Pyrethrins

As the dangers of some of the chemicals used as pesticides have come to light, gardeners and farmers have sought less damaging compounds to battle pests. The use of organic pesticides, such as pyrethrins derived from chrysanthemum flowers, has increased. Organic does not necessarily mean non-toxic. Gardeners should use caution when handling the pesticides and resist overusing them. Overuse can kill beneficial insects, may lead to the development of resistance in pest species and surplus chemicals in runoff from fields and gardens may concentrate in streams.

Last year scientists at UC-Berkeley found pyrethroids at a level toxic to organisms that live in sediment in three streams in a predominantly residential area of California. Pyrethroids are a synthetic version of pyrethrins designed to last longer. While the compound is different, the research points to the potential for pyrethrins and other organic, but toxic compounds to build up in the environment if overused.

The recent increase in the use of pyrethrins or pyrethroids for municipal misting programs introduced to reduce mosquito populations in hope of curbing the spread of West Nile disease, has raised concerns about the chemicals' safety. The amount of exposure from this type of a blanket mist is reported to be very low, but the quantity of the compound released into the environment and its effect on beneficial insects may be cause for concern.

Perhaps more concerning is the introduction of backyard mosquito misting systems, which automatically release a mist of pyrethrin from a 55-gallon drum three or four times per day. Few regulations exist to monitor the use of the devices. Critics of the systems worry about frequent exposure for children and pets, the possibility that mosquitoes will develop tolerance, and since pyrethrins are expensive users might look for cheaper alternatives to fill their 55-gallon drums.

• Chrysanthemum Flowers… and other mysteries of pest control from the North Coast Journal Weekly of Humboldt County California


• Pyrethroid pesticides found at toxic levels in California urban streams a UC-Berkeley press release


• Backyard Mosquito Misters Have Some Experts Worried an Associated Press story from FortWayne.com


• Natural Pesticides For Your Garden from Texas Agricultural Extension Service, Texas A&M University


• Organic Gardening — Natural Insecticides from New Mexico State University - Cooperative Extension Service

Posted by Eric La Fountaine at 1:42 PM on February 1, 2006

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