FEDERAL agencies are currently investigating the possibility that two pesticides the Buildings and Grounds Department regularly uses may cause birth defects in experimental animals.

Last December, the HEW Commission on Pesticides and their Relationship to Environmental Health suggested that Carbaryl-an insecticide sprayed to combat the elm leaf beetle-was a potential health hazard to man. It apparently causes bone malformations in litters of mice and beagle dogs.

But the Commission's report emphasized that the birth defect experiments used large doses of Carbaryl and that the experiments were still inconclusive concerning effects on people.

However, the Commission recommended that Carbaryl use "be immediately restricted to prevent risk of human exposure." Last year, a Harvard contractor sprayed some 25 gallons of Carbaryl, and elm sprayings are again scheduled for early June and possibly later this summer.

The HEW Commission delivered a similar warning against several forms of the herbicide 2,4-D. The particular salts of 2,4-D used to kill crabgrass here were not condemned, but the Commission urged further research into their possible side effects.

The manufacturer of the other major herbicide used on Harvard's lawns states that the fertilizer mix (containing the compound polychlordicyclopentadiene) is "toxic to fish and wildlife." The label warns that birds and small children may be harmed for brief periods after the mix is applied.

MOST biologists here are not very worried about B and G's herbicide program: the questionable chemicals are used in very small quantities and the evidence of direct danger to humans is inconclusive. The current furor over herbicides focuses on the massive acrial sprayings in Vietnam, where huge doeses of herbicides sometimes drift into drinking water supplies.

However, B and G's insecticide program has received mixed reviews.

"There is a great difference between hard pesticides and biodegradable ones," Ernest Mayr, professor of Zoology in the Museum of Comparative Zoology, noted recently.

"The important thing is that they stopped using hard pesticides here." B and G phased out its use of DDT in 1968.

But of Harvard's four major insect spraying projects, the ivy moth program has come in for particular criticism.

This small black and white moth known as the Eight-Spotted Forester ( Alypia Octomaculata ) emerges in early May, Several generations of its caterpillars fatten themselves on the University's ivy each summer.

"This bengn little Lepidopteran was not known to be a pest anywhere else in the world," commented Carroll M. Williams, Bussey Professor of Biology.

So why did the plague come to Harvard?

Williams and other biologists suspect that over the past 40 years chemical sprays have killed the moth's natural parasites more thoroughly than they controlled the moths.

Frank M. Carpenter, Fisher Professor of Natural History, discovered evidence that might support this theory. He simply noticed that the unsprayed ivy on the Shannon Hall side of the Bio Labs was much less moth-eaten than the sprayed ivy on the Divinity Avenue side of the building.

A group of biologists including Carpenter, Mayr, and Philip J. Darlington, Jr., Alexander Agassiz Professor of Zoology, urged B and G to stop spraying the ivy long enough to allow the moth's natural predators and parasites to return.

In 1965 B and G halted all ivy spraying on seven buildings north of the Yard. None of these have been sprayed since, but B and G will apply some 20 gallons of meta-systox-R, an organic phosphate insecticide, to the ivy in the Yard and elsewhere next month.

This chemical is called a systemic insecticide because it permeates the entire ivy plant, making the whole plant-not just its surface-poisonous to insects.

For two years after the spraying stopped north of the Yard, the caterpillar population skyrocketed.

Many old ivy plants, weakened by a severe drought, failed to survive despite special feeding and watering treatments. It may take a decade to replace the lost ivy.

But the moth's enemies, including a parasitic wasp that lays its eggs on the caterpillars, have apparently staged a comeback. And many biologists suspect that the new ivy around the Bio Labs is less moth-eaten than the sprayed ivy in the Yard and Business School areas.

If the ivy moth population remains in check this year, the biologists may suggest a de-escalation of the ivy moth war elsewhere in the University.

However, the ivy caterpillar population has the nasty habit of peaking in June-just about the time when the old grad population peaks in the Yard. A year or two without spraying there could defoliate the ivy for several Commencements.

A state entomologist at the Shade Tree Laboratory Field Station in Waltham suggested that a commercial preparation of the bacterium Bacillus thuringiensis might keep the moth population down for several years while the natural predators re-establish themselves. This particular biological control has recently halted the cabbage looper and fruit cankerworm, but it has not been tried against the ivy moth.

After five seasons of reduced ivy spraying, the biologists believe that the moths and parasites have struck an equilibrium. But "we haven't put in a recommendation yet because we have only had one good summer," Darlington said. "We need one more good summer before we know where we really stand."

ASMALLER number of biologists have also taken exception to the University's spraying program for the Dutch elm disease-a fungus infection imported from Europe. Two species of bark beetle known as Scolytus multistriatus and Hylurgopinus rufipes, inadvertently carry the fungal spores that cause the disease. B and G tries to control the beetles by spraying Harvard's clms in early April before the insects emerge from hibernation.

This year, a B and G contractor sprayed 90 gallons of methoxychlor, a chlorinated hydrocarbon that does not accumulate in the natural food chain as its close relative, DDT, does.

Later in the summer, a contractor also sprays for the clm leaf beetle, Galerucella xanthomelaena. This beetle does not spread the elm disease itself, but large infestations of these insects may weaken the elms and reduce their resistance to the fungus.

It is not quite clear whether spraying actually controls Dutch clm disease. Government studies indicate that spraying does reduce the disease on well-controlled experimental plots, but whether spraying is effective under field conditions is still open to debate. Some communities simply remove the dead wood that the beetles breed in, and they claim to have good disease control without spraying.

