To increase the effectiveness of lime-sulfur as an insect control material, a dormant oil material may be added to the spray mixture. Peach leaf curl is a good example of a disease where a single application of lime-sulfur applied during the dormant season provides excellent control. This fungus disease is frequently severe in Mississippi following wet springs. Symptoms are most noticeable on leaves although twig and fruit infections may also occur. Leaves become distorted, puckered, and curled.
Infected leaves turn yellow, red or purple and soon drop from the tree.
Yearly premature defoliation resulting from peach leaf curl can seriously weaken trees, and control of this disease is necessary if trees are to maintain a good state of vigor. A related disease on plums, referred to as plum pockets, is also reduced by lime-sulfur application in the dormant season. This disease shows up as small blisters on fruit shortly after fruit set. Blisters enlarge and soon the fruit becomes spongy. Black knot on plum and cherry is characterized by the production of elongated swellings or knots on the limbs of susceptible tissue.