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Bacillus Thuringiensis

Crucifers

cabbageworm :Control offered is good to excellent

diamondback moth :Good to excellent control

cabbage looper :Variable results (poor to excellent); especially useful on pests that have become resistant to traditional chemical sprays

Newly hatched larvae of the cross-striped cabbageworm are gray with small black tubercules and large round heads; mature larvae are green to bluish gray with at least three distinct black bands across each segment. Long dark hairs grow out of the black tubercules, and the slender worms grow to 2/3 inch long. The adult is a small pale yellow moth, with mottled brown patterns on the forewings and partially transparent hindwings. See imported cabbageworm, below.

The fat, smooth, pulpy cutworm [color] is as troublesome as it is ugly. Of the many species, you are most likely to run into the black, bronzed, and dingy cutworms. The black cutworm (or greasy cutworm) is gray to almost black and has a broken yellow line down the center of its back with a pale line to each side. It grows to 1 1/2 inches or even longer and has a shiny, greasy appearance. As its name suggests, the bronzed cutworm is bronze in color and displays five pale lines from head to tail. It is a pest in the northern states. A northern cousin is the granulate cutworm, which has a rough, granulate-appearing skin and a dusty brown color. It burrows very shallowly in the soil, often exposing its back. The dingy cutworm, a northern species, is also aptly named--it is a dull, dingy brown, and has a wide, pale stripe running the length of its back, flanked by a thin dark stripe on each side. It sometimes crawls up the stems of plants to feed.

Although the larva of the diamondback moth is a relatively minor pest, it at times can cause considerable damage to the cabbage family by eating small holes in the outer leaves. These caterpillars grow only to 1/3 inch long, are greenish yellow with black hairs, and when disturbed will wriggle and drop to the ground. The adult is a gray to brown, small (3/4-inch-across} moth, with fringed back wings; when the moth is at rest, look for the diamond on its folded wings. See BACILLUS THURINGIENSIS for an effective biological control. Southernwood is an herbal repellent.

The fall armyworm [color] is so called because it travels in veritable insect armies to consume everything in its path and because it does not appear until fall in the North. The larvae vary greatly in color, from light tan to green to almost black, and have three yellowish white hairlines down the back from head to tail. On each side is a dark stripe paralleled below by a wavy yellow one splotched with red. The head is marked with a prominent white V or Y. They eat leaves, stems, and buds of plants. Naturally occurring enemies include parasitic ichneumon wasps and, of the braconid wasps, Chelonus texanus, Meteorus laphygmae, and species of Apanteles. Other beneficial insects are tachinid flies, ground beetles, and the commercially available nematode Neoaplectana carpocapsae. For other control measures, see armyworm under CORN.

The very visible harlequin bug [color] is black with brilliant orange to red markings. It is shield-shaped, flat, and 3/8 inch long. Although attractive to the eye, the bug has a disagreeable odor at all stages. It is among the most important pests of the cabbage family in the United States, as local infestations often destroy whole crops, especially in the South. The bugs spend the winter around old plants and other trash that accumulates in the garden. In early spring they lay their eggs on the undersides of early blooming plants. The distinctive eggs are easy to spot --they look like small white pegs with black loops, standing on end, lined in two neat rows. Look for and destroy these eggs whenever possible; if allowed to hatch, the immature nymphs drain the juices out of the plants, causing them to wilt, turn brown, and die.

Plant a trap crop of turnips or mustard greens near or around the cabbage patch to lure away harlequin bugs. Patrol the trap area, remove the bugs, and drop them into a jar of water topped with kerosene. Insecticidal soap sprays give good control. Sabadilla and pyrethrum, two plant*derived insecticides, are effective.

The bright green, velvety smooth imported cabbageworm [color; see Cabbageworm] is covered with close-set hairs and grows to one inch or longer. A yellow green stripe runs down its back. The worm is found in every state.

No member of the cabbage family is safe from its appetite, although sea kale is rarely bothered. It eats huge, ragged holes in leaves and spots the feeding area with bits of excrement. It also bores into heads of cabbage. The adult is the well-known white cabbage butterfly, whose white to pale yellow wings have either three or four black spots; the tips of the front wings are grayish. In the early spring, these butterflies may be seen depositing their lemon yellow, bullet-shaped eggs at the base of leaves. The eggs usually take from four to eight days to hatch, depending on temperatures. They turn straw yellow just before hatching.

The cabbageworm may be attracted to your land by weeds of the cabbage family--wild radish, wild mustard, and wintercress. These wild plants should be cleared from the vicinity of the vegetable garden. Cole plants can be protected by a border of plants that are shunned by the cabbage butterfly; these include onion, garlic, tomato, sage, tansy, mint, southernwood, nasturtium, hemp, hyssop, and rosemary.

