In a landmark decision, the Environmental Protection Agency recently banned the use of the pesticide diazinon, in both its granular and liquid forms, on golf courses and sod farms.

The ruling will have little effect on personal gardening in Utah but will call for changes in pest control on large expanses of lawn.Diazinon is used to control "a variety of pests on turfgrass, fruits, nuts, vegetables, and ornamental plants, as well as household pests," according to the Federal Register of April 5, l988.

This is the first time the EPA has canceled registration of a pesticide solely because of risk to birds, said Howard Deer, USU Extension pesticide specialist.

During the EPA hearing, the Federal Register says, the chief pathologist for the state of New York presented evidence of more than 50 bird kills, involving one to 800 birds per incident. Experts estimated these incidents to be a small percentage of actual kills, since the chances of "any particular bird being examined (and diagnosed) are infinitesimal."

Bird kills have occurred in every region of the United States, and diazinon is the most popular pesticide in the West and Southwest.

Species known to have been killed by the pesticide include the Atlantic brant Goose, Canada goose, American wigeon, mallard, American black duck, gadwall, bluejay, robin, redwinged blackbird, brown-headed cowbird and sparrow.

Waterfowl tend to ingest the pesticide as they graze on grass or drink from ponds. The Register said golf courses are sometimes the "only refuge in an urban environment" for water birds.

In a single 1985 incident, approximately 700 Altantic brant geese, 28 percent of the New York state population, were killed after exposure to diazinon on a golf course. The pesticide had been applied according to label directions, said Deer.

The pesticide can also be absorbed through the birds' feet.

And one study showed that ingesting just five diazinon granules can kill a significant portion- - 50 percent- - of sparrow-sized birds.

While the EPA has banned any further use of diazinon on commercial golf courses and sod farms, it is still available for homeowner use.

This leaves some questions: what will owners of golf courses and sod farms use now to control lawn insects? What alternatives are there for homeowners with expanses of lawn that attract birds? There is no simple solution, said Jay Karren, USU Extension entomologist.

He says the main insect problems in Utah are lawn bill bugs, grubs and two species of lawn moths. The advantage of diazinon against these bugs is that the pesticide residue is carried by water into the roots and soil, thus attacking both surface and underground lawn pests. Karren has not tested another pesticide which is as effective.

In a test of pesticides at a Utah sod farm last year, sevin (or Carbaryl) was much less effective than diazinon, according to Karren. He says malathion is also less effective at entering the root zone and has a short life.

"We're going to have to recommend to people pesticides that offer less control, are less effective and more expensive," he says.

On the positive side, both sevin and malathion are much less toxic to birds.

The Federal Register did list several alternatives to diazinon which are registered for use on grubs, but Karren says further study is needed before he will recommend their use on lawns.

"For example, trichlorphon (or Dylox) is being used on some crops with success, but insects quickly develop a resistance to it," he says. That was not a problem with diazinon.