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Tea scales can cause heavy damage to plants

Posted: April 26, 2014 - 11:02pm

Gardeners who have camellia plants are probably familiar with tea scale. Tea scale is a small insect around 1/10th of an inch long that resides on the undersides of the leaves of camellias, hollies and a few other host plants.

These tiny insects damage plants by sucking out juices inside the leaves. Heavy infestations can severely damage affected plants, resulting in major leaf drop and occasionally plant death if not properly treated. Tea scale damage appears as yellow splotches on the top sides of camellia leaves. The actual tea scale can be identified by examining the underside of the leaf. Female tea scales are brown and the males have a white waxy coating. The outer coating of the mature scales makes it difficult to control this stage of the insect life cycle with pesticides.

In spring, new scales, called “crawlers,” hatch out and move to infest new leaves. This stage of the insect is the most susceptible to pesticides, so targeting the crawlers is the best method of control. The goal is to kill the new crawlers before they attach themselves to the undersides of new leaves, start feeding and develop their waxy outer coating. Timing your insecticidal control during crawler emergence is important. It can be a small window. Tea scale crawler initial emergence usually coincides with blooming of tulip, poplar and honeysuckle, and when chickweed and henbit are blooming. You can also be more precise and set out double-sided sticky tape around several branches on your camellias. Once you catch some crawlers on the tape, begin your insecticide application. Heavy tea scale infestation can be treated with broad-spectrum insecticides such as carbaryl and malathion. Again, time these sprays with the first emergence of crawlers for best control. Light to moderate infestations can be controlled with horticultural oil sprays. Be sure to purchase the correct oil spray for the weather conditions. Some can only be used in cooler weather, and others are more refined and can be used throughout the growing season.

Because tea scales live on the undersides of leaves, it is important to get good coverage while spraying. Always read product labels when using pesticides. Tea scale has several generations per year here in Georgia. Repeat insecticide treatments may be needed for heavy infestations. Some may even require two to three years of spray applications before the infestation will subside. Pruning out heavily-infested interior branches can help open up the plant for better spray coverage. This may also allow for better predation from tea scale’s natural predators, such as spiders, wasps, lady beetles and lacewings. Using horticultural oils instead of regular insecticides will help preserve these natural predators.

After treatment, it can be difficult to determine if the tea scale is dead or alive. Because of their waxy coating, the scale won’t immediately fall from the leaves when dead. The easiest way to tell is to take a sharp-pointed tool, like a pocket knife and crush several of the scale. Dead scale will be dry and living scale will be juicy when crushed.

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