(back)

Pesky whiteflies can be controlled—if you act soon

By Bill Mercer

If you have lived in the Kyrene Corridor for any length of time, you’re probably familiar with whiteflies. Whiteflies normally are seen in large numbers toward the end of summer and into fall, about the time summer crops begin to decline.

In years past, clouds of these pinhead-sized insects have plastered car windshields and forced runners and bicyclists to wear dust masks.

As time goes on and acreage is converted from agriculture to residential, there may be some relief.

However, as a result, we may have a permanent relationship with those that do not migrate back to the crops. They are capable of over-wintering in order to be ready for the spring.

One type of whitefly that recently has become a serious pest is the sweet potato whitefly or a close relative of that species.

Farmers express concern over this pest since it can cause extensive crop damage.  Homeowners also have a tremendous problem with the clouds of whiteflies as the farmers harvest their crops. 

The biggest fear among homeowners is that they will have to replace all the plants in their yards. Some plants can turn yellow and become sticky with sap, known as honeydew. Some begin to show an unsightly black growth called sooty mold.

Whiteflies are attracted to lantana, hibiscus, annual flowers, herbs and vegetables. 

They lay eggs on the undersides of leaves along the veins. The eggs hatch into “crawlers,” then move around on the underside of the leaf until they find a good place to feed.

They then molt and become what looks like tiny, transparent scales.

During this time they are hard to control because they are protected from most chemicals.

Even more perplexing, whiteflies are hard to see without a magnifying glass. The underside of the leaf will have the texture of sandpaper and probably will have tiny droplets of honeydew.

There is really no total effective control.

If you wait until the numbers of whiteflies are too high, no control will be effective.  When whiteflies are numerous, they may be found resting on virtually every plant in the yard, but they are not necessarily causing damage or reproducing.

Heavily infested plants with immature whiteflies may turn yellow and wild, possibly begin to grow sooty molds.

The number one defense is to keep plants as healthy as possible. Stressed plants are often more susceptible to infestation and damage.

Lacewings are natural predators that attack whiteflies. They normally appear naturally when whitefly populations build up. They are attracted to lights at night, and may be mistaken for moths. Lacewings are not dangerous to your plants.

The control method that has been shown to be most effective is a spray of detergent and water.

To start, use one teaspoon of liquid detergent per gallon of water. If the plant appears to tolerate the low dose, you may want to gradually increase the dosage per gallon up to two teaspoons.

Make sure to cover the underside of leaves  and repeat every three to four days as needed. Night treatment may be more effective.

Neighbor Bill Mercer is a longtime South Tempe resident, a former community association manager and former president of the Central Phoenix chapter of Community Associations Institute.

(back)