Coping With Culprit in Compost Gone Bad

For 10 years, Arthur Biggert has run a small organic farm in Bainbridge Island, Wash. He spades compost into his vegetable plots every year to improve the soil. This is a timeless cornerstone of good garden management, essential for soil structure, water retention, good drainage, microbial activity and nutrient uptake by plants.

In spite of all his care, last May, after planting out 60 tomato seedlings, 40 of Biggert’s crop failed to thrive. “It took them about two weeks before they started any growth,” he says. “And when they did, many had cupped leaves and twisted stems. As time went on, in June and July, I didn’t have any blossoms, which is really unusual.”

No flowers meant no fruit, just withering, deformed vines. Biggert investigated every possible cause, starting with transplant shock. He finally had his compost tested.

The humus-rich mix of rotted grass, straw and manure, the very plant health food that he had so religiously spaded into his garden, was the culprit. It had traces of a weedkiller called clopyralid, a product marketed by Dow Agro- Sciences for the control of dandelions and clover in lawns and thistle in fields and pastures.

Biggert was not alone. At the same time, Washington State University officials began publishing alarming studies showing that clopyralid residues on straw and residential grass clippings had found their way into most compost in the state. By June, clopyralid had been found in compost in California.

The San Diego Environmental Services Department discovered the chemical in its compost processed from Southern California grass clippings. By January, so did the Los Angeles Bureau of Sanitation. Again the suspect source was grass clippings from treated lawns that had been put in green bins by homeowners and sent for recycling into compost. On Wednesday, the California Department of Pesticide Regulation announced that the chemical is under review.

Compost makers from across the West gathered in San Francisco this week at a conference sponsored by the journal BioCycle to discuss how to protect compost and how gardeners should protect their tomatoes.

There were some words of comfort for California gardeners from veteran clopyralid investigator Dan Caldwell, director of Washington State University compost operations at the Pullman campus.

“California,” he said, “is lucky.” Clopyralid has been in use here since 1997, 10 years less than in Washington. The contamination levels here are far lower--on average five times less--than in Washington state. So far, unlike Washington, there are no reports of crop failure.

But Californian compost companies are still worried. Unlike Washington state, where the local Department of Agriculture tested compost for the herbicide, here the job of testing has so far been left to compost companies.

At the conference, the California Compost Quality Council announced that of 20 anonymous tests carried out by its members up and down the state, another 13 had been positive. This, they said, suggests contamination in California could run as high as two-thirds of all our compost.

On Wednesday, San Diego’s Environmental Services Department was in Sacramento demanding a ban on clopyralid in landscaping, a measure taken by Washington’s Department of Agriculture last week.

Clopyralid does break down and wash out with rain, but very slowly. Biggert is not going to have many tomatoes this year. As Caldwell warns, “Contamination is so pervasive, we will have to get used to living with it for a while.”

This is a hard adjustment. For any gardener committed enough to buy compost in the first place, the choice between growing summer vegetables and using compost is a case of shooting or hanging. Summer would not be summer without tomatoes. Forgoing compost, however, is not an option for most serious gardeners. Yearly compost amendments are crucial to a healthy garden.

What should be done? There are no hard answers--yet. In addition to the Washington emergency ban, the federal Environmental Protection Agency has started collecting contamination reports, and the California Department of Pesticide Regulation has only just clicked into action.

To spur it on, Assemblyman Fred Keely (D-Santa Cruz) is drafting a bill to restrict use of clopyralid in California. But as regulators and politicians duke it out in Sacramento, Caldwell and fellow veteran investigators offer the following advice:

* Do not worry about your children or pets. Clopyralid is safe for humans and mammals.

* Don’t worry about clopyralid residues on woody shrubs, grass and trees. It does not damage these plant types and will break down eventually. Applying any compost is fine here.

* Clopyralid can only be applied by professional applicators. Check with landscape maintenance teams at schools, parks, golf courses and with your own residential mow-and-blow guys to make sure they do not use the following products containing clopyralid: Lontrel, Curtail, Transline, Stinger, Reclaim, Confront, Hornet, Scorpion, Redeem, Millennium, Momentum, Chaser Ultra, Battleship, Strike Three and TruPower.

* If you do use products that contain clopyralid, ensure that grass clippings are not put in green bins and sent for composting but used to mulch shrubs.

* Know vulnerable plant types: legume, nightshade and composite families. These include peas, beans, tomatoes, potatoes, chili peppers, petunias, asters, daisies, chrysanthemums and artichokes.

* When spading in compost for vegetable beds for these plants, use no more than an inch of compost, and dig it well into existing soil.

* If you are worried, grow a test plant in a 4-inch pot using one part compost to three parts garden soil. Deformities should appear with the second true pair of leaves.

* If you have stunted, sterile or grossly deformed tomatoes, to compare them to clopyralid damage, go to the Washington State University Web site at css.wsu. edu/compost/.

* Information is also available from the university on how to treat badly contaminated gardens with activated charcoal.

* If you want to test your garden soil, the cost is $150, and the lab with the most experience and sophisticated protocol is Anatek of Moscow, Idaho. For information: (800) 943-2839.

Finally, don’t give up on compost, but be cautious; ask questions. There are lots of ways to kill a plant, and the most common way is poor soil condition, not clopyralid. Maybe we should even take fresh looks at clover and dandelions and ask ourselves if they’re such bad plants, after all.