Recognize the problem
Late blight (“Bakajani chelewa" in
Swahili) is a fungus-like mould disease. First, it causes small, water-soaked,
greyish-green, irregular areas on leaves. Later, the areas become dark grey and
grow over entire leaves. On the undersides of leaves, a fuzzy white fungal
growth might be seen early in the morning or after rain. Stem infections can
girdle the plant, causing death. Large brown leathery areas may occur on
The disease affects tomatoes but can
also live in Irish potato, peppers and eggplants. The disease likes the cool,
wet weather in Tanzania.
Late blight is devastating in the wet season and early blight, another fungus,
affects crops in the dryer season. Blight can be blown by wind from far away,
and can infect your field.
To prevent the problem:
resistant varieties e.g. Meru, Tengeru 97, Duluti & Tengeru 2010, Shengena
- Plant away from Irish potato, pepper, eggplants, night shade and infected fields
- Avoid planting
during wet and cool periods
- Keep wide plant
spacing of more than ½ metre to improve air flow
- Support plants
with sticks, and prune plants for better air flow
- If possible,
disinfect knives with bleach before working on the next plant. Wear gloves or
wash hands with plenty of water afterwards because bleach is toxic.
- Remove tomato
residues and volunteer Irish potato, pepper and eggplants.
spray a mixture of 1/2 kg ash, mixed with 1 litre fresh milk and 10 litres
water. This can be used in dry weather.
Regularly observe plants. When dry
weather is expected, some infection symptoms might be tolerated and infected
plant parts can be removed. When wet, cool weather is expected, 2 plants with
symptoms are enough to consider immediate action because the disease will
- Remove and destroy
diseased plants but avoid openly carrying materials through your field as much
as possible because this will spread the disease
- Finely chop 20
garlic cloves, soak for 1 day in 10 plastic-bottle-lids of mineral oil, then
add 1 plastic-bottle-lid of soap, stir, add 2 litres of water, stir. Spray
over plants max. twice with min. 1 week interval
- Prevent disease
spread by spraying products with chlorothalonil or mancozeb (WHO class
U). Do not enter the
sprayed field for 3 days. Do not spray two weeks or less before harvest. Spray
maximum twice per season.
- Prevent disease
spread with mancozeb products combined with copper oxychloride, copper
hydroxide or metalaxyl. These are toxic to farmers and consumers (class II moderately hazardous). Do not enter the sprayed field for 3
days. Do not spray two weeks or less before harvest. Spray max twice per
When using a pesticide, always wear protective clothing and follow the instructions on the product label, such as dosage, timing of application, and pre-harvest interval.