Organic vegetable production systems in the Deep South may not be pesticide-free, especially under high pest-pressure conditions. Prevention is a key strategy for producers, since insect pest damage occurs rapidly, and pest management can be difficult with some organic insecticides.
This publication provides transitioning producers a broad outline of the federal categories of pesticides approved by the Organic Materials Review Institute (OMRI). Producers should read Insecticides for Organic Commercial and Backyard Vegetable Production (Extension publication ANR-1428) for specific organic insecticides and modes of action.
In general, insecticides are categorized based on their mode of action and toxicity. In a sustainable agriculture system, the goal is to minimize the need for insecticides by using Level 1 (cultural control) and Level 2 (mechanical control) tactics. These are described in Understanding NOP Standards for Pest Management in Specialty Crops (Extension publication ANR-2084).
Biorational Pesticides and Nontarget Effects
Approved insecticides should be the last resort for organic producers. USDA National Organic Program (NOP) standards allow for the use of biorational pesticides that have minimum environmental impacts. NOP standards reflect specific requirements that must be verified by a USDA-accredited certifying agent before products can be labeled USDA organic.
Biorational pesticides are generally understood to be derived from natural sources and have short residual action. Some biorational pesticides can have nontarget effects. For example, insecticidal oils can harm some species of lacewing larvae and whitefly parasites (Encarsia pergandiella). Some biorational insecticides are synthetic and can be toxic to insect predators and parasites (e.g., insecticidal soap can be toxic to lady beetle larvae).
EPA Categories of Toxicity for OMRI-Approved Insecticides
Organic insecticidal formulations approved by OMRI must be applied in the recommended manner. Producers must read the insecticide label before use; the label is the law. On the basis of exposure route, the Environmental Protection Agency (EPA) has established four levels of toxicity that apply to all insecticidal formulations. Note that organic insecticides may not need EPA registration; however, most established products carry an EPA registration number and a full insecticide label for promoting correct usage.
Category I: These products have the word DANGER on the pesticide label. None of the approved insecticides fall within this category. Rotenone, which has now been removed from the OMRI list, is an example of a botanical pesticide that had both Category I and Category III ratings, indicating high nontarget impacts.
Category II: These products have the word WARNING on the pesticide label. None of the approved insecticides fall within this category.
Category III: These products have the word CAUTION on the pesticide label. Most of the OMRI-approved insecticides available today fall within this category. They include kaolin clay (mineral particle film), pyrethrum (botanical), synthetic and natural oils, neem (azadirachtin, neem oil, neem soap), Bacillus thuringiensis (Bt), and spinosad (microbial derivative). Some of these products may cause respiratory illness. They should be handled with proper care, and personal protective equipment should be worn when available.
Category IV: These are the safest products for the applicator and environment. They do not need any specific signal word on the label. An example is insecticidal soap (synthetic low-residue formulations).
Organic Insecticide Classification Based on Mode of Action
Based on the mode of action, approved insecticides fall within four categories as described below. Whole- plant systemic insecticides are not allowed in organic farming. In the description below, some insecticides with multiple modes of action also have been included.
Physical barrier and desiccant: A good example of this is kaolin clay, which is a naturally occurring clay formed by weathering of certain rocks. Kaolin clay forms a suspension in water that can be applied over the plants and fruits to confuse insect pests.
Contact poisons: The majority of OMRI-approved insecticides belong in this category. These insecticides could be fast- or slow-acting and leave very little residue on plant surfaces; that is why they are organic approved. These insecticides are easily degraded by sunlight, so repeat application and thorough coverage of foliage is necessary to protect growing plant parts. Some contact insecticides can have systemic activity. Most contact poisons have some effect on natural enemies and pollinators, so use caution when applying these formulations.
Stomach poisons: These are insecticides that have to be consumed by an insect for activation internally (for example, Bacillus thuringiensis-Bt). In many cases, the insect-specific enzyme systems activate the product, making it internally toxic. Stomach poisons may disrupt the digestive and nervous systems very rapidly, but the mortality could take several days.
Volatile action: These insecticides mask the odor of host plants and deter feeding or oviposition. Cinnamite (cinnamon extract) and Garlic Barrier (garlic extract) are sold online and should first be applied in a small area to observe any phytotoxicity. These products are not rain- fast and may lose effectiveness quickly due to heat and sunlight. Several applications are necessary to maintain the repellent action.
General Insecticide Application Recommendations for Organic Producers and Gardeners
- Minimize the use of insecticides and conserve natural enemies using various tactics. Cultural insect control and mechanical practices should be used first to reduce pest pressures. Refer to Understanding NOP Standards for Pest Management in Specialty Crops (Extension publication ANR-2084) and visit the Alabama Vegetable IPM website for more information about IPM approaches suitable for small- and medium-sized farms.
- Calibrate your spray equipment. Invest in a high-quality sprayer with a pressure gauge and appropriate nozzles. Replace nozzles as needed and check calibration every year to cut down on the cost of insecticide.
- Rotate insecticides with different modes of action after correct insect pest identification. Use the pest diagnostic laboratory for quick identification of pests, or consult a regional Extension agent in your county. Insecticide rotations also reduce the potential for resistance in insect pests.
- Target insecticidal treatments where the insect pests are located. Use water-soluble or emulsifiable formulations with a spreader/sticker added. Direct your spray to the underside of leaves to increase persistence of insecticides. Apply dust formulations with proper applicator and avoid treating large open areas to reduce drift.
- Never spray directly over the top of natural enemies. Immature stages of natural enemies are generally more susceptible to insecticides as compared to adults.
The Alabama Cooperative Extension System is committed to serving all food producers and consumers. Consult the regional Extension agent in your area for updates or thorough consultation before and as you start organic crop farming. Regional Extension agents regularly organize special training meetings to teach producers and consumers the methods that correctly utilize science-based organic practices on the farm and in the home garden. To learn more about the progress of organic farming in Alabama, check the Alabama Sustainable Agriculture Research and Education (SARE) website (www.southernsare.org/SARE-in- Your-State/Alabama) and/or contact state SARE coordinators with any questions or concerns.
Disclaimer: Product availability may change from time to time. Other products or suppliers can be recommended by regional Extension agents. Call the toll-free numbers provided for each manufacturer or visit company websites to find a current list of products. Mention of names does not mean endorsement of products by the Alabama Cooperative Extension System.