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Pests
Fungus Gnats in Cactus Soil
Commonly affects: Cactaceae (Cactus)
Small dark flies hover around the plant and soil surface, thriving in consistently moist potting mix.
Potential Causes
- 1Overly moist potting mix, often from overwatering a plant that needs to dry out fully between waterings
- 2Organic matter in the mix breaking down and attracting egg-laying adults
Solution Steps
- 1Allow the soil to dry out completely between waterings, which cacti need anyway
- 2Use yellow sticky traps to catch and monitor adult gnats
- 3Apply a BTI product to the soil to target larvae if a persistent infestation continues despite drier watering habits
- 4Consider a mix with more inorganic material (pumice, grit) which retains less moisture overall
Prevention Tip
Fungus gnats on a cactus are almost always a sign of overwatering â correcting watering frequency usually solves the problem without any pesticide.
