Expert: Jim Hyland - 11/11/2006

Question
I have a problem with the fruit rotting on the tree before they are ripe. It starts out like a bruise, them spreads to the whole fruit. It's on all the fruit on the tree

Answer
BROWN ROT
Brown rot is one of the most common and serious diseases affecting peach fruits. It is caused by the fungus Monilinia fructicola, and can also infect flower blossoms and shoots. The disease begins at bloom. Infected flowers wilt and turn brown very quickly. Shoot infections (usually from flower infections) result in small (1 to 3 inches), gummy cankers, which provide the source of infection for fruit rot. Spores from infected flowers and cankers infect aborting fruit and healthy green fruit during long wetness periods. Infected, aborted fruit remain attached in the tree and provide an additional source of spores for more infections instead of dropping off in a normal fashion. Infections in apparently healthy green fruit remain inactive until the fruit begins to ripen.

Fruit rot starts with a small, round brown spot, which expands to eventually rot the entire fruit. Infected fruit turns into a mummy on the tree. The fungus survives the winter on fruit mummies (on the tree and on the ground) and twig cankers.

Prevention and Treatment: Collect and remove diseased fruit from the tree as it appears. In the fall remove all dried fruit mummies from the tree, since this is where the fungus survives the winter.

Fungicides are usually required if fruit ripening occurs during a period of warm, wet weather. It is important to begin spraying just before the fruit begins to ripen. Look for the first tinge of change in the yellow background color. Starting a spray program when rotten fruit is evident will result in poor disease control. Select a fungicide containing thiophanate methyl, captan, or azoxystrobin that is labeled for use on peaches. These fungicides are only effective if complete and thorough coverage of the tree(s) can be obtained. Always apply all pesticides according to directions on the label.