My leaves have spots……

My leaves have spots……
Disease diagnosis can be hard, symptoms of different diseases may be similar to each other or difficult to distinguish from insect damage. Microorganisms that cause diseases are called pathogens.

Pathogenic fungi cause many different symptoms, including leaf spots, wilts, curled leaves, dieback, enlargements, and stunted or dead plants. Fungal spores and bacteria can be spread by wind, water, soil movement, machinery, insects, even people. Prolonged spring rains or foggy conditions make a hospitable environment for Anthracnose, Shot Hole, Septoria Leaf Spot and Entomosporium Leaf Spot.

Shot Hole affects Prunus species (almond, plum, apricot). It causes discolored spots on buds, leaves, shoots, and fruits. Holes can appear in affected leaves and foliage may drop prematurely. Concentric lesions may develop on branches*.

Shot Hole first appears in the spring as reddish, purplish, or brown spots about 1/10 inch in diameter on new buds, leaves, and shoots. The spots expand and their centers turn brown. Tiny dark specks, visible with a hand lens, form in the brown centers, especially on buds. These dark specks (spores of the fungus) distinguish shot hole form other diseases. Spots on young leaves have a narrow, light green or yellow margin and their centers often fall out as leaves expand, leaving ‘holes’. Leaves may fall from the tree. Fruit spotting may occur, usually on the upper surface.

Spores are spread by splashing rain or overhead irrigation. Adjusting the irrigation to keep the foliage from getting wet, will help. Prune out and dispose of infected tissue as soon as it appears. After leaf drop in the fall prune out twigs with lesions and ‘varnished’ appearing buds. Diligent sanitation and water management can control a mild case. Copper spray can be used where disease incidence is high.