Cherry rots

Sweet cherries are now ripe, or nearly so. The fruit on the right looks good; the one on the left not so good. Rains such as we had yesterday lead to cracking of ripening fruit and increased susceptibility to rots. The fruit above left is a good example of two common rot fungi- the tan colored sporulation on the right side, characteristic of brown rot and the dark green sporulation of Alternaria rot in the center. The grayish area to the left side is probably a mixture of both of these fungi growing together. A pre-harvest application of a sterol-inhibiting fungicide such as fenbuconazole (Indar) should give excellent control of brown rot but will be weak on Alternaria unless it is supplemented with something with a broader spectrum of activity such as captan. Pristine (a mixture of pyraclostrobin and boscalid) should be excellent for control of both Alternaria and brown rot.

Brown rot pressure is often influenced by warm, rainy weather during the period immediately before harvest. Because cherries are the first stone fruit to ripen, a brown rot problem there may signal a potential inoculum source and problem to follow on adjacent stone fruits which ripen later, including peaches, plums, nectarines and apricots.