By Art Biggert

I have been farming using organic methods for 10 years. Compost has always been the right arm of my soil fertility program. Cover cropping is the other arm. I usually add 7 tons of finished compost per acre as either a soil conditioner or as mulch for weed control. These soil fertility management tools have worked to improve my soils over a decade of careful monitoring. I have documented my soil improvements with a comprehensive soil analysis every two years. But this year, my compost caused damage to my bean and tomato crops. The parent material of the compost I had problems with was horse manure and straw from stable sweepings.
Last June I was shocked to see what appeared to be herbicide damage on one of my pole bean cultivars and my entire tomato crop. They had cupped leaves and deformed shoot development, significantly decreased and delayed bloom and fruit development.
I happened to read an article in the July issue of Biocycle about research performed by Washington State University (WSU) Extension identifying two persistent herbicides found in their compost. Their finished compost has damaged plants in a number of places for over 18 months. To date, this incident has cost WSU over $250,000 in testing, damages, and lost sales.
I contacted the faculty member in charge and the research associate doing the research. They directed me to a lab where my compost could be analyzed for the two persistent herbicides they had found, clopyralid (pronounced klo-peer-ra-lid) and picloram.
My compost was found to contain clopyralid. The sample had 3 micrograms per Kg (3 parts per billion). According to a Pennsylvania State University researcher, 3 micrograms of clopyralid per Kg is enough to cause the crop damage I witnessed. It may also be enough to revoke a certificate for organic production.
Now, to put this number in perspective, consider the entire human population of spaceship Earth. Combined estimates put that number at around 6 billion people. This herbicide affects susceptible plants at a level equal to six persons out of the entire population of the planet (1ppb). This effect is closer to a homeopathic dose than an allopathic therapy.
I suspect the clopyralid concentration was higher last spring because the compost windrow I sampled in September had been uncovered since May and was less than a foot deep. Interestingly, the windrow has grown no broad leaf weeds since it was uncovered six months ago.

Source of herbicide
My source of clopyralid came from straw and timothy grown on conventional farms in Eastern Washington. I was unable to source the straw used for bedding or the timothy fed to the horses. They were sold by a local feed store that buys from a bulk distributor. The distributor buys straw from 17 different farms in Eastern Washington.
Therefore, there is no way to identify the farmer or licensed pesticide applicator responsible for damages caused by composting the timothy and straw sold in violation of the restrictions on the herbicide label.
Here lies the problem. There is no chain of custody for plant material used as organic waste for composting operations. As the end-user of a waste stream, I am not aware of the chemicals applied in production of the plant material. Producers of hay and straw are not aware of the end-use of their plant material as compost feed stock.
The Washington State Department of Agriculture (WSDA) has found clopyralid contamination of compost in several commercial composting facilities across the state. This discovery means the problem is not a local issue. It has national economic and waste management implications.
Dow ArgoSciences currently markets clopyralid under the brand names Curtail, Lontrel, MCDA, Millennium, Battleship, Lesco Momentum Premium, Spring Valley Weed & Feed, United Hort Supply Chaser Ultra, Reclaim, Riverdale, Stinger, Transline, Confront, Accent Gold, Hornet, Redeem, and Scorpion. These herbicides are approved to kill unwanted plants in lawn and turf, range, pasture, rights-of-way, sugar beets, asparagus, mint, wheat, barley, strawberry, blueberry, and balsam fir Christmas trees.

Biological effects
Residual clopyralid in compost has been documented to affect susceptible plants in concentrations as low as one part per billion. It is extremely toxic to legume-family plants used as cover crops such as peas, beans, and favas. Other susceptible plants are found in the nightshade family such as tomatoes, potatoes, eggplant, peppers, parsley and tobacco. Flowers such as safflower, sunflowers, marigolds, pansies, and petunias are also susceptible to these herbicides at homeopathic doses.
Clopyralid is “persistent” in soil, according to a U.S. Environmental Protection Agency (EPA) review, field studies have measured persistence as long as 14 months. Research at WSU demonstrates persistence continues longer than 18 months.
It has the chemical characteristics that make it a likely water contaminant. Because these herbicides have demonstrated abilities to resist bioremediation they will move with the ground water into streams and rivers unchanged where they may affect our endangered salmon and other aquatic life.
In 1998 a U.S. Geological Survey found clopyralid in 2 of the 20 river basins studied despite its relatively low level of use at that time.
Clopyralid caused what an EPA reviewer called “substantial” reproductive problems. Due to the inert additives, other health hazards of four clopyralid products include permanent impairment of vision or irreversible damage.
The International Organization for Biological Control found clopyralid to be toxic to three species of beneficial insects. Ladybug, pirate bug, and lacewing populations are all damaged by clopyralid direct application and volatilization.
For more specific information on the biological effects of clopyralid check out the Northwest Coalition for Alternatives to Pesticides (NCAP) at www.pesticide.org/clopyralid.pdf .

