We had five extended wetting events the last week of May, and temperatures of several of these ranged into the high 60s and 70s, favorable for summer diseases as well as secondary scab infection: May 24, 9 hr wet at 57-50° with 0.04 in. of rain, May 26-27, 12 hr wet at 70-64° with 0.08 in. of rain, May 27-28, 15 hr wet at 73-63° with 0.2 in. of rain, May 29-30, 15 hr wet at 73-61° with 0.04 in. of rain and May 30-31, 12 hr wet at 72-60° with 0.04 in. of rain.
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 again chosen May 4 as our petal fall date for Winchester, and the start of wetting hour accumulation is from May 14. As of Monday, May 30, accumulated wetting hours (ACW) toward the 250 wetting hour threshold for specific treatment against the SBFS fungal complex were: at 909 ft elevation, 172 hr; at 952 ft elevation, 128 hr; and at the 983 ft elevation, 116 hr ACW.
At Tyro, VA we started wetting hour accumulation May 4, and as of May 30, a sensor placed at 1465 ft. elevation had accumulated 153 wetting hours, the one at 1165 ft. elevation had accumulated 124 wetting hours, and the one placed at 941 ft elevation had accumulated 175 hr.
Mildew-susceptible cultivars are showing considerable secondary infection, a result of the earlier 28 dry weather mildew infection days through May.
