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[GreenYes] Clopyralid and Compost (Dow ArgoSciences)
- Subject: [GreenYes] Clopyralid and Compost (Dow ArgoSciences)
- From: "Spivey, Susie" <SSpivey@beerscc.com>
- Date: Fri, 19 Oct 2001 16:26:19 -0400
Clopyralid and Compost
Weed-control products containing clopyralid have been used safely and
effectively for more than 14 years. Recently, incidents have been reported
in which clopyralid traces were detected in compost material at a level
sufficient to cause damage to sensitive plants grown in the compost medium.
These incidents appear to involve unique or unusual circumstances.
Nevertheless, Dow AgroSciences, the manufacturer of clopyralid products, is
concerned and committed to resolving issues regarding the use of clopyralid.
The company is working with university researchers, the compost industry and
grower groups to develop a thorough understanding of actual use practices of
the products and the potential of the products to contribute residues to
compost materials. The labels on all Dow AgroSciences clopyralid products
state that manure and foliage treated with clopyralid should not be used as
a source for compost. Dow AgroSciences is working with the U.S.
Environmental Protection Agency to further emphasize the label language, and
the company is developing an educational program to increase awareness of
this compost restriction among farmers, ranchers, homeowners and lawn care
providers who use clopyralid products.
Clopyralid is an important tool for integrated weed management because it is
effective against hard-to-control weeds that other methods cannot control.
These include noxious weeds such as Canada thistle, knapweed and yellow
starthistle, which pose a serious threat to crops, rangelands and wildlife
areas. It is also effective against kudzu, an invasive species that chokes
out native plants in vast areas of the Southern United States. In turf uses,
clopyralid is very effective against clover and dandelions. Prior to its
introduction, lawn care companies treated three to five times per year with
other products, which are applied at much higher rates. Clopyralid has
helped applicators reduce the amount of herbicides applied and allowed
operators to be more efficient with their time, fuel and equipment.
Clopyralid is the active ingredient in a number of products, including
Confront®, Curtail®, Lontrelā, Redeem,ā Stinger® and Transline® herbicides.
Clopyralid is a selective herbicide, meaning it is effective only on certain
plant species, primarily members of the Leguminosae, Solanaceae and
Compositae families. These families include weeds such as clover, thistle
and dandelions, but also crops such as peas and beans, tomatoes and
sunflowers. Studies show that clopyralid affects susceptible plants at
concentrations as low as 3 parts per of billion. Clopyralid has a favorable
toxicological profile and according to U.S. Environmental Protection Agency
criteria is "practically non-toxic" to humans and wildlife.
INVESTIGATION OF REPORTED TURF INCIDENTS
Confront herbicide is the most widely used clopyralid product for turf.
Other turf products with clopyralid include Battleship, Chaser Ultra,
Millenium Ultra, Momentum, ProScape fertilizer and Strike Three Ultra.
The labels on these products state that grass clippings from treated lawns
should not be used for composting. In investigating reported incidents
involving clopyralid residues in compost, several key factors have been
Those factors include:
· The percentage of treated lawns that contribute grass clippings for
compost in violation of label precautions;
· The ratio of grass to other material in the compost, such as leaves
· The amount of soil that was blended with compost during planting.
INVESTIGATION OF REPORTED TURF INCIDENTS (continued)
Spokane, WA, area. In Spokane, which had recently implemented curbside
collection of lawn waste for use in the regional composting facility,
compost was linked in a few instances to damage to tomatoes and other
susceptible plants. Significant clopyralid residues were found in finished
compost. An investigation showed that several factors worked together to
create a situation that would not be expected in other communities.
· A high percentage of lawns in the Spokane area (pop. 400,000) are
professionally treated. Applicators estimate the percentage of treated lawns
may be as much as twice the national average. The majority of lawns are
treated with Confront herbicide because of its effectiveness on weed species
that are prevalent. More Confront was sold in Spokane (by volume and on a
per/acre basis) than anywhere else in the U.S. In 2000, 1,367 gallons were
sold in and near the community. For comparison, only about 460 gallons were
sold in all of western Washington State, stretching from 50 miles north of
Portland, OR, to the Canadian border, an area with five times more
· A very large percentage of homes in the Spokane area contribute
grass clippings to the community's composting facility via curbside pickup
· The compost involved in reported Spokane incidents contained a high
percentage of grass to other organic matter, estimated at 85 percent.
· In some reported incidents, the compost users did not sufficiently
blend compost with soil, as recommended by the composting industry. In one
incident, the compost was used 100 percent as potting material for tomato
plants. In another incident, a large amount was used in a garden. The
compost industry recommends that compost be blended with soil at a 10
percent rate (4 cu yd per 1000 sq ft, or 1-in. layer incorporated).
Because of the unique situation in Spokane, Dow AgroSciences voluntarily
suspended sales to residential areas in the community pending further
evaluation. Even with its unusually high percentage of treated lawns,
Spokane had operated a regional compost facility since 1993 without
incident. However, in 1998 the city initiated curbside collection of lawn
clippings in an effort to reduce landfill waste. Homeowners, many of whom
may not have collected clippings in the past, began contributing to the
compost effort. It is apparent that some whose lawns were treated with
clopyralid also contributed clippings, contrary to label instructions.
