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Early and Late Blights

Published Oct 22, 2022

Early and Late Blights

Blights can cause significant yield losses if left uncontrolled. Long periods of wetness on the leaves favor the disease infection. Let’s have a deeper look at early and late blights:

1. Early Blight:
Alternaria solani is a fungal pathogen that produces a disease in tomato and potato plants called early blight. The pathogen produces distinctive “bullseye” patterned leaf spots and can also cause stem lesions and fruit rot on tomatoes and tuber blight on potatoes.

Symptoms:

In tomatoes, foliar symptoms generally occur on the oldest leaves and start as small lesions that are brown to black in color. These leaf spots resemble concentric rings (a distinguishing characteristic of the pathogen) and measure up to 1.3 cm (0.51 inches) in diameter. Both the area around the leaf spot and the entire leaf may become yellow or chlorotic. Under favorable conditions significant defoliation of lower leaves may occur. As the disease progresses, symptoms may migrate to the plant stem and fruit.

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Early blight in tomato leaves

If early blight gets on the fruits, spots will begin at the stem end, forming a dark, leathery, sunken area with concentric rings. Both green and ripe tomatoes can be affected.
 

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Stem lesions caused by blight

 

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Early blight fruit symptom

 

In potatoes, primary damage is attributed to premature defoliation of potato plants, which results in tuber yield reduction. Initial infection occurs on older leaves, with concentric dark brown spots developing mainly in the leaf center. The disease progresses during the period of potato vegetation, and infected leaves turn yellow and either dry out or fall off the stem. On stems, spots are gaunt with no clear contours (as compared to leaf spots). Tuber lesions are dry, dark and pressed into the tuber surface, with the underlying flesh turning dry, leathery and brown.

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Early blight on potato leaf

 

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Early blight on potato tuber

 

2. Late blight:

Late blight is a potentially devastating disease of tomato and potato, infecting leaves, stems, tomato fruit, and potato tubers. The disease spreads quickly in fields and can result in total crop failure if untreated. It is caused by fungus phytophthora infestans

Symptoms:

Leaf symptoms of late blight first appear as small, water-soaked areas, that rapidly enlarge to form purple-brown, oily-appearing blotches. On the lower side of leaves, rings of grayish white mycelium and spore-forming structures may appear around the blotches. Entire leaves die and infections quickly spread to petioles and young stems. Infected fruit turn brown but remain firm unless infected by secondary decay organisms; symptoms usually begin on the shoulders of the fruit because spores land on fruit from above.

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Late blight on tomato fruits

 

 

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Late blight in tomato leaf

 

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Late blight in potato

 

Blights Management:

Prune or stake plants to improve air circulation and reduce fungal problems.

Observe proper field hygiene. Keep a free-weed field and avoid plant debris in the soil below the crop

Drip and furrow irrigation can be used to help keep the foliage dry. Avoid overhead irrigation.

Apply appropriate fungicides. Treatment should begin early enough before the disease sets in.

Protective Fungicides

Curative Fungicides

Visit our products catalogue ( https://www.agropests.co.ke/products?subcategory=fungicides ) or simply contact us  https://www.agropests.co.ke/contact  
Remove and destroy all garden debris after harvest and practice crop rotation. Burn or bag infected plant parts. Do NOT compost.

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