For such a small insect, whiteflies create big problems in the vegetable garden. They not only damage plants by sucking the juices from tender leaves and stems, but also spread viruses to your vegetable plants as they feed. Eliminating whiteflies requires a combination approach. Sticky traps on their own won't completely control whiteflies but in combination with other methods they provide additional control and help monitor the effectiveness of the control plan. Reflective mulch is an effective control method, proven to reduce populations of whiteflies as well as the diseases they carry. Unfortunately, whiteflies are resistant to most insecticides, which must come in direct contact with the insects and require several repeat applications.
Things You'll Need
- Hand-held vacuum cleaner
- Plastic bag
- Yellow sticky traps
- Yellow paint
- Petroleum jelly
- Mineral oil
- Shovel or rototiller (optional)
- Garden rake
- Drip irrigation hose
- Aluminum or plastic reflective mulch
- Insecticide labeled for use against whiteflies
Examine the leaves of your vegetable plants for small whitefly numphs, paying particular attention to the undersides of leaves. In their early stages, whitefly nymphs have legs and crawl around on the leaves. In later stages they loose their legs and look like tiny white raised spots on the leaves. Remove infested leaves by pinching them off where the leaf stem attaches to the main stem.
Spray the vegetable plants with a strong, fine spray of water to dislodge adult whiteflies.
Vacuum the vegetable plants with a hand-held vacuum cleaner to remove adult whiteflies. Vacuum when temperatures are cool and the insects are relatively inactive.
Place the vacuum cleaner bags and any leaf or stem material removed from the vegetable plant in a plastic bag and place it in the freezer overnight to kill the whiteflies. Dispose of the bag the following morning.
Yellow Sticky Traps
Make your own sticky traps from pieces of cardboard painted yellow and coated with a mixture of petroleum jelly and mineral oil, or buy commercial sticky traps.
Attach the traps to a stake and place them in the garden so that they sit just above the vegetable plants. Use one trap for every two plants.
Clean or scrape the insect debris from the traps when they are full of insects. Reapply the petroleum jelly and mineral oil mixture.
Take down the traps when whitefly populations are decreasing to avoid trapping beneficial insects including those that pollinate vegetable plants.
Prepare a row by removing weeds and loosening the soil with a shovel or tiller, if necessary. Add any amendments necessary for the type of vegetable you are planting and level and smooth out the soil with a garden rake.
Lay a drip irrigation hose down the length of the row. Once the mulch is in place, traditional watering is ineffective. The drip irrigation hose allows you to water under the mulch.
Roll out the reflective mulch over the row. Cut holes in the mulch at proper intervals for the type of vegetables you intend to grow and plant your seedlings as usual.
Bury the sides and ends of the sheet of mulch with dirt to keep it in place.
Remove the mulch in summer. High temperatures cause it to overheat.
Apply insecticides as soon as you notice whiteflies or the silvery debris that the nymphs leave on vegetable plant leaves for the best chance of control.
Spray the entire plant with an insecticide approved for use on vegetables, paying particular attention to the undersides of leaves.
Apply insecticides at five-day to seven-day intervals. You may have to make four or five applications. Consult the label for information about how soon you can harvest vegetables after spraying.
Tips & Warnings
- Use insecticides as a last resort. Insecticides kill the whiteflies' natural enemies and may actually make the infestation worse.
- Choose insecticides containing insecticidal soap or neem oil for the best chance of control.
- Don't use insecticidal soap when vegetable plants are drought-stressed.
- Store insecticides in their original container and out of the reach of children.
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