by George Looby
For as long as we have been growers, we have been trying to find ways to keep pests from our plants.
One naturally-occurring product used as a pesticide was nicotine sulfate (for years marketed as Black Leaf 40), lethal to most crawling things that chewed in the garden. It has been banned for garden use because of its potential for serious side effects to both humans and nearby fauna. Paris green is a substance that contains copper and arsenic, probably one of the first widely used insecticides (first used in France in the early 1800s). Yet another element is arsenate of lead, the residue of which can still be found in old orchard soils.
In 1945-46, DDT came on the scene. It had worked remarkably well in Italy in controlling mosquitos. Within a few years it became apparent the insect population was rapidly developing a resistance to its use, and beneficial insects, birds and mammals were suffering ill effects.
One product that triggered an increasingly hard look at alternative pesticides was glyphosate, which found worldwide acceptance in both commercial agriculture and backyard use. It was predictable and economical – but it proved to have some serious flaws, including causing cancer, especially among those who used it regularly.
Over the years, the organic movement found footing with its strict adherence to growing crops with the use of only fertilizers and pesticides that were natural in origin. Many consumers caught onto this approach and are willing to pay a premium for crops grown this way.
The organic movement has prompted industry leaders in the area of pest control to re-think their production goals and look at some of the more natural alternatives that might control the same pests without causing potential harm to the environment, the applicator or the consumer.
What then are biopesticides? The term has come under government control, with the EPA responsible for their uses. They are pesticides derived from natural materials such as animals, plants, bacteria and certain minerals. There are three major classes of biopesticides, the first being biochemical pesticides – naturally-occurring substances that control pests by non-toxic mechanisms. An example of this might be substances that interfere with mating, such as an insect sex pheromone.
The second group are microbial pesticides, which have microorganisms as the active ingredient. They might be bacteria, fungi, viruses or protozoans. The most commonly used microbial pesticides are strains of Bacillus theringiensis (Bt). Each strain produces a different mix of proteins which kill one or a few related species of insect larvae.
The third group are those produced by the plant itself as the result of specific genetic material produced by Bt that is added to the plant’s own genetic material, prompting it to create a substance that kills the target pest.
Biopesticides are inherently less toxic than conventional pesticides. Generally, biopesticides affect only the target pest and those closely related to it. This is in contrast to the more commonly used broad spectrum pesticides which may affect a far larger group of organisms. They are effective in very small quantities and decompose rapidly, resulting in lower exposures and residues, thus avoiding the pollution problems often associated with conventional pesticides. When used as a component of integrated pest management (IPM), they can greatly reduce the use of conventional pesticides while maintaining high crop yields.
The EPA is able to approve biopesticides far more rapidly than conventional pesticides. In some instances, approval can take place in less than a year, whereas conventional products may take up to three years – but this does not imply that the application process is any less rigorous. Those seeking approval are required to submit detailed information about the composition, toxicity, degradation and other characteristics of the pesticide.
Several of the leaders in the field of agricultural pest control have already begun to explore a number of natural materials that may have the potential to provide growers with biopesticides. Mustard seed-derived products have been found to be satisfactory in replacing synthetic chemicals presently used in fruit, vegetable and tobacco crops.