Damage caused by scale insects is usually serious, but not deadly to the camellia plant. If the problem goes undetected for a long period of time with no treatment it is possible for all or part of the plant to be killed. Camellias infected with scale insects appear unhealthy and produce very little new growth. Scale insects that attack foliage are usually seen on the underside of the leaf. Symptoms on the upper leaf surface appear as chlorotic areas. Heavily infested leaves will often drop off. Other types of scale insects attack twigs and branches and may cause death when infected severely.
Scale insects appear very different from many other types of insects. They are usually quite small and have sucking mouthpieces with which to feed on plant juices. Scales are divided into two groups - the armored scales which have a hard protective covering that is not an integral part of the insect's body and the soft scales in which the waxy secretion is a part of the body.
Armored scales which attack camellias include the Florida Red Scale, Chrysomphalus aonidum; Tea Scale, Fioriniae theae; Oyster Shell Scale, Lepidosaphes ulmi; Camellia Scale, Lepidosaphes camelliae; and Greedy Scale, Hemiberlesia rapax. The adult female varies from 1/12 to 1/8 inch in length. Adult males generally are small, two-winged gnat-like insects which are seldom seen. An exception is the tea scale where adult males are white in color and more conspicuous than females. The female scale insect lays her eggs under the scale covering which hatch in 1 - 2 weeks.
The newly hatched scale, known as a crawler, has the ability to move about the plant to find succulent new growth. After about a week it inserts its mouthparts into the plant tissue. If it is a female it remains there for its lifetime. Crawlers can spread from plant to plant with the wind. They will attach a silk strand to the plant, raise their tails, and blow away with the wind.
Because insecticides are much more effective against the crawler stage of the scale life cycle applications should be timed to coincide with this stage if possible. The adult stage is usually reached 5 - 11 weeks after eggs hatch and there may be several overlapping generations each year. The crawler stage is observed in the spring.
Soft scales are larger than the armored scales and vary from 1/12 to 1/4 inch in length. The number of eggs per female range from 100-1000 and these hatch in 1 - 3 weeks. Some soft scales may bear their young alive. The newly hatched crawlers move about the plant for a few days to several weeks before attaching to feed. Soft scales develop slowly and it may be several months to a year before the females become adults. The different softscales that attack camellias include the brown soft scale, Coccus hesperidum; Hemishpherical scale, Saisettia coffeae; and the Cottony Camellia Scale, Pulvinaria floccifera.
Scale insects can be controlled by proper culture and use of insecticidal sprays. Plants should by spaced to allow air to circulate between them and pruned to open them and allow air to circulate through them. This will aid in the reduction of insect populations.
Petroleum oil sprays are environmentally friendly and they are non-toxic to humans or pets. They are effective only if sprayed directly onto the insect because they work through suffocation. Applications are usually made during the spring after bloom and in the fall prior to blooming. Spring applications will greatly increase mortality of scale crawlers. There are other more toxic insecticide sprays which can also be used. Consult the label for specifics.
Aply two types of controls (read the label and make sure that the active ingredient is different) so the scale insects will not get used to applications of a single insecticide.
- Oil emulsion sprays will give you effective control if applied early in the morning on days when the temperatures are mild (45-85 F).
- Systemic insecticides like Cygon and Orthene can also control tea scale.
- Contact insecticides like Malathion, Dursban and Sevin are very effective but repeat applications may be necessary.
The Landscape Alert: April is the Time for Tea (Scale Control)by 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 that attaches itself to the leaf and sucks plant juices. Adult female tea scales are about 1/10 inch long and are covered with a hard brown cover. The males produce white waxes that cover their bodies. In heavy infestations, these white waxes make the underside of the leaf appear cottony. Affected leaves will develop yellow blotches on the upper surface. Heavily affected plants may be thin and unsightly and have fewer blooms.
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. rune 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.
Source: University of Florida IFAS Extension and University of Georgia Center for Urban Agriculture, An Outreach of the UGA Center for Urban Agriculture - www.gaurbanag.org