Fruit turns brown with white spores forming when moist. Fruit are not affected.īuckeye fruit rot. Septoria leaf spot. Leaf and stem spots are all much smaller than with late blight and often have a characteristic tan center. Leaf, stem and fruit spots are all smaller than with late blight and often have a characteristic concentric ring pattern or target-shape appearance. Affected tissue always extends from the leaf margin whereas late blight can cause spots in the center part of leaves.Įarly blight. View images of late blight that resemble drought stress from July 2011 heat wave.īacterial canker.Sometimes canker causes large areas of leaf tissue to die without the characteristic yellow border for this disease. Under some circumstances, late blight can be more difficult to distinguish from drought stress. Also, no symptoms develop on stems or fruit. In contrast with late blight lesions, symptoms of drought stress always extend from the leaf edge, they lack a border of wilted tissue, and there is no fuzzy pathogen growth. The late blight pathogen produces white spores.ĭrought stress.When plants’ roots cannot deliver enough water to leaves, large sections of leaf tissue can die. Spores are produced on the underside of leaves. And most notably for distinguishing this disease from late blight, the causal pathogen produces spores that initially are greenish gray to brown, becoming darker brown with age and developing a velvety appearance. Color of leaf mold spots on upper leaf surfaces progresses from pale green to yellow. They are smaller than typical late blight lesions and lack a distinct margin. The pathogen growth is fuzzier and gray to brownish, not white as with late blight. Affected fruit are soft and are not brown. The pathogen typically needs to become established on these dead tissues before it can attack living plant tissue. These symptoms are often associated with dead plant tissue (flowers, leaves). This is the disease most commonly confused for late blight because the pathogen causes large leaf spots, stem lesions, and affects fruit. Affected fruit develop large, brown, firm areas. When petioles are affected, the whole leaf can collapse. Large, dark brown lesions develop on stems and petioles, and sometimes the pathogen sporulates on these, too. The best place to look for the white fuzzy growth of spores is on the underside of leaf lesions. Characteristic leaf symptoms are very large spots, which look water-soaked at first then turn brown, often with a border of light green wilted tissue. Late blight can affect all parts whereas some of the ‘imitators’ cannot. The late blight pathogen produces most of its spores at night, so it’s usually more visible in the morning. The first step in diagnosis is to examine affected plants thoroughly for symptoms. Contact your local Cooperative Extension office for help. Unless you are able to conclude with great certainty that your plants do have one of the other maladies, get help by submitting a sample to a diagnostic clinic. The most common are below, and you can also view an entire online webinar presentation on the subject.Ĭlick on images to view more (and larger) images of the disease. ![]() (See Avoid the late blight blues.)īut before you pull up plants that have symptoms that look like late blight, make sure they aren’t one of the ‘imitators’! There are several diseases and disorders with symptoms that could be mistaken for late blight. Then spreading the word to others to be on the lookout. That means inspecting plants regularly and quickly destroying any that show signs of the disease. ![]() How to distinguish late blight from other diseases and disorders with similar symptomsīecause late blight is so highly contagious and destructive, it’s important to take an aggressive, community-wide management approach to nip any potential infections in the bud before the disease has a chance to spread.
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