Pesticides vary in their toxicity to people and to non-target organisms, and in their potential ecological impact. Pest control materials that are relatively non-toxic to people with few environmental side-effects are called “biorational” pesticides in this Guide. Biorational pesticides mostly include the following categories further defined in this section: biopesticide, organic pesticide, minimum-risk pesticide, and biological control. Federal law governs pesticide registration through the EPA, and materials derived from living things are defined as “biopesticides”. Organic production is regulated through the USDA National Organic Program which defines what inputs are allowed for pest management. “Organic” and “biopesticide” are partially overlapping categories, and each is defined by specific criteria that are unique. “Minimum risk pesticide” is another category that is defined by EPA; these are exempt from federal registration. “Biological control” describes living organisms that suppress pests. Some biological controls are naturally occurring, some are insects purchased by farmers for pest control, and some are microbes formulated for sale as biopesticides.
All tables in this section include products that are registered as pesticides as well as some that are exempt from EPA registration. None are federally restricted-use products. Most have low dermal and oral LD50 values and they carry the minimum EPA signal word of “Caution”. However, some organic pesticides such as copper sulfate have a high dermal and oral LD50 value and carry the EPA signal word “Danger” on their label.
Types of Biorational Pesticides
Botanicals are plant-derived materials such as pyrethrin, azadiractin, and extracts of plants such as Chenopodium ambrosioides and Swinglea glutinosa. Plant-derived oils such as neem oil, canola oil, and sesame oil are also included in this group. Botanicals are generally short-lived in the environment, as they are broken down rapidly in the presence of light and air. Products generally have low mammalian toxicity and a broad spectrum of activity. Many botanicals are considered minimum risk pesticides and are exempt from registration by EPA (see below).
Microbial pesticides are formulated from living microorganisms and/or their by-products. Microbial insecticides tend to be selective, so specific pests may be controlled with little or no effect on non-target organisms, while most microbial disease control products have a wider spectrum of activity. Microbial insecticides may be derived from bacteria (e.g. Bacillus thuringiensis, spinetoram and spinosad, Chromobacterium subtsugae), virus (e.g. nuclear polyhedrosis virus of corn earworm) or fungi (e.g. Beauvaria bassiana). Microbial disease control products are living organisms, including beneficial fungi and bacteria. Examples of microbial disease control organisms are the fungus Trichoderma harzianum and the bacterium Bacillus subtilis. While these active ingredients are generally approved for organic production (OMRI listed) because of their natural origin, certain formulated products are prohibited because the inert ingredients or procedures used in making the product are prohibited.
Minerals. Some pesticides made from minerals, mined from the earth and minimally processed, are allowed in organic production. Kaolin clay, copper hydroxide, and iron phosphate are examples (see Table 21 and Table 23).
Synthetics. Minerals and other natural materials that are heated, chemically reacted, or mixed with surfactants may be considered synthetics. Synthetics also include insect growth regulators (IGR), which interrupt or inhibit the life cycle of a pest. They may also work by strengthening plant defenses. National organic standards include some allowed synthetics.
Biopesticides, as defined by EPA, are certain types of pesticides derived from such natural materials as animals, plants, bacteria, and certain minerals. As of August 2020, there are 390 registered biopesticide active ingredients. EPA generally requires less data to register a biopesticide than to register a conventional pesticide, thus the registration process is faster. Categories of biopesticides include:
- Microbial pesticides, in which a microorganism (e.g., a bacterium, fungus, virus or protozoan) is the active ingredient
- Plant-Incorporated-Protectants (PIPs), in which pesticidal substances are produced by crop plants as a result of genetic material being added to the plant (e.g., Bt insecticidal protein). With plant-incorporated protectants, the toxin and its genetic material, but not the plant itself, are regulated by EPA.
- Biochemical pesticides, which are naturally occurring substances that control pests by non-toxic mechanisms, such as sex pheromones that interfere with mating and scented plant extracts that attract insect pests to traps.
Biopesticides generally fit well into an integrated pest management (IPM) strategy, which relies on monitoring for early detection of pests and emphasizes the use of selective products that protect crops while minimizing negative effects on water, air and soil, and on pollinators and beneficial insects. The purpose of this section is to bring these types of products together to help growers make decisions about pesticides and biological controls to use on their farm.
Pesticides in Organic Production
The USDA National Organic Program allows application of biological, botanical, or mineral inputs, when cultural practices are insufficient to prevent or control crop pests, weeds, and diseases. Most of these are non-synthetic and/or minimally-processed.
NOTE: not all biopesticides are labeled for use in certified organic agriculture. The grower is responsible for determining whether materials are allowed under organic standards. Sometimes this may be a challenge because some materials labeled as organic by the manufacturer may not actually be allowed by the USDA National Organic Program. The Organic Materials Review Institute (OMRI) is recognized by the National Organic Program as an organic material review organization. It lists products it finds suitable for certified organic production. These products are generally allowed without restriction, but some are regulated and subject to restrictions. In some cases, OMRI notes that certain formulations of a product are permitted and others are not. The list of substances approved by OMRI is subject to change.
Be sure to check with your certifier in advance to be certain that the materials and practices you plan to use are approved by your certifier, and that you understand any restrictions on use. For the most up-to-date OMRI list, visit the OMRI web site at: www.omri.org. When mentioned in tables or in crop chapters, this Guide designates approved organic materials with a superscript OG ( OG ), which means they were "OMRI listed" at the time of publication (June 2022).
Minimum risk (exempt) pesticides. These are a special class of pesticides that are not subject to federal registration requirements because their ingredients, both active and inert, are demonstrably safe for the intended use. This exemption falls under section 25(b) of the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). Of the New England states, CT, ME, NH, RI and VT all require state registrations for these products while MA allows exemption for all products that meet the minimum risk criteria and are on the federal 25(b) list. For more information, please contact your state's pesticide registration office (see Pesticide Safety and Use). The list of 25(b) exempt materials includes the following: corn gluten meal; sodium chloride; corn, linseed, sesame, soybean, and cottonseed oil; garlic and garlic oil; and essential oils including rosemary, mint, thyme, geranium, lemongrass, cinnamon and rosemary. Some pest control products listed in this guide meet the criteria for exemption and do not have EPA pesticide registration or a pesticide label. More on this class of pesticides can be found at: https://www.epa.gov/minimum-risk-pesticides.
Biological Insect Control
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. Parasitoids lay eggs in their host insect, which hatch into larvae that 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. Beneficial insects may be killed by broad-spectrum insecticides, and pest outbreaks can occur as a result. Conservation of beneficials by use of selective insecticides when pests exceed threshold levels is recommended wherever practical.
The release of commercially produced 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. See Table 22 for information about biological controls for the field, and also Biological Control for Insects and Mites in the Vegetable Transplants section.
Biological Disease Control
Biological disease control products (fungicides, bactericides, and nematicides) fall into the same classes as the insecticides. Botanicals, minerals, and synthetics are listed in Table 23. 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 these materials. 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 23 require thorough coverage, application at the first signs of disease, and frequently repeated dosages to be effective. For products that may be used in vegetable transplant production, see Table 19.
Microbial products are listed in Table 24 and are all living organisms which require specialized storage and application procedures. The table includes beneficial fungi and bacteria such as Streptomyces, Gliocladium, and Trichoderma, which compete with plant pathogens, 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 disease control products 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 desiccation 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.