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:
Photo. Symptoms of black rot on cabbage
Management:
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:
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:
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:
Biological control of DBM using parasitoid wasp Diadegma semiclausum has proven very effective
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: