Organic Crops and Gardens Increasingly Contaminated by Persistent Herbicides

by Linley Dixon, PhD

This sunflower shows the leaf curl characteristic

of poisoning by aminopyralid herbicide. In this

case, the herbicide contamination came from

horse manure.

Photo by John Mason, www.geologywales.co.uk

Nothing is more infuriating than first-hand accounts of “Big Ag” putting sustainable organic farmers out of business. Herbicide carryover in compost embodies this travesty in the same vein as chemical drift, GMO contamination, and the monopolies created when seeds and genes are patented. [[1]]

Herbicide carryover (when persistent herbicides remain in compost, which then damages crops) may be initially hard to fathom, but occurrences are increasing due to the expanded use of certain persistent chemicals.

Here’s the calamity, for many family farmers, in a nutshell: broadleaf-specific herbicides sprayed on conventional pasture and hay fields pass unchanged through the digestive tract of farm animals, ultimately ending up in their manure, where the herbicides do not break down for many years, even when properly and thoroughly composted. [[2]] When contaminated compost finds its way into garden soil, crops will suffer. When that garden is your livelihood, it is tragic.

Soil type and environmental conditions affect the length of time that persistent herbicides are active, but damage to crops from a single application of contaminated compost is commonly reported to last several years. Symptoms resemble diseases caused by plant viruses and nutrient deficiencies; therefore, the problem is often misdiagnosed by extension agents, agronomists, and other experts. Testing is expensive and doesn’t detect the small amounts of herbicide that crops react to. Highly susceptible cash crops include tomatoes, potatoes, eggplant, peppers, lettuce, beans, peas, spinach, carrots, and berries, among others. [[3]]

In the last few years, herbicide carryover has garnered attention as gardeners, organic farmers, commercial composting companies, and extension agents learn to recognize the diagnostic symptoms on crops and understand how prevalent persistent herbicides in compost and irrigation water have become. [[4],[5],[6],[7]]

In fact, the problem of persistent chemicals contaminating farms has become so mainstream that the National Organic Standards Board (NOSB) has been discussing the issue for the past year through a formal discussion document entitled “Protecting Against Contamination in Farm Inputs.” [[8]] On February 24, 2015, the NOSB Crops Subcommittee released a “Contaminated Inputs Plan.”[[9]] The plan considers various off-farm materials and addresses what contaminants might be present, whether they are of concern, and if they can be avoided. Unfortunately, this plan continues to place the burden on the farmer, not the contaminator. Nothing short of a ban on persistent herbicides by the EPA will prevent continued crop failures from these materials.

The NOSB plan to avoid contamination is nearly impossible to implement when contaminants arrive through irrigation water, or drift, and organic matter is sourced from multiple farms over many years. Currently, crop failures occur when inaccurate information regarding source material is relayed through the long supply chain (hay farmer to livestock rancher to composter to vegetable grower).

The NOSB proposal to require the farmer to conduct bioassay tests on compost to determine whether or not a contaminant may be present places an unrealistic burden on organic farmers given the time it takes for symptoms to develop, greenhouse space required, qualifications needed to properly diagnose symptoms, lack of uniformity in compost piles, and a continuous supply of varying source materials.

The suggestion that it is up to the farmer to prevent compost contamination is directly in line with the advice given by the chemical companies that profit from the sale of these persistent herbicides. In other words: it’s your problem, not mine.

Unacceptable Persistence

The EPA should never have approved herbicides that have the potential to persist for several years in the environment. Ironically, their ratings are designed to give potent, persistent chemicals the best EPA scores.

For example, chemicals are rated highly for requiring lower doses (i.e., highly potent) and less frequent applications (i.e., highly persistent). [[10],[11]] While low doses and fewer sprays sound good at first, chemicals that require low doses are more likely to cause damage to neighboring farms from drift. Chemicals that control weeds for a full season are more likely to contaminate other farms due to their persistence. Why chemicals receive the best environmental ratings for traits likely related to potency and persistence is counterintuitive.

