contamination by following a few simply safety rules.

o Use an insecticide less toxic to bees whenever possible and use sprays instead of dust formulations. Insecticidal soaps, rotenone and bacterial insecticides are less harmful to honeybees.

o Apply pesticides only when bees are not present. Honeybee activity is usually greatest in the morning and diminishes in the evening. Also, there is usually less wind in the evening, which means less chance of pesticide drift.

o Before applying pesticide, remove any flowering weeds nearby that attract bees, such as dandelions, asters, mustard, sweet clover, milkweed and goldenrod.

o Quickly clean insecticide spills. Never allow sprays to puddle on the ground where bees may drink the liquid.

Of course, the first rule is to only apply pesticides when absolutely necessary. When a plant problem occurs, it is essential to correctly identify the cause. The beetle you see near a hole in a leaf may be a beneficial insect, but if it is damaging your plants, simply pick it off. Also consider that doing nothing at all -- letting nature take its course -- is often the best approach. Always use simple, non-invasive remedies first. The honeybee will thank you.

University of California Cooperative Extension Master Gardener Volunteers can provide additional gardening information upon request. Call the San Luis Obispo office at 781-5939 on Mondays and Thursdays from 1 to 5 PM, the Arroyo Grande office at 473-7190 on Wednesdays from 9 AM to 1 PM, or the Paso Robles office at 237-3100 on Wednesdays from 9 AM to Noon.  The San Luis Obispo Master Gardener website is at http://groups.ucanr.org/slomg/. Questions can be e-mailed to mgsanluisobispo@ucdavis.edu.