Test Your Knowledge - March

Tea scale injury on a camellia leaf
Tea scale injury on camellia leaf
Clemson University - USDA Cooperative Extension Slide Series

Yes, these symptoms are the result of tea scale damage.

Tea scales (Fiorinia theae) infest the lower leaf surfaces of camellia foliage, which results in noticeable chlorotic (yellow) blotches on the upper leaf surfaces.  With a heavy infestation the entire leaf will turn yellow and drop prematurely.  The tea scale is one of numerous armored scales that are pests of many ornamental shrubs and trees, as well as fruit trees, in South Carolina.

Tea scale adults on the lower surface of a camellia leaf
Adult scales on lower leaf surface
Clemson University - USDA Cooperative Extension Slide Series

Other common scale insects encountered in South Carolina landscapes include the false oleander scale, the white peach scale, the euonymus scale and the oyster scale.

Euonymus scale on leaves
Euonymus scale on foliage
John A. Weidhass, Virginia Tech University

White peach scale on peach limb
White peach scale on peach limb.
Eric R. Day, Virginia Tech University

Some armored scales damage only branches, while others infest foliage or fruits.  Adult scales may be round, pear-shaped or oyster shell shaped, but vary somewhat depending on the species. Scale adults are the most noticeable on plants, and these may be white, gray or brown. They secrete a waxy protective covering over their body, which makes control difficult. Some or all life stages of the scale may be found throughout the year (eggs, crawlers or immatures, nymphs and adults).

Plants should be kept as healthy as possible to reduce the chance of scale infestation. Be sure to irrigate during drought, mulch properly, and provide sufficient fertilizer for normal growth. Minor scale infestations can be pruned out, but dispose of any removed plant material.

Avoid using contact insecticides as much as possible as they will often kill the naturally occurring enemies of scale insects. Most contact insecticides cannot penetrate the waxy covering on scale nymphs and adults, so the crawler stage is usually the best target. Failure of contact sprays to work often results from not timing the applications to coincide with crawler activity.

Monitor the crawler emergence with sticky cards, double-faced tape wrapped around a branch, or by put an infested shoot or leaf into a baggie and watch for crawler movement. The presence of crawlers can sometimes be determined by sharply tapping an infested twig on a piece of white paper. Crawlers are very small and will appear as moving specks of dust. Crawler activity often coincides with the flush of new plant growth in the spring. However, there may be overlapping generations with an extended crawler emergence period and additional sprays may be required.

Horticultural oils and insecticidal soaps are safe to use and are especially good choices for sensitive areas, such as where people are present soon after treatment. Because of their short residual, they help to conserve beneficial insect species. Time spray applications to coincide with the scale crawler stage, which is most susceptible to all insecticides.

Apply these spray applications when new leaves start to expand in the spring. At least three applications are needed at five- to six-week intervals. Even when sprays are properly timed, repeated applications may be needed if crawler activity extends over time. Failure of insecticidal soaps often results from not timing the applications to coincide with crawler activity. Spray the plants thoroughly, so that the oils or soaps drip or "run off" from the upper and under sides of leaves, twigs, and plant stems. It is best to spray horticultural oil or insecticidal soap when the temperatures are between 40 and 85 degrees.

Horticultural oil is an excellent, proven product for scale control. It alone will control all stages of the armored scales on landscape plants. Follow label directions for mixing rates with water. Since the horticultural oils kill by suffocation, they also may be applied in early spring to begin killing the overwintering adults. Examples of insecticidal soaps are Safer Insecticidal Soap and Concern Insecticidal Soap. Examples of horticultural oils are Ortho Volck Oil Spray, Ferti-lome Scalecide, Green Light Horticultural Oil Spray, and Sunspray Horticultural Oil.

For safety reasons, one must be very careful when spraying contact insecticides upward onto tall shrubs and trees. See the product label for protective clothing and protective equipment that should be used. Examples of contact insecticides to control the crawlers are acephate (Ortho Japanese Beetle Killer), permethrin (such as, Bonide Eight Vegetable, Fruit & Flower Insect Killer), bifenthrin (Ortho Bug B Gon Max Lawn & Garden Insect Killer), cyfluthrin (Bayer Advanced Garden Multi-Insect Killer), lambda cyhalothrin (Spectracide Triazicide Once & Done Insect Killer), malathion and carbaryl (Sevin). To reduce the chance of killing pollinating insects, make pesticide applications when camellias are not in bloom. Soil drenches of imidacloprid do not control these armored scales.

Joey Williamson
HGIC Extension Agent

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This information is supplied with the understanding that no discrimination is intended and no endorsement by the Clemson University Cooperative Extension Service is implied. All recommendations are for South Carolina conditions and may not apply to other areas. Use pesticides only according to the directions on the label. All recommendations for pesticide use are for South Carolina only and were legal at the time of publication, but the status of registration and use patterns are subject to change by action of state and federal regulatory agencies. Follow all directions, precautions and restrictions that are listed.