Sooty blotch and flyspeck

Sooty blotch symptoms were observed on unprotected fruit at our AREC July 5, with symptoms probably appearing in lower areas of the farm late last week.

Last week we accumulated 26 hours of wetting from rain and dew, bringing us to a total of 288 hours, 38 hr past the 250-hour action threshold for development of sooty blotch and flyspeck on unprotected fruit. There were two extended wetting periods from rain in the last week: June 27 (11 hr at 67º with 0.05 in. rain) and July 4-5 (14 hr at 84-66º with only 0.01 in. rain at our AREC, but with lightning to the north of Winchester as a backdrop for the fireworks display).  The last two nights brought an additional accumulation of 16 wetting hours from dew.

Wetting hour accumulation from dew may be more likely in lower areas, while wetting from rain will probably affect higher and lower elevations in an orchard more uniformly. Typically, symptoms appear earlier in lower areas but it is prudent to begin scouting for symptoms in those areas most likely to show symptoms, whether because of low elevation or lack of recent fungicide protection.

Appearance of sooty blotch/flyspeck symptoms probably also indicate a lack of fungicide residue to effectively control rot development. Where present, fire blight-killed shoots should be viewed as a potential fruit rot inoculum source.