It is not found before June or July. Infections appear as reddish brown, more or less circular spots. These spots cross over the leaflet veins. Some spots may show grayish concentric rings at the margin. As the spots age, they become irregular in shape.
Brown spot is more common in areas of high rainfall and low fertility.
Under these conditions brown spot can cause severe leaf drop in unsprayed orchards. Trees properly fertilized and sprayed with fungicides are seldom bothered by brown spot. Stuart is reported to be more susceptible than many other varieties. Brown spot is most common in young orchards or orchards with no crop set as growers tend not to spray these sites as intensely as bearing orchard.