Clopyralid and Other Pesticides in Composts

tions that affect human health, garden plants, or crops. Studies done in the early 1990s on pesticide residues at composting facilities which accept yard trimmings showed that although many commonly used pesticides are occasionally found on yard trimmings entering the facilities, very low or undetectable levels are present in commercially produced composts. Two exceptions are DDT metabolites and chlordane which, although banned for many years, still persist in the environment. Laboratory studies have confirmed that most commonly used pesticides, including diazinon, 2,4-D, pendimethalin, and atrazine, are degraded to very low levels either chemically or by microorganisms during composting. However, recently an herbicide called Clopyralid (sold under the trade names: Reclaim, Stinger, Transline, Confront, Lontrel, Curtail A question that compost users frequently ask is, “What happens to pesticides during composting?” This question is important since even at low levels, certain commonly used pesticides can be toxic in the environment. For example, diazinon (now banned) and pendimethalin (Prowl) are toxic to fish even at concentrations of parts per billion (ppb) in water. Birds are quite sensitive to diazinon poisoning, and as little as 2 parts per million (ppm) of 2,4-D (Weed-B-Gone) or 50 parts per billion of Clopyralid significantly reduce the growth of sensitive plants like tomato.