By Paschal Nnaemeka, Crop Scientist – Early blight, caused by Alternaria solani, is a persistent threat to tomato crops, and managing this disease effectively is key to maintaining healthy plants and ensuring good yields. Farmers must understand the disease’s lifecycle to implement proper control measures. Early blight starts with small, dark brown lesions on older leaves, which soon develop a distinctive “bulls-eye” pattern of concentric rings. Left unchecked, these infections can lead to  defoliation, reduced plant vigor, and lower fruit production.

One of the best ways to manage early blight is through a combination of cultural practices and timely fungicide application. Removing plant debris, rotating crops, and avoiding prolonged periods of leaf wetness can reduce the risk of infection. However, when conditions are favorable for disease development, fungicides become essential.

Several active ingredients have proven effective in combating early blight:

– Chlorothalonil and Mancozeb are contact fungicides that protect plants by preventing the fungus from germinating and spreading.
– Copper-based fungicides, such as Copper Hydroxide and Copper Oxychloride, offer protective and curative actions, inhibiting fungal cell metabolism.
– Systemic options like Difenoconazole and Propiconazole penetrate plant tissues and halt fungal development by interfering with sterol biosynthesis, which is crucial for fungal cell membrane formation.
– Azoxystrobin and Pyraclostrobin, both from the strobilurin class, work by blocking the fungus’s ability to produce energy, leading to its eventual death.
– Boscalid disrupts the energy production mechanism in fungal cells, offering another strong line of defense.

To minimize the risk of fungicide resistance, it’s important to alternate between different modes of action. Farmers should apply these fungicides preventatively or at the first signs of early blight, ensuring consistent coverage of the plant foliage. By integrating these chemical controls with good farm management practices, farmers can effectively reduce the impact of early blight and maintain healthy, productive tomato crops.