What are the fast crawling little insects that look like fruit flies, but...

Asked December 1, 2014, 1:25 AM EST

What are the fast crawling little insects that look like fruit flies, but don't fly. Sometimes they gather near the top of a houseplant's pot dirt, after the plant has been overwatered.

Wake County North Carolina

1 Response

I suspect that you have fungus gnats. Read more about them at http://www.ext.colostate.edu/pubs/insect/05584.html. From that site:

Nuisance problems with fungus gnat adults tend to be most noticeable during late fall and winter. There are several factors that may account for this seasonal peak. First, houseplants maintained outdoors during summer will commonly be colonized by fungus gnats and when these plants are brought indoors, populations may subsequently increase in response to the warmer temperatures encountered in homes. Second, fungus gnats may be more noticeable during cooler weather, when people spend more time indoors, thus increasing the likelihood that fungus gnat populations will be highly noticed.

However, the primary reason why fungus gnats are abundant in homes is related to changes in moisture levels associated with the growing media of houseplants. Fungus gnat adults are highly attracted to moist-growing media. Furthermore, as the growing medium ages or degrades it tends to retain more moisture, which will also attract fungus gnat adults. In addition, decreased day length and cooler temperatures slow plant growth and water usage. If watering practices are not altered, particularly during fall and winter, the growing medium will remain moist, which improves conditions for fungus gnat development.

I suggest that you let your plants dry out more between waterings or repot plants which are particularly problematic.