Regulatory response
Not only does this inhibit my cover cropping and composting operations, it also affects municipalities that are composting yard waste as an alternative to dumping it in landfills. Thirty-seven states have mandates that prohibit the dumping of green waste into landfills. Recycling through composting is the only means for responsible stewardship of green waste.
The U.S. Composting Council Environmental Policy and Regulatory Affairs Committee has taken this threat to task. They have released a position paper describing Dow’s inadequacies in the label instructions for clopyralid. They document Dow’s economic liability for multimillion-dollar commercial composting operations across the country that inadvertently produce and sell contaminated compost. Among other compensation demands, they propose that Dow compensate organic growers for lost produce markets and loss of organic certification.
Washington and Oregon State public utilities have sent a letter to the EPA urging them to reconsider its criteria for registration and re-registration of herbicides to include the ultimate end-use of urban yard trimmings, food scraps and agricultural wastes. They emphasized that no residual herbicides should remain after the normal 60-90 day composting cycle.
In Washington State, the WSDA regulates herbicide use and the Department of Ecology regulates commercial composting operations. At a regulatory meeting held on October 18, 2001, neither regulatory body expressed concern for on farm composting operations since neither department regulates such operations. An EPA representative was present and said that they will wait and see what regulatory action Washington State would take before taking action.
Cliff Weed of the WSDA commented that it was unlikely that clopyralid would be banned. Instead, any new rule-making process would probably restrict clopyralid applications to licensed applicators with improvements on the packaging label.
Concerned professionals from the composting industry and public utility districts expressed opinions that package labeling has not protected the tobacco and tire industries from liability for damages caused by their products. They strongly suggested that Dow seriously consider the risk management aspects of manufacturing persistent herbicides.
Self defense
Both picloram and clopyralid are classified as pyridine carboxylic acids, growth regulator herbicides in the same class as 2,4-D, which are very persistent and pass through animals and the composting process with very little breakdown. Both herbicides are excreted in their active forms in the urine of animals fed “weed free hay” produced with these weed killers. Farmers making compost to produce crops in the legume and nightshade families must be confident that the animal feeds and bedding used for the manure feed stocks they are composting are free from herbicide residues. I have switched my feed stocks for composting exclusively to stable sweepings from an organic goat dairy and my own crop residues and animal manure. I no longer accept plant residues or manure from sources I cannot verify as organically produced.
A bioassay is the most economical means to test for persistent herbicides if you suspect that your compost is contaminated. Mix 15-25% finished compost with any known clean soil in 4-inch pots and plant your favorite pea or bean. Make several test samples. Herbicide damage will show up on the second set of true leaves. The leaves will appear cupped and slightly twisted. A distortion of the stem appears because the plant will loose its apical dominance at the junction of the second leaf if the plant survives. If you get no growth response, it most likely was not mature compost.
If you want analytical confirmation of the bioassay it cost $250 per sample at Anatek Labs, Inc. (208) 883-2839. This lab is in Moscow, ID. I have heard of a lab in California that also performs highly sensitive analytical tests for clopyralid. But I do not have contact information for that lab.
As frustrating as this problem is, I wish to commend WSU Extension for being on top of this major threat to organic soil fertility methods and fresh water contamination. The Cooperative Extension Service system has come a long way in the last ten years. I am grateful for their new focus on sustainability. For a history and the “latest news” on the compost research going on at WSU go to www.css.wsu.edu/compost/.

Art Biggert and his partner are community health nurses who share a commitment and dedication to the health benefits of organic and sustainable farming methods. They can be contacted at www.oceanskyfarm.com.