Pest Control Tips – Whiteflies
Adult whiteflies look like small white moths, but are actually closely related to sap-sucking aphids.. They are approximately 1mm long. Whiteflies do not hibernate and must need a suitable host all year. Consequently mild, warm Florida weather provides an ideal environment for whiteflies. An adult female whitefly can lay up to 200 eggs. In warm weather egg-laying increases. Whiteflies lay eggs on the undersides of leaves and hatch in about 8 days. After the hatchlings complete 4 nymph stages they form a black pupa, which is visible under the leaves and looks like a black speck. Most whitefly species can complete a full life cycle in 20-30 days, or less during the summer.
One way to test if you have whiteflies is to brush against your hedge or plants. Whiteflies will quickly flutter up and fly away when disturbed. Whiteflies go round in hordes, so a severe attack can do major damage to plants. Whiteflies suck sap from the plant, this causes a yellow mottling on the surface of the leaf, as well as leaf loss, wilting and stunting. Not only do they feed on plants, but they also produce honeydew, which spoils the plants’ appearance, attracts ants and black sooty mould. Whiteflies can also transmit plant viruses.
Whitefly seems to be a modern pest, created by the over-use of pesticides that have killed off its natural enemies. One study has even demonstrated an increased whitefly reproductive capacity when sprayed with certain insecticides.
Organic management strategies are often the best approach to controlling white fly populations. You can try all of the following if you discover you have whiteflies.
- Introduce a parasitic wasp Encarsia formosa. It is commercially available as a biological control.
- Natural predators include spiders, ladybird larvae, lacewings, hoverflies and damsel bugs. So do not eliminate populations of these pests.
- Hang sticky yellow traps above the plants, in early spring, to detect an invasion. Tapping the plants with a stick will make the whitefly fly up and onto the traps. Whiteflies are strongly attracted to the colour yellow, so don’t wear yellow clothing around whiteflies or you may carry them from plant to plant.
- Vacuuming in the early morning when whiteflies are cold and slow-moving with a small hand-held battery operated vacuum is useful particularly for the adults before a great deal of egg-laying is done. After vacuuming enclose the section of the machine containing the bag with plastic and put in the freezer for 24 hours.
- Companion plants like nasturtium may help repel the whiteflies.
- Physical barriers like mosquito netting work very well for early-season protection.
- Handpick older leaves to remove young whitefly stages.
- Avoid using a lot of nitrogen fertilizer, including manures, as succulent growth will increase whitefly populations. You may need to check your phosphorus and magnesium levels, as deficiencies in these are believed to contribute to whitefly infestations.
- Try high pressure hosing in the early morning, 3 days in a row.