Spring and summer disease update

In the past five days we have had two more apple scab and cedar-apple rust infection periods at our AREC June 4-5: 23 hours wetting at 73-60°, and June 8-9 at 74-66°. Note that cedar rust galls are still actively producing spores.

In addition to developing activity by the usual summer diseases, with the recent warmer wetting periods, be alert for possible early indications of Alternaria leaf blotch on Red Delicious and Glomerella leaf spot on Gala, Golden Delicious and Cripps Pink (Pink Lady) apples. This is also a critical time for protection against Brooks fruit spot.

For purposes of predicting development of the sooty blotch and flyspeck (SBFS) fungal complex, we record accumulated wetting hours (CWH) from rainfall or dew, starting 10 days after petal fall. As of this morning, June 8, we had accumulated 80 wetting hours toward the 250-hour threshold for specific treatment against the SBFS fungal complex. 

At Tyro, VA we selected May 11 as the start date for accumulation of wetting hours by weather stations at Tyro, VA. As of June 5, a sensor placed in an apple tree at 1165 ft. elevation had accumulated 62 wetting hours from May 11, while one placed at 941 ft elevation had accumulated 128 hr. It is interesting that the station at the highest elevation (1465 ft) registered more wetting hours than the intermediate one, 81 CWH.