Q: I put mothballs in my vegetable garden to protect it from insects. I've been told they are toxic to plants. Will my vegetables be safe to eat? A: The chemicals in mothballs are not translocated into edible plants. Some gardeners use mothballs to keep out rabbits and squirrels but the results are questionable. Mothballs can kill the vegetables by touching them. Q: One of our mimosa trees appears to be dying. It was all right and then overnight the leaves turned brown and shriveled. What could have caused it? A: Mimosa trees are susceptible to a fungus disease called Fusarium wilt, which has killed many of them. For a positive diagnosis, look for partial or complete brown rings in the sapwood when an infected branch is cut through. There's no cure, and infected trees often die within a month. They should be removed and destroyed immediately. Mimosa trees believed resistant to the disease are being tested and may be available for purchase in a year or two. Q: Ants are all over my strawberry bed. How can I get rid of them? A: Aphids, or plant lice, suck plant juices from the foliage and excrete a sticky substance called honeydew, which ants love. Get rid of the aphids and the ants will leave. High-pressure water sprayed from your garden hose can help remove the aphids. Q: How can you tell when Irish potatoes are ready to dig? A: Potato tops usually turn brown when the tubers reach maximum size. However, they can be eaten before that: when they are large enough to taste good to you, they are ready. Dig a few at regular intervals and try them. Q: I planted rosemary, lemon balm and savory in my garden this spring. When can they be harvested? A: Fresh leaves can be picked as soon as the plant has enough foliage. To ensure good oil content, pick leaves or seeds after dew has disappeared but before the day becomes hot. Q: My oak trees have been getting bigger and bigger and now there's too much shade for the iris. I'd like to plant it in a new bed. When is the best time to do it? A: The best time is soon after it finishes blooming in June or July; but it can be done successfully almost any time of the year. Q: My tuberous begonias stay green but the leaves curl and droop. What kind of care do these plants need? A: They do best with morning sun until about 11, but filtered sunlight beneath tall trees is adequate. They need good drainage; otherwise flower buds drop before they open. Mulch the plants to prevent rapid drying of the soil. With good care, the plants should bloom until fall.