Yellow sticky cards are a practical way to monitor adult fungus gnats near houseplant soil. They help you see whether control measures are working, but they are not a complete solution while larvae remain in damp media.
Place cards close to the soil
Position the card slightly above the growing medium using its holder. Keep the adhesive away from leaves, pets and children. Follow the trap maker’s instructions for indoor use.
Record a baseline
Check the number of adults on a fresh card after a consistent interval and note how wet the soil is. Comparing similar time periods is more meaningful than comparing different trap locations or card sizes.
Adjust the growing conditions
Reduce unnecessary watering, ensure drainage and address standing saucer water. Recheck the cards while keeping the placement consistent; falling catches can indicate fewer flying adults.
Know what the numbers cannot tell you
A sticky card only reflects insects that reached it. It does not directly count larvae or establish root damage. If numbers stay high, inspect nearby pots and consider appropriate labeled larval control.
Frequently asked questions
How often should I replace the card?
Replace it when the adhesive is dusty, full or no longer effective, following the manufacturer’s advice.
Will a card attract gnats from outside?
Sticky cards can attract nearby adults, but indoor populations are usually linked to existing moist potting media.
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