T'was the night before Christmas and all through the house not a creature was stirring…except the fungus gnats.
I thought I had gotten them all during the last infestation in the late fall when they arrived in newly purchased potting soil. Last week they reappeared.
At first I thought this group of random holiday visitors rode in on the Frosty Fern (Selaginella Krausianna Variegatus) that I just bought. But then on close examination of a background fact sheet the second paragraph names poinsettia as one of the fungus gnats' favored plant species.
Small, nimble and quick, fungus gnats breed in moist soil. Some people may say they have fruit flies but it is probably not case if they brought plants home recently from a greenhouse. Fruit flies are larger and have different colored eyes, though you need a microscope to see them.
Twinkling past the white of computer screen, they seem particularly attracted to its light. Search out a new infested plant. You will see more swirling around it or directly emerging from the soil. If your problem seems to be originating in the bathroom, you may have neither. Instead it may be moth flies, whose preferred environment is the residual debris in shower and sink drains.
Fungus gnats are the only ones of this insect group that can damage plants. However, it is not the adult gnat that causes problems but the larvae that are in the soil. The larvae feed on and damage plant roots and other vegetation in the soil. While they do not spread disease to humans, they can spread plant diseases.
If you have an infestation and after some practice manage to catch one relatively intact, Essex County Cooperative Extension (621a Eagle Rock Avenue, Roseland, NJ 07068 phone: 973-228-2210) can help you determine the exact type if you bring in your sample.
Regardless of the type, the method that works best to eradicate the nuisance is yellow sticky tapes. These can be hard to find. Bartell's in Westfield is the nearest place to purchase them. Place several in the infested plant. Cut back on watering since the larvae need moisture to survive.
Some sources suggest using a cut raw potato bit placed on the top of soil to attract the larvae. I tried this once and it did not seem to work. It probably was too late. With my traps all in place, I can only hope that my gnats now dash away. Dash away all.