Small white insects on tomatoes are often whiteflies, but pale specks can also be shed insect skins or other material. Look for movement, wings and immature stages underneath leaves before treating the plant.
Check for whiteflies
Whitefly adults are small, pale, winged insects that rise from foliage when disturbed. Their immature stages remain on leaf undersides. Feeding can contribute to yellowing and sticky honeydew, on which sooty mold can grow.
Use UC IPM’s whitefly identification guide to compare what you see. Inspect several leaves rather than identifying the problem from one blurred photograph.
Rule out lookalikes
White fragments among an aphid colony can be shed skins, not another active infestation. Cottony material warrants a closer inspection for mealybugs or another cause. A white patch that does not move may be unrelated to insects.
Take photographs of the leaf underside and the whole plant. Record whether the insects fly when disturbed and whether the plant has sticky leaves, stippling or distorted growth. Local extension help is useful when the identification remains uncertain.
Respond to the amount of damage
On a small infestation, washing suitable foliage and removing a few heavily infested leaves may reduce numbers. Avoid stripping the canopy. Sticky yellow cards help reveal adult activity but do not reach immature stages attached to foliage.
Inspect neighboring host plants and new transplants. A continuing nearby source can produce returning adults even after one tomato is treated. Remove spent infested annual plants when the crop is finished.
If a spray is needed
Choose a product labeled for tomatoes and the identified pest. Soap or oil products require coverage of the relevant leaf surfaces and have plant-safety limitations. Follow the directions for concentration, temperature, repeat applications and harvest timing.
Do not substitute dish detergent or assume neem is harmless to all beneficial insects. Avoid broad routine spraying and protect natural enemies. More fertilizer is not a whitefly treatment.
Separate insects from other tomato problems
Some whiteflies transmit plant viruses, with risks depending on species and region. That is different from blossom-end rot, which is a physiological disorder, not a disease spread by whiteflies. Dark damage at the blossom end of a fruit needs its own diagnosis.
After treatment, watch for living insects and new damage. Old yellow or scarred leaves will not necessarily recover their appearance. If symptoms continue despite reduced insect activity, investigate watering, roots and disease rather than repeating sprays automatically.
