Anthracnose of Avocados

Colletotrichum gloeosporioides

Anthracnose symptoms can develop on flowers, fruit, leaves, or twigs. Infected fruit is the most serious concern, but most fruit damage does not develop until after harvest. External symptoms are difficult to see on ripe 'Haas' fruit because of its dark skin color. Unhealthy or dead leaves are the most obvious symptom in groves. Spots form on leaves, beginning as yellow, then brown discolorations that coalesce into large dead areas. Necrosis occurs across or between leaf veins, on leaf margins, and most often at leaf tips. If disease is severe, trees drop many leaves prematurely. New shoots can develop brown or purplish lesions, and shoots may dieback. Infected flower heads can turn dark and die without producing fruit, or young fruit may form and then drop.
Before harvest, brown to black lesions less than 0.2 inch (5 mm) in diameter develop around lenticels on infected fruit. These small discolorations can be overlooked while fruit are still on the tree, and lesions usually do not enlarge until fruit ripens after harvest. Large lesions sometimes occur on avocados on the tree, usually after infected fruit is injured by insects or mechanical wind rubbing.
After harvest, lesions become blacker, larger, and increasingly sunken. Lesions eventually spread over the entire fruit surface and throughout pulp. When the fruit is cut in half through one of the lesions, rot extending into the flesh often exhibits a hemispherical pattern. Decayed pulp initially is firm, but becomes soft and putrid as decay advances. Pink spore masses may form on the fruit surface and, under wet conditions, a slimy mass of pink spores erupts through the fruit skin.

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