Sunday, July 24, 2011

Last week we accumulated an additional 16 wetting hours which brings us to a total of 360 hours, 110 hr past the 250-hour action threshold for development of sooty blotch and flyspeck on unprotected fruit. Total rainfall for the week was 0.22 inches.

Below is a picture of brown rot on Klondike White peach, taken last week. The dieback of shoots indicates high susceptibility of this cultivar, similar to what we have occasionally seen on Redgold nectarine. Klondike White is also very susceptible to bacterial spot. In this case the brown rot infection was probably initiated by hail injury followed by cracking of the fruit with increased growth. At our AREC, brown rot pressure has not been unusually high yet this year but this does not bode well for this local situation, and removal of early infected fruit might be beneficial to prevent spread to later ripening cultivars.

Sunday, July 10, 2011

Summer disease pressures

Last week we accumulated an additional 58 wetting hours to brinus to a total of 344 hours, 94 hr past the 250-hour action threshold for development of sooty blotch and flyspeck on unprotected fruit. There was an extended wetting periods with rain July 8-9 (8 hr at 69º). Total rainfall for the week at our AREC was 0.42 inches.

Friday, July 8, 2011

Summer diseases

Extended wetting last night, July 7-8:  8 hr at 70º with 0.15 in. rain. Consider wetting periods 70º and above to be more favorable for rot diseases, especially bitter rot.

Thursday, July 7, 2011

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.