1.1.3 Persistent Herbicides

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Click here to return to the discussion on maximising crop yield, quality and profit using HIBRIX^TM products.

PERSISTENT HERBICIDES IN COMPOST : KILLERS ON THE LOOSE

By Chrys Ostrander

Back in the summer of 2000, folks involved with community gardens in Moscow and

Pullman began noticing plants dying in their vegetable gardens.

Farmers in the Northwest and elsewhere around the country reported similar problems. "I usually add 7 tons of finished compost per acre as either a soil conditioner or as mulch for weed control", says Art Biggert of Ocean Sky Farm on Bainbridge Island, WA. "This year I

was shocked to see what appeared to be herbicide damage in one of my pole bean

cultivars and my tomato crops. They had deformed shoot and leaf development,

significantly decreased and delayed bloom and fruit development."

Since the summer of 2000, researchers at Pennsylvania State University have documented widespread herbicide contamination of finished compost products manufactured by the University.

Beans, potatoes, sunflowers, squash, tomatoes and other plants shrivel up and keel

over on affected farms and gardens.

After some good detective work, the community gardeners south of Spokane traced

their problems to contaminated compost they had gotten from the research compost

facility at Washington State University in Pullman.

The culprits were found to be two persistent herbicides, clopyralid and picloram, both manufactured by DOW AgroSciences, and used on farms, in city parks and on residential lawns.

The discovery caused quite a stir. Suddenly, not only could WSU not sell its compost, incurring over $250,000 in losses, but the Spokane Regional Solid Waste System, which relies on sales of compost from their Colbert, WA composting facility, was left with tons and tons of compost they could not sell either.

Additionally, several organic farms suffered de-certification due to the contaminated compost, with WSU paying them compensation for their losses.

Clopyralid and picloram are weed killers that keep on killing, season after season. Their longevity and extreme potency (studies show toxic effects to sensitive plants at concentrations as low as one part per billion for clopyralid) are their big selling points.

Picloram is an active ingredient found in products intended for use in hay crops and is still active in animal manure after passing through the intestines of cattle fed on pasture that has been sprayed with it, even after the manure and bedding has been composted.

Clopyralid, on the other hand, is found in several products used for broad-leaf control in turf-grass maintenance and row crop production.

But as with many chemically derived "great ideas", there's a very dark side to these miracles of modern chemistry. Not only do they persist through the composting process to kill the plants in your garden, they are dangerous poisons.

According to the Journal of Pesticide Reform (Winter 1998), published by the

Northwest Coalition for Alternatives to Pesticides, "clopyralid and the products

containing it are irritating to eyes, some severely.

The eye hazards include permanent impairment of vision or irreversible damage. In laboratory tests, clopyralid caused what a U.S. Environmental Protection Agency (EPA) reviewer called "substantial" reproductive problems.

These include a reduction in the weight of fetuses carried by rabbits who ingested clopyralid, an increase in skeletal abnormalities in these fetuses at all doses tested, and an increase in the number of fetuses with hydrocephaly, accumulation of excess fluid around the brain.

Wow! And it could be in the compost destined for your garden!.

According to the Journal of Pesticide Reform, "In laboratory tests, picloram causes damage to the liver, kidney, and spleen. Other adverse effects observed in laboratory tests include embryo loss in pregnant rabbits and testicular atrophy in male rats. The combination of picloram and 2,4-D causes birth defects and decreases birth weights in mice.Picloram is distinguished even more by being one of the few "legal" pesticides known to be contaminated with the carcinogen hexachlorobenzine. Hexachlorobenzine is a highly toxic chemical that persists and bio-accumulates in ever-increasing levels in the food chain and fatty tissues, causes reproductive abnormalities at very low doses and is easily transferred from mother to infant through breastmilk.

Hexachlorobenzine was used, until it was banned worldwide, as a seed fumigant. It killed scores of nursing infants in Turkey after a mass poisoning of grain in the late '50's.

Picloram and clopyralid are found in various products with a wide array of brand

names. The most common, made by DOW, are Pathway and Tordon (contain picloram) and Confront, Curtail and Stinger (contain clopyralid).

Frank Pownall : Sales & Marketing
FAX : +61 8 6380 1499 TEL : +61 418 364 880 EMAIL : frank@plantsfood.com

David Martin Menne : Technical Support
FAX : +61 8 9389 5647 TEL : +61 500 54 65 32 EMAIL : david@plantsfood.com