Curatives are usually from the DMI group of fungicides. There is a high possibility that the black spot pathogen will develop resistance to the DMI group, so they must be used sparingly. The black spot inoculum overwinters in leaf litter. Therefore, removal or breakdown of the leaf litter will help to prevent the carryover of the disease. Urea is often applied in autumn to speed up the breakdown of the previous season's leaves.
Some growers graze sheep under the trees in autumn or winter which eat the fallen apple leaves.
Remove all the apples from the trees after harvest to reduce the risk of carryover infection. At HortResearch we are trying to help apple growers reduce their use of fungicides by developing a full disease management system for black spot control. An effective black spot infection-period monitoring system has been tested extensively and is now part of the Orchard 2000 network. Now that the weather monitoring system is up and running, the next step is to develop a routine ascospore monitoring service. HortResearch has also investigated organic fungicides.