Ornamental & Turf Insect Note Logo

TEA SCALE

Prepared by: Steven D. Frank & S. B. Bambara, Extension Entomologists

CAUTION: This information was developed for North Carolina and may not apply to other areas.


[General Information] [Biology] [Control] [Other Resources]

Fiorinia theae Green, Diaspididae, HOMOPTERA

General Information

       Tea scale has been reported on camellias throughout the Deep South and in California. It probably originated in southeast Asia. In the Southeast, tea scale is a serious pest of camellias as well as Chinese and Japanese hollies. It  has  also been reported on bottlebrush, dogwood, ferns, euonymus, mango, Satsuma orange, tea plant, orchids, and yaupon.
      Tea scales occur primarily on the undersides of leaves. The most conspicuous characteristic of an infested plant is yellow splotching  on the upper leaf surfaces, an effect of feeding insects underneath. The whole plant may appear unhealthy, and the leaves drop prematurely. The number of blooms decreases  or  cuttings  may  die before roots develop.

Biology


    The  armor  or  test of female tea scale insects is first flat and light yellow, later becoming  hard and brown. The armor is elongate  oval or  boat-shaped, it is about 1/16 inch long, with the residue from the first molt attached at one end.  Male armor is soft, white, and narrow with a ridge down the middle of the top. Eggs are yellow and lemon shaped.  Eggs are always found within the armor of the female scales. The nymph is a flat, yellow "crawler" that has six tiny legs, and two  antennae.
     Each female deposits from 10 to 15 eggs under her armor. They hatch in 7 to 21 days, depending on the weather. The flat, yellow crawlers migrate to the newer growth on the plant and soon attach themselves. At first they secrete thin, pale tests. Males sometimes produce great quantities of white strands. When the population of nymphs is dense, the undersides of the leaves may be covered with this cottony secretion. The nymphs molt 18 to 36 days after hatching, and a second molting occurs about a week later. From 41 to 65 days after hatching, female scales begin to lay eggs. The adult males have wings. The life cycle is usually completed in 60 to 70 days.  Crawlers hatch throughout  the  year,  although less frequently  in  cold  than in warm weather. Because of the many overlapping broods, crawlers hatch continuously from February to November.

Monitoring

Monitoring includes scouting to determine if pests are present and when they are active or vulnerable. Tea scale is relatively easy to scout because they make yellow blotches on the tops of leaves.  In addition, the white male tests are very abundant and noticeable on the undersides of leaves.  However, scale covers, like turtle shells, do not disappear when the insect dies. Therefore, the first thing to do is flip the over female covers to determine if the scales are alive. A live female will be an yellow blob that releases juice when you smash it.  If no live scales are present it is important to educate clients that these will eventually weather away but require no further treatment.

Decision Making

Deciding if intervention is required will start with whether live scales are present.  If just a few leaves have scales, as indicated by yellow spots, picking these leaves off could prevent an outbreak and any further treatment.  For larger, established infestations more aggressive intervention will be required.  You will have to decide which chemical or other intervention to use and when to apply it.

The hard waxy cover protects scale from contact with insecticides. Therefore, if adults are treated with a contact insecticide the scales will live to produce another generation later that year.  Crawlers can be killed easily because they are small and unprotected by a cover. Thus, nearly all products specifically target this stage.

Tea scale has 2 – 3 overlapping generations so crawlers and adults are present almost all the time after the first crawlers emerge in May.  Thus applications will kill crawlers but may leave some adults. Follow up later in the year to determine if the population is growing and crawlers are still being produced.

Intervention/Control

Scales are often treated with broad spectrum insecticides such as pyrethroids or organophosphates that kill beneficial insects.  Horticultural oil is very effective at killing crawlers as long as it hits them.  Therefore, coverage is important with these products. 

Some newer products are available that offer systemic activity for longer control and are softer on beneficials (Table 1).  Systemic or translaminar activity allows the product to be absorbed into plant tissue.  Product that lands on top of the leaves will be absorbed into the tissue and kill insects feeding below.  Others can be applied as a drench to be taken up by the roots.  Thus, it reduces the need for thorough coverage on difficult to spray plant parts such as the underside of leaves.  It also means that some products will kill those adult scales that are so well protected from contact insecticides.

An Alabama Cooperative Extension test showed Dinotefuran (Safari) is also effective as spray or soil drench for greenhouse and outdoor use. Be sure to follow the directions for safe use found on the label of whatever pesticide is used. 

If only a few leaves are infested, hand picking and destruction of infested leaves is very effective.  Camellias can sustain a high degree of leaf removal and refoliate well. Remember, check undersides of leaves, especially any with yellow splotching.  Another intervention option is removing problem plants.  Plants that are severely damaged from years of scale infestation or that require yearly treatment to keep scale free may not be worth the work.  Horticultural oil is recommended for homeowners.

Conserving beneficial insects:

            Conserving beneficial insects is not just an environmentally responsible thing to do.  It can improve control of pests such as scale.  Research at the University of Maryland documented that the older broad spectrum insecticides, drastically reduced the abundance of predators and parasitoids in home landscapes.  Many of the affected parasitoids specialize on killing scale insects.  These contact insecticides could not penetrate waxy covers to kill scales but did kill natural enemies that specialize on killing scales.  The result was an increase in scale infestations where these products were applied over the long-term.  Remember, an insecticide application will never kill every individual of a pest population.  It is the job of natural enemies to clean up after and between insecticide applications.  Otherwise, a few individuals that escape an insecticide application can rapidly return to damaging levels. 

Active ingredient

Trade name

Scale stages affected

Labeled location1

Activity

Signal word

IRAC MOA group

Compatible with beneficials

acetamiprid

TriStar

Crawler, adult

G, N, L

TranslaminarSystemic

Caution

4A

Yes

dinotefuran

Safari. *Green Light Tree & Shrub with Safari

Crawler, adult

G, N, L, I

Systemic

Caution

4A

Yes

*horticultural oil

many

Crawler

G, N, L, I

Contact

Warning

-

Yes

*insecticidal soap

many

Crawler

G, N, L, I

Contact

Warning

-

Yes

pyriproxyfen

Distance

Crawler

G, N, L, I

TranslaminarSystemic

Caution

7C

Yes

*Good choice for homeowners


Other Resources

For assistance with a specific problem, contact your local North Carolina Cooperative Extension Service personnel.

Published by North Carolina Cooperative Extension Service

Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. Employment and program opportunities are offered to all people regardless of race, color, national origin, sex, age, or disability. North Carolina State University at Raleigh, North Carolina A&T State University, U.S. Department of Agriculture, and local governments cooperating.
© 2001 NC Cooperative Extension Service

Prepared by: S. B. Bambara, Extension Entomologist.  Revised by Steven D. Frank. Photos from J.R. Baker

ENT/ort-50    July 1994 (Revised) Oct. 2001. (Revised May 2009)  

Web page last reviewed January, 2011 by the webperson.