Pesticide expert warns that lingering herbicides can contaminate gardens, ornamental plants

May 04, 2012

Herbicides can linger in grass clippings, compost and manure, so Montanans should be sure to read product labels to keep from contaminating gardens and ornamental plants, says Montana State University Pesticide Education Specialist Cecil Tharp.

Many that target broadleaf weeds can damage other broadleaf plants, such as peas or tomatoes, Tharp said.

MSU's Schutter Diagnostic Laboratory reported 103 plant samples that exhibited symptoms of pesticide toxicity between 2009 and 2011, Tharp said. The plants came from Montana gardens and had symptoms that made it appear they had been exposed to a class of herbicides known as "plant growth regulators. " Almost 80 percent of the contaminated samples were thought to be linked to compost, manure and grass clippings that had been introduced into the soil.

Plant include the common active ingredients 2,4-D, dicamba, picloram, aminopyralid, clopyralid and the new active ingredient aminocyclopyrachlor. Of greatest concern are picloram, clopyralid, aminopyralid and aminocyclopyrachlor because they can remain active in hay, grass clippings, manure piles and compost for an unusually long time, Tharp said.

To avoid contamination, producers using those active ingredients should pay special attention to the pesticide product label requirements, Tharp said. Instructions vary slightly between products, but they often contain re-cropping , haying, composting and manure restrictions

One restriction that may be found on an aminopyralid product indicates that producers shouldn't use manure in compost or mulch if the manure comes from animals that have grazed forage or eaten hay harvested from treated areas within the previous three days. It takes about three days for the forage or hay to run through the animal's system, Tharp said.

Applicators should also be aware of new requirements regarding the products Milestone, ForeFront and Chaparral, Tharp said. Hay from grass treated in the preceding 18 months cannot be distributed or sold off the farm or ranch where harvested unless allowed by supplemental labeling. Montana, however, doesn't have supplemental labeling to allow off-farm distribution. As a result, applicators must wait 18 months to cut and distribute hay off treated sites, thus allowing adequate time for the grass to metabolize the pesticide product.

Hay also cannot be used for silage, haylage, baylage and green chop if treated within the previous 18 months. Producers cannot use from animals feeding on treated hay in compost. Applicators may follow the less restrictive pesticide product label language of earlier purchased stocks of Milestone, Forefront and Chaparral products until stocks are exhausted.

Explore further: Pipeline that leaked wasn't equipped with auto shut-off

Related Stories

Study looks at turning manure into revenues

Sep 23, 2009

( -- Livestock manure isn't often thought of as a value-added product, but researchers at Montana State University and MSU Extension are trying to change that.

Dairy manure goes urban

Jun 23, 2011

When natural ecosystems are replaced by roads, homes, and commercial structures, soil is negatively impacted. Studies have shown that, among other issues, distressed urban soils are often significantly compacted, ...

A new way to use herbicides: To sterilize, not kill weeds

May 05, 2010

Using herbicides to sterilize rather than to kill weedy grasses might be a more economical and environmentally sound weed control strategy, according to a study by Agricultural Research Service (ARS) scientists and a cooperator.

Recommended for you

Pipeline that leaked wasn't equipped with auto shut-off

May 24, 2015

The pipeline that leaked thousands of gallons of oil on the California coast was the only pipe of its kind in the county not required to have an automatic shut-off valve because of a court fight nearly three ...

California farmers agree to drastically cut water use

May 23, 2015

California farmers who hold some of the state's strongest water rights avoided the threat of deep mandatory cuts when the state accepted their proposal to voluntarily reduce consumption by 25 percent amid ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.