Contamination events are still grossly underreported both in the U.S. and globally. Farmers are not always qualified to know why crops are failing or showing reduced yields. Even scientific professionals often mistake symptoms from pathogens, nutrient toxicities, and herbicide damage without expensive, comprehensive testing. In addition, if farmers are able to determine that herbicide contamination has occurred, they may be unlikely to come forward due to potentially losing the ability to market their produce. If a system is in place to be compensated for financial losses due to herbicide carryover, farmers are much more likely to investigate and report when contamination has occurred.

Organic Farmers Should Have the Right to Clean Organic Matter

The incorporation of organic matter into the soil from a wide range of sources has been used to maintain soil fertility for over 10,000 years and is central to organic and sustainable farming. Incorporating organic matter and nutrients back into the soil prevents the need for synthetic fertilizers and mitigates pollution elsewhere. On- and off-farm inputs include compost, mined minerals, animal byproducts (fish, slaughterhouse waste), hay, mulches, and manures. Organic farmers provide a great benefit to society by recycling these waste products that will end up as hazards if not properly handled.

When organic matter becomes contaminated, humic acids and nutrients cannot be returned to the soil. Manure can contain other synthetic agrochemical residues that may not cause crop failures but still pose risks to consumers and the environment. Other contaminants include heavy metals, insecticide residues, and antibiotics. Herbicide contamination is perhaps “the canary in the coal mine” because of its direct impact on crop plants and farmer livelihood, but these other contaminants should not be discounted.

With the increase in the use of persistent chemicals, including herbicides and insecticides, organic farmers are no longer able to trust that organic matter inputs and irrigation water are free of these prohibited materials. Much like GMO contamination, it is nearly impossible for organic farmers to be clean of these materials once they are produced. Until persistent materials are banned, farmers should not be held responsible for contamination and should be compensated by the manufacturer of the herbicides for losses incurred.

NOSB: Action Steps Needed

The following items are currently missing from the NOSB’s Contaminated Input Plan. The Cornucopia Institute urges the NOSB to:

Pressure the EPA to ban the persistent herbicides that have already caused widespread crop losses, including those in the pyridine carboxylic acid class.[[12]] The EPA must seriously consider the fate of herbicides in compost when evaluating the registration of products. Require organic manure and compost to be utilized when commercially available, much as is the case with organic seed. Require the manufacturer of persistent herbicides to be held liable for losses incurred to farmers from unintentional contamination. Increase awareness of the issue of contaminated farm inputs.

Please join The Cornucopia Institute in our fight to ban persistent herbicides by contacting your local and state representatives about your concerns.

This story was previously published in the Summer 2015 Cultivator, Cornucopia’s quarterly newsletter.

[1] http://www.ag.ndsu.edu/weeds/weed-control-guides/nd-weed-control-guide-1/wcg-files/15-CO.pdf

[2] http://www.dowagro.com/range/aminopyralid_stewardship.htm

[3] http://www.the-compost-gardener.com/picloram.html

[4] http://csuhort.blogspot.com/2014/04/herbicide-carryover.html

[5] http://www.motherearthnews.com/organic-gardening/milestone-herbicide-contamination-creates-dangerous-toxic-compost.aspx

[6] http://smallfarms.oregonstate.edu/sfn/wtr11Aminopyralid

[7] http://www.theguardian.com/environment/2008/jun/29/food.agriculture

[8] http://www.ams.usda.gov/AMSv1.0/getfile?dDocName=STELPRDC5108939

[9] http://www.ams.usda.gov/AMSv1.0/getfile?dDocName=STELPRDC5110812

[10] http://www.epa.gov/pesticides/ecosystem/ecorisk.htm

[11] http://www.epa.gov/opp00001/chem_search/cleared_reviews/csr_PC-005100_10-May-05_a.pdf

[12] http://vtdigger.org/2013/06/10/herbicide-that-contaminated-green-mountain-compost-now-effectively-banned-in-vermont/