Heavy scab and rust infection period; fire blight risk moderate to low

Scab and rusts: Extended wetting began at our AREC, Winchester, at 3 PM Monday Apr 28 and will likely extend through the night to Thursday morning, May 1, a total of more than 60 hours. Temperatures for this heavy scab infection period ranged from 59 F to 46 and back up to the mid-50s. Because the beginning and ending temperatures also favored quince rust and cedar-apple rust infection at peak susceptibility of blossoms to quince rust, follow-up fungicide mixtures should be selected that include after-infection rust control. 

This extended wetting also favors peach scab infection.

Central Virginia has had similar conditions this week, with almost continuous wetting, starting at 2 PM Apr 28 and about 2.5 inches of rain recorded at Tyro.

Fire blight outlook: With cooler than predicted temperatures, the fire blight risk through this weekend remains moderate to low. But the 10-day forecast shows warmer temperatures toward the middle of next week, and with an extended bloom period, this will bring higher risk of fire blight to later bloom. The fire blight outlook will be updated May 3.

Powdery mildew: The 10-day forecast shows dry weather, favorable for mildew infection through the period. Earlier we had 13 dry weather mildew infection days since Apr 9, so secondary mildew pressure on susceptible cultivars will be heavy in the coming weeks, and tank mixes of fungicides should also include a material for mildew suppression.