KATHLEEN LEAHY spends a lot of time counting insects in Massachusetts apple orchards this time of year, but she's no bug collector. Ms. Leahy, a farm extension technician, is an advance scout in the age-old battle of farmers against insect pests. She and her associates have been experimenting with a new set of weapons in that battle. Their goal: to reduce dependence on insecticides and chemicals.
Their method has become known as Integrated Pest Management, and it is seeing some dramatic successes in the United States and around the world.
IPM employs a flexible strategy to reduce chemical use. It can include insect monitoring that ends regular chemical spraying in favor of as-needed spraying, as it does in Leahy's work, or the use of traps to lure bugs where they can either be destroyed or sterilized for release during mating season.
IPM also employs natural insect enemies of crop-damaging bugs, planting strategies that decrease bug populations or lure bugs away from crops, and techniques to combat weed growth and the attendant use of herbicides.
Ronald Prokopy, an entomologist at the University of Massachusetts at Amherst, who works with Leahy in the state's Cooperative Extension IPM Program, says farmers have often been forced to consider IPM for more than environmental reasons. One is that some insecticides are no longer doing the job: The targeted insects have either become resistant or the chemical has killed off so many of their natural enemies that their population explodes. In some instances, secondary pests move to the fore when the targeted insect is suppressed.
Add those problems to the more common concerns about farm chemicals - cost, and the discovery of their residues in the food chain and in ground water - and you have a tidy set of arguments for IPM, Mr. Prokopy says.
IPM programs are in use in all 50 states on a wide range of crops, according to a recent report by the Virginia Cooperative Extension Service. But the most dramatic IPM success stories have come in the third world. The case of the cassava mealybug in Africa is one of them.
In a recent report, Sandra Postel of the Washington-based Worldwatch Institute told of how the mealybug, first detected in Zaire in 1973, infiltrated almost all of Africa's 34-country cassava belt. Some 200 million Africans rely on cassava as a major food crop, she says.
By 1982, mealybugs and another pest had slashed cassava yields by 10 to 60 percent across Africa, forcing some growing areas to be abandoned, Ms. Postel says. Two agricultural institutes, one in Nigeria and the other in Britain, joined forces to combat the problem biologically. An extensive search in Latin America, cassava's place of origin, uncovered several natural enemies of the mealybug.
One, a tiny wasp that destroys mealybug eggs, produced remarkable results when released in Africa. The wasp now effectively controls the mealybug over 65 million hectares (160 million acres) in 13 countries, Postel says, and is soon to be introduced over a larger area. The cost of the program as of late last year was $12 million.
Postel and other researchers have documented similar results in many countries including Brazil, where pesticide use on soybeans has been cut between 78 and 93 percent, and Costa Rica, where use of IPM techniques on banana trees has eliminated pesticides in one region.
Massachusetts has one of the strongest programs in the US, according to state IPM coordinator William Coli, a University of Massachusetts entomologist. Funding from the state's Department of Agriculture and farmers has supported IPM research on apples, sweet corn, potatoes, strawberries, home lawn turf, and cranberries, the state's No. 1 cash crop.
There have been results. Massachusetts apple growers using IPM have cut pesticide use by 43 percent in the past 10 years, while maintaining per-acre yields of marketable fruit equal to that of farmers who don't use IPM and pulling in greater profits, according to Prokopy.
The most closely watched IPM experiment at present may be in Indonesia, where an insect called the brown planthopper has developed a resistance to virtually every rice insecticide and is threatening the country's hard-won self-sufficiency in rice.
Left with little choice, Indonesian President Suharto banned 57 rice insecticides in November 1986 and declared a national campaign to promote different pest control strategies.
Postel says the program is ``an important development. If it works, it could be a springboard that gets other countries involved in IPM because of the high level of official support there.''
Back in Massachusetts, Prokopy is planning a new phase for the now mature apple IPM program that goes beyond pesticide management. Program workers are hoping to combine enhanced biological controls, mating disruption techniques, and methods for controlling pests before they reach the orchard to achieve a 70 percent reduction in chemical use compared with pre-IPM levels.
Prokopy says farmers can use a lot of old-fashioned methods, like planting disease- and insect-tolerant crop varieties, rotating crops, and cultivating intensively to control weeds, as a first line of defense against the need for chemicals.
Increased use of IPM is not yet reducing the use of pesticides. Postel says she fears IPM will be pushed aside by the development of a new generation of chemical-resistant crops or by new chemicals that are supposedly less harmful to the environment.
That, she says, would be a mistake. ``A more integrated approach is more ecologically sound than reliance on a chemical package. That's still a quick-fix mentality. We're still not looking at agriculture as an integrated system in an ecological sense.''