Issue 18, October 22, 2012

Neonicotinoid Concerns

Recent research studies have shown a connection between several neonicotinoid insecticides and bees. These highly systemic insecticides have been increasingly shown to translocate into the flower pollen of various plants where they are picked up by pollinating insects including honey bees and bumble bees. Following are some research papers and review articles on this subject.

It is difficult to time insecticide applications to avoid pollen contamination because several of these insecticides persist in plants for about a year. Research shows that there are reduced levels of these insecticides in flower pollen and pollinators when application is made after flowering has ended, particularly with trees and other plants that only flower once per year.

Insecticides of concern include imidacloprid, sold as Merit, Xytect, Imicide, Allectus, and other brand names, thiamethoxam, sold as Meridian and Flagship, and clothianidin, sold as Arena and Aloft. Dinotefuran, sold as Safari, is also a neonicotinoid, but it has not been implicated in any of the research studies.

Merit, Allectus, Meridian, Arena, and Aloft are commonly used to control white grubs and other turf insects. Although turfgrass is not very attractive to pollinators, clovers, dandelion, and creeping Charlie are very attractive. We suggest that you avoid applying to turf where these weeds are common. Application to turf areas with a high level of weed control is unlikely to cause serious effects to pollinators.

Merit, Xytect, Imicide, and other imidacloprid insecticides are used to control Japanese beetles, soft scale, and other insects on trees and shrubs. It is known that imidacloprid translocates into linden blossoms, and linden is probably the tree most heavily attacked by Japanese beetles. Other trees heavily attacked by Japanese beetles are crabapple, rose, and others in the rose family. Imidacloprid is labeled for use on apple, which is in the rose family, which indicates that it probably does not translocate into apple flowers. Many rose varieties are so highly derived that they no longer attract bees or other pollinators, but others, particularly those with a single row of petals, do. It is known that imidacloprid does not translocate significantly into the flowers of some plants.

Ash and many other trees are wind-pollinated. Generally, these trees' pollen is not collected by bees and other pollinators. Applications for emerald ash borers and other insects are unlikely to seriously affect pollinators. Avoid soil applications where dandelions, annual flowers, and other flowers that attract pollinators are present.

Imidacloprid and/or clothianidin are labeled and effective against a wide range of borers, scale, caterpillars, and other insects of many trees and shrubs. When selecting an insecticide for treatment, consider the plant's flowering and attraction to pollinators. Until we know more about translocation into pollen in various plants, it is prudent to avoid these neonicotinoid insecticides in applications to plants attractive to pollinators. (Phil Nixon)

Phil Nixon

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