Another wet week in Winchester

Wet weather continued this past week at Winchester and other parts of Virginia. At our AREC in Winchester we recorded three more extended wetting events: May 31-June 1, with 15 hr of wetting at an average of 70° with 0.65 in. rain; June 1-2, with 11 hr of wetting at 68° with 1.47 in. rain; June 2-3, with 28 hr of wetting at an average of 65° with 1.95 in. rain. Again these heavy rains and extended wetting at relatively warm temperatures favored secondary apple scab, early summer disease activity on apples, peach scab, cherry leaf spot and brown rot on ripening cherries. 

For purposes of predicting the development of the sooty blotch and flyspeck (SBFS) fungal complex, we record accumulated wetting hours from rainfall or dew, starting 10 days after petal fall. This year we have chosen May 7 as our petal fall date for Winchester, so the start of wetting hour accumulation is from May 17. As of 6 PM June 3, accumulated wetting hours (ACW) toward the 250 wetting hour threshold for specific treatment against the SBFS fungal complex were: at 909 ft elevation, 207 hr; at 932 ft (the AREC NEWA station), 196 hr; and at the 983 ft elevation, 209 hr ACW. One of the purposes of following three weather stations is to compare wetting hour accumulation at different elevations. This year the wetting hours have been more a result of rainfall rather than dew, so wetting hour accumulation at different elevations is quite similar compared to previous years. 
The sooty blotch/flyspeck model on NEWA is now functioning and indicates accumulated wetting similar to the ACW shown at our NEWA station. To use this model, go to the drop-down menu for diseases and select the petal fall date to calculate the risk for that location.

Sooty blotch/flyspeck risk summary for Winchester AREC, using May 7 as petal fall date.

For central Virginia, we selected Apr 24 as the petal fall date for accumulation of wetting hours by weather stations at Tyro. As of June 3, a sensor placed at 1465 ft. elevation had accumulated only 127 wetting hours from May 4, while the one at 1165 ft. had accumulated 129 wetting hours, and the one placed at 941 ft elevation had accumulated 319 hr, and passed the 250-hr threshold for specific treatment for sooty blotch and flyspeck on May 29. Also east of the Blue Ridge, the NEWA station at Batesville has passed the 250-hr threshold with 255 ACW while the NEWA station at Gadino Cellars near Washington, VA has recorded 220 ACW with May 1 as the petal fall date.