Whitefly in Vegetables: How to Spot It and Stop It

A study found that B. tabaci is not one thing but a group of at least 41 biotypes, which differ in host choice, in their resistance to insecticides and in how well they carry viruses. In the Philippines, researchers found the B biotype on cotton, eggplant, squash and tomato, and also Asia biotypes on eggplant. That mix is one reason sprays often fail.

How to Identify Whitefly

Shake a plant gently, or turn over a young leaf. Adults are tiny, about 1.5 mm, with yellowish bodies and white wings, and they fly up in a small cloud. On the underside you will see the pale, flat, scale like nymphs that do not move. Leaves may be yellow, curled or covered with a sticky shine and black sooty mold. Aphids and thrips also make leaves sticky or silvery, but they do not fly up as a white cloud.

• Small white flying insects that rise from the leaves when you shake the plant.
• Pale, flat, scale like nymphs on the underside of the leaves.
• Yellow and curled leaves, and plants that grow slowly.
• A sticky honeydew on the leaves and a black sooty mold on top of it.
• Fruits that ripen unevenly in tomato.
• Plants with virus symptoms, such as curled, yellow, stunted leaves, near the whitefly colonies.

How Whitefly Hurts Your Crop

The direct damage comes from sap loss and from the honeydew, which feeds sooty mold. But the bigger loss usually comes from the viruses the whitefly carries. In tomato these include the begomoviruses behind tomato leaf curl. A virus cannot be cured, so one early infestation can ruin a planting.

UC IPM uses a treatment threshold of about 4 adults per leaf for sweetpotato whitefly in tomato in California. That number comes from another climate and another crop, so treat it as a guide only. Because a virus cannot be cured, act on young plants as soon as you see adults.

How to Control Whitefly

1. Use clean seedlings from a nursery covered with a fine net, and inspect the seedlings for nymphs and eggs before transplanting.
2. Install yellow sticky traps at planting, around the field, to catch adults that fly in from other crops. Use them also to monitor the numbers.
3. Plant a barrier of maize around the field or a trap crop of cucurbits to hold the adults off the main crop, as the Pacific Pests fact sheet advises.
4. Remove weeds, old crop remains and neighboring volunteer plants that harbor whitefly. Avoid planting new crops right next to old ones, so the generations do not overlap.
5. Use reflective silver mulch where you can. UC IPM reports it can delay the build up in tomato by 4 to 6 weeks.
6. Protect the natural enemies, such as parasitic wasps, lacewings and lady beetles. The fungus Verticillium lecanii is also used against the nymphs. See the integrated pest management guide.

When a Spray Makes Sense

Pacific Pests warns that strong insecticides lead to resistant strains and advises soap, oils and plant products first. If you still need to spray, use the underside of the leaves and rotate groups. Follow the FPA registered label.

• Beta cyfluthrin: Pyrethroids kill the wasps that hold whitefly down, and whitefly comes back worse after them.

Resistance. Bemisia whitefly in Asia widely survives organophosphates, pyrethroids and imidacloprid, and in places other neonicotinoids and pyriproxyfen. Keep one group per window of 2 to 3 weeks: spiromesifen or spirotetramat (23), then afidopyropen (9D) or cyantraniliprole (28), then dinotefuran (4A) or flometoquin (34). Never two neonicotinoids in a row.

Keep It Out Next Season

• Raise seedlings under fine net and check them for eggs and nymphs before transplanting.
• Hang yellow sticky traps around the field from planting, to catch adults flying in and to count them.
• A border of corn around the field, or silver plastic mulch, keeps many adults off young plants.
• Remove weeds, volunteer plants and old crop remains, and never plant a new crop beside an old one full of whitefly.
• Plant on the same dates as your neighbors and pull out the crop right after the last harvest.
• Choose varieties that tolerate leaf curl virus where they are sold for your area.

Natural Enemies and Biological Help

• Encarsia and Eretmocerus wasps, lacewings and lady beetles eat whitefly. Pyrethroid sprays kill them and the whitefly comes back worse.
• Insecticidal soap, oil and neem sprayed under the leaves kill nymphs with little harm to the wasps.
• Fungi such as Beauveria bassiana and Lecanicillium lecanii work on nymphs in humid weather.

Not Sure What You Are Seeing?

Take a clear photo of the insect, the damage and the whole plant, then ask Anee, the smart farm technician in anee.io, in Tagalog or English. Anee tells you what it most likely is and what to do at the age of your crop. You can also put your scouting days on the cropping calendar, so the team knows when to walk the field.

Questions Farmers Ask About Whitefly