Whitefly

Tiny but destructive

Adult whiteflies are tiny — 1–2 mm — and look like miniature white moths due to their waxy white wings and pale yellow body. Despite their small size, they cause enormous agricultural damage through two mechanisms:

1. Direct feeding — masses of nymphs extract phloem sap continuously, causing leaf yellowing, wilting, and reduced plant vigor
2. Virus transmission — Bemisia tabaci is one of the most significant vectors of plant viruses, transmitting over 100 different viruses including Tomato Yellow Leaf Curl Virus, which has devastated tomato production in tropical and subtropical regions

The honeydew-mold cycle

Like aphids, whiteflies excrete honeydew — a sticky, sugar-rich waste product. This honeydew coats leaf surfaces and supports the growth of black sooty mold, which blocks light and further reduces plant photosynthesis. A heavily infested plant looks coated in black grime.

The shake test

Disturbing a heavily infested plant produces a characteristic cloud of tiny white insects flying off in all directions — the “whitefly cloud.” This is the easiest diagnostic for a serious infestation.

Control

• Biological control — the parasitic wasp Encarsia formosa is widely used in commercial greenhouses; it lays eggs inside whitefly nymphs
• Yellow sticky traps — attract and capture adults
• Insecticidal soap — effective against soft-bodied nymphs
• Pyrethroid insecticides — effective but can develop resistance rapidly; Bemisia tabaci has evolved resistance to hundreds of chemical compounds