Scab and rust infection period; tracking sooty blotch and flyspeck development

We recorded another apple scab and cedar-apple rust infection period at our AREC May 26-27: 12 hours wetting with 0.4 inches of rain at 72-63°. Most cedar rust galls now seem to be depleted of inoculum.

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 4 as our petal fall start date for Winchester, so the start of wetting hour accumulation is from May 14. As of Friday, May 30, we had accumulated 74 wetting hours toward the 250 wetting hour threshold for specific treatment against the SBFS fungal complex. 

A caution to those further south and east of the Blue Ridge: Your petal fall date may have been a week or more ahead of ours and we have arbitrarily selected Apr 27 as the start date for accumulation of wetting hours by weather stations at Tyro, VA. One of the purposes of having three weather stations at this location was to compare wetting hour accumulation at different elevations. As of May 29, a sensor placed at 1465 ft. elevation had accumulated 50 wetting hours from Apr 27, the one at 1165 ft. elevation had accumulated 90 wetting hours from May 11, while one placed at 941 ft elevation had already accumulated 204 hr!