Friday, June 23, 2017

Extended wetting event June 16-17, and accumulated wetting hours

The past 10 days there was one extended wetting at our AREC event that could contribute to summer disease pressures in the coming weeks: Jun 16-17, wet 20 hr at 70° with 0.62 in. 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 our petal fall date at Winchester was Apr 24, so the start of wetting hour accumulation was from May 4. As of Friday morning June 23, accumulated wetting hours (ACW) toward the 250 wetting hour threshold for specific treatment against the SBFS fungal complex were: at 909 ft elevation, 316 hr (with the 250-hr threshold reached Jun 7); at 932 ft (the AREC NEWA station), 226 hr; and at the 983 ft elevation, 183 hr ACW.  Reaching of the 250 hr threshold predicts that the fungi causing SBFS symptoms are now present on unprotected fruit and that symptoms on such fruit should appear in about 2 weeks.

For Nelson County in central Virginia, the petal fall date was Apr 20, and accumulation of wetting hours from Apr 30 is recorded by weather stations at different elevations at Tyro. Wetting hour accumulation in central Virginia was slow last week. As of June 23, a sensor placed at 1465 ft. elevation had accumulated only 90 wetting hours from Apr 30, while the one placed at 941 ft elevation had accumulated 341 hr- just over the 250-hr threshold).

The NEWA station at Gadino Cellars (elev. 665 ft, in Washington, VA) passed the threshold of 250 ACW last week, and has now recorded 286 wetting hours since May 1. A NEWA station at Fishersville has also passed the 250-hr threshold with 294 ACW.