Early season apple disease outlook, March 27.

Overnight wetting March 26-27 at our AREC, Winchester, ranged from 11 to 15 hr at 46-55 degrees and resulted in a possible apple scab infection period at the longer wetting interval. There was a rather wide range in bud stages during this wetting event, from tight cluster in the more advanced Granny Smith and Red Delicious to only 1/4-inch green tip in Golden Delicious, York, and Rome Beauty. 

Tight cluster stage on Granny Smith apple, Winchester, VA, March 27, 2017.

Mildew conidiospores were observed on Idared apple at early tight cluster stage (below) and conditions Monday afternoon, March 27 were favorable for infection. 

Mildew-infected Idared bud (center), compared to healthy fruit buds, upper left.

This extended wetting also brought maturity to the cedar apple rust teliospores on overwintering galls (below), as well as to quince rust spores in cankers on the eastern red cedar. It is not too likely that spores were available in time for rust infection to occur in the Winchester area during this wetting event, but consider additional wetting events this week as probable rust infection periods wherever rusts are an annual problem.

Cedar apple rust gall with mature telial horns.

A check of weather stations east of the Blue Ridge Mountains in Rappahannock County and central Virginia indicates similar length of wetting, and some at warmer temperatures. Generally, expect similar or more advanced stages of bud development and mature disease inoculum in these areas to the south and east.