Whiteflies a troublesome enemy to leafy greens
[CourierPostOnline 2006-02-10]

Friday, February 10, 2006

Whiteflies are tiny, but troublesome pests.

They have a complicated life cycle, including immature stages that are difficult to detect and they reproduce rapidly. Even worse, gardeners now have to contend with the Q-biotype whitefly, which reached New Jersey in November.

As common pests of greenhouse plants, whiteflies travel along with plants as they are shared among greenhouses. Once brought home, whiteflies spread quickly on houseplants and in gardens. Poinsettias are the most common hosts, but many other plants, such as fuchsia, rose, chrysanthemum, gerbera daisy and herbs, may be infested.

Whiteflies damage plants by sucking sap, which weakens plants and may result in yellowing and sooty mold.

During the late 1980s, a close relative of the Q-biotype whitefly first infested poinsettias and almost was impossible to control until an effective insecticide (imidacloprid) was developed. This new whitefly is not as susceptible to most consumer insecticides.

The key to avoiding troubles is to inspect and purchase only pest-free plants. Adults are very tiny flies, only 1 to 2 millimeters. They vary in color from white to yellow. If high numbers of adults are present, they will fly about as leaves are disturbed. However, if adults are not present, detection is more challenging because whiteflies in immature stages do not fly and are small. A magnifying glass will aid in detection.

If you have poinsettias, closely inspect the undersides of leaves. If whiteflies are present, see if they have spread to other plants.

For infested poinsettias, the best option is to put plants in a plastic bag, seal and place outside. Freezing temperatures will kill them.

If valuable plants have become infested, treat with an insecticide. Bayer Advanced (with imidacloprid) is effective on most whiteflies, but less so on the Q-biotype. It can be applied to either the soil or sprayed on plants. Products with insecticidal soap or horticultural oil also can be effective.

Jim Willmott and Mary Eklund work for Rutgers Cooperative Extension of Camden County. Reach them at njgarden@camdencounty.com.