Regional Gardening Reports :: National Gardening Association

In the Garden:
Southwestern Deserts
November, 2010
Regional Report

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A wildflower mix will attract beneficial insects to your yard to consume pests for you!

Integrated Pest Management Part 5: Chemical Control Methods

Integrated pest management (IPM) strategies typically resort to chemical controls as the method of last resort, after combinations of other attempts (cultural, mechanical and biological that were described in earlier reports) failed, and if the gardener decides that the damage (or potential damage) requires intervention.

A pesticide is defined as any substance that kills a pest. They are grouped by the type of pest they control, such as miticides, insecticides, fungicides, or herbicides. Pesticides are further classified as botanical, mineral based, microbial or synthetic.

Botanical pesticides are derived from plants. Examples include pyrethrum, made from the pyrethrum daisy, and rotenone, obtained from certain legume roots.

Mineral-based pesticides are derived from mined substances, such as sulfur, copper and diatomaceous earth.

Microbial pesticides are naturally occurring microbes that kill specific pests. Bacillus thuringiensis (Bt), which targets caterpillars and is harmless to other creatures, is an example. (These might also be classified as biological controls.)

Synthetic pesticides are synthetically produced from chemicals and contain carbon and hydrogen in their structure. Examples include glyphosate (herbicide), malathion and carbaryl (insecticides).

Organic or Inorganic?
Determining whether a pesticide is organic or inorganic can be confusing. "Organic" has a variety of definitions, depending if one is approaching it from a scientific, popular or legal perspective. Generally, organic refers to the presence of carbon, or once-living things. However, synthetic pesticides that contain carbon are not considered to be organic and cannot be sprayed on crops by certified organic growers. On the other hand, some pesticides that do not contain carbon, such as sulfur, are acceptable for use on organic produce.

From the perspective of many home gardeners, organic pesticides are those that are derived from a natural source and have minimal adverse effects to users and the environment. Synthetic pesticides typically take longer to break down after use than other types and may leave toxic residues in the soil or groundwater. It's important to realize that just because a pesticide is "organic" doesn't mean it isn't harmful. Nicotine, derived from the tobacco plant, is classified as a botanical pesticide, but it has a much higher toxicity level than most synthetics. In my next report, I'll cover how to use pesticides responsibly.

Pesticides Generally Accepted for Organic Use

Bacillus thuringiensis (Bt)
Bordeaux mixture
Corn gluten meal
Diatomaceous earth
Insecticidal soap
Horticultural oil
Pyrethrum (not to be confused with pyrethroids, which are synthetics)
Various copper and sulfur compounds
Home remedies, such as pepper or garlic sprays

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