Albuquerque Journal (Albuquerque, NM)

Drying soil will repel fungus gnats.(Homestyle)

Byline: Yard and Garden LYNN ELLEN DOXON For the Journal

Q: I have a problem with little black flies in the soil of my Christmas cacti. When I water, the little flies come out and fly around. They are very annoying. I tried systemic insecticide but that didn't seem to work. What can I do? Mrs. M. Johnson, Albuquerque

A: These bothersome little insects are fungus gnats.

The systemic insecticide didn't work because a systemic insecticide is taken up into the plant and through the system of the plant. At no stage of its lifestyle does the fungus gnat feed on the plant. It feeds on fungi and other organic material in the soil.

When you have an organic potting soil that is kept moist, as you have probably been keeping the Christmas cacti in while they have been budding and blooming, fungi tend to start growing in the soil and so do fungus gnats.

The best way to get rid of them is to let the soil dry out thoroughly between watering. Now that they have finished blooming, the Christmas cacti can tolerate that. …

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