Disease and insect pests threaten crucifer crop production and marketing by reducing yield and sales.
These risks can be minimized by using integrated pest management systems

Select commercially acceptable varieties with some resistance to insects, nematodes, and diseases.

Select loamy, fertile, well-drained fields free of hardpans, residues, and troublesome weeds. Sample soil annually for pH, nutrients, nematodes, and soil insects.

Use a minimum two-year crop rotation. Avoid fields previously in sod, fallow, or crucifers (cabbage, collards, broccoli, kale and turnips).

Use only disease and insect free planting stock. All purchased plants originating off-farm should be certified or approved by the North Carolina Department of Agriculture.

Establish good stands either by transplanting, or directly seeding. Nitrogen, boron, copper, zinc, magnesium, sulfur, molybdenum and other nutrients may be needed to ensure growth and prevent deficiencies. inspect plant beds for disease and insects prior to using transplants.

Promptly identify or diagnose all plant abnormalities, disease and insect pests. Also identify and release beneficial insects.

Install pheromone traps near field to detect and monitor for diamondback moth, cabbage looper and other insects.

Select appropriate pesticides, follow label directions , use a high pressure (250 psi) sprayer to ensure proper placement and coverage, and rotate chemical classes to reduce resistance problems.

Practice sanitation in the field, irrigate to insure 11/2 inches of moisture per week, use postharvest practices and market quality produce.

Knowing and Managing Crucifer Pests

Cabbage Worm Complex

Cabbage looper, Trichoplusia ni (Hubner), adult is a brownish-gray moth with a figure-eight design in the forewing. It is a night flyer that migrates into North Carolina in June in most years. Moths are attracted to black-light insect traps, and males are attracted to sex pheromone traps (Hartstack screen traps).

Management: Some varieties of cabbage are tolerant, and natural enemies help somewhat to control these pests, but in most cases, chemical control of larvae is necessary.

Adults of the diamondback moth Plutella xylostella (L), (a), cabbage looper (b) and imported cabbage worm, Pieris rapae (L) (c).

Management: Monitor with sex pheromone water traps (DBM) and sex pheromone traps (CL).

Diamondback moth, Plutella xylostella (L), is a small (1/4" long) and grayish-brown (a). When at rest, their wings come together to form a line of white diamonds down the back. Moths are active during the day, and males are attracted to sex pheromone traps (water pan traps). Also note pupal case (b).

Management: Diamondback moth caterpillars can be controlled with the same insecticides used on other caterpillars. If pests are resistant to certain insecticides, tank mixes of frequent sprays may be necessary Although a number of parasites, diseases, and other predators prey on larvae and pupae, these natural enemies are often destroyed by insecticides.

Diamondback moth adults (a), adult (b), larva (c) and feeding damage. Larvae remove tissue on the undersides of leaves. These tissues later dry and a large hole appears.

Management: Monitor for insect stages, damage, and parasites and predators. Select an insecticide specific for DBM. Use a Bacillus thuriengensis insecticide.

Eggs of cabbage looper (c), are round and laid singly. White diamondback moth eggs (a), are small and laid in small groups. Imported cabbage worm eggs (b), are elongated and laid on end singly.

Management: Trichogramma wasps exist naturally and can be introduced to attack eggs.

Early instar larva of the diamondback moth (a), cabbage looper (b) and imported cabbage worm (c). DBM have black heads, cabbage loopers have black heads and spots on the body, and white imported cabbage worms have brown heads and are light-green and hairy.

Management: Scouting for larvae before and after insecticide application with records will give control level obtained and indicate whether additional sprays are needed.

Late instar larva of the imported cabbage worm (a), cabbage looper (b) and diamondback moth (c). Cabbage worms are velvety green, hairy, and slow moving. Cabbage loopers are light-green, smooth, and loop when they move. Diamondback moth larvae are very light green, pointed at both ends, and wiggle when disturbed. They also spin a silken thread.

Seven larval stages (a) and pupal stage (b) of the cabbage looper.

Larva of the diamondback moth.

Pupal stages of the diamondback moth (a), imported cabbage worm (b) and cabbage looper (c).

Larval stages of the variegated cutworm, Peridroma saucia (Hubner).

Management: In small gardens, barriers around plants can prevent serious cutworm damage. By encircling individual plants with cardboard or metal collars pressed into the soil, cutworms are barricaded from the plants. This prevention method, however, is not practical for large acreages. Therefore, apply insecticides as needed.

Corn earworm, Heliocoverpa zea (Boddie), referred to as the cabbage headworm, is a late season pest.
Management: Check cabbage closely for earworms between June and September. Avoid planting cabbage near field corn. Cultivating fields after harvest kills numerous pupae in the soil and exposes many to birds and other predators. Direct selective sprays to cabbage heads as soon as earworms or damage are observed.

