Whiteflies in the garden

No flies on these guys. Warm temperatures have helped these Genoa tomato plants put on the fruit.

No flies on these guys. Warm temperatures have helped these Genoa tomato plants put on the fruit.
Photo by Kurt Hildebrand.

You planted a variety of vegetables and were looking forward to harvesting, but veggies aren’t producing as you had hoped. You notice many quick-flying tiny white critters darting around as you work in the garden. Turning over a leaf or two you see a collection of white insects on the undersides. These are whiteflies.

Whiteflies are not actually flies at all, but relatives of sap-sucking aphids. Because whiteflies suck the juices out of vegetables and leaves, they weaken plants and reduce yields. Leaves may yellow, shrivel and drop prematurely. With high populations, plant death can occur.

However, sucking the life out of the plant isn’t enough. These pests transmit viruses through their mouthparts. On top of that, because whiteflies exude the sticky “honeydew” of sugary excess plant juice just like aphids, sooty mold fungus often grows on your poor plants, leaving them blackened and dirty looking. And, as with aphids, ants may be in abundance harvesting the honeydew and protecting the whitefly colonies.

Whiteflies are hard to control. Spraying isn’t always the answer because you may not hit the little buggers and because you may also kill the tiny parasitic wasps that are one of the whitefly’s natural predators.

First, don’t purchase plants already infested with insects. Then, use slow-release fertilizers to avoid over-fertilization with high nitrogen fertilizers, which stimulate succulent new growth, an enticement to whiteflies (and aphids). Organic fertilizers release nutrients more slowly. Hang sticky traps throughout your garden to help catch early invaders.

Encourage beneficial insects by planting flowers and insect-attracting plants in and around your garden. Lady beetles, lacewings, and big-eyed bugs, as well as spiders and birds, eat whiteflies and other pests.

Hose off sturdy plants, particularly the undersides of leaves, to get rid of the honeydew and the pests. University of California researchers found that hosing off, also known as syringing, was just as effective or even better than chemical treatments. Be vigilant and do this daily for a week or two to break the reproductive cycle.

Vacuuming up whiteflies on leaves early in the morning when they are lethargic can help. Or prune away severely infested parts of the plant. Be sure to bag up the vacuumed or pruned remains and seal them up before putting in the trash. Do not compost these materials. Spraying horticulture oils or insecticidal soaps may help, but you have to thoroughly cover the undersides of the leaves.

Next year, before whiteflies get established, cover plants with row covers. These covers allow light and water in but keep pests out. This information is taken from www.ucanr.edu/sites/VCMG/Controlling_Whiteflies_in_Your_Garden/

JoAnne Skelly is Associate Professor & Extension Educator Emerita at University of Nevada Cooperative Extension. Email skellyj@unr.edu



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