Wednesday, August 17, 2016

Bitter rot weather and comparative wetting hours

Summer disease pressures remain high, with continued accumulation of wetting hours and a recent extended wetting period at warm temperatures.  The extended wetting event was Aug 15-16: 17 hr at 78-70° with 0.24 in. rain.  This favored bitter rot, initiated by rain-splashing of conidia, followed by extended wetting at these warm temperatures.

As of Monday, Aug 15, wetting hour accumulations (ACW) at Winchester: at 909 ft elevation, 770 hr (more than 3 times the 250-hr threshold which was reached June 5); at 952 ft elevation, 594 hr; and at the 983 ft elevation, 450 hr ACW. 

Accumulated wetting hours in central Virginia are quite similar to Winchester this year: At Tyro, VA  as of Aug 15, a sensor placed at the 941 ft elevation had accumulated 777 hr (with the 250-hr threshold reached June 6); the one at 1165 ft. elevation had accumulated 436 wetting hours, and the one 1465 ft. elevation had accumulated 484.