Beet armyworm, Spodoptera exigua (Hubner), hatch from egg masses and feed in groups on the undersides of leaves.

Management: The beet armyworm has few effective parasites, diseases, or predators to lower its population. However, effective chemicals for beet armyworm control are available to commercial vegetable producers.

Cross-striped cabbageworm, Evergestis rimosalis (Guenee), is a late season pest. Larvae are bluish-gray with tiny black transverse stripes.
Management: Examine fall-planted plants for cabbage webworms. as soon as they emerge or are set out. Apply insecticides as needed. Early detection on the fall crop and sprays are required to control the cross-striped cabbageworm.

Cabbage maggot, Hytlemya brassicae (W.), is the major soil pest of the crucifers grown in higher elevations of North Carolina. The white, legless maggot has a pointed head and grows to be ¼ inch long. The fly resembles a small, common house fly. It is ¼ inch long, is gray with three distinct black stripes along the abdomen.

Management: Cultural practices such as planting in late May or early June, careful selection of seedbed location, and elimination of weed hosts can help prevent severe infestations. If planting is delayed until the last the week of May or first week of June, few flies will be present to deposit eggs. Locate seedbeds as far as possible away from growing areas, protect from egg_laying flies with a row cover. Obtaining transplants grown at elevations below 3,000 feet will eliminate the danger of introducing the maggots on transplants. Destroying turnip and cabbage stumps and weeds such as wild mustard in the fall will eliminate many larvae or pupae. Proper fertilization and good soil practices also lessen maggot damage by improving plant growth. Cabbage maggots often require chemical control. An insecticide can be broadcast and incorporated just before planting seed or setting transplants. A drench applied after transplanting may also be effective.

Striped flea beetle, Phyllotreta striolata (Fab.), together with other flea beetles, are common pests of collards, turnips, and other greens. Adult beetles are black, measure less than 1/4 inch long, and have a wavy yellow line on each wing. Other flea beetles are entirely black. They have thickened hind legs that allow them to jump when disturbed.
Management: Cultural practices and the use of resistant varieties help prevent flea beetle infestations. Row covers physically protect seedbeds from these insects. Good weed control and the destruction of crop residue reduce overwintering populations. Planting resistant varieties may also help. Apply chemical treatments as needed.

Cabbage aphid, Brevicoryne brassicae (L.), and turnip aphid, Lipaphis erysimi (K.), are troublesome. Aphids cluster on the underside of leaves and suck sap, causing the foliage to curl, wilt, or become distorted. Plants may be killed or rendered unmarketable. Aphids are pale green and have cornicles, or points, on the abdomen. Cabbage aphids have a gray, waxy coat and can be winged or wingless.
Management: Cultural practices and the use of resistant varieties help prevent flea beetle infestations. Row covers physically protect seedbeds from these insects. Good weed control and the destruction of crop residue reduce overwintering populations. Planting resistant varieties may also help. Apply chemical treatments as needed.

Harlequin bug, Murgantia histrionica (H.) is a hemiptera, or a true bug, and is a major pest of collards, turnips, and many crucifers. This black, shield shape bug is brightly colored with orange, red and yellow markings. The oval nymph looks like the adult is slightly smaller and lacks wings.
Management: Populations of overwintering adults can be reduced by plowing under field debris as cold weather arrives. Destruction of weeds within fields and among fence rows also limits overwintering sites. In addition to cultural practices, resistant varieties should be planted when possible. Insecticides should be selected and applied when bugs are small and first appear. Repeated applications are often needed.

Parasite of cabbage worm.

Diseased looper

Adult parasite on imported cabbage worm pupa.

Predatory stink bug

Syrphid larva feeding on an aphid.

Diseases

Sclerotinia head rot (white mold) is caused by the fungus Sclerotinia sclerotiorum. Symptoms first appear as water-soaked spots on leaves. As the disease progresses white-cottony fungal growth appears on infected leaves with small, black structures (sclerotia).
Management: Avoid planting in fields with a history of Sclerotinia disease, maintain adequate fertility, proper insect and weed management.

Bacterial soft rot, is caused by several species of bacteria (Erwinia and Pseudomonas). Symptoms initially appear as water soaked areas on wounded leaves. As the disease progresses, leaves become soft and begin to liquify.
Management: Avoid wounding plants during cultivation and harvesting. Control insects. Bury crop residue and rotate with corn or small grain to reduce bacterial populations.

