Scab and rust infection period and start of sooty blotch and flyspeck development

An apple scab and cedar-apple rust infection period occurred last night and today, with 14 hr wetting at 63° F, and 0.4 inch rainfall.


For purposes of predicting the development of the sooty blotch and flyspeck (SBFS) fungal complex, we record accumulated wetting hours, starting 10 days after petal fall. This year’s petal fall date was April 28 so the start of wetting hour accumulation will be from May 8. This is nine days later than last year’s start date. Today's infection period represents 14 wetting hours accumulated toward the 250 wetting hour threshold for specific treatment against the SBFS fungal complex.