Gardening columnist Tim Daly answers the following questions from readers:

Question: I have noticed many small holes with mounds of soil piled by them in my lawn. Small insects are observed going in and out of them. What are these bugs, and how can I get rid of them?

– Lois from Grayson

Answer: Lois, what you are observing are digger bees, which unlike honeybees, are solitary and do not form hives. Their activity poses no threat to people or the lawn. The insects are beneficial in that they are pollinators. In a few weeks, they will go away. If you do find their presence bothersome, apply an insecticide labeled for controlling insect pests of lawns.

Q: My Bermuda grass lawn is starting to green up for the season. If I removed the old growth from last year, will it help my lawn? What is the best way, burning or using a lawnmower? Should I have the lawn aerated?

— George from Buford

A: George, in the spring, Bermuda grass and other warm-season grasses begin to come out of dormancy and turn green. The process takes a few weeks depending on the temperatures and rainfall. The old growth from last year does not have to be cut back, but the practice is beneficial by allowing more sunlight, water, and air to infiltrate.

The grass can be scalped down one-half of an inch to remove the dead grass and to reduce thatch buildup, which is a layer of dead grass and roots that form at the soil surface. Once it gets over one-half of an inch, it inhibits air and water infiltration and can increase pest issues. You should never burn the grass under any circumstances due to the hazard that it poses to your home and your neighbors. It is also illegal to do so.

For other warm-season grasses, avoid scalping zoysia grass since it has a slower growth rate and is more susceptible to damage. Centipede grass and St. Augustine grass also should not be cut back in this manner. In regards to aerating, wait until the grass greens up entirely before doing so. It needs to be actively growing for the aeration to have maximum benefits.

Timothy Daly is an Agricultural and Natural Resource Extension Agent with UGA Extension Gwinnett. He can be contacted at 678-377-4011or tdaly@uga.edu.