Penn State University. The university, which operates a composting facility
on campus, experienced plant growth problems primarily in covered greenhouse
type settings. Clopyralid found in the compost was traced to the vegetative
material collected from the university's lawns in the fall of the year.
Grass clippings from about 300 acres of treated lawns were not saved for
compost, but leaves on the lawns were collected by a leaf vacuum and used
for compost. Investigation showed that some of the leaves were apparently
over-sprayed with clopyralid during September and October applications. In
addition, some grass clippings left in the lawn were also vacuumed up with
the leaves. As a result, a high percentage of the material used for
composting contained clopyralid residues. The university continues to use
clopyralid on athletic fields, which do not contribute leaves or clippings
Dow AgroSciences is working with the U.S. Environmental Protection Agency
and state regulatory agencies to develop a revised product use label that
will ensure that homeowners and other turf customers are informed about the
restrictions regarding composting and mulching. In addition, the company is
developing an awareness effort aimed at composters, professional lawn care
operators and their customers.
EXAMINATION OF AN INCIDENT RELATED TO NON-TURF USE
An incident at the composting facility at Washington State University in
Pullman has demonstrated that agricultural use of clopyralid products can
affect composting operations. The clopyralid issue at that facility emerged
during the investigation of an issue with another herbicide. It is believed
that when farmers in the surrounding area provided straw to the university's
veterinary facility, it apparently contained traces of the herbicide. When
bedding and manure were collected from veterinary stables, traces of
clopyralid were detected in the stable waste. The labels for
clopyralid-containing agricultural products prohibit the composting of hay
or straw from treated fields or manure from animals that have grazed in
treated areas. However, the farmers may not have been aware that the straw
would be used for compost. Currently, the university composting site is only
accepting straw from acres that have not been treated with clopyralid.
Based on this incident, Dow AgroSciences is conducting an investigation of
non-turf uses of clopyralid and is committed to resolving any issues that
may be identified.
Clopyralid, sold under the trade names of Curtail, Redeem and Stinger
herbicides, is an important tool in agriculture and ranching for spot
control of thistles and other noxious weeds. Producers of wheat and barley
use clopyralid, as do people who produce mint, asparagus, Christmas trees
and grass seed. Growers of these "minor crops" have limited choices of
agricultural pest control products because a limited number of products are
registered for these uses. All agricultural labels state that hay, straw and
manure from crops treated with clopyralid cannot be used for compost or
Some agricultural uses, such as rangeland and Conservation Reserve Program,
contribute little if any material to composting. In other applications,
which may contribute material to composting, the use of clopyralid is not
widespread. For example, less than 2 percent of wheat and barley acres are
treated with clopyralid. Some of the minor crops are grown by a small
number of growers, so that targeted communication and education could be
possible. In some cases, a food processor and not the grower may be the most
likely contributor to compost.
Dow AgroSciences is committed to improving awareness through education,
stewardship and label changes where necessary. While there is potential for
agricultural uses to contribute clopyralid to compost, a preliminary
investigation indicates that the potential is low and manageable.
ROADSIDE AND INDUSTRIAL USES
Clopyralid, sold under the brand name Transline herbicide, is used to
control specific weeds along highways, railways or utility rights-of-way. It
is used in spot applications to control thistle and various other noxious
weeds. Dow AgroSciences is investigating whether and to what extent
industrial and transportation rights-of-way contribute materials to
composting, but the potential appears to be low.
WILDLIFE HABITAT MANAGEMENT
Clopyralid is used to stop the spread of invasive weeds, such as
spotted/diffuse knapweed, Canada thistle, yellow starthistle and hawkweeds,
which can crowd out native vegetation and diminish wildlife habitat. Less
than 1 percent of wildlife management acres are treated with clopyralid.
Vegetative material from wildlife management areas is not used for
COMMITMENT TO SOLUTIONS
Dow AgroSciences is concerned about the recent reports of clopyralid being
found in compost at levels that can harm beneficial plants. The company is
actively engaged in investigating the potential for any labeled use of the
product to contribute to compost. Where the problem exists, the company is
committed to solutions, which may include new label instructions, increased
communication and improved product stewardship. The company is actively
working with universities and governmental agencies to develop more data
that will answer emerging questions. In addition to the already robust body
of data on clopyralid, ongoing efforts include:
· Studies to determine how fast clopyralid breaks down in various
· Studies to identify how much clopyralid residues in grass decrease
with subsequent mowings.
· Mitigation techniques to speed degradation if clopyralid is detected
at a phytotoxic level in compost.
· Developing educational programs concerning proper disposal of
treated lawn clippings when lawns have been treated with clopyralid.
· Working with commodity groups, ag extension agents and others to
increase understanding of label restrictions.
*Trademark of Dow AgroSciences LLC
Clopyralid is an important herbicide for use in integrated vegetation
management programs because it controls many noxious weeds that are not
adequately controlled by other methods. It also is important to minor crops,
which have few herbicide options. Very few compost incidents have occurred
with clopyralid despite years of use in agriculture, vegetation management,
and turf and ornamental industries. The incidents that have occurred can be
traced to off-label uses or misunderstanding. Dow AgroSciences is committed
to improving product labels and to developing educational efforts to reduce
the likelihood of future incidents involving compost.
Dow AgroSciences LLC
9330 Zionsville Road
Indianapolis, IN 46268-1054
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