I am wondering if anyone has practical examples on how to differentiate between early blight and late blight infection on tomato leaf? To me, I feel a bit difficult to identify them at the early stage of infection.
The difference is the yellow ring over the spots in early blight. In late blight the necrotic spot doesnt hace that yellow ring.
Early blight is due to Alternaria solani (kingdom Fungi). The symptoms on leaves and the stem are brown spots with concentric rings acompanied later on by a diffuse yellow disclouration of a large portion of the leaf. The disease spreads rather slowly compared with the late blight.
Late blight is caused by Phytophthora infestans (Kingdom Chromista). The symptoms start with pale green diffuse irregular spots on the leaf upperside and a purplish-black velvety spot on the leaf underside, which later on develops a white ring (of mycelia) arround the spot. Later on the spot on the upperside turns black-brown (on potaoes it is surrounded by pale whitish ring) thereafter big patches of the leaf turn necrotic (dead tissue of brown colour). The disease attacks also tomato fruits starting with brown spots which enlarge in time and end often with soft rot of the fruit. The disease spreads rapidly to neighbouring plants. Late blight can by controlled up to now with fungicides based on copper compounds or mancozeb, unfortunetely there are no really resistant tomato and potato cultivars available.
In early blight, symptoms will first appear on the older leaves near the base of the plant, spots have tan centres with concentric rings in them and yellow halos around the edges.
In late blight fuzzy growth will found on the underside of the tomato leaf. Spots start out pale green, usually near the edge of the tips of foliage and turn brown to purplish black
Late blight lesions have not defined border. Early blight have concentric rings and defined border
Early blight is a fungal disease caused by Alternaria sp. The appearance of circular or irregular dark spots on the lower, more mature leaves is one of the first symptoms of infection. Eventually, the spots enlarge into a series of concentric rings surrounded by a yellow area.
Late blight is caused byPhytophthora infestans (Mont.) de Bary. Symptoms of late blight on tomato leaves and stems are similar to those on potato. Irregularly shaped watersoaked lesions can be observed on young leaves at the top part of the plant. Under humid conditions, lesions become brown and pathogen sporulation can be seen. Eventually the leaves shrivel and become necrotic and die. Brown lesions can occur on stems and leaf pedicels. The pathogen can also infect tomato fruit and causes circular greasy lesions. The fruit remain firm but spots eventually become leathery and chocolate brown and can enlarge to cover the entire fruit.
Early blight Characteristic Symptoms is “bullseye” type lesion is characteristic of early blight, which give the spots a target-like appearance . Late blight Characteristic Symptoms is appear at first as water-soaked spots, usually at the edges of the lower leaves, enlarge rapidly and form brown, blighted areas with indefinite borders.
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