Farming cabbages in Kenya: We take a look at some of the major diseases you will face in cabbage farming.
1). Cabbage worms, Cabbage loopers
Affected Area: Leaf
Description: Loopers are caterpillars that are generally green or greyish, taking on the color of the host plant. They may blend well and be difficult to see. They eventually develop into white- or yellow-winged butterflies often seen fluttering about the plants. Caterpillars feed on the underside of leaves leaving ragged holes sometimes to the extent that plants starve and die.
Control: Spray with Bacillus thuringiensis (Bt) Comercially available as Dipel or Thuricide.)
2). Cutworms
Affected Area: Stem
Description: Plants chewed off just above ground level. Cutworms are caterpillars 1 1/2″ long and mottled or striped green, brown or gray. When they are disturbed, they roll up in a coil. They usually position themselves at the moisture line in the soil moving up and down according to the water content. If the soil surface is dry, they will be found a couple of inches below the surface where the moisture begins. When newly watered, they will be at the surface.
Control: Put cardboard collar around new transplants to extend 1″ to 2″ above and below soil level.
3). Root Maggots
Affected Area: Root
Description: Leaves wilt and growth is stunted. Insect is common, white, root feeding maggot. 1/4″ long adult flies emerge from the soil about the time cherries bloom and lay eggs at base of plants in surrounding soil. Legless larvae feeds on host plant for three weeks, riddling the roots with brown tunnels before they pupate Two or three generations can occur each growing season.
Control: Use Diazinon before planting as a soil treatment. Rotate from year to year.
4). Flea Beetle
Affected Area: Leaf and Root
Description: Tiny holes ?pinholes? chewed in leaves by adult insect. Adult insects are 1/16″ long, hard shelled, shiny, dark-colored beetles that jump when disturbed. Slender, whitish, cylindrical larvae feed in or on roots but root damage is generally minimal.
Control: Dust with Rotenone. Keep debris removed. Rotate location of planting from year to year.
5). Aphids
Affected Area: Leaf
Description: Green, red black or white insects that cause curled yellow leaves and exude a honeydew substance
Control: Insecticidal soaps or a strong stream of water or most labeled insecticides like Diazinon or Sevin. A layer of aluminum foil under plants reflects light to underside of leaves making them an undesirable habitat for aphids.
6). Damping Off
Affected Area: Seedling
Description: Young seedlings wilt and die
Control: Use treated seed and let soil dry out between waterings
7). Bacterial soft rot
Affected Area: Leaf
Description: Leaves turn yellow (chlorotic) beginning at margins and spreading inwards. Veins within area turn black. Infection enters main stem turning the inside black.. Plants either die or are dwarfed when young, become defoliated if more mature.
Control: Plant resistant varieties and rotate crops from year to year.
8). Black Rot
Affected Area: Leaf
Description: Humid rainy conditions are ideal for the development of black rot. Yellow to light brown patches appear at the margins of leaves and later black veins develop within the yellowed areas. Affected areas turn brown and dry out, often leaving a triangular-shaped lesion on the leaf margin with one point of the triangle directed toward the midrib.
Control: The best form of control is to avoid sprinkler irrigation and plant tested seed.
9). Alternaria Leaf spot
Affected Area: Leaf
Description: During wet seasons, a brown velvety spore-bearing lesion appears on the older leaves. Leaf spots begin as a small dark spot and enlarge to form a large circular lesion forming a bull’s-eye pattern.
Control: The best form of control is to apply fungicides.
10). Diamondback moth caterpillar
Affected Area: Leaf
Description: This caterpillar causes small holes in the leaves and weaves cocoons about 1/3 inch long on the leaves.
Control: The best form of control is to apply an effective insecticide.