Camellias are a beautiful part of our landscapes this time of year, providing cool weather blooms while the tropicals look brown and dry. While most camellia maintenance takes place after flowering, one pest is on the move and needs to be identified and kept under control now.
Tea scale is an insect that feeds and infests the underside of camellia, sasanqua and Burford holly leaves. The scale insects are concealed underneath a cottony white material. The actual insects are small, brownish grey and scabby in appearance. They feed by sucking the plant juices and can cause a lot of damage, even killing a plant if left untreated.
There are armored and unarmored species of scale insects that attack camellias, Fioriniae theae being the one commonly referred to as tea scale. Female scale insects are able to reproduce every one to two weeks, increasing the population exponentially.
Newly hatched scale insects are called crawlers and are able to move about the plant to colonize new sections. Crawlers can move to new plants using the wind by flying a silk kite. Insecticides are much more effective when used to treat the crawlers, which typically emerge in the spring. In our area, they emerge in February or mid-January depending on the temperatures. Camellias and other tea scale-infested plants should be treated with oil in this time frame.
Spray the entire plant, top to bottom, including the underside of the leaves, with neem oil or horticultural oil. Systemic insecticide products also work well at this stage and control crawlers as well as adult scale insects. Contact insecticides can work but are much less effective than oil treatments or systemic insecticides.
Adults also can be smothered by using a light horticultural oil. Follow all label directions and thoroughly saturate the insects with the mixture.
Another treatment is to mix light horticultural oil with some warm water in a ratio of one part oil to one part warm water. Use a sponge or rag to wipe the oil onto the scale on the undersides of the leaves. Be sure to thoroughly coat the scale, really wetting and saturating the cottony material and the scabby insects themselves. Typically, this treatment works with one pass, but you may need to reapply in a week.
Dead scale insects turn a darker shade of brown or black and easily flake off the underside of the leaf. Live scale insects are fairly moist, while dead ones are dry to the touch.
There are several generations of tea scale crawlers each year, so monitor your plants weekly to catch any new outbreaks. Catching the issue early is the best way to avoid heavy infestations. Heavily infested shrubs should be monitored and treated as needed, and may require several years of control. Pruning out heavily infested branches or leaves can help. Increasing air circulation within the plant helps to open the insects up to natural predators such as lacewings, ladybugs and spiders. Be sure to move or protect these natural allies when treating tea scale.
For information on camellia care and other gardening topics, visit lsuagcenter.com.
Joe Willis and Anna Timmerman are LSU AgCenter agents. Questions? Email questions to firstname.lastname@example.org.