IMPORTED CABBAGEWORM (Pieris rapae).
Large, irregular holes in cabbage
leaves, also broccoli and other crucifers, lettuce, nasturtium, sweet
alyssum, and mignonette are eaten by velvety green worms. They have
a faint orange stripe down the back, are about 1 1/4 inches long, and drop
masses of green or brown pellets. The adult is our familiar white cabbage butterfly which emerges from a chrysalid hung on a plant or building
near the vegetable garden. There are 3 to 6 generations. Another green
caterpillar, the cabbage looper, has thin white stripes along the abdomen
and the same looping habit as cankerworms.
Control. Spray or dust widi DDT before edible plant parts are formed,
then with rotenone.
LEAF ROLLERS or LEAF TIERS
are caterpillars which feed protected
by the rolled up leaf of the host plant. Some species act also as budworms. The red-banded leaf roller in orchards has been increased by the
use of DDT but can be controlled by lead arsenate. For other species, such
as canna leaf rollers, DDT can be used.
TOMATO HORNWORM (Protoparce quinquemaculatd) and TOBACCO HORNWORM (P. sextd).
Both of these very large, 3 to 4 inches long, worms
are green with a slender horn protecting from the rear. This horn is
black in the tomato worm, which has 8 diagonal white stripes along the
body (Figure 23). The tobacco worm has a red horn and only 7 white
stripes. Both species feed on tomato, tobacco, eggplant, pepper, potato,
and petunia, and one or two worms can defoliate a plant in short order.
In the South there may be two generations, but in the North there is but
one, hibernation being as a pupa in soil. The adults are the large hawk
or humming bird moths that fly around at dusk sipping nectar. They
are gray or brown with white and dark mottlings, orange-yellow spots
on the abdomen, and a wingspread of 4 or 5 inches.
Control. Dust plants with 5% DDD or 10% toxaphene or with calcium
arsenate. Natural enemies keep hornworms in bounds, including a
braconid wasp that covers the caterpillars with white cocoons that look
like eggs. Do not destroy such hornworms; let the parasites escape to
keep up the good work.
Yellowing of foliage, loss of normal green color, is called chlorosis.
It may be due to a virus, as in aster yellows, or to a deficiency of nitrogen
or other nutrient, or to lack of oxygen in a water-logged soil, but most
frequently it is due to unavailability of iron in a too-alkaline soil. Broad-
leaved evergreens which prefer an acid soil are frequently affected, but
in regions where the soil is normally alkaline all plants may become