Frequently Asked Questions: Organic Field Crops Section

Pest, Weed and Disease Control:

• Are there any synthetic products approved for weed control?
• How do organic producers manage pests and diseases?
• Are there any products approved for disease and pest control?
• I wish to identify the weeds that are present in my fields. Where can I find information on weed identification?
• What is Bt?
• Is there a website dedicated to organic weed management?

Are there any synthetic products approved for weed control?
No, the use of chemical and hormone herbicides, within the crop, at the edge of fields, within or below hedgerows, headlands and pathways is prohibited. In an organic system weed control is based on cultural and mechanical strategies, e.g., crop rotation; composting of manures; manipulation of crop competitiveness (choice of crop species, varieties, seed rates, undersowing, timing of sowing); mechanical cultivation; thermal weed control and in vegetable crops, there may be a need for a degree of hand weeding.

How do organic producers manage pests and diseases?
For many organic producers managing pests and plant diseases starts with the soil because a healthy soil grows healthy plants. A healthy plant is better able to resist disease and insect predation. A plant disease will usually attack plants from the same plant family, therefore, rotations that alternate crops from different plant families are the main defence against diseases. The use of cover crops and intensive crop rotations including perennial forages helps disrupt the habitat or niche for insects and disease organisms. The diverse population of soil organisms, beneficial insects, and birds also help keep pests in check. As a last resort, organic producers can turn to biological control methods and certain non-synthetic pesticides.

Are there any products approved for disease and pest control?
As stated above, organic farmers as a last resort may turn towards a number of products that are approved for pest and disease control. For example, lime-sulphur, bordeaux, and vinegar, and botanicals are often used as for disease control. The Organic Materials Review Institute (OMRI) is an organization that tests products that are suitable for organic agriculture. The OMRI list, however, is not the final determinant if a product can or cannot be used - that responsibility lies with the certifying body. Most certifying bodies will have their own permitted substances list.

What is Bt?
Bacillus thuringiensis (pronounced as bah-sill-us thur-in-jee-en'-sis) is a living bacterium that has been used by organic growers, non-organic growers and in genetically modified crops to control a plethora of insect pests. Bt is a naturally occurring biological organism that is considered to be remarkably safe for both humans and the environment, due to its specificity against target insects and limited persistence in the environment. Bt products have had widespread, versatile and long-term use and are commonly promoted as an environmentally safe pesticide alternative. Click here for more information about Bt.

Is there a website dedicated to organic weed management?
Yes, there is a good website in the UK called organicweeds.org.uk that specializes in reporting on the latest weed research and techniques and acts as a focal point for farmers and researchers to share their experiences.