If a few early morning golfers noticed an eerie green fog creeping through the gulch near the rear of Mountain Dell golf course Wednesday, they shouldn't call Ghost Busters - it was just a test of a government computer model.

Actually, Wednesday's test, carried out jointly by the U.S. Forest Service and Dugway Proving Ground, was a failure. But they'll keep trying."It was an unsuccessful day because of the cloud cover," said Jack Barry of Davis, Calif., who supervised the test for the Forest Service. "The cloud cover did not let the normal wind develop."

Little puffs of green smoke from five smoke grenades only carried about a quarter of a mile, as far as any of the observers could tell.

But the crew of scientists, volunteers and technicians - about twenty altogether, including five from the state - will be back for more definitive measurements when the Forest Service begins spraying a bacterium to wipe out the gypsy moth infestation near here. Altogether, three applications of the Bacillus thuringiensis will be carried out, spaced about 10 days apart.

Both the Forest Service and the Army are interested in measuring the amount of bacteria spray - or, in Wednesday's test run, the amount of green smoke - that gets through the tree cover. The agencies want to field-test the predictions of a computerized mathematical program called the FSCBG Model, which uses information about wind speed, humidity and a host of other factors.

"After you spray an area, it predicts how much material is on the top of the canopy, on top of the trees," said Gary Sutton, a physical scientist for Dugway. The base develops chemical and biological warfare protective devices like detection equipment and gas masks.

The scientists inject information into the model about the density of the foliage, "then it tells how much of this material that's on top of the trees gets through the trees and onto the ground."

Who cares, other than the moths? "If you're in a chemical or a biological attack, you want to know what the heck gets through the trees to the ground," he said.

The Army is forbidden to spray live bacteria in the atmosphere to test its defensive biological warfare capabilities. It can use simulants, but that's not the same as real, live organisms.

But nobody said it can't tag along with the Forest Service when it sprays anti-caterpillar bacterial agents and see how they get through the tree cover.

"They're considered a pesticide, but it's a natural pesticide because it occurs in the soil," Barry said of the bacteria.

So, in about two weeks when spraying of the bacteria begins, both agencies will be back at Mountain Dell Golf Course, setting up their equipment again.

This consists of three portable meteorological towers and 10 sampling sites. Most of these are strung out along a two-mile course from the edge of the golf course, but one of the towers is across the I-80 freeway, where a separate experiment is to be carried out.

Each tower has an anemometer to measure wind speed, supporting guy wires, an array of solar cells to measure sunlight, other weather instruments, and a radio to transmit information to a personal computer.

"Dugway provided all this equipment. The Forest Service doesn't have any of this stuff. They provided it, no cost," Barry said.

The system has been tested elsewhere, notably in moth-infested oak forests in the East, where the model jibed well with the predictions. But it has rarely been tested in a landscape like Utah's.