Continued heavy summer disease pressures

This past week marked a return to the heavy disease pressures noted from mid-May through early July. At our AREC in Winchester we recorded three extended wetting events: July 24, with 14 hr of wetting at 72° with 0.67 in. rain; July 24-25, with 12 hr of wetting at 70° with 0.44 in. rain and July 25-26, with 17 hr of wetting at 69° with 1.17 in. rain. Rainfall volumes varied considerably over the region, but with similar temperatures and length of wetting. These wetting events favored all summer diseases and rot activity on apples, and brown rot on ripening peaches and other stone fruits. 

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 (from May 17 at Winchester). As of 8 AM July 27, AREC weather stations at three elevations had greatly exceeded the 250 wetting hour threshold for specific treatment against the SBFS fungal complex. These totals were: at 909 ft elevation, 678 hr; at 932 ft (the AREC NEWA station), 459 hr; and at the 983 ft elevation, 528 hr accumulated wetting hours (ACW). Sooty blotch and flyspeck are common on unprotected apple fruit in all areas of the AREC, including the higher elevations. Because early wetting hours this year were more a result of rainfall rather than wetting from dew, expect unusual SBFS pressures in higher elevation orchards, not typically threatened by these diseases. 

For central Virginia, we selected Apr 24 as the petal fall date for accumulation of wetting hours by weather stations at Tyro. As of July 5, a sensor placed at 1165 ft. has accumulated 322 wetting hours while one placed at 941 ft elevation has accumulated 733 hr. 

We see continued bitter rot activity at our AREC and there have been several reports of bitter rot and Glomerella leaf spot, as well as SBFS, from central Virginia orchards. 

Sooty blotch /flyspeck, bitter rot and Glomerella leaf spot activity

In the last week at  our AREC in Winchester we recorded two more extended wetting events: June 27-28, with 9 hr of wetting at 70° with 0.06 in. rain; July 4-5, with 15 hr of wetting at 70° with 1.27 in. rain. These wetting events favored early summer disease and rot activity on apples, peach scab, and cherry leaf spot and brown rot on ripening stone fruits. 

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 (from May 17 at Winchester). As of 6 AM July 5, AREC weather stations at three elevations had accumulated more than 110 hr beyond the 250 wetting hour threshold for specific treatment against the SBFS fungal complex. These totals were: at 909 ft elevation, 485 hr; at 932 ft (the AREC NEWA station), 369 hr; and at the 983 ft elevation, 391 hr accumulated wetting hours (ACW). Last week we observed sooty blotch and flyspeck unprotected apple fruit in all areas of the AREC, including the highest elevation. Because early wetting hours this year were more a result of rainfall rather than wetting from dew, expect unusual SBFS pressures in higher elevation orchards, not typically threatened by these diseases. 

Early presence of sooty blotch and flyspeck on Ginger Gold apple in an area not usually affected by these diseases.

For central Virginia, we selected Apr 24 as the petal fall date for accumulation of wetting hours by weather stations at Tyro. As of July 5, a sensor placed at 1465 ft. elevation has now reached 393 wetting hours, while the one at 1165 ft. had accumulated 266 wetting hours, and the one placed at 941 ft elevation has accumulated 466 hr. Also east of the Blue Ridge, the NEWA station at Batesville has passed the 250-hr threshold with 425 ACW while the NEWA station at Gadino Cellars near Washington, VA has recorded 338 ACW using May 1 as the petal fall date. 

We have seen early bitter rot activity at our AREC (pictured below), and there have been several reports of bitter rot and Glomerella leaf spot, as well as SBFS, from central Virginia orchards. 

Early bitter rot infection on unprotected Granny Smith fruit, Virginia Tech AREC, Winchester.