Greg Grant

Camellias are a beautiful part of our East Texas landscapes this time of year, providing cool weather blooms while much else is still dormant. Most camellia maintenance takes place after flowering, however you should be scouting for one pest in particular now.

Tea scale is an insect that feeds and infests the underside of camellias and Burford holly leaves. When scale numbers are high, the top portion of the leaves become mottled with patches of yellow and green. The scale insects are concealed underneath a cottony white material beneath the foliage. The actual insects are small and brownish grey and often appear to be white and brown flecks. They feed by sucking the plant sap and can cause a lot of unsightly damage if left untreated.

Tea scale gets its name from the tea that we drink which is made from the related Camellia sinensis. 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. Camellias and other tea scale-infested plants should be treated with an oil spray when the temperatures are mild (not cold or hot).

Spray the entire plant, top to bottom, especially the underside of the leaves, with dormant oil, neem oil or horticultural oil. These are all very low in toxicity and do not leave behind any residue that harms beneficial insects. Contact insecticides can work but are much less effective than oil treatments or systemic insecticides. However, including a contact insecticide labeled for scale with your oil spray does make it more effective. Systemic insecticide products also work well at this stage and control crawlers as well as adult scale insects. Imidacloprid (Bayer Advanced Tree and Shrub Insect Control and other brands) is a systemic insecticide that is effective against tea scale. It is available in both granular and liquid forms. When a very heavy infestation is observed, use both horticultural oils and imidacloprid. A two-prong approach will provide the best results. Oil sprays can be used now, but only use systemic insecticides when the plant finishes blooming, so no pollinators will be affected.

Dead scale insects turn a darker shade of brown or black and slowly flake off the underside of the leaf. There are several generations of tea scale crawlers each year, so monitor your plants monthly 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.

Greg Grant is the Smith County horticulturist for the Texas A&M AgriLife Extension Service. He is co-author of “Heirloom Gardening in the South.” You can read his “Greg’s Ramblings” blog at arborgate.com, follow him on Facebook at “Greg Grant Gardens” or read his “In Greg’s Garden” in each issue of Texas Gardener magazine (texasgardener.com). More science-based gardening information from the Texas A&M AgriLife Extension Service can be found at aggie-horticulture.tamu.edu.