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.
Control
If only a few leaves are infested, hand picking and destruction of infested
leaves is very effective. Remember-check undersides of leaves, especially
any
with yellow splotching.
The two main spray mixtures recommended for the control of tea scale are dimethoate
and horticultural oils. These sprays should be applied thoroughly to the undersides
of leaves. The best
time to spray is in spring, after the plants have finished blooming and
the danger of cold weather has passed. Two applications, 10 days apart,
should be sufficient. 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. (Dimethoate
may cause defoliation on hollies, especially at higher
application rates.) Horticultural oil is recommended for homeowners.
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.