Mayr and Darlington both suggested that the disease would probably take a larger toll of Harvard's elms if the trees were left unsprayed. But others argue that spraying is simply a desperate attempt to "do something" about a crisis when every other approach has failed.

The bark beetles emerge in April and sometimes fly large distances before burrowing into an clm to lay their eggs. Since the insecticides do not penetrate the bark of the elms, the argument goes, the beetles are essentially safe before they emerge from the winter and once they enter the new tree. This leaves only a few days for the insecticide to hit the adults before they lay their eggs.

Some experimenters have found the beetles unharmed after laboratory exposure to DDT. Others have gotten the opposite results.

"No amount of spraying will save the elm trees." Williams commented last month. "The only way of combatting the disease is to cut out the dead wood and cart it away."

The University has lost some two percent of its elms in the last 10 or 15 years, including five trees last year. Many of these trees were weakened by age and were easy targets for the Dutch elm disease.

Since no thoroughly effective control of the disease is in sight, B and G has replaced dead trees with oaks and other species of shade trees rather than risk losing more elms.

INSECTICIDES have created a particular problem for entomologists at the Bio Labs. When an organic phosphate insecticide was sprayed in the Laboratory's greenhouse last year, it drified into a ventilation fan and wiped out a colony of silk moths in another room. Ironically, these moths were part of a study on moth development and hormones-a project that may lead to a safer class of insecticides. (see box).

"In the old days, the watchman would see a cockroach running down the corridor, and he'd spray the whole place with DDT," Williams complained. "Of course I went right out through the ceiling. They can put you out of business overnight."

Williams's group has raised its moths in Medford during the summer toavoid pesticide fogs that may drift into the Bio Labs from nearby areas.

Before tree specialists stopped using hard pesticides like DDT to combat the elm disease, insecticide killings of birds were apparently common in Cambridge. Charles F. Walcott, a retired physician and amateur ornithologist, recalls seeing three insect-eating species-the robin, hermit thrush, and flicker-in "typical DDT convulsions" on his property off Sparks Street.

Several years ago, Matthew S. Meselson, professor of Biology, noticed robins in similar convulsions outside the Bio Labs after an insecticide spra?ing.

The long-term effects of pesticides on the ecology of Cambridge are much more difficult to isolate. The City has grown so rapidly in the past 60 years that changes in the local habitat could account for many shifts in animal? populations. For example, only 40 years ago, toads, raccoons and foxes ran around some of the city's vacant lots. Undergraduates in the nineteenth century reportedly shot woodcock-a small woodland gamebird-in the area between Harvard Square and the River.

Yet local wildlife experts have drawn two correlations of pesticide use and wildlife loss.

In 186? a French naturalist in Medford imported some gypsy moths for a breeding experiment. A few of the moths escaped, and the species had become ? severe pest by the turn of the century. The caterpillars completely defoliated Cambridge's trees, and most of Harvard's elms died, only to be replaced by more elms in 1915.

Carpenter recalls some areas around Boston "that sounded like rain from the excrement of the caterpillars."

Arsenate of lead was used to fight this outbreak, and soon afterwards, the orioles that had nested in the elms slowly disappeared. The small insect-eating vireos and warblers in the area apparently suffered also.

Thanks to biological controls, the gypsy moth is no longer a pest here, but in the long run, spraying did more harm than good, many entomologists claim. Some 25 parasites and predators were introduced to control the moth, and insecticides allegedly hindered these parasites in establishing themselves in some areas.

When DDT came on the scene after World War II. Cambridge's robin population took a sudden drop. "Once, every morning before dawn, there was a rolling chorus of robins." Walcott noted. "To my cars, there has not been a robin chorus in Cambridge since 1951."

Presumably, DDT reaches the ground on falling leaves, and earthworms surfacing at night accumulate the toxin when they feed. DDT then passes up the food chain to the robins.

The most thorough studying linking DDT to robin kills in New England was done five years ago at Dartmouth. After a "typical" DDT application, the robin population dropped 70 percent. Many robins and other birds were found in convulsions.

However, the same study reported no effect on the robin population after a methoxychlor spraying.

The actual numbers of birds in Cambridge may not have changed much in recent years, but the composition of the population has. At the turn of the century, some five dozen species nested here, including 16 varieties of warblers and vireos. Except for the unsprayed area around Fresh Pond Reservoir, none of these warblers and vireos regularly nest here now. Only half a dozen native species next here in any numbers today. The commonest birds-the starlings, English sparrows, and pigeons-were all imported from Europe during the nineteenth century. Insecticides may account for some of this lack of variety.

HARVARD'S one other spraying program has received a clean bill of health from biologists: B and G uses about 40 gallons of oil on lilacs and about 90 gallons of oil on lilacs and hibernating scale insects. The solution dissolves the insects' protective wax and the petroleum then suffocates them.

Faced with possible adverse side effects of pesticide use. B and G is caught in a tough position. "The trees, shrubs, and lawns are really worth improving." said Donald C. Moulton. Deputy Director of Buildings and Grounds, but "people's disregard" for B and G's efforts to keep Harvard green is increasing, he added.

"How do you keep a laborer interested when a week after planting a lawn it looks like the Battle of the Bulge?" commented another B and G official.

Given this uphill battle to fulfill its groundskeeping task, B and G is understandably cautious about proposals to reduce spraying. Even if such a proposal could produce a more natural ecological balance in the long run, most options to stop spraying run the risk of losing some green plant cover, at least for the first few years.

"You get hooked on these controls or drugs." commented William H. Drury '43, a biologist with the Massachusetts Audubon Society, "and once you stop, you get withdrawal symptoms."