Biopesticides: A Safer Approach to Pest Control

Biopesticides: A Safer Approach to Pest Control

  • By Penelope Fenner-Crisp
  • /
  • March 2020-Vol.6 No.3
  • /
  • 1 Comment

What are Biopesticides?

Let’s begin with the legal definition of “pesticide.” Under U.S. law, a pesticide is defined as any agent that will “prevent, destroy, repel or mitigate any pest.” Anyone wishing to sell a product which makes a pesticidal claim must have that product approved by the EPA and each state in which s/he wishes to sell the product (with a few exceptions).  But thirty-one substances are considered so innocuous that they have been declared exempt from the pesticide approval process. Most of them are naturally-occurring constituents of foods, such as cinnamon, garlic, mint, peppermint, sesame, thyme, and their oils, corn and cottonseed oil, citric acid, and eugenol. These substances are referred to under the EPA as the “Section 25b Chemicals.”

     

                  Peppermint                                        Cinnamon

   

                Cottonseed oil                                              Garlic

 

Biopesticides are a subset of pesticides derived from natural materials such as animals, plants, bacteria, viruses and certain minerals. In general, products containing biopesticides as active ingredients are considered more environmentally-benign than are conventional chemical pesticides, but they often possess a narrower scope of efficacy.  Biopesticides fall into three major categories:

Biochemicals

Microbials, and

Plant-incorporated Protectants (PiPs).

About 400 biochemical and microbial active ingredients are or have been approved for use in the U.S., but only about 25 PiPs.

What are Biochemical pesticides?

Biochemical pesticides control pests by mechanisms that, generally, do not directly cause death to, or inactivation of, a pest. Some are insect sex pheromones, which interfere with mating.

Codling moth

“ I want to make babies, but I’m so frustrated!”

 Some biochemical pesticides are scented plant extracts that attract insects and other pests to traps, or repel insects, birds, dogs, cats and other vertebrates. Others are plant or insect growth regulators. Some have pesticidal activities against bacteria, fungi, nematodes, mites and insects.

Like the 31 regulation-exempt substances noted above, many of the biochemicals also are constituents of foods. In this case, however, they are subject to registration for which some information is required concerning their proposed uses and potential impact on human health and the environment. When you see a list of these, it may cause you to wonder why they are “in” while the 31 are “out.”  A very good question for which there is not a clear-cut answer.

Examples of biochemicals that are also food constituents include canola oil, capsaicin (the “hot” in hot peppers), ethanol (pick your favorite cocktail), lactic acid (present in sour milk products such as yogurt), oils of anise, lemongrass, mustard and orange, and vinegar.

   

Canola blossom

 

Whiskey sour

                                                                                                                                           

hot peppers

Apple cider vinegar

      

Anise

yogurt

A product containing a biochemical biopesticide may be deemed acceptable for use in organic agriculture if all of its ingredients (active and inert) and all of its uses meet the criteria defined in the United States Department of Agriculture’s (USDA) National Organic Program (NOP) Rule. This is communicated through EPA approval of relevant language on the product label.

The three-leaf Organic logo, with or without the text, then can appear on the label, sometimes along with the logo of the Organic Materials Review Institute (OMRI), an international nonprofit organization that determines which products are certifiable for use in organic production and processing under the USDA National Organic Program.

What are Microbial pesticides?

Microbial pesticides consist of a microorganism (e.g., a bacterium, fungus, virus, or protozoan) as the active ingredient. They control many different kinds of pests, although each separate active ingredient is relatively specific for its target pest[s]. For example, some fungi control certain weeds, while others affect specific insects.  Some microbial pesticides may qualify for use in organic production.

The most widely used microbial pesticides are the subspecies and strains of Bacillus thuringiensis, or Bt. Each strain of this bacterium produces a different mix of proteins, and specifically kills one or just a few related species of insect larvae. While some Bt’s control moth larvae, others are specific for larvae of flies and mosquitoes. The target insect species are determined by whether the particular Bt produces a protein that can bind to that target species’ larval gut receptor, thereby causing the larvae to starve to death.

Microbial pesticide products are applied in a manner similar to that of conventional and biochemical pesticides, e.g., as a foliar spray, soil drench, or in granular formulations.

There are a plethora of biochemical and microbial products available for use by home gardeners.

Plant-incorporated Protectants (PiPs) are pesticidal substances produced by plants and the genetic material necessary for the plant to produce the substance. For example, scientists can take the gene for a specific Bt pesticidal protein, and introduce that gene into the plant’s genetic material. Then the plant manufactures that pesticidal protein, controlling the pest when it feeds on the plant. Every part of the plant will contain the Bt gene, including the edible portion(s). Both the protein and its genetic material are regulated by EPA, but not the plant itself.

PiPs are found primarily in high production volume crops destined for the commercial market (e.g., corn, cotton, soybean) and are not marketed for the home gardener.

This small subgroup of biopesticides carries a mantle of controversy and concern in some quarters because their production involves genetic engineering (GE), albeit by GE methods different from those used to create genetically-modified herbicide-resistant crops such as RoundUp-ready corn or soybeans.   The U.S. federal government has declared these to be functionally and  nutritionally equivalent in all respects to their conventional counterparts.  However, not all parties share this opinion, and have offered study results which each assert show differences.  The dispute remains an active source of discussion.

   

         Conventional Corn???               GE/GMO  Corn???

                                     Can you tell the difference?

 

Check before you buy

And, finally—a word of caution.  It is often tempting (and more convenient) to buy pesticide products online from sites such as Amazon or a commercial pesticide supplier.  However, not all of the products available on those sites may be registered in the Commonwealth of Virginia.  It is illegal to use unregistered products in Virginia. So, I would suggest that, before spending that money online, check to see if what you want to buy is okay to use here. The Virginia Department of Agriculture and Consumer Services (VDACS) maintains a database of state-registered products which can be accessed at http://www.kellysolutions.com/VA/pesticideindex.htm. If you search by product name, you’ll find out quickly if you’re on the right side of the law.

 

References:

Photo of Bacillus thuringiensis (Bt) strain 4A4, as viewed at 1000x magnification after gram staining.  Photo by Sam LaRussa.

“Beyond Pesticides. Insecticide Incorporated GE Crops,”at  https://www.beyondpesticides.org/programs/genetic-engineering/plant-incorporated-protectants)

“Section 25(b) Chemicals,” University of Nebraska Institute of Agriculture and Natural Resources. 2020.  https://cropwatch.unl.edu/potato/section25b_chemicals.

“Biopesticide Registration,” U.S. EPA. Office of Pesticide Programs. https://www.epa.gov/pesticide-registration/biopesticide-registration)

“Pesticide Chemical Search: Conventional, Antimicrobial and Biopesticide Active Ingredients,” U.S. EPA. Office of Pesticide Programs,  https://iaspub.epa.gov/apex/pesticides/f?p=chemicalsearch:1).

“Pesticide Database Searches,” Commonwealth of Virginia Department of Agriculture and Consumer Services,  http://www.kellysolutions.com/VA/pesticideindex.htm

 

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