Pests and diseases management of kales

1. Damping-Off

Damping-off is another leafy vegetable disease caused by Rhizoctonia solani. It is also caused by Fusarium spp or Pythium spp. The fungus causes decay and wilt in seeds and seedlings respectively. The infected seedlings have light brown stems.

The pathogen survives is cold and wet soils, so you need to keep the soil temperature and moisture at optimum levels to prevent the occurrence of this disease in your garden. You need also to use certified seeds.

Symptoms of Damping off on Kale seedling

Management

Uproot infected plants. Avoid leaving debris of Kale plants or residues of brassicas in the field. Rotate crops every 4 years. The soil should always be water drained and airy. 

2. Black rot (Xanthomonas campestris pv. Campestris)

Black rot is one of the most serious cabbage diseases during high rainfall and heavy dew conditions. The black rot bacterium can over-season on infected cabbage seeds, in weeds from the family Cruciferae or in infected plant material in the soil. Disease is common during wet conditions with high temperatures.

Symptoms:

• Yellow, brown or black v-shaped patches at the edge of the leaves. 
• In later stages, head turns black with an offensive foul smell. Bacterial ooze also will be visible on the surface of diseased tissue.

Photo. Symptoms of black rot on cabbage

Management:

• Disease-free transplants should be used.
• Remove all infected plants and debris from the field and destroy by burning
• Spray the remaining healthy plants using a copper-based protective fungicide (eg. Copper-oxychloride: 250g/250ml water/has) to suppress further damage.

3. Downy mildew(peronospora parasitica)

The characteristic symptoms are appearance of purplish brown spots on under-surface of leaves. Upper surface of leaves has lesions in tan (yellowish brown) to yellow color. Infection exposes heads to soft rot.

Photo: Symptoms of downy mildew on cabbage

Management:

• Destruction of diseased debris after harvest of the crop
• Spray the plants using Mancozeb or a copper-based protective fungicide at 15 days interval soon after appearance of the disease.

4. Cabbage alphids

Several species of aphids attack brassicas in East Africa: the cabbage aphid (Brevicoryne brassicae), the false cabbage aphid (Lipaphis erysimi), the green peach aphid (Myzus persicae).  In particular, the cabbage aphid is a major pest in the region. Cool, dry weather is most favourable for aphid development. Large numbers of aphids may kill small plants. Their feeding can distort leaves of older plants and causes leaf curl.

Photo: Aphids on cabbage

Management:

• Intercrop with onion, garlic, spider plant, coriander to attract natural enemies.
• Avoid too much N.
• Plant in a well prepared fertile seedbed to promote crop vigour.
• Keep the fields free of weeds and alternative hosts.
• Manage the field to favour natural enemies such as lady bird beetles and hover flies.

• Mulch with wheat/rice straw or clear/transparent polyethylene sheet as reflectors of UV light discourage aphids from landing on the crop
• Use overhead irrigation to knock aphids off the leaves
• For chemical control, spray insecticides like Cypermethrine, Roket,etc.

5, Diamond back moth (DBM)(Plutella xylostella)

DBM is a serious pest of Brassicas and attacks all Brassica species. A full grown diamondback caterpillar is about 1cm long.Young larvae feed on leaves, leaving intact parchment like epidermis. Growth of younger seedlings is inhibited and also produces holes in leaves.

Photos: DBM damages on cabbage

Management:

• To control DBM in small size farms, cover seedlings with row covers (fine nylon mesh) to prevent moths from laying eggs on the leaves and or next to the plant.
• Intercropping Brassicas with repellent plants such as tomato, reportedly reduces DBM infestation in cabbage. When intercropping with tomato, the cabbage crop is planted 30 days after tomato.

Biological control of DBM using parasitoid wasp Diadegma semiclausum has proven very effective

• in the highlands of Kenya, Tanzania and Uganda.
• Botanicals such as neem-based pesticides are very effective for control of DBM.
• Physical protection method: dense planting of maize or sorghum around the field like a fence may be effective because the insect cannot fly over the maize and sorghum.
• Chemical control: Cypermethrine based chemicals like DUDU-CYPER and ROKET (at 1ml/1L of water) may be effective. But insecticide application is less effective for egg, mature larvae and pupae.

6. whitefly (Aleyrodes proleltella)

Whiteflies (Bemisia tabaci, Trialeurodes vaporariorum and Aleyrodes proletella) feed on Brassicas. Adult whiteflies are about 1 mm long.

Photo: Whiteflies on cabbage

Management:

• In East Africa, whitefly populations on Brassicas usually do not build up to such an extent that control measures are required.
• Natural enemies such as ladybird beetles, predatory mites and lacewings can play an important role in reducing whiteflies
• Proper fertilizer application because application of high doses of nitrogen fertiliser favours development of the pest
• Use mineral oils, neem products or spray with soapy water solutions.