In humanity's ancient battle with insect pests, biochemistry has stepped forward to begin to supply a new type of weapon. In laboratories, scientists have been able to isolate and Re-create the sex scents emitted by the female member of several insect varieties. These sex scents, called pheromones, are given off by the female insect to attract a male mating partner.
We believe that by synthetically simulating the sex lure, and attaching it to a specially designed trap or other device, we reduce the number of male insects available for mating. This should lead to a lowered number of matings, fewer eggs, and a reduced insect population for the next year.
It is the beginning of a promising new era of pest control.
To understand better how pheromone technology works, and where it has been applied successfully, consider the problems posed by both the Japanese beetle and gypsy moth.
The Japanese beetle, a plant pest of foreign origin, was first discovered in the United States in 1916, feeding in a New Jersey nursery. A native of the islands around Japan, the insect is not a serious problem in its native land because of natural insect enemies, small food supplies, and a restricted landmass.
Here in the US, however, the beetle has few enemies. It also enjoys vast food supplies and a large landmass for expansion. The beetle has a voracious appetite and will devour at least 275 varieties of flowers, plants, vegetables, and even tree blossoms. It is particularly fond of, and a notorious destroyer of, roses.
According to statistics compiled by the US Department of Agriculture, the Japanese beetle has spread from New Jersey to 22 other Eastern states.
Over the years, chemical spraying of products such as Dieldrin and Carbaryl were used to check the beetle's ravages. Bacteria strains such as Bacillus popilliaem and Bacillus lentimorbus,m which affect the beetle during grub states, have also been used with varying degrees of success. In addition, mechanical traps employing floral lures were brought into the battle. Nothing was totally effective.
The USDA, recognizing that a definite solution to beetle control still hadn't been perfected, turned to its scientists for an answer.
Testing began at the agency's National Japanese Beetle Laboratory in Wooster, Ohio. Quickly, scientists determined that male beetles were attracted to the female by a sex pheromone emitted by the latter. Dissection of the female beetle showed the sex attractant was in the insect's abdomen. Through careful analysis, the USDA scientists were able to discover the exact chemical composition of the attractant. More important, they re-created small amounts of the pheromone in the lab.
Because of the attractant's complex chemical structure, however, it was difficult and costly to produce any sizable amounts.
The J. T. Baker Chemical Company, Phillipsburg, N.J., was asked by the USDA to produce the synthetic Japanese beetle sex pheromone in large quantities.
Baker, after delivering the pheromone to the USDA for further field testing, perceived a consumer need for a pheromone-based trap. In early 1977, development of a Japanese beetle trap for home gardeners began in earnest.
The product combined a floral lure with its powerful sex attractant. Indeed, the pheromone contained in the trap literally equals the scent emitted by 80,000 female beetles.
Testing at the Ohio laboratory proved the trap to be up to five to seven times as effective as any trap previously available. It was test- marketed in 1979 and introduced last summer.
The results were both immediate and impressive. One gardener in Indiana eliminated 200,000 Japanese beetles over a four-week period. The number was verified by weighing the discarded bags from the traps with an electronic scale.
The trap itself is of simple, yet sturdy, construction. Two rectangular pieces of plastic fit together to form a vane. The floral and sex bait fit into the vane, and a replaceable bag hangs below. Beetles, attracted by the scents, fly directly into the vane and suffocate in the plastic bag.
Proper timing is an essential element in controlling the Japanese beetles. They are most active when the average mean temperature is 70 degrees F. They begin to appear in June in some Southern states and emerge in the Northern states in early July. The beetle infestations generally last 8 to 11 weeks in a given area. But unprotected gardens are vulnerable to beetles throughout the long summer growing season.
Then there are the gypsy moths. They have been with us for over 100 years.They were introduced into the country by a short- sighted biologist bent on producing a super silk-producing caterpillar. Unfortunately, some of the moths escaped near Medford, Mass., and began their century-long attack on forests and woodlands.
Today, the gypsy moth is a problem in most Northeastern states. Last year alone, it defoliated over 5 million acres of trees.
Pheromone technology in the gypsy moth area dates back some 15 years, to the mid- 1960s, when the USDA first determined the existence of a sex attractant in the female moth, called "disparlure." At the same time, however, scientists didn't realize that the disparlure contained more than one active ingredient ("plus" disparlure and "minus" disparlure).
During the course of the '60s and in the '70s, the USDA employed disparlure in traps that were used for only one reason - to monitor the spread of the gypsy moth population.
It wasn't until 1977 that the Department of Agriculture, acting independently , discovered the existence of two separate ingredients in the female moth pheromone. Its studies indicated that "plus" disparlure was the only true active ingredient in the synthetic pheromone.
The Baker Company, already involved in producing the beetle pheromone, recognized the need for a consumer, pheromone-based gypsy moth trap. Earlier this year the company introduced such a trap, using only the active plus disparlure.
The trap is designed for use when the gypsy moths emerge from the pupa, or larva, stage and begin mating. This period takes place in the month of July.
A strange quirk in the gypsy moth life cycle, in which the male moth hatches a week before the female, makes the traps especially effective. Knowledgeable homeowners should take advantage of this one-week "bachelors only" period to set traps.
The male moths are attracted to the traps, which resemble green lanterns, by the synthetic female sex pheromone. Once inside the trap, the male moths are killed by a pesticide strip similar to the one found on a dog's flea collar.
By reducing the number of eligible male moths, consumers can aid in limiting next year's gypsy moth population. This pheromone technology should not be perceived as a cure-all. It isn't. It is, however, an important part of integrated pest management. Gardeners concerned with protecting flowers and vegetables should use pheromone-based traps as one element in an overall garden protection plan.
Homeowners should understand the life cycle and mating habits of the gypsy moth before trying to control it. Timely setting of traps, combined with spraying of the gypsy moth caterpillar in the spring, can reduce future populations.
Intergrated pest management should extend beyond the scope of the individual gardener/homeowner. Unless everyone pitches in, these two ravaging insects will continue to expand their territories.
Clearly, pheromone technology is still in an embryonic stage. We, the scientific community, have really only scratched the surface of future potential.
Research is under way in both the public and private sectors to develop additional pheromone-based products for consumers. Some of that research is focused on controlling such garden and household pests as the aphid, cabbage looper, cockroach, fire ant, house fly, and even the mosquito.
Clearly a new era in pest control is dawning.