Q: I notice white flying insects on my orange tree. Should I be concerned?
Leo V., Los Osos
A: It sounds like your citrus tree has become the landing pad for the woolly whitefly. When few in number, these pests will not hamper fruit production, but if the population increases dramatically, problems may soon follow. Found on all variety of citrus trees, guava and rarely ornamentals, the wooly whitefly tends to become a nuisance during late summer through early November.
This tiny insect (1.5 mm in length) gets its name from the waxy, wooly-appearing filaments that protect it. The female lays her eggs on the underside of fully extended leaves in a circular or semi-circle shape. Newly laid eggs are pale white in color but darken to brown as time progresses. It takes 4-12 days for eggs to hatch, except when overwintering. The female whitefly is able to lay up to 200 eggs. Each egg is a diminutive 0.3 mm. Good luck finding them without a magnifying glass.
In comparison to other whiteflies, the woolly variety is best described as indolent. When disturbed from its leafy post, it is likely to move slowly as it is forced from its cozy seat. The disgruntled creature will then, just as slowly, find another location to recline. These are not the high achievers of the insect world, but they are pests nevertheless and should be noted with caution. Searching for the woolly whitefly and its eggs may prove difficult based on their microscopic size, but there are other subtle hints that your plants have been invaded.
Woolly whiteflies obtain nutrients from the leaves of trees and plants. Leaf drop results which compromises the health of your tree. Additionally, these pests produce honeydew which creates a perfect environment for sooty mold and attracts ants. Sooty mold blackens leaves, limits photosynthesis and reduces fruit size and quality. Ants will protect whiteflies against natural predators.
Monitoring plants in the spring prevents the population from proliferating. During late summer and fall, the simplest control method for the home gardener is a strong spray of water to the underside of plant leaves. This will dislodge insects, eggs, and clean away harmful honeydew.
Andrea Peck is a UCCE Master Gardener.
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