fungas gnats, their eggs and larva

(Question)

Hi,

how long does fungas gnats, eggs and larva survive in dry soil with sunshine and circulating air….I didnt see any larva per se, but I would nt know how the eggs look like. I have removed my plant from an infested pot, and re-used a different uninfected pot and uninfected soil.

I gave the plant roots a cool to warm water bath twice before leaving the plant and roots exposed overnight outside. I plan to repot it the next morning.

The spider plant had long roots and I had to use a deeper pot, and I think that’s what I believed had built up moisture.

J

(Answer)

Fungus gnats are small, slender, dark insects that fly around when plants are disturbed. While the adult flies are annoying it is the larvae which may cause problems. The adults lay their eggs in soil that contains decaying organic material.  Larvae, particularly if a large number are found in the soil, may cause root damage or stunted growth.  Repotting the plant into fresh potting mix and moving your plant to a new pot was the correct strategy.

According to the University of California Integrated Pest Management System:

” Fungus gnats develop through four stages—egg, larva (with four larval stages or instars), pupa, and adult. The tiny eggs and oblong pupae occur in damp organic media where females lay eggs and larvae feed. At 75ºF, eggs hatch in about 3 days, the larvae take approximately 10 days to develop into pupae, and about 4 days later the adults emerge. A generation of fungus gnats (from female to female) can be produced in about 17 days depending upon temperature. The warmer it is, the faster they will develop and the more generations will be produced in a year.”

Larva cannot survive in dry soil, so letting the top inch of your potting mix dry out inbetween waterings in the best way to break the cycle. According to the University of California” Most of the fungus gnat’s life is spent as a larva and pupa in organic matter or soil, so the most effective control methods target these immature stages rather than attempting to directly control the mobile, short-lived adults. Physical and cultural management tactics—primarily the reductions of excess moisture and organic debris—are key to reducing fungus gnat problem. “

God Luck with your spider plant.