Early season disease update; sooty blotch and flyspeck wetting hour accumulation

A scab and cedar-apple rust infection period occurred May 13-15 (26 hours wet at 61°, 0.4 in. rain). There was still cedar rust inoculum available for foliar infection but galls are now mostly depleted at our AREC. If you have a recurrent cedar-apple rust problem in your orchard, check the cedar galls in your area for remaining inoculum potential with wetting today.

Through May 20 there have been 38 days favorable for powdery mildew infection since spores were first available Mar 19. Secondary scab and mildew infection are heavy on non-treated trees.

Some shoot blight was reported last week, resulting from scattered hail in some areas of Frederick County May 2. These "trauma blight" symptoms appeared near the time predicted by Maryblyt for May 15. Numerous early reports of fire blight have come from areas east of the Blue Ridge and the Roanoke area south. These likely occurred as blossom infection where bloom was open earlier than in the Winchester area.

For purposes of predicting the development of the sooty blotch and flyspeck (SBFS) fungal complex, we record accumulated wetting hours, starting 10 days after petal fall. With the extended bloom period this year, the petal fall date was somewhat subjective, but we have settled on Apr 8 for petal fall. So the start of wetting hour accumulation will be from Apr 18, 20 days ahead of last year and 11 days ahead of 2010. Through this morning we have accumulated 189 wetting hours toward the 250 wetting hour threshold for specific treatment against the SBFS fungal complex.