Organic Pest Control

Having a pest control plan in place and understanding the pests that are common in your crops will help when transitioning from conventional to organic production. Ann Baier, agriculture specialist at ATTRA, the National Sustainable Agriculture Information Service, offers several pointers on organic control measures for insects, disease, and weed pests.

Insect Control

1. Use integrated approaches to prevent pest problems. Most pest problems, says Baier, can be prevented using integrated approaches. The first thing she recommends to growers is getting to know the pests that are common in their crops, their lifecycles, and what conditions are not conducive to the pests’ growth. And remember different crops attract different pests.

2. Choose crops and varieties that are well adapted to the climate and the season. Appropriate and well-timed cultural practices (tillage, fertility management, irrigation, cultivation, etc.) are critical to preventing pest problems. Monitoring is critical in organic, as it is in conventional, to determine economic threshold levels.

3. Manage aphids by using insectary plants to attract beneficial organisms. For example, Earthbound Organic Farm plants rows of sweet alyssum intermittently among the crop rows, and other insectary plants along field borders to attract syrphid flies that combat cabbage and lettuce aphids, says Baier. The number of rows and location and type of plants can be adjusted to meet the needs of the individual farm, row spacing and width, and equipment operations.

4. Worms, including loopers and cabbage worms, can be managed by planting beneficial insects to attract predators such as spiders, syrphid flies lacewings, big-eyed bugs, minute pirate bugs, soldier beetles, assassin bugs and damsel bugs that prey on worm eggs and small worms. Other natural enemies, she says, include specific parasitoids such as Trichogramma wasps that lay their eggs inside lepidopteron eggs.

"Monitoring pests and beneficial levels is critical to anticipate when reliance on natural biological control of pests may be insufficient," explains Baier. "Organically approved pesticides such as Bts (Bacillus thuringiensis) can be used when threshold levels exceed the capacities of preventative practices to control them."

5. Use physical controls to keep pests away from your crops. For example, cucumber beetles can be a problem in cucurbits and other crops. To help prevent damage from those pests, Baier suggests growers use row covers to prevent pest access to young plants until they outgrow the stage of development when the crop is most susceptible to pest damage.

Disease Control

6. Good air circulation and water drainage are key factors in preventing disease development and reducing disease outbreaks. Dense plantings on poorly drained soils are a recipe for disease development, Baier says, "It also is important to manage plant nutrients appropriately. Fertility management, soil management, and pest management all need to work together."

7. Applying compost teas can introduce enough beneficial organisms that compete with disease-causing organisms and reduce disease incidences. "Systemic-induced resistance is often the result of the complex interaction between plants and the microorganisms in the rhizosphere, or root zone," she explains.

8. There are organically approved pest control products available to growers. Sulfur is approved for organic use and. it suppresses the growth of powdery mildew. However, before growers reach for the sulfur or any other material approved for organic use, Baier says they need to have a plan in place - as specified in the National Organic Standards - to prevent powdery mildew or other pests from occurring in the first place.

Weed Control

9. Growers must use a variety of complimentary approaches to prevent weeds from germinating, getting established, and competing with the crop, plus stops them from going to seed.

10. Crop rotation and cover crops are excellent weed prevention tools. By not planting the same crop year in and year out, growers are reducing the number of weeds they have to battle. Cover crops also are a big help in reducing weed populations.

"A cover crop, if planted thickly, takes up space and light so that weeds can’t grow in between it," says Baier. "The weeds can’t grow and they can’t set seed."

On top of the weed issues, cover crops help improve the soil. Baier suggests using legumes for increasing nitrogen. Grasses can also produce a great deal of organic matter. The best cover crop is often a combination of different plants chosen according to a farm’s particular needs. Cover crops also help build the soil and prevent soil erosion.

A useful resource, "Managing Cover Crops Profitably," is available on line from the Sustainable Agriculture Network at http://www/sare.org/publications/covercrops/covercrops.pdf

11. Keep weeds in check before plants are established via a pre-irrigation technique. In California, where most vegetables are irrigated, pre-irrigation is commonly used to help with weed prevention. Growers irrigate the field prior to planting and allow the weeds to come up. Next, they will do a light cultivation or flaming, and then plant the crop. The result, says Baier, should be less competition from weeds. She adds that transplanting plants rather than direct seeding allows plants to get a jump start on the season and grow faster than weeds.

12. A variety of tools are available to help keep weeds at bay. Baier says good implements for effective mechanical cultivation weed control are needed in organic productions. In order to achieve close cultivation without damaging plants, one also needs good land preparation, including straight rows and accurate seeding or transplant lines in the beds.

A few useful resources for choosing apprioriate implements are:

• Steel in the Field; A Farmer’s Guide to Weed Management Tools; for more information on the book, go to http://www.sare.org/publications/steel/index.htm.
• The September-October, 2006 issue of the ATTRA newsletter was dedicated to weed management:
  http://www.attra.org/attra-digest/ATTRAnews_Sept-Oct06.pdf
• The European Weed Research Society, Physical and Cultural Weed Controls Web site http://www.ewrs.org/pwc/glossary.htm This multi-lingual site has photos as well as a description of the use and application of each tool.

If you need more information on managing weeds, ATTRA has several publications on different approaches to weed management. Like other ATTRA publications, this can be printed directly from the Web site www.attra.org or by calling 800-346-9140.