Plant Pathology: Extension: Plant Disease Library

Cladosporium

Important diseases: Scab diseases of Pecan, Peach, and Cucumber

Cladosporium is a most commonly a saprophyte, living off of decaying plant tissue. It also can be a pathogen causing numerous scab diseases, as well as leaf spots and blights.

Cladosporium attacks developing leaves, shoots, nuts and fruits. Mature tissues seem to be resistant to infection. Symptoms of scab diseases on pecan nuts and peach fruit are similar. Small, round, sometimes sunken, olive-black to black spots appear on developing fruits and nuts. Spots may grow together so that the entire surface of pecan nuts turn black. On peach, the spots are usually on the upper side of the fruit which may crack following infection. Cladosporium produces spores mostly on the underside of leaves. Elongated brown, velvety lesions are usually formed along leaf veins. Infected leaves and nuts tend to drop prematurely. Cladosporium infection of cucumber fruits results in small, sunken, sometimes oozing spots similar to insect damage.

Conidiophores are tall, dark, and upright with branching near the apex. Conidia are 1-2 celled, darkly pigmented, and often appear brown to dark green in mass. Conidia are produced in singly or in chains of two or three and vary in size and shape (oval, cylindrical or irregular). Branching also be seen in some conidia.