- The Washington Times - Wednesday, May 31, 2006

Farmers once fought off insects with sulfur, arsenic and mercury compounds. Today, the buzzing, crawling critters are held at bay with advanced insecticides meant to protect vegetation without harming anything, or anyone, else.

If only it were that simple.

Because there’s no free lunch in science, researchers are working continually on ways to improve the efficacy of insecticides while minimizing their impact on the environment — and its inhabitants.

An insecticide is any product or solution that prevents the proliferation of bugs, particularly when dealing with homes or vegetation. Advances in insecticides, which can kill, disrupt or limit bug populations, have helped agriculture explode in developed countries.

University of Maryland entomology professor Mike Raupp says not all bug-prevention methods are the same.

Some insecticides are administered via pressure pumps — workers shoot pesticides roughly 100 feet into the air.

“This is a technology that puts an awful lot of material into the environment. A good deal of it doesn’t go where you wish it to go,” Mr. Raupp says. “It can drift with a little bit of wind.”

If a neighborhood uses this method to, say, swat away mosquitoes, the side effects could have an adverse impact on another part of the ecosystem.

“You can knock out parasitic wasps that help control the pests on our trees,” he says.

That happened recently when local workers, trying to protect regional hemlock trees, unwittingly created a spike in the spider mite population through insecticides.

“Ultimately, the way I tell my landscapers is, ‘You’ve got to make a choice. Use this material and save a 300-year-old tree and suffer a mite outbreak,’” he says.

A modern approach to insecticide dispersion involves injecting chemicals directly into the soil or, in some cases, directly into the plants or trees.

The material “is taken up by the roots,” Mr. Raupp says. “It’s a major breakthrough.”

Frank Meek, an entomologist and technical director for Atlanta-based Orkin, says the biggest change in the pesticide field has come in the amount of active material used to defeat insects.

“Twenty years ago, we may have treated a house with [an insecticide with] 2, 5 or 10 percent active ingredient,” Mr. Meek says.

Today, the same home might be treated with a solution featuring .012 or .0125 percent active ingredient.

“We’ve been able to maximize the effectiveness of the chemistry while minimizing the toxic itself,” Mr. Meek says. “That trend is going to continue.”

“The dose makes the poison,” he adds, noting that something as innocent as table salt can be toxic in large quantities.

Years ago, a pesticide control worker might enter someone’s home, fire up the pesticide compressor valve “and not let go of the trigger” until the whole house got coated, he says.

“Today, it’s pinpoint precision toward the specific target. There’s very little general spraying done in this industry,” Mr. Meek says.

That precision trickles down to the pesticides used in each case.

“Even the species of cockroach may dictate what you use,” he says.

Researchers have a better understanding of how insects tick, and the insecticides often react accordingly.

One insecticide targets a one-cell organism that lives in a cockroach’s digestive tract and that the creatures need to survive.

These products “have zero effect on birds, mammals and fish. They don’t have the same enzymes as the insect does,” Mr. Meek says.

Other chemicals disrupt the insect’s molting process to inhibit population growth.

Yet the system remains imperfect.

“There are still materials that can harm other non-target organisms should they become exposed,” he says.

Jeffrey R. Bloomquist, professor of toxicology and pharmacology with Virginia Tech’s Department of Entomology, says most insecticides work by affecting the insects’ nervous systems. The nerve poisons offer a quick way to kill insects, he says.

While Mr. Bloomquist confirms that the concentration of insecticide solutions has dropped dramatically over the years, another beneficial development involves removing some pesticides from the marketplace.

Some chemicals, such as dichlorodiphenyltrichloroethane (DDT), were discontinued during the early 1970s because they don’t break down fast enough after distribution and could be stored in an animal’s fatty tissue.

One known side effect of DDT exposure was that it affected the density of some birds’ eggshells, causing the shells to break.

In Africa, where malaria is a large problem, many scientists have asserted that limited use of DDT could be helpful in killing infected mosquitoes.

Some ill effects can be avoided just by varying the time of day when an insecticide is distributed. Harmless honeybees don’t forage at night, so agriculture workers who want to chase away harmful insects but not the bees will spray at night.

Other insecticides can be delivered via a farm’s irrigation system.

“There’s no spraying at all. It’s just a drip,” he says.

Galen Dively, a professor with the University of Maryland’s College of Agriculture & Natural Resources, says the biggest advance in recent years deals with transgenic plants, vegetation with insecticides “built in.”

These plants have been spliced with a bacterium to make them impervious to certain strains of insect, Mr. Dively says.

Roughly 40 percent of corn acreage features this process, Mr. Dively adds.

The Food Quality Act of 1993 helped spark the movement toward healthier insecticide practices, he says.

Under the law, companies using insecticides deemed less harmful to creatures or the environment don’t have to endure the amount of testing other chemicals require. That could save businesses up to $40 million per compound in testing fees and research, he says.

Mr. Meek understands that no matter how many innovations occur in the industry, his work and that of others fighting on behalf of crops will never be done.

“Insects have learned the art of survival,” he says.

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