Whiteflies are tiny sap-feeding insects that often rise in a cloud when a cucumber plant is disturbed. Early identification helps you use gentle controls before leaves yellow, curl, or become coated with sticky honeydew.
Check the leaf undersides
Turn over newer leaves and look for small pale insects, scale-like nymphs, and scattered eggs. Adults may fly briefly when the plant is brushed. Also look for yellowing, wilt during warm afternoons, sticky residue, and dark sooty mold.
Confirm the problem
Compare several leaves and nearby plants because dust or ordinary leaf hairs can be mistaken for insects. A hand lens helps distinguish whiteflies from aphids and mites. Note whether the damage is limited to one plant or moving through the row.
Start with low-impact controls
Remove badly affected leaves and place them in household waste. A gentle water spray aimed at the undersides can reduce adults and nymphs without injuring the plant. Yellow sticky cards near, but not touching, the foliage can help monitor adults.
Protect beneficial insects
Avoid broad-spectrum sprays when possible because they can remove predators that help control whiteflies. If a labeled product becomes necessary, follow the label, observe harvest intervals, and spray when pollinators are not actively visiting flowers.
Improve airflow, avoid excessive nitrogen, and inspect new plants before adding them to the garden. Persistent infestations may need local extension advice because whitefly species and permitted treatments vary by region.