Q. I have a compost pile. During the past year, I have been bothered with ants, flies, gnats and grub worms. Sometimes the compost also smells but so far either the neighbors have not noticed it or ignoring the odor. Can you help me control these problems this year?
— L. F. of Columbia
A. There will always be some insects around a compost pile. When you notice a large number and especially certain types, something is usually wrong. It usually involves keeping the compost too wet or not aerated enough.
A foul odor is an indication that there is not enough oxygen helping to break down the plant parts. When there is a lot of rain, the pile can get too wet, but you can control this by covering the pile with a plastic cover. Keep it covered when a lot of rain is predicted. You can uncover it during dry periods. This will also prevent some of the odors from becoming a problem.
Ants prefer cool, wet compost. As the compost pile heats up, the ants will leave. Grass clippings mixed in the pile contain nitrogen and, as the nitrogen breaks down, it will heat up the compost. You will have to turn the compost every three to five days to keep it from getting too hot. If you do not notice the compost heating up, it is either too wet or too dry. If it is too wet, you will have to turn it every day so that it is just moist but not soggy. When the compost becomes dry enough, it will heat up again. Ants can also be problem if the compost is not layered — plant material covered with a layer of soil. Each layer should be about 4 inches in thickness.
Flies and gnats are an indication your compost is not breaking down properly as there is not enough oxygen. They are attracted to the bad odors. A tarpaulin placed over the pile will prevent the flies and gnats from laying eggs in the compost.
Grub worms are the larval stage of May and June beetles. These beetles are attracted to the smell of decaying plant material found in the compost. They can also be attracted to plants you may be growing nearby. There they can feed on the roots and damage the plants. You may notice that there are ads for small worms called nematodes which feed on these beetles. You can introduce these nematodes into the edges of your compost. Again a plastic covering can prevent the grubs from developing and being introduced into your compost.
I commend your desire to compost as compost is one of the all-purpose answers to your plants’ needs. It supplies fertilizer for your plants, and it is free from leftovers of decayed plant parts. You never have to worry about burning your plants with too much fertilizer, and it provides all the nitrogen and potassium a plant needs, as well as the micronutrients such as copper, calcium and boron.