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Disease Management

Orchard location is important. Trees planted in orchards having poor air movement, and thus slow drying conditions, are more likely to have blossom blight and brown rot. Successful management of blossom blight and brown rot involves a combination of sanitary practices to reduce the amount of initial inoculum and the judicious use of fungicides. When compared to the results of good sanitation and cultural practices, biological control has had minimal success in the orchard. Biological control has shown better potential for prevention of post-harvest fruit decay.

Sanitation practices

The removal of diseased fruit mummies and blighted twigs from the trees and removal of fruit and mummies from the orchard floor following the final harvest can substantially reduce sources for overwintering inoculum. The orchard floor can be kept clean of vegetation, or the area can be raked or lightly cultivated to bury mummies and prevent the development of apothecia. However, care must be used not to cultivate too deeply to avoid damaging tree roots. If practical, wild Prunus spp. adjacent to the orchard should be removed.

Fungicides

Blossom blight occurrence is very much dictated by the weather conditions. In areas where blossom infection occurs, 1 to 3 fungicide sprays beginning just as the blossoms open (Figure 7) control blossom blight

Figure 7

Figure 28

For brown rot control, 2 to 3 fungicide sprays are usually applied during the 2 to 3 week period leading up to harvest. When combined with good cultural practices, currently registered fungicides are highly effective (Figure 28). In addition, insect control, especially for insects that directly damage fruit, is important during this period.

Disease Risk Analysis and Decision Support Systems

In an effort to more judiciously use fungicides to manage this disease, risk analysis and support systems for decision-making have been developed. These link temperature and moisture conditions, inoculum potential, potential for latent infections and tree growth stages such as bloom and fruit ripening. Such risk analysis systems may provide a risk predication for anticipated disease severity and aid in making decisions as to the need for fungicide sprays.

Post-harvest control

Practices used during harvest can significantly impact the amount of fruit decay following harvest. Picking and handling fruit carefully to avoid injuries, cooling fruit promptly after harvest by hydrocooling or forced air cooling, using clean containers to hold the fruit, and timely harvesting of ripening fruit all help reduce post-harvest brown rot problems.

Fungicides are commonly used to reduce post-harvest fruit decay, but there has been considerable research on alternative control methods. Antagonistic isolates of Bacillus and Pseudomonas spp. have been used experimentally as biological control agents. Substances that induce fruit resistance, such as calcium treatments applied to fruit several weeks before harvest, or surface coatings that provide a physical barrier have also been evaluated in experiments, but are not yet used on a commercial scale.

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