White Ash Flies

Description

• Adult whiteflies are about 1/20-inch-long and covered with a bright-white, waxy coating. The pests have white wings, yellow head, thorax and abdomen, and red eyes. Infestation in dense colonies on foliage undersides appears as waxy, lighter green patches. The young or the nymphs look like white, oval specks. The females have a lifespan of one to two months while males typically live for nine days.

Native Range

• Ash whitefly occurs in low densities throughout California, the main site of its infestation in the United States. The insect is not found in the mountainous areas as the low temperatures do not support survival. The pest has also spread into other states since its arrival. Geographical distribution includes all continents and countries such as Argentina, Mexico, Australia and New Zealand.

Damage

• The pests are sap feeders and suck plant juices with their needle-like mouths both in their young and adult stages. Nymphs rarely move and continue feeding in the same spot until reaching adulthood. Infested foliage starts to wilt and drops prematurely. As they feed, the nymphs produce sticky honeydew that promotes the growth of black-mold fungus on infested sites. The fruit is also affected in cases of severe infestation and the excessive loss of nutrients from the tree, resulting from greater pest population feeding, can lead to excessive defoliation and even the death of the host tree.

Management

• Biological control agents have proven greatly effective in controlling ash whitefly. Natural predators include the tiny wasp Encarsia inaron imported from Italy and Israel. A number of parasites such as Eretmocerus corni are also effective natural enemies. Chemical control methods include the use of insecticides containing imidacloprid or dinotefura.