Apple scab infection April 5-6.

The first general apple scab infection occurred in the Winchester area and east of the Blue Ridge from Rappahannock County and south to Lynchburg April 5-6. At our AREC in Winchester, scab ascospores were released, and we recorded 33 hr of wetting at 40-47° F with 0.5 in. of rainfall. Many apple cultivars such as Cripps Pink, Red Delicious, Gala (shown below), and Idared are in the tight cluster stage, and presented a sizable target of exposed green tissue for scab infection. Hopefully, there was opportunity to apply protective fungicides prior to this infection.

Gala apple buds at tight cluster stage at Winchester 4/6/19.

Cedar-apple rust gall spore horns (shown below)  are expanding and will probably discharge the basidiospores that infect apple with the next wetting period. By tight cluster stage powdery mildew spores are usually available for infection, which occurs on dry days above 53° F

Cedar-apple rust gall at Winchester 4/6/19

Where the bud stage is more advanced to pink or open blossoms, as in central Virginia and the Roanoke area and south, be alert for fire blight infection with warmer weather and shower or thunderstorm activity this week.