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Gardening: Insecticide choices may affect bees

A little more than a year ago, upward of 50,000 bumblebees died while feeding on linden trees in Wilsonville, Oregon.

The culprit? A spray company that applied a neonicotinoid-based spray to blooming trees in violation of label directions. This incident has been a lightning rod for the debate about the use of neonicotinoids in a wide range of pesticides available to homeowners.

The Spokane City Council voted to ban city purchase and use of neonicotinoids on Monday. The ban does not apply to private use.

Neonicotinoids – the name means “new nicotine-like insecticide” – have been around about 20 years and have become popular because of their low toxicity in mammals, birds and other higher-order animals while controlling insect pests. They were preceded by nicotine-based insecticides made from tobacco processing waste. Neonicotinoids act on specific types of receptors in the nervous system of insects. There are currently seven different kinds of neonicotinoids commonly available in insecticides for home and garden use on shrubs, trees and lawns. They also provide control of certain beetles, fleas, wood-boring pests, flies and cockroaches.

When the neonicotinoids were first released they were popular for their low-toxicity to many beneficial insects, including bees. Over time, however, these claims have been called into question. Several recent studies have indicated that prolonged exposure to low-level contamination of pollen and nectar may build up in bees and other beneficial insects. As a result, the bees’ ability to forage for nectar, their ability to learn and remember where flowers are located, and their ability to find their way back to the hive may be affected.

While these studies indicate the possibility of impact on honeybees, there is still no conclusive evidence that neonicotinoids are the cause of the huge declines of honeybees and other pollinators (including colony collapse disorder).

While research answers may be a few years off, home gardeners can make choices about using neonicotinoids in their gardens.

First, if you have a pest problem, get the bug in question properly identified before you apply any insecticide. Second, choose other chemicals. There are plenty of other conventional and organic chemicals out there that will do the same job. To ensure you are getting a non-neonicotinoid-based chemical, check the label for one of the active ingredients listed in the box above; if one of them is listed, don’t buy it. Third, if you choose to use a neonicotinoid, be sure to follow the label directions carefully using the correct dosage at the correct times with the proper application methods. Lastly, restrict neonicotinoid applications to soil drenches that keep the chemical off plant leaves and apply late in the evening when bees have returned to the hive.