Disease update- apple scab, mildew and wetting hours

We recorded an apple scab and cedar-apple rust infection period at our AREC June 2-3: 18 hours wetting with 1.1 inches of rain at 74-62°. (Yes, the cedar-apple rust galls are still active).

As of today, June 3, we have had 38 dry weather apple powdery mildew days since spores were first released Apr 11. Today I see a flush of terminal shoot growth that is very susceptible to mildew under this year's heavy infection conditions. On susceptible cultivars, maintain mildew suppression until shoot growth ceases to prevent bud infection, which leads to overwintering and a recurrent problem next year.

For purposes of predicting development of the sooty blotch and flyspeck (SBFS) fungal complex, we record accumulated wetting hours, starting 10 days after petal fall. This year the start of wetting hour accumulation is from May 13. As of this morning, June 3, we had accumulated 86 wetting hours toward the 250 wetting hour threshold for specific treatment against the SBFS fungal complex. Last year we reached the 250-hr threshold May 25. Some areas east of the Blue Ridge may now be approaching the 200-hr mark for wetting hour accumulation.