Stone Fruit Disease - Rusty Spot
Rusty spot is recognized only on the fruit. The earliest symptoms on young green fruit appear as small, orange-tan spots. K. Peter.
Symptoms
Young peach and nectarine fruit become infected and exhibit white non-powdery lesions that are small, spherical, and later turn orange-tan in color. Leaves and stems are not affected.
Disease Cycle
The disease cycle is unknown; however, spores are available starting at petal fall and continue for approximately one month after shuck split.
Disease management
Highly susceptible cultivars include Biscoe, Bounty, Jefferson, Redskin, Autumnglo, Jerseyqueen, and Rio-Oso-Gem. John Boy, Loring, and Messina are cultivars considered moderately susceptible. Redhaven has low susceptibility. Routine fungicides aimed at powdery mildew control this disease. Effective fungicides include sulfur, and those in the FRAC Groups 3, 7, and 11 fungicides. Practice fungicide resistance management by rotating modes of action. The standard rusty spot program consists of four sprays: petal fall, shuck split, first cover, and second cover. Fruit develops resistance as the pit hardens, which typically is around the second cover through the third cover. Controlling mildew in adjacent apple orchards reduces rusty spot incidence in peach orchards.Â
