Most active during cool, rainy springs, this fungal disease slowly weakens infected trees. If left unchecked, afflicted leaves show a coating of white spores; these can reinfect the host tree the following year.
Target: Peach, nectarine. Damage: Midribs thicken, causing the leaves to pucker and curl, leaves are tinged with red or yellow and drop early. Fruiting is poor; fruit may be spotted. Repeated infections cause branches to die back. Control: Sanitation, fungicide
Notes: Apply fungicide in late winter, before new growth appears. You can also control infection by keeping trees covered with plastic film until the leaves unfurl (this is easiest to do with genetic dwarf varieties). Pick off and destroy infected leaves.