How to Get Rid of Whiteflies

Whiteflies are small, sap-sucking insects, about 1/16 inch long, that look like tiny white moths. They gather on the undersides of leaves, and the telltale sign is a small cloud of them lifting off when you brush against or shake the plant. Both the winged adults and their flat, scale-like nymphs feed on sap, weakening the plant and causing leaves to yellow and drop.

Like aphids and scale, whiteflies excrete sticky honeydew that coats foliage and grows black sooty mold, which further reduces a plant's ability to photosynthesize. They breed quickly in warm indoor conditions and the nymphs are far harder to kill than the mobile adults, so effective control combines trapping adults, treating the immobile nymphs on leaf undersides, and repeating over several weeks.

Signs to look for

• A cloud of tiny white moth-like insects flying up when the plant is disturbed
• Flat, oval, semi-translucent nymphs clustered on the undersides of leaves
• Sticky honeydew on lower leaves and surfaces beneath the plant
• Black sooty mold growing on the honeydew
• Yellowing, weakening, and dropping leaves as feeding intensifies

What causes it

How to fix it

1. 1
   Isolate the affected plant

   Move it away from others immediately, since adults fly and will colonize nearby plants if left in place.

2. 2
   Hang yellow sticky traps to capture adults

   Whiteflies are strongly attracted to yellow. Place sticky cards near the plant to trap flying adults and to gauge whether the population is shrinking.

3. 3
   Vacuum or rinse off the adults

   Gently vacuum the flying adults early in the morning when they are sluggish, or shower the plant to knock adults and loosen nymphs from leaf undersides.

4. 4
   Spray leaf undersides with insecticidal soap or neem

   Thoroughly coat the undersides of all leaves, where the nymphs live, with insecticidal soap or neem oil to kill the immobile stages that traps cannot reach.

5. 5
   Repeat every 5 to 7 days for three weeks

   Because eggs and nymphs survive single sprays, reapply on a 5-to-7-day cycle for at least three weeks to catch each newly emerged generation.

6. 6
   Prune and bag heavily infested lower leaves

   Remove the most affected lower leaves crowded with nymphs and dispose of them sealed in a bag to cut the breeding population quickly.

How to prevent it

• Quarantine and inspect new plants, checking leaf undersides for adults and nymphs
• Hang yellow sticky traps near susceptible plants for early warning
• Check leaf undersides during routine care, since that is where whiteflies breed
• Treat at the first cloud of flies before nymph numbers build on the undersides
• Keep plants spaced so adults are less able to move from one to the next