Horticulture
Roger Ort, Horticulture Educator, [email protected]
Brown Rot on Stone Fruits
Article from Cornell IPM program authored by T.J. Burr in consultation with J.D. Gilpatrick and M. Szkolnik.
INTRODUCTION
Brown rot (BR) can be extremely devastating to crops of cherries, peaches, plums, prunes, nectarines, and apricots. Under favorable conditions fruit set is reduced, twigs become cankered, and mature fruit may be completely rotted.
DISEASE CYCLE
Dormant
The BR fungi can overwinter in dried infected fruit called mummies (Fig. 1 ) or in infected twigs. In the winter BR mummies may remain hanging in the trees or be scattered on the orchard floor.
Spread
The fungus resumes growth in the spring, providing inoculum for blossom infections. Two types of spores may be produced: Ascospores are only produced on mummies which have fallen to the ground and are at least partially covered with soil. Conidia are produced in abundance on mummies and infected twigs and may be spread by wind and rain.
INFECTIONS
Blossom Infections
Infections during bloom cause blossoms to turn brown, wither, and drop. Under wet conditions, a powdery mass of conidia develop on infected blossoms. The blossoms may also become gummy in appearance. Blossom infections not only reduce fruit set, but increase the inoculum available for fruit infections.