Q: Is there a way to control slugs in my vegetable garden without using poisonous chemicals? A: Researchers at the Beltsville Agricultural Center found that beer in a shallow pan caught more than 300 slugs during a four-day test. Stale beer works as well as fresh beer, they said. Q: Is sawdust all right to use for mulching my vegetable garden? Will it make the soil too acid? A: Sawdust is very good for mulching vegetable gardens, flower gardens, berry bushes, trees and shrubs. It reduces crusting of soil, conserves moisture, keeps the soil cool during hot summer weather, and helps control weeds. Contrary to popular belief, sawdust does not make the soil acid. Tests by research workers in different parts of the country bear this out. Actually, it helps maintain or slightly increase the alkaline reaction of the soil. Q: I've been spraying my lawn with 2,4-D to get rid of some weeds. My neighbor protested, said I was killing plants in his yard. Could that be true? A: Only a trace of 2,4-D is needed to damage susceptible plants. When the wind is blowing, the active ingredient of 2,4-D may be carried by air currents and cause injury a considerable distance away. When you use 2,4-D, keep pressure very low, nozzle directed downward, and spray with it only when the wind is not blowing. Q: The leaves on my holly tree are drying up and appear to be dying. Is there any way I can help the tree? A: American holly trees usually lose most of their leaves in the spring and get new ones. It is a natural thing for the tree to do. Q: We dug up our lawn and seeded it with Kentucky bluegrass. Now we have thousands of weeds. Could there have been weed seeds in with the grass seeds? A: In many soils there are quantities of weed seeds buried deep, waiting for someone to come along and get them to the surface where they can get light enough to germinate. Digging up the lawn did just that for them. What can be done about it? There is no satisfactory answer at this time. Q: Can you give us a rule as to the size of a planting hole for trees and shrubs? A: The planting hole should be a maximum of one foot wider and six inches deeper than the root ball or mass of roots. Q: Is there a way to keep crabgrass from getting started in my bluegrass lawn? A: Cut the grass 2 1/2" to 3" high so sunlight can't reach the soil surface. This will prevent crabgrass seed from germinating.