Black rot is caused by the bacterium Xanthomonas campestris pv. campestris. Black rot symptoms appear initially as V-shaped areas along the outer leaf edges. As the disease progresses leaf veins turn black, plants become stunted, wilt and usually die.
Management: Use disease-free seed and transplants, bury (destroy) crop residues and rotate with a non-crucifer crop for at least 2 years. Tolerant varieties are available.

Black leg is caused by the fungus Leptosphaeria maculans. Symptoms first appear as black, round spots on leaves and sterns. As disease progresses, spots enlarge and become gray in the center with small black dots. Severely infected plants are stunted and may have a constricted stem at the soil line.
Management: Use disease-free seed and transplants. Bury (destroy) crop residue and rotate with a non-crucifer crop for at least 2 years. Apply fungicides when needed.

Club root is caused by the "fungus-like" organism Plasmodiophora brassicae. Club root symptoms include leaf wilting and yellowing (particularly on hot, sunny days), stunting and formation of club-like galls on roots.
Management: Use disease free transplants. Avoid moving infected transplants and/or infested soil on farm equipment to clean fields. Maintain soil pH at or above 7.3 with hydrated lime.

Fusarium yellows , is caused by soil fungus Fusarium oxysporum f.sp. conglutinans. Symptoms first appear as a yellowing of lower leaves. As the disease progresses, wilting (often on one side of the leaf or plant) and plant death occur.
Management: Use disease-free transplants and resistant varieties.

Alternaria leaf and head spot are caused by the fungi Alternaria brassicae and A. brassicicola. Symptoms first appear as brownish-black, target-like spots on leaves and stems that spread to the head under wet conditions.
Management: Use disease-free seed. Apply fungicides when needed.

Downy mildew is caused by the fungus Peronospora parasitica. Symptoms first appear as a purplish, irregular spots on leaves and stems. In the early morning, a purplish, fluffy growth is evident on the underside of diseased leaves. Cauliflower heads and stems can be invaded internally by the downy mildew fungus.
Management: Tolerant varieties, fungicides, bury (destroy) crop residue and rotate with a non-crucifer crop for at least 2 years.

Physiological Disorders

Broccoli suffers from brown bead, which can be caused by poor growth, disease, or excessive temperature It is typified by flowers that are small, turning brown, and not growing.
Management: The damage can be lessened by ensuring that crops receive enough nutrients.

Cracking of the head, can occur when soil moisture is increased suddenly. Cracking is particularly a problem when cabbage nears maturity. With sudden increase in soil moisture, young leaves inside the head expand rapidly and crack the head.
Management: Uniform moisture supply through irrigation will reduce head cracking. Good soil drainage will remove excess rainfall.

Tipburn, is a calcium deficiency-related disorder associated with rapid plant growth, high relative humidity and excessive ammonium nitrate and potassium fertilization. Symptoms appear as brown to black necrotic areas of young developing leaves within and outside cabbage head.
Management: Maintain proper nitrogen and potassium fertilization and soil pH. Use a broadcast method for applying fertilizer rather than injecting fertilizer into row. Some tolerant cultivars are available.

Hollow stem, is one of the greatest concerns of broccoli growers because fungi can enter the plant through the damaged openings. Hollow stem is caused by rapid growth and boron deficiency. Avoid varieties that tend to have hollow stem.
Management: Maintain uniform plant growth and provide boron as soil and tissue samples indicate.

Phytotoxicity, Insect Borer and Insecticide Sprays

Ethylene injury

Stem borer

Sevin injury

Lannate injury

Spray coverage

Rhizoctonia, (not shown) (damping-off, wirestem and bottom rot) are caused by the soil fungus Rhizoctonia solani. Damping-off symptoms appear as brownish lesions on stems and roots. Infected seedlings that are not killed may later develop a smaller stem near the soil surface (wirestem) which reduces plant productivity. As the cabbage plant develops, the fungus causes a dark discolored area on the bottom of the cabbage head.

Management: Use a biological or chemical-based soil treatment to reduce damping-off. Seed when soil temperature are favorable for germination and seedling emergence. Use disease-free transplants.



MANAGEMENT




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 IPM Cole Crops and Lettuce 11 2pp., 1987, Estimated cost $ 25.00
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Insect and Related Pest of Vegetables
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North Carolina Agricultural Chemicals Manual
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Cabbage, Broccoli, Cauliflower and Greens Production
AG-487, 26pp, rev.,
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Biological Control of Insect Pests of Cabbage and other Crucifers
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This publication is published by the North Carolina Cooperative Extension Service. The poster may be cut in quarters for use in a notebook.

Prepared by:
  • Kenneth A. Sorensen, Extension Entomologist
  • Marc Cubeta, Extension Plant Pathologist
  • Doug Sanders, Extension Horticulturist
  • Michael Sunday, Poster Design and Production
  • Theo Davis Sons Inc., Printers

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