Saturday, July 8, 2017

Summer disease update July 8

After a relatively dry month of June in the Winchester area, summer disease activity has increased this past weekThere was an extended wetting event at our AREC that will contribute to summer disease pressureJul 4-7, wet 38 hr at 70° with 0.88 in. of rain. Some areas east of Winchester and in central Virginia reported more than 2 inches of rain. We are now seeing early sooty blotch symptoms and bitter rot at our AREC in Winchester.

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 July 7, accumulated wetting hours (ACW) toward the 250 wetting hour threshold for specific treatment against the SBFS fungal complex were: at 909 ft elevation, 380 hr (with the 250-hr threshold reached Jun 7; sooty blotch observed Jul 7); at 932 ft (the AREC NEWA station), 283 hr; and at the 983 ft elevation, 230 hr ACW.  Reaching of the 250 hr threshold predicts that the fungi causing SBFS symptoms are now present on unprotected fruit and that is confirmed by symptoms at our AREC.

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. As of July 7, a sensor placed at 1465 ft. elevation had accumulated only 96 wetting hours from Apr 30, while the one placed at 941 ft elevation had accumulated 410 hr, with the 250-hr threshold reached on June 12).

The NEWA station at Gadino Cellars (elev. 665 ft, in Washington, VA) passed the threshold of 250 ACW June 16, and has now recorded 337 wetting hours since May 1. A NEWA station at Fishersville also passed the 250-hr threshold June 16 and now has 319 ACW. Three Albemarle County NEWA stations have also passed the 250-hr threshold, listed with CWH as of July 7 and date the was threshold reached : Batesville (273 CWH, July 2); Crozet (272 CWH, July 5); Carter Mt. (252 CWH, July 6).

Glomerella leaf spot activity has been reported from central Virginia.