Prevention and control: Controlling early blight once it has established is very difficult. The most important way of controlling early blight is attempting to prevent its establishment and further spread.
Use clean seed: Make sure that seeds/tubers for sowing and planting are certified and not taken from plants that were previously infected by the early blight. If possible, use potato and tomato varieties that are resistant to the disease.
Use tolerant or resistant varieties: Use plant varieties that are tolerant or resistant to early blight. Examples of tolerant / resistant tomato varieties in Kenya: 'Floradade', 'Hytec 36', 'Julius F1', 'Rio Grande', 'Rossol', 'Summerset F1', 'Zeal F1' and 'Zest F1'.
Destroy crop debris after harvest: Plough under all the crop residues after harvest to physically remove the inoculum (infection) source from the topsoil. Remove also weeds as they may serve as alternate hosts. Burn the infected material and plant debris.
Crop rotation: Fields should not be planted with tomato, Irish potato, or eggplant for at least 2 cropping seasons, since they are hosts to early blight. Also avoid planting new plots of these vegetables alongside old ones. Rotations with small grains, maize or legumes are preferable.
Avoid injury to potato tubers during harvesting and handling: Harvest potato tubers when the soil is not wet and when the vines are dry.
Practise proper plant spacing and staking: Prevent tomato plants from soil contact and prune and stake indeterminate varieties to promote good air circulation. Mulch determinate tomato varieties.
Water management: If possible avoid over-head irrigation. Otherwise, irrigate early in the morning so that the canopy would dry in the evening. In case of Irish potatoes, furrow irrigation should not be used especially after tuber formation.
Soil management: Use plenty of compost or well decomposed animal manures. Maintain soil fertility at optimal levels. Nitrogen and phosphorus deficiency can increase susceptibility to early blight. Also excess nitrogen could induce early blight infection.