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Landscape Alert - Tea Scale
An Outreach of the UGA Center for Urban Agriculture - www.gaurbanag.org
April is the Time for Tea (Scale Control)
Willie Chance, UGA Center for Urban Agriculture and
Kris Braman, Professor, UGA Entomology Department
Tea scale is the most serious insect pest of flowering camellias. Tea scale also attacks hollies, citrus and the tea plant (Camellia sinensis) as well as a few other plants.
Tea scale is a small insect
In the spring, the next generation of scales hatches from eggs and move to find succulent leaves. These young, mobile scales are yellow and called ‘crawlers’. The scales attach themselves to the underside of leaves, begin feeding and develop their waxy, protective covers.
The timing of the first generation of crawlers is important since this is the best time of year to treat tea scale with insecticides. The time of emergence of the first generation of crawlers is dependent upon temperature and can vary greatly from year to year. For example, the first emergence of tea scale in Athens, GA has been as early as the first week of February (1999) and as late as the first week of May (1997). March and April are the most typical months for emergence in Georgia.
Tea scale crawler emergence timing for your area can be estimated based upon the time of flowering of certain plants. Tea scale crawler emergence occurs about the same time as the beginning of bloom for honeysuckle or tulip poplar, the time of 50% bloom for Chinese wisteria or sugar maple or when the weeds henbit and chickweed are blooming. Begin first crawler sprays for tea scale when you see these events.
Another method of timing crawler sprays is by looking for the crawlers themselves before spraying. Place pieces of double sided sticky tape on small stems. The sticky tape will capture the crawlers as they emerge and make them easier to see. Begin sprays when you find crawlers stuck on the tape.
There are several generations of tea scale in Georgia each year. Female scales lay eggs for several weeks and these eggs hatch continually. Later in the season, landscapers may find all stages of the tea scale life cycle on the plant at the same time.
Several factors make tea scale control difficult:
- Tea scale infestations often develop on the interior of the plant and may not be noticed until the infestation is heavy.
- It is difficult to get sprays into the interior of the plant and on the underside of the leaves where most tea scales are found.
- The scale’s waxy covers make adult scales very difficult to control with pesticides. Crawlers are much easier to kill but pesticide application must be timed to crawler emergence.
For best control
- Adult scales are very resistant to insecticides. Time insecticide treatment to correspond to the first emergence of crawlers. Use the information mentioned earlier under ‘Tea scale crawler emergence timing for your area’ to decide when to begin treatment.
- Apply insecticides so that they cover the bottom surface of the leaves.
- Repeat treatments may be needed with heavy infestations. Select insecticides from the Pest Management Handbook.
- Prune out heavily infested branches. Remove 2 to 4 inch long non-flowering branches on major limbs inside the plant since these can harbor scale.
- Thin the plant by removing selected branches. This can improve control by increasing air circulation and improving pesticide penetration into the plant.
- Light to moderate infestations can be treated with oil sprays. Oil sprays are effective against crawlers and adult scales. There are two types of oil sprays – those that are used in the cooler weather of spring and fall and the highly purified oils that can be used during the growing season. Read and follow all label directions to select the correct oil spray.
- Cover scales very well when using oil sprays since oils work by smothering the insect.
- Beneficial insects help control tea scale - small parasitic wasps, convergent lady beetles, green lacewings and spiders. Preserve these natural enemies by using oil sprays instead of traditional insecticides and only spraying when absolutely necessary.
Heavy tea scales infestations may require 2 - 3 years for control. The bodies of the tea scale will usually remain on the plant after they die. Examine plants carefully after treatment to determine the level of control. Living tea scale will be moist when crushed while dead scale will be dry.
Tea Scale articles - University of Florida IFAS Extension and University of Georgia Center for Urban Agriculture