Of hornets, ants,and tree-climbing ivy

Is there any way other than spraying to keep hornets from nesting in an awning? Also, can ants destroy a tree? Can ivy running up a tree eventually kill it? Mary Mann Glen Burnie, Md.

Our pest-control consultant says he knows of no other way to keep hornets from nesting other than by spraying. He also suggests that the nests be destroyed in the late evening so as to minimize any stinging rebukes from the evictees.

Use an approved labeled insecticide and read the instructions beforehand.

The same man says that it is unlikely that ants could destroy a large tree; however, if ants start excessive working around the roots of a small tree, they would leave formic acid which may destroy it.

According to a dictionary definition, formic acid is ''a colorless, pungent fuming vesicatory liquid acid that occurs naturally in most ants.'' It is usually made by acidification of sodium formate, which is used chiefly in dyeing and finishing textiles as an acidifying reducing agent, says the definition.

Does that leave you, as it does me, unsure of just why formic acid from ants could wipe out a little tree? In case you don't already know, the word vesicatory means ''tending to produce blisters.''

An East Coast professional says that carpenter ants tunnel through moisture-affected areas of wood providing ant lodging. While carpenter ants do not feed on wood, they can damage a tree by encouraging fungus encroachment.

Our Arizona expert says he never heard of ivy killing a tree by strangulation. To confirm his opinion he says he even checked with the state department of agriculture.

Our Eastern consultant says that common creepers, such as English ivy and poison ivy, do not kill trees.