Early Blight of Tomato
Tomato a vegetable crop belonging to the family (solanaceae) grown throughout the world. Tomato is the most consumed vegetable after the potato due to its high nutritional value. Tomato considered as a good source of vitamin A, C, and E and also contains a valuable amount of antioxidants. Tomato also plays an important role in the metabolic activities of human beings due to presence of high amount of water 95.3%, calcium and niacin about 0.07% and some other metabolic compounds. Tomato production gain high importance due to its compatibility to each type of climate and soil.
Tomato crop is being affected by the number of biotic and abiotic factors which may causes the reduction of the final yield. Among the biotic factors different fungal pathogens especially Alternaria found to be responsible for blight diseases which causes heavy losses throughout the world. The genus Alternaria is known as a soil born plant pathogen. Early blight caused by the Alternaria solani found to be a most fatal disease of tomato crop throughout the world. Early blight is the most devastating disease in the tropical and subtropical regions of the world. There are several factors like as high rain fall, humidity, extended period of leaf wetness found to be most conducive for the disease development.
Symptoms: the pathogen can attack at all the growth stages of the plants. When the pathogen attacks the seedlings small blackish colored spots produced on the leaves and stem. In case of young plants the water soaked spots produced on the older leaves along with yellow hallow around them which are near the soil surface. Later on these lesions coalesces together to make concentric rings. In severe cases theses leaves turn brown and defoliation take place. The pathogen also attacks the fruits of the plants just at the point of attachment to the branches. In severe cases it causes the premature falling of the fruits. The affected area appeared leathery with masses of black spores on these rings.
Epidemiology: The temperature range of 22-25 0C and the relative humidity of more than 88% for 24 hours found to be most favorable conditions for the pathogen attack. The pathogen can attack at all stages of growth but 1-6 week older plants found to be more susceptible for the attack of early blight of tomato.
Control:
- The crop rotation of 3-5 years with non host crops.
- By using different types of protecting fungicides.
- Use of different chemicals especially Pyraclostrobin, Mancozeb and azoxystrobin 23% SC along with biocontrol agents is an economic way to avoid the catastrophic effects of disease.
- The best way to control the disease is the use of resistant varieties e.g Rio grande and Naqeeb.
Syed Muhammad Ali Shah, Rozina shaheen
Msc (hons) Plant pathology
