These spores (ascospores) are carried by wind to the open or unopened blossoms and young shoots. Note the tufts of fungus on the surface of rotted fruit. At this stage, the slightest disturbance of air movement will cause an apothecium to forcibly discharge millions of spores.įigure 3. The inner surface of each bowl is lined with thousands of spore-containing sacs (asci). As an apothecium matures, it becomes thicker and the cup opens to a bowl-like disc 1/8 to ½ inch in diameter across the top. At about blossom time, a mummified fruit that has fallen on the ground produces up to 20 or more small, tan, cup-like structures on slender stalks that are called apothecia. Both sources may produce spores that can infect blossoms and young shoots. The brown rot fungus survives the winter in mummified fruits (either on the ground or still on the tree) and in twig and branch cankers produced the preceding year. Causal Organismīrown rot is caused by the fungus Monilinia fructicola. A canker may form encircling the twig, causing death of the twig beyond the canker (twig blight). Succulent shoots are sometimes infected by direct penetration near their tip. The fungus may then invade and cause diseased areas (cankers) on the twigs below. The fungus may move from diseased blossoms or fruit into the spurs. Fruit infection may spread rapidly, especially if environmental conditions are favorable and fruits are touching one another. The entire fruit rots rapidly, then dries and shrinks into a wrinkled “mummy.” Rotted fruit and mummies may remain on the tree or fall to the ground. Fruit infections appear as soft brown spots which rapidly expand and produce a tan powdery mass of conidia. As fruits mature they become more susceptible to attack, even in the absence of wounds. Young fruits are normally resistant, but may become infected through wounds. The diseased flowers usually remain attached into the summer. Diseased flowers wilt, turn brown, and may become covered with masses of brownish-gray spores. Symptoms first appear in the spring as the blossoms open. The symptoms of brown rot are very similar on all stone fruit. Brown rot producing spores on the surface of an infected peach fruit. Note that the fungus has invaded the twig causing a twig blight as well.įigure 2.
Peaches not kept in cool storage may be rotted in two to three days by the fungus.įigure 1. Under favorable conditions for disease development, the entire crop can be completely rotted on the tree.
The disease is most important on fruits just before ripening, during and after harvest. The brown rot fungus may attack blossoms, fruit, spurs (flower and fruit bearing twigs), and small branches. Brown rot is a common and destructive disease of peach and other stone fruits (plum, nectarine, apricot, and cherry).