Organic Broadcaster

Biopesticides offer effective, progressive pest management

By Bill Stoneman, Biopesticide Industry Alliance

“All the pests that out of earth arise, the earth itself the antidote supplies.”
Lithica circa 400 B.C.

Through organic soil management practices, farmers foster a very important soil microbial and biochemical resource for successful biological control of potential pests affecting their crops or livestock. Within the soil are a great diversity of microorganisms and biochemicals produced by those microorganisms and plants, some with roles very important to the natural management of pests. Soil microbiologists know that a single gram of soil (about a thimble full) may contain as many as 1 billion living cells of microorganisms from up to 10,000 different species. Many of these microorganisms are unknown or cannot be cultured. In organic-matter-rich soils and those well managed with organic practices the numbers are likely much higher. It is from this biodiversity that many microbial and biochemical biological pesticides (biopesticides) are born.

The soil is the source of nearly all microorganisms used in food processing and agricultural applications. Yogurt cultures, cheese cultures, cheese molds (blue and green), and meat-curing cultures all originate from the biodiversity of the soil. Organic dairymen are familiar with silage inoculant bacteria and enzymes, as well as the nitrogen-fixing bacterial cultures important to establishing alfalfa. Foresters and growers who practice permaculture rely on mycorrhizal fungi to conduct essential nutrients and moisture to plants’ roots. Livestock producers know the value of direct-fed microbials (probiotics) for animal health. These important microbes are all from the vast biodiversity of the soil.

The active ingredients in biopesticides—or biorationals, as some refer to them—are all of the Earth and, by definition, naturally occurring. Not all biopesticides are made up of microorganisms, however. The U.S. Environmental Protection Agency (EPA), which regulates biopesticides, defines them as “certain types of pesticides derived from such natural materials as animals, plants, bacteria, and certain minerals.”¹ The EPA further defines biopesticides by three main categories: microbial, biochemical, and plant-incorporated.

These grasshoppers are infested with the biological pesticide Beauveria bassiana, a fungus that grows naturally in soils throughout the world and acts as a parasite on various arthropod species, causing white muscardine disease. Photo by Stefan Jaronski, USDA-ARS

Microbial pesticides have a microorganism (e.g., a bacterium, fungus, virus or protozoan) as the active ingredient. Biochemical pesticides are naturally occurring substances that control pests by non-toxic mechanisms.

Plant-Incorporated-Protectants (PIPs) are pesticidal substances that plants produce from genetic material that has been added to the plant. PIPs are genetically modified plants (GMOs) and are not allowed in organic agriculture. Outside of the EPA’s definition, PIPs are not widely considered “biopesticides.” Biopesticides in the United States are regulated by the EPA much like conventional pesticides and undergo much of the same evaluations for human health and safety as well as environmental effects.

The National Organic Standards allows biopesticides under certain conditions after all other potential cultural practices and other methods (e.g., variety selection) have been attempted to control the weed, insect or disease. Of course it is not only the active ingredients that are considered when determining if a biopesticide is allowed in organic agriculture, but also the inert ingredients (carriers, surfactants, diluents and others).

The most widely used microbial biopesticide is Bacillus thuringiensis, more commonly known as Bt. A well-known brand used in organic agriculture is Dipel® for caterpillar control. Bt is a naturally occurring bacterium common in soils throughout the world. It produces proteins that react with the gut lining in susceptible insects, paralyzing their digestive system so they stop feeding and die from starvation. In 1901, Bt was isolated from a diseased silkworm by Japanese biologist Shigetane Ishiwata. 10 years later, German biologist Ernst Berliner rediscovered it in a diseased flour moth caterpillar and named it after the German town of Thuringia. The French began to use Bt as a biological insecticide in the 1920s.

Other well-known products widely used in organic farming include Actinovate® and Serenade® (bacterial agents) for control or suppression of a variety of plant diseases, Contans® WG (a fungal agent) for control of white mold or lettuce drop, and Bio-Save® 10LP (a bacterial agent) for postharvest treatment of potatoes and fruit to prevent damage from blue mold or gray mold in storage.

Paecilomyces fumosoroseus is a naturally occurring fungus used in a greenhouse environment to control several species of insects including whiteflies, thrips, aphids, and spider mites. Paecilomyces lilacinus is used to control nematodes that attack plant roots in field crops, including many vegetables, fruit, turf, and ornamental crops. It is sold in the United States under the brand MeloCon® WG.

Perhaps the best-known biochemical pesticide is pyrethrum, which is derived from chrysanthemums (natural plant extract) and sold under the brand Pyganic®. However, it is not regulated as a biopesticide and does not fall under that definition within the EPA because it has what is considered a “toxic” mode of action to the insects it controls. Because Pyganic’s active ingredient is naturally derived, however, it is allowed in organic agriculture.

To be defined as a biopesticide by the EPA a biochemical must have a non-toxic mode of action—which can be confusing since, in order to be of any value, the material must control or suppress a pest (insect, weed or disease), implying it is toxic to that pest. What the EPA means by “non-toxic” is that the activity of the biochemical pesticide must not be by a biochemical pathway within the pest, but by a more mechanical activity such as smothering, breaking a weed’s waxy leaf cuticle or by damage due to strong oxidative activity. Vinegar is an example of a non-toxic weed control agent. It damages the weed it is sprayed on causing desiccation or drying action that eventually suppresses or even kills the weed.

Plant extracts were likely the earliest biochemical biopesticides, as history records that nicotine was used to control plum beetles as early as the 17th century. Neem oils have been used for hundreds of years to control pests. Neem oil is a naturally occurring biopesticide found in seeds from the neem tree. Azadirachtin is the most active component in neem oils, and some biopesticide products contain this compound in purified forms. Neem has several modes by which it controls or suppresses insects, including activity as a natural repellent and as an insect growth regulator. Neem and its active components are generally considered safe for beneficials because pesticidal activity is directed at sucking and chewing insects.

Another widely used biochemical biofungicide is Regalia®. It is derived from the extraction of certain components of giant knotweed. It creates a defense response in the treated plants and stimulates additional plant pathways that strengthen the plant structure and act against the pathogen.

Pest resistance to conventional chemical pesticides is a significant grower and industry concern. Scientific research has repeatedly demonstrated that continuous use of the same class of pesticides (especially those reliant on a single mode of action) will result in the emergence of a pest population resistant to those products. Populations of insect pests, plant pathogens and weeds all have the ability to develop resistance quickly, even to different types of functionally similar chemistries. This phenomenon is called cross-resistance and is caused by multi-chemistry detoxification mechanisms present in many pest populations. Biological pesticides often offer multiple activities against pests and are not prone to resistance development.

Today’s consumers are increasingly sensitive to chemical use in food production. Many consider produce grown organically with the judicious use of biological control and biopesticides as healthier, safer, and friendlier for the environment.

Biopesticide use reduces consumer exposure to regulated chemical residues. Most biopesticides are exempt from residue limits on fresh and processed foods around the world. For growers, food retailers, and consumers alike, this means that biopesticides can be used to manage pests without sacrificing food safety or quality.

Bill Stoneman is the Executive Director of the Biopesticide Industry Alliance (BPIA) and an Independent Organic Inspector. He also serves on the Organic Materials Review Institute (OMRI) Board of Directors and the Wisconsin Organic Advisory Counsel.

¹www.epa.gov/pesticides/biopesticides/whatarebiopesticides.htm

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