Insect predators and parasites claim a lot of these pests, but don't expect too much help from the birds around your garden; because of toxic body fluids, the caterpillars aren't favorite foods. Brownheaded cowbirds, song sparrows, and redwing blackbirds eat some cabbageworms. Yellow jackets have been found to thrive on these pests, and their presence should not be discouraged. The braconid wasps Macrocen trus ancylivorus, Apanteles glomeratus, and Agathis diverse are extremely helpful control agents. They are small insects with short abdomens, and rank as important parasites of aphids too. Numbers of dead aphids about the garden with a round hole in the back testify to the presence of these wasps. You can encourage M. ancylivorus by planting strawberries near the garden, as it also feeds on the strawberry leafroller, and by avoiding poison sprays. Another friend, the trichogramma wasp, is a commercially available parasite that attacks many worms of the Lepidoptera order, including the cabbageworm. This wasp lays its eggs inside the eggs of harmful insects by the use of a pointed egg-laying apparatus. When the trichogramma egg hatches, the young parasite proceeds to eat out the contents of the egg in which it lives, causing the egg to blacken and preventing one more insect from harming the garden. See TRICHOGRAMMA. Bacillus thuringiensis was found to be far more effective than Sevin, a popular chemical insecticide. Nuclear polyhedrosis virus also works to control the larvae. The two pathogens can be sprayed at the same time for maximum effect; see individual entries for each.

Homemade remedies may help. Simply spoon a little sour milk into the center of each cabbage, say some gardeners, and the heads will be trouble-free. But a test at the University of Illinois showed that sour milk actually increases damage. A repellent drench can be made by blending, in a mixer, spearmint, green onion tops, garlic, horseradish root and leaves, hot red peppers, peppercorns, and water. Add some pure soap, dilute, and pour on each plant. Or make a powder of to cup of salt and one cup of flour and shake it on the cabbages while dew is still on the leaves. Sprinkle up to an ounce on the worst heads. When the worms eat the mixture they bloat up and fall off dead. These two ingredients can also be mixed with water to produce a safe spray. Other gardeners get by with an occasional sprinkle from a saltshaker. This should be done right after rain or when there is dew on the plants. A sprinkling of straight rye flour (it's stickier than whole wheat} will gum up the worms if the plants are wet.

Protective canopies of lightweight polyethylene or nylon netting can keep egg-laying cabbageworm moths from tender young broccoli and cabbage plants. The netting is easy to stretch over rows and is available from most garden supply stores and mail-order houses. Simple frames of wood can be constructed to support the netting. Although the netting will keep butterflies from laying eggs on the plants, the pupae spend the winter underground and often surface around the plants to cause trouble. Till the soil several times in fall and early spring to expose these pupae to the air so that they will dry up and die. You should also relocate the patch to keep from perpetuating problems with these latent underground pests. Some gardeners trap cabbage loopers in stems, and the outer layers of leaves of cabbage heads; they also enjoy collards. In the Northeast and Utah, the larva of the purplebacked cabbage moth feeds from inside a silken web. The zebra caterpillar is a velvety black with two bright yellow stripes on each side and many thin, yellow transverse lines. The southern cabbageworm looks similar to the imported cabbageworm, but its appearance is distinguished by alternating longitudinal stripes of bright yellow and dark greenish purple, and it is scattered with black spots. The yellow woollybear caterpillar is bright yellow and very hairy.

You may find any of several species of the nocturnal mole cricket eating or flying about the garden at night or on very cloudy days. They may be drawn to lights near the garden. The northern and southern mole crickets are the species of most concern to gardeners. They are large ( 11/4 inches long) and have sturdy shovel-like forelegs that are adapted for digging into the soil. The northern species is brownish gray above and paler underneath, while the southern is a pinkish buff. Both species are a problem only in the South and are at their worst in warm, moist weather. Their tunnel cuts off the roots of seedlings, and some young plants may be totally uprooted. Moles may also chew off stems at the soil surface and pull the plants down into their tunnels. See GRASSHOPPER.

The seedcorn maggot also attacks young crucifers, especially cabbage and radishes. They are dirty-yellowish-white, l/4 inch long, and have pointed head finds. For control measures, see cabbage maggots, above.

Thy malodorous green stink bug [color] is smooth oval, bright green, and about ah inch long. They are occasional pests of cabbage and mustard, piercing stems and leaves to suck sap and leaving tiny holes in the center of surround ing cloudy spots. Small plants are stunted and distorted. Control by keeping down weeds. Spray with soapy water. See SNAPDRAGON.

The vegetable weevil [color] is a dull buff color with a pale V on its wing covers. The head has a short, broad snout. They are 3/8inch long, rarely fly, and attack cabbage, carrot, cauliflower, mustard, radish, and Swiss chard. The adults devour foliage at night and hide close to the ground during the day. The green or creamcolored larvae are also destructive. sheets of colored plastic that are folded twice and placed on the ground every three days or so. The captives are then shaken into a bucket of water.

Not all of the many worm pests of the cabbage and its relatives can be discussed here, but a few of occasional or regional importance deserve mention. Control as for the imported cabbageworm, above. The yellow, purple-striped gulf white cabbageworm feeds on the leaves,

Copyright 1997


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