COTTONY-CUSHION SCALE (Jcerya purchast). Very common on pittosporum,
found often on rose, boxwood, citrus, and many ornamentals this
scale is present throughout the southern half of the country. It arrived
on acacia from Australia nearly a hundred years ago. The female scale
is reddish brown but at egg-laying she attaches to herself a large, white
fluted cottony sac which sticks out at right angles from the twig and
is very conspicuous (Figure 50C). Inside the cotton are 600 to 800 bright
red eggs. Young larvae are red with black legs; winged males are very
small, covered with long white filaments. A great deal of sooty mold is
the usual accompaniment to cottony-cushion scales.
Control. The saga of the search for a biological enemy of this scale,
which once threatened the whole citrus industry, has been told many
times. Vedalia, the Australian lady beetle, was finally brought here and
proved to be the first successful example of an imported predator cleaning
up a dangerous insect. When DDT is used in the spray schedule, it kills
Vedalia and so allows the scale to increase. Parathion gives good control;
oil sprays are partially effective.
COTTONY MAPLE SCALE (Pulvinaria vitis).
A northern scale destructive
to soft maple and attacking other trees and some shrubs. I find it
rather often on dogwood. The female is small, brown, flat, 1/8 inch long;
she winters on twigs and in spring deposits cottony masses of wax several
times her own size and covering 1500 to 3000 eggs. When the eggs hatch
in June and July, young scales crawl to leaves, later migrating back to
twigs. Branches die if scales are abundant for 2 or more consecutive
Control. Dormant spraying with a miscible oil gives best results, but
oils may injure soft maples. In summer, foliage can be sprayed with nicotine sulfate and soap.
ELM SCURFY SCALE (Chionaspis americana).
The female is pear-shaped,
convex, dirty white or gray; eggs are purple. Young elms are most
affected. Use a dormant oil spray with nicotine.
EUROPEAN ELM SCALE (Gossyparia spuria).
This armored scale is common
on all elms, covering underside of limbs and branches, weakening
and sometimes killing trees, and dropping honeydew on walks and
benches. Females are 1/6 to 3/8 inch long, oval, plump, reddish brown
surrounded by a waxy fringe; they lay eggs over a long period. Yellow
crawling nymphs feed on leaves but return to bark for winter. Male
scales are like red gnats, winged or wingless. When scales are numerous,
leaves turn yellow and drop and the bark is black with sooty mold.
Control. Use a dormant spray, 1 gallon of miscible oil to 15 of water.
A 2% summer oil or DDT emulsion or wettable powder can be used
for crawling young nymphs.