Herbicides causing problems for gardeners

Gardeners finding their crops damaged by residual herbicides in manure

Editor, The Times:

Have you spotted a strange curling disease in your homegrown vegetables?

Have you heard the words Aminopyralid or Clopyralid? How about picloram, triclopyr, or 2,4-D? If not, I am sure you know the word herbicide and, for some of you, Grazon is a familiar word. These herbicides are used to control the growth of broad-leaved weeds like docks and thistles in grassland and pasture. Grasses are unaffected by the chemical, but it’s taken up and incorporated into the lignin, the woody tissue in the plant. There it remains, is eaten by horses, cows and other ruminants and is expelled, still lethal, in their manures. Mammals do not metabolize Grazon so, when ingested, it is rapidly excreted from the body in the urine and feces.

Some local suppliers of manure may not be aware of its presence, so have supplied their product in good faith to those of us who grow organically here in the valley. Also, straw, hay and silage used for winter-feed and bedding has come previously sprayed with this herbicide. Most farmers assume the herbicides they use will degrade quickly. Most (so we’re told) do. Aminopyralid, and its precursor Clopyralid, do not.

Evidently the problem isn’t new, though the scale of its effects – in the U.K. and the USA at least – appear unprecedented. Problems began to emerge when farmers and gardeners in northwestern Washington state used compost made with manure from farms on which Aminopyralid had been applied (one farmer reported more than $200,000 in crop losses).

Problems with manure contaminated with Aminopyralid residue surfaced in the U.K. in June and July 2008. At the end of July 2008, Dow Agro Sciences implemented an immediate suspension of U.K. sales and use of herbicides.   Small farmers and gardeners in Britain reported symptoms of Aminopyralid injury to vegetable crops in July 2011.

The problem may be traced locally to incorrect use of the herbicides. Farmers and ranchers are not reading the labels correctly. Milestone’s label states: “Do not spread manure from animals that have grazed or consumed forage or eaten hay from treated areas within the previous three days [of application] on land used for growing susceptible broadleaf crops.” That label goes on to explain that such manures may only be safely applied to pasture grasses, grass grown for seed and wheat and warns: “Do not plant a broadleaf crop in fields treated in the previous year with manure from animals that have grazed forage or eaten hay harvested from Aminopyralid-treated areas  …”

Aminopyralid is of concern to vegetable growers, as it can enter the food chain via manure that contains long-lasting residues of the herbicide. It affects potatoes, tomatoes, peppers, eggplants and beans, causing deformed plants, and poor or non-existent yields.

I urge gardeners and farmers/ranchers alike to inform yourselves about the dangers of these herbicides. Make sure of the source of the manures for your gardens as this chemical will not be destroyed by your composting process and must be left from two to five years to break down in the soils. It does not travel out of soils or compost bins. You will lose the ability to grow your broadleaf vegetable crops for the years it takes to break down this herbicide.

Here are several other Internet resources you can check out to learn more about this problem. I have learned first-hand and never want a repeat of this danger in my gardens.

• www.biocycle.net/2011/06/the-aminopyralid-challenge-continues/

• myfolia.com/journals/21643-aminopyralid-theres-muck-in-the-muck

• www.guardian.co.uk/environment/georgemonbiot/2011/jul/15/vegetables-disease-aminopyralid-pesticide (he means herbicide)

Suzanne Gravelle

Clearwater, B.C.