Young infected shoots and cluster stems may curl, distort, show thickening of the infected tissue and may be covered with a whitish fungal mass. Infected berries turn brown and eventually shrivel. Infective spores are produced during rainy periods if temperatures are above 50F and infections are triggered by warm, humid nights followed by rain. This disease makes rusty spots which look very much like iron rust on the under side of leaves, and the tops of the leaves show yellow color to match the rust spot below. Rust can cause severe defoliation.
Sulfur is a very effective control if applied before, or at the first sign of rust.
Almond scab , caused by another fungus, Fusicladium carpophilum , makes greasy gray spots on the leaves and on the tops of the nuts. These symptoms will usually start showing about mid-June. Control is best done at 2 weeks to 5 weeks after petal fall. There is still some chance to control scab in orchards where scab has been a problem in the past years. Control is very poor if you wait until scab shows in the orchard - scab control is a preventive program based upon past history and weather conditions.