Pesticides vary in their toxicity and in their potential ecological impact. Pest control materials that are relatively non-toxic to people with few environmental side-effects are sometimes called “biorational” pesticides. These fit well into an integrated pest management strategy, which relies on monitoring for early detection of pests and emphasizes the use of selective products that provide control while preserving the ecological health of the farm and minimizing negative effects on beneficial insects that suppress pests. The term “biorational” is a qualitative term intended to help provide information and guidance for decision making. All pesticides have some toxicity; always read and follow the label regarding agricultural use requirements and personal protective equipment. All of the insecticide products listed as biorationals in Table 13 carry the signal word “Caution,” the least toxic classification, on the label (see Pesticide Safety and Use, page 28). None are federally restricted-use products. Most have dermal and oral LD50 values over 2,000 mg/kg (see Table 20).

Some, but not all, biorationals are approved for use on certified organic crops. For a given active ingredient, some products or formulations may be approved for use in certified organic crops, while others are not. Products that are generally approved for organic production are designated “OMRI” or “OMRI listed,” which indicates they are listed on the website of the Organic Materials Review Institute at the time of publication (July 2009). Growers should consult with their certifying agency to be sure about what products are approved for use.

Table 13 lists biorational insecticides and Table 14 lists biological controls for insect management. See also Table 20 and the Alphabetical Listing by Trade Name  for more details on specific active ingredients or products. The major categories of biorationals include botanicals, microbials, minerals, and synthetics.

Botanicals are plant-derived materials and include pyrethrin, azadiractin and neem oil, garlic, capsaicin, and vegetable oil. Botanicals are generally short-lived in the environment, as they are broken down rapidly in the presence of light and air. Products derived from the seeds of the neem tree, including azadiractin and neem oil, are selective and have low mammalian toxicity. Garlic and capsaicin act primarily as repellents and thus need to be reapplied as long as pests are present. They are registered for use on a wide range of crops and pests. However, none are listed in this Guide for commercial use unless they carry the proper agricultural use requirements on the label. Vegetable oil may be derived from soybean, corn or other plants; the only labeled product for commercial use is produced from soybean oil.

Microbial pesticides are formulated microorganisms or their by-products. They tend to be selective, so specific pests may be controlled with little or no effect on non-target organisms. Microbial insecticides include bacteria (Bacillus thuringiensis and spinosad) and fungi (Beauvaria bassiana). While these active ingredients are generally approved for organic crops because of their natural origin, certain formulated products are prohibited because the inert ingredients or procedures used in producing the product may be prohibited.

Minerals and synthetics. Some biorational pesticides are minerals, mined from the earth and minimally processed. Kaolin clay, insecticidal soap, and iron phosphate are examples (see Table 13). Minerals that are heated, chemically reacted, or mixed with surfactants may be considered synthetics. Synthetics include growth inhibitors or insect growth regulators (any of which is commonly known as an IGR), materials that interrupt or inhibit the life cycle of a pest.

Biological Control of Insect Pests

Biological control is taking place in vegetable crops all the time, because native and naturalized populations of natural enemies overwinter on the farm and move into crops to feed on or lay their eggs into pest insects. Predators consume several insects over the course of their development. Parasites (also called parasitoids) tend to lay eggs in their host insect, which then feed internally, develop and kill the host. Pathogens invade the body of the host insect. The impact of beneficial insects is often underestimated because it is easy to overlook and difficult to measure. It may become obvious if they are killed by broad-spectrum insecticides and pest outbreaks occur as a result. Conservation of beneficials by use of selective insecticides when pests exceed threshold levels is recommended wherever practical.

The release of lab-reared beneficials can also aid in suppressing pests. These tend to be more successful in greenhouses than in the field, but there are several instances where releases in the field have been proven to suppress or completely control key pests. Trichogramma are tiny wasps that lay their eggs inside the eggs of insects, and wasp larvae develop inside, killing the egg. Several species are commercially available, but the most useful in vegetable crops are T. pretiosum for caterpillar eggs and T. ostriniae, against European corn borer in sweet corn and pepper. Releases should be timed to coincide with egg laying.

Biorational Disease Control

Biorational disease control products (fungicides, bactericides, and nematicides) fall into the same classes as the insecticdes. Botanicals, minerals, and synthetics are listed in Table 15 (Biorational Disease Control Materials). Sulfur, potassium bicarbonate, phosphites and copper compounds are examples of minerals or synthetics that can control fungal and bacterial diseases. Not all of these products are OMRI listed; be sure to check with your state certifying authority for more information on thse materials. A new category of non-toxic pesticide is based on naturally occurring proteins called harpins that are produced by bacteria and other microbes. Pathogenic bacteria need harpins to infect their host plants. When applied to plants, synthetic harpins stimulate the plant’s defense systems. They do not have any direct pesticidal effect, but reduce disease progress by strengthening plant defenses. (See Table 15).  Botanicals such as rosemary oil, soybean oil, or garlic extracts also appear in this table and are generally approved for use in organic production by OMRI. Products listed in Table 15 require thorough coverage, application at the first signs of disease, and frequent repeated dosages to be effective.

Microbial products are listed in Table 16 (Biological Disease Control Products) and are all living organisms which require specialized storage and application procedures. The table includes beneficial fungi and bacteria (Streptomyces, Gliocladium, Trichoderma harizanum) that compete with plant pathogenic fungi, produce toxic metabolites, or actively parasitize pathogens. Their effectiveness in university research trials has been inconsistent because of variations in environmental conditions and disease pressure. Microbial fungicides perform best in a greenhouse environment where they can establish and flourish. Control of plant pathogenic organisms on the phylloplane (leaf surface) is especially problematic, as the competing organisms must establish themselves and can fail due to dessication and exposure to sunlight. These materials have a limited shelf life, must be protected from temperature extremes, and correctly applied (plenty of water and under the correct environmental conditions) for effectiveness.