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Showing posts from July, 2015

Late season disease management considerations

Some of our early cultivars such as Alandale is changing it color.  It is just a matter of time to see other cultivar to enter phase of veraison.  Hopefully, we will keep seeing dry weather with little bit of rain here and there.... There are several diseases to be considered at this stage.  One of them is Botrytis.  The spray timing for Botrytis is at bloom, bunch closure, and veraison.  The pathogen seems to be active throughout the season, but Botrytis likes berries when they get mature and accumulate more sugar.   As usual, canopy management is the first line of defense against grape disease management and this is particularly true for Botrytis since it tends to develop after a long period (15-17 hours) of high humidity condition. Please keep in your mind that Botrytis is very well known for its capability to overcome fungicides.  Thus, a rotation of mode of action groups is very important aspect for Botrytis management.  The mode of action for a particular fungicide ca

You start to see black rot now, so, what should you do?

I have received several emails about black rot recently.  With the frequency of rains we observed so far, it is not surprising to see small amount of black rot even if you had a very good coverage of fungicide. Typically black rot starts off as brown discoloration on the berry, and associated with production of fruiting bodies which are often look like black dots (the size of ground black pepper?).  The picture above is not the best, but you see black dots on the one at the top of the picture.  Eventually, the infected berry will become hard and dry mummified berry with a lots of fruiting bodies, which you can see here and there in the picture. If you are seeing something like the picture above, chances are the infection happened at least two weeks ago when berries were susceptible to the infection by black rot pathogen (and so as by powdery mildew or downy mildew pathogen).  I can say that because it takes about 2 weeks after infection for black rot pathogen to cause symptoms