This archive report was first published on 9 May 2020.
As the rains continue to pour down in various parts of the country, farmers are facing a growing concern: grey mould in tomatoes. The disease, caused by the fungus Botrytis cinerea, is affecting crops in both greenhouses and open fields.
According to John, a farmer in Baringo, the disease has caused his tomato fruits to turn whitish and soft, with some even rupturing near the centre of the decayed area. The anomaly has affected plants in both greenhouses and open fields.
Identifying the disease as Botrytis, commonly referred to as grey mould, the fungus is characterised by tan to brown soft spots or blotches and affects many vegetable crops, including pepper, potato, and onions.
Botrytis affects all the above-ground parts of tomatoes, and the fungus occurs as both a pathogen and a saprophyte. It can also cause diseases such as damping off, stem girdling, foliar blighting, and post-harvest rots.
Grey mould is favoured by cool and humid conditions that stress the plants, making them susceptible to the disease. To minimise incidents of transmission of the disease from an open field to the greenhouse, farmers should avoid planting tomatoes or susceptible crops outside the structure.
Additionally, farmers should avoid carrying out management practices in the open field then moving into the greenhouse, as this increases the chances of introducing the pathogen in the structure. It is also essential to ensure good air circulation on the crop by pruning regularly and removing old laterals and dense leaves.
Greenhouse sanitation is also crucial, with farmers advised to remove all infected plants and ensure good ventilation to reduce the relative humidity and prevent grey mould. Consider installing fans to move air within the greenhouse and check on the crop spacing to allow good air circulation between the plants.
Other measures to prevent the spread of the disease include using certified seeds that are resistant or tolerant to such diseases, practicing crop rotation, and using chemicals with copper as an active ingredient to prevent the occurrence of the disease.
