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Insect, weed and disease pests have the ability to "learn" and pass their "schooling" down to
their offspring. The learning takes place as a change in the inherited genetic material within
the pest population. For example, year in and year out your neighbor has been spraying pesticide "A" to
suppress aphids, his number one pest. Each time he sprays, 99 percent of the aphids are killed.
The aphids are never entirely eradicated, and over the course of a season millions of new aphids are
born. A small portion of those aphids have slight, accidental changes, or "mutations" in their genetic makeup.
Most of the defective, mutant aphids don't live long enough to pass on the mutation to their offspring.
However, one summer day, an accidental change in the genetic makeup of a single aphid turns the pest
into a "super bug." The aphid is now no longer susceptible to a formerly toxic pesticide.
Pesticide resistance is a genetically based phenomenon. Resistance occurs when a pest
population— insects, for instance— is exposed to a pesticide. When this happens, not
all insects are killed. Those individuals that survive frequently have done so because
they are genetically predisposed to be resistant to the pesticide.
Multiple resistance (resistance to more than one pesticide and to pesticides in more than one
chemical class) is increasing rapidly. There are over 1,000 insect/insecticide resistance
combinations, and at least 17 species of insects that are resistant to all major classes of insecticides.
Pesticides should not be considered the sole or even the primary solution to a pest problem.
Pesticides kill not only the pests but also the natural enemies of these pests. That means
that natural control mechanisms are disrupted and it allows the pest populations to rapidly
build up again to levels that can cause serious crop damage.
When scale infests a plant in sufficient numbers for you to begin to see damage, it is very likely
that the plant was already experiencing some degree of stress. Most plants that are truly healthy
don’t seem to have scale problems. Pest insects prefer to go after weakened plants that are struggling
and lack vigor. Often it is the very young or older plants that are targets. Researchers examining
the effects on insects of glutathione, a chemical produced by stressed plants have found that it
actually benefits certain harmful insects, aiding their reproduction, growth, and possibly
bolstering their ability to resist pesticides. This may explain why scale is attracted to struggling plants.
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Texas A&M University Study
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Water sprays reduced aphids and spider mites by 70% to 90%. Vigorously growing plants will
resist attack by insects and disease. Unhealthy plants are more susceptible to pests and disease.
Insects actually seek out stressed plants.
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