Rapid bud development; powdery mildew, scab and rust activity

The past two days we have seen rapid apple bud development in the Winchester area. Friday morning, Apr. 13, we saw heavy powdery mildew sporulation on Idared buds at tight cluster stage. Powdery mildew infects on dry days at temperatures above 53°F, so there were several infection days this week.

Powdery mildew on Idared, Friday morning, Apr. 13, 2018.

By Friday evening, many buds were showing color at the pre-pink stage. With warm temperatures over the weekend, expect open bloom by early next week.

Pre-pink stage of Idared buds Friday evening, Apr. 13, 2018

There is a forecast for thunderstorms and rain with temperatures in the 50s Sunday and into Monday, Apr 15-16, and that would bring a scab infection period as well as our first cedar-apple and quince rust infection period in the Winchester area. 

Cedar-apple rust gall with developing spore horns Apr. 11, 2018

 Generally, the forecast is similar for the areas south to beyond Roanoke and east of the Blue Ridge, with a trend toward earlier and a shorter wetting period, but with warmer temperatures to the south. In short, scab, the rusts, and powdery mildew are now active, and there is a potential for fire blight infection in more advanced areas with open bloom.

These conditions also favor cherry leaf spot and brown rot infection with cherry trees now in bloom, and brown rot and scab on peaches in bloom or petal fall stage.