How to Manage Pests

Whiteflies are tiny sap-sucking insects that damage leaves of many plants. Adults are white, sometimes with darker markings on wings. Nymphs, which cause most of the damage, are oval, legless, and don’t move. Many species occur in California landscapes. Most are kept under good control by natural enemies. Prevent whitefly problems by using reflective mulches, avoiding dust, choosing less susceptible plants, and eliminating pesticides that kill whitefly natural enemies. When management is required, consider insecticidal soaps, traps, or removing infested plants.

• Tiny nymphs on undersides of leaves.
• Sticky honeydew on leaves, fruit, or beneath plants; or a covering of black, sooty mold.
• Yellowing, silvering, or drying leaves that have whitefly nymphs on them.
• Deposits of white wax with some whiteflies.

• Avoid use of pesticides such as pyrethroids, organophosphates, cabaryl, or foliar sprays of imidacloprid.
• Prevent dusty conditions.
• Keep ants, which protect whiteflies from natural enemies, out of plants.
• Recognize signs of parasitization such as circular holes in nymphs or change in color.

• Use aluminum-coated construction paper or reflective plastic mulch products.
• Apply to bare soil before you plant; bury edges with soil and insert seedlings or seeds into holes in mulch.
• Plastic mulches require drip irrigation beneath; paper mulches can be sprinkle or furrow-irrigated.
• Mulches repel whiteflies and other small flying insects like aphids while plants are small. Remove mulches when plants get large and temperatures get hot.

• Prune out isolated infested leaves when first detected.
• Hose adults off or use a hand-held vacuum.
• Install ready-to-use sticky-coated yellow traps or make your own. Use up to one trap for every medium-size vegetable plant.
• Promptly destroy infested annuals when flowering or fruiting ends.

Even the most toxic insecticides are only partially effective. If you decide to treat, choose products that are least harmful to natural enemies, such as insecticidal soaps and oils including neem oil, and combine their use with other practices listed above. Good coverage, including undersides of leaves, is essential. Repeat applications may be required. Avoid using even these pesticides if many natural enemies are present.

See the Whitefly Pest Note for more details

a b c

Greenhouse whitefly adult (a) and mature nymph (b), and silverleaf whitefly nymph(c).

d e

Examine empty nymphal cases for signs of parasitization. The T-shaped hole in nymph (d) indicates a healthy adult whitefly emerged whereas an adult parasite emerged from the round hole in (e).

What you use in your landscape affects our rivers and oceans!