PYRACANTHA SCAB (Fusicladium pirinutn var. pyracanthae).
This is a
disfiguring disease for an ornamental. Leaves, twigs, and fruit
are infected with unsightly black scabs, spoiling the appearance of the
bright berries and making them drop long before their time.
Control. Puratized Agricultural Spray and Fermate seem to be more
effective than bordeaux mixture.
VIOLET SCAB (Sphaceloma violae).
There is so much overgrowth of tissue
this disease is called scab, but it really is a spot anthracnose (see
page 23). Reddish spots with white centers grow into elongated raised
scabs often with much distortion on leaves and stems of violet, viola, and
Control. Bordeaux mixture has always been recommended in the past,
but it may injure pansies, and more work is needed on newer materials.
Scales are sucking insects, close relatives of mealybugs, in the orde
Homoptera. Females are alone responsible for plant injury. After a brief]
crawling period, a female sticks her beak into a plant cell and remair
in that position the rest of her life, if she is an armored scale, covering
her body with a hard shell made of cast skins and special secretions. *
Unarmored or soft scales do not have such a hard covering, and some
may make sluggish movements. Only the males have wings. Dormant
oil sprays have been generally used for hard-shelled scales, summer
oils or other contact insecticides for soft scales. DDT controls some
scales and has been valuable for orchids, but it increases other scales.
Parathion, despite its toxicity to humans, has been successfully used by
nurserymen in the South and greenhouse operators to control scales, but
one or two species are not only resistant to parathion but increased by it.
Malathon may help in such instances.
BLACK SCALE (Saissetia oleae).
This is an unarmored scale, a most destructive citrus pest in California, found also on other fruits and on.
oleander, pepper tree, and rose. It is not important in the Gulf States.
It is hemispherical, black with white lines on the back forming an H,
1/5 inch across. Its honeydew encourages a profuse growth of sooty mold.
Oil sprays were used for control until the insect developed resistance to
them; DDT and parathion are current usage.
CALIFORNIA RED SCALE (Aomdiella aurantii).
This is another California
pest, also found in Texas, destructive to citrus and some ornamentals. Leaves, fruit, and twigs are injured by a toxin introduced during
feeding. Scales are roundish, red, small, 1/12 inch in diameter, with a slight
hump in the center, and they thickly cover twigs and branches. Young
are born alive. Forms have developed resistant to oil sprays or cyanide
fumigation. DDT emulsion kills crawling stage but encourages citrus