Fungus Gnats

• The group of insects commonly called fungus gnats include several species of long-legged flies. Adult gnats are 1/16 to 1/5 of an inch long and look similar to small flies or mosquitoes. Their larvae live in the upper 1 to 3 inches of the soil, look like maggots and may be either transparent or white, but have black heads. Adult gnats are not a major pest, but can be a major annoyance to humans. Adult gnats do not feed on plants, but lay eggs that lead to the next generation of maggots. Adults and larvae can spread plant diseases.
  
  

Light

• Lemon geraniums need the equivalent of four hours a day of direct sunlight, and indoor plants require as much light as possible. Fungus gnats are attracted to light, so you may notice them near plants under grow lights or near windows. Adult gnats may be drawn indoors by light or brought inside on newly purchased plants or plants that were kept outdoors.
  
  

Water

• The practice of allowing the soil to dry between waterings is good for lemon geraniums and for deterring fungus gnats. According to the University of Minnesota Extension, geranium plants withstand dry soil conditions better than they tolerate over-watering. Over-watering will not only lead to root rot, but it will also encourage the breeding of fungus gnats. Do not mist your plants. Keep the leaves dry to prevent fungal diseases of the foliage and leaf drop.
  
  

Containers and Soil

• Lemon geraniums need a growing medium that drains well. Use a sterile potting soil, advises the Utah State University Extension, as reducing the humus content of the growing medium creates an environment less attractive for gnats. If moisture is an issue, or you tend to over-water, consider a switch to a clay pot. They breathe better than plastic pots, allowing water to evaporate faster.
  
  

Food Source

• Remove dead flowers from your plants. This encourages more flowers to develop and prevents the buildup of plant material on the surface of the growing medium. Gnat larvae feed on rotting plant matter and may also consume plant roots, damaging your plant.
  
  

Considerations

• Avoid the use of insecticides if you plan to use your lemon geraniums in food or drink preparations. Fortunately, insecticide use is rarely required to control fungus gnat populations, notes the Utah State University Extension.