Monday, July 27, 2009

Many thunderstorms...

We had a series of thunderstorms passed by the area. In terms of the duration of rain, all are short; however, it was wet afterwards because many of these rains happened after 5pm and the relative humidity stayed high until following morning.

On 25th, we had rain started from 9:40 pm and RH was high until 10:00 am next morning (>12 h of wetness). On 26th, the strong thunderstorms passed starting 5:00 pm, and RH was high until 8:00 am this morning (>15 h of wetness). Average temperature during these events were mid-60F, thus, infection of downy mildew, black rot, Phomopsis, and Botrytis could happen. But as I mentioned several times here, if you passed the critical period (4-5 weeks after bloom), your berries should be resistant to downy mildew and black rot infections.

Since we had such a strong wind with the thunderstorms, some of you may have experienced damages on berries (and/or even shoots and trunks). Hopefully they will dried out, but these wounds can be a course of entry for Botrytis and other rotting organisms. This (from bunch close to veraison) is the time for protection against Botrytis nonetheless, so, I would recommend including a Botrytis fungicide in your next application.

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