Question of the Week
Answer: Farmers and dairy producers, including organic farmers, use a wide variety of management practices and techniques for weed control. Synthetic herbicides are just one tool that conventional farmers use that organic farmers cannot. However, all farmers have many more management tools and strategies that can be used to prevent and control weeds. Many people think first of cultivation when they think about weed control on organic farms. For a review of cultivating tools and implements, guidance systems, and flame weeding equipment, the following book (also available in its entirety online) is a useful reference:
Steel in the Field; A Farmer’s Guide to Weed Management Tools
Edited by Greg Bowman. 1997. Sustainable Agriculture Network, National Agricultural Library, Beltsville, MD
A recent issue of ATTRAnews was dedicated to weed management. It also appears online.
Another useful Web site is: European Weed Research Society, Physical and Cultural Weed Controls. This multi-lingual site has excellent photos as well as a description of the use and application of each tool.
Below I have pasted in a section of the USDA’s National Organic Program (NOP) standards that include general guidelines for preventative pest management practices, and suggestions for approaches to weed control. These are important because they clearly show that cultivation is just one of several strategies for successful weed management.
§ 205.206 Crop pest, weed, and disease management practice standard.
(a) The producer must use management practices to prevent crop pests, weeds, and diseases including but not limited to:
(1) Crop rotation and soil and crop nutrient management practices, as provided for in §§ 205.203 and 205.205;
(2) Sanitation measures to remove disease vectors, weed seeds, and habitat for pest organisms; and
(3) Cultural practices that enhance crop health, including selection of plant species and varieties with regard to suitability to site-specific conditions and resistance to prevalent pests, weeds, and diseases.
(b) Pest problems may be controlled through mechanical or physical methods including but not limited to:
(1) Augmentation or introduction of predators or parasites of the pest species;
(2) Development of habitat for natural enemies of pests;
(3) Nonsynthetic controls such as lures, traps, and repellents.
(c) Weed problems may be controlled through:
(1) Mulching with fully biodegradable materials;
(3) Livestock grazing;
(4) Hand weeding and mechanical cultivation;
(5) Flame, heat, or electrical means; or
(6) Plastic or other synthetic mulches: Provided, That, they are removed from the field at the end of the growing or harvest season.
Two ATTRA publications are also particularly relevant:
Thistles are often a problem in pasture settings on dairy farms.
ATTRA’s other current offering of publications on weed management are: Field Bindweed Control Alternatives; Alternative Control of Johnsongrass; Flame Weeding for Agronomic Crops; and Flame Weeding for Vegetable Crops.
Regarding organic compliance, please notice that that both of these publications include a section on least-toxic herbicides with specific materials mentioned. These publications are more that two years old, and the allowability of brand-name materials is subject to frequent change.
I strongly recommend that certified organic producers follow these steps for any material inputs they are considering for use (before use):
1) Become familiar with NOP regulations about materials. The regulatory text can be found at
See sections 205.105 and the National List of Allowed and Prohibited Substances in sections 205.600-606. These state that natural materials are allowed unless they are prohibited, and that synthetic materials are prohibited unless they are allowed. Lists 205.601 and 205.603 list Synthetic substances allowed for use in organic crop and livestock production respectively, and 206.602 and 205.604 list natural materials that are prohibited. List 205.605 lists Non-agricultural substances allowed for use in or on processes products labeled as “organic” or “made with organic…”; and 205.606 lists Non-organically produced agricultural products allowed as ingredients in products labeled as organic or made with organic ingredients. Each list is intended to be specific to its type of production, and several products include annotations that restrict or specify their uses (i.e. crop fertilizers, pest, disease or weed control; livestock feed, feed additive or supplement, disinfectant, medical treatment or topical use).
2) List every material you use or plan to use in your Organic System Plan (OSP) that you submit to your certifier. Include the identity and source, or brand name and manufacturer of every material.
3) Verify whether your organic certifier has a current list of approved brand name materials. Many use OMRI and WSDA lists, and some maintain their own lists in addition to these:
• The Organic Materials Review Institute (OMRI) Products List
In addition to the OMRI Products List of brand name materials, OMRI also publishes a Generic Materials List for subscribers, which is a very useful source of information to help interpret the NOP’s National List, to determine whether a material is natural and whether it is allowed for use in organic production. Inclusion on the OMRI list must be renewed every year. Some products may be listed one year and not the next. Reformulations (common in the industry) may render a product non-compliant, or possibly make it compliant. In some cases, producers will be required to document which lot number of a product they used in order to verify compliance. For the same reasons, producers should review and update their OSPs annually or as needed to verify current materials compliance.
While OMRI is a nonprofit organization that is not officially recognized by the NOP, their services facilitate understanding of the National List, and many certifiers use the OMRI lists as their own list of approved brand name materials.
• Washington State Department of Agriculture (WSDA) Brand Name Materials List http://agr.wa.gov/foodanimal/organic/materialslists.html
The WSDA list is also recognized as a valid list of approved brand name materials.
United States EPA has begun a labeling program with a seal for products that are allowed under the NOP standards for organic crop production. However, it is not yet widely used.
4) Check whether the material you are interested in using it is on an approved list of Generic or Brand Name materials. Please note: always use the most current information available. The Web sites (above) are best to verify any claim of listing. A very recent printed guide is next best. It is the producer’s responsibility to verify the truth of that statement by checking the current lists on the Web site.
5) If the material/product you are interested in using is not listed in an approved list, follow your certifier’s instructions to verify its allowability. For example, attach a product label with a list of all ingredients, including inert ingredients, or a letter from the manufacturer that provides information sufficient to verify and document that all ingredient are allowed.
6) Be sure every material and supporting documentation is in OSP that it is approved by your Certifier before you use it. Your certification depends on it!
7) Keep documentation of every input material purchase and application for 5 years.
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