The most common of the fungal fruit rots is bitter rot.
Initial infections begin as early as bloom and continue until about one month after petal fall. Early symptoms are small, slightly sunken lesions that eventually develop concentric rings (bulls eye pattern). Under moist conditions, spores turn a distinct salmon color. Cutting into infected fruit reveals a V-shaped internal rot.
The fungus overwinters in mummified fruit, crevices in bark,
and dead wood such as fire blight damaged tissue. Removal of mummified fruit, cankers, and dead
wood helps reduce inoculum for the following season. Diseased fruit should be discarded
immediately. Fungicides are only
effective with good sanitation, so these cultural practices are a necessary
step in disease prevention and control.
Current recommendations indicate fungicide applications soon
after petal fall (no later than first cover) and continue until harvest. Fungicides
captan, mancozeb (dithane, manzate, penncozeb), polyram, and ziram are
recommended on 10-14 day schedules.
Note: Symptoms do not always
occur immediately after infection, and it is sometimes late in the season
before symptoms appear. However, fruit
should be protected in the early stages of development.
Some cultivars are more resistant or tolerant of bitter rot
disease than others. Cultivar
susceptibility table available at http://www.caf.wvu.edu/kearneysville/tables/bitterrotsus.html
.
