debor039

It was very nice to see you all at the beginner's workshop held today at AHS AREC.  Here are: 1) my presentation (Google drive will open) and 2) disease management guide for non-bearing vines. I hope to see you guys in the future!!

With this week's precipitations that we (including many meteorologists) did not anticipated last week, some of you have contacted me to seek options for the late season application, especially for red-fruited cultivars that need to stay on the vine for a few more weeks.  Here's a table for late season fungicide options, with materials that has 7 or fewer PHI (it will open Google Drive's spread sheet).   The efficacy information is based on our PMG, which can be downloaded from the right hand side of the blog.  (It says 2014, but the file is updated to 2015).  Hopefully we will see the sun soon! Good luck with the rest of the season.  It's almost done!!!

I have heard from several growers that they are seeing downy mildew despite the fact that they have not seen much precipitations.  It could happen because of the humidity, especially during the night.  Warm, humid, and dark condition (just like we have been having during the last few weeks) promotes downy mildew pathogen to produce spores. In addition to these conditions, we had lines of rain storms passed in our areas in the past two days. The length of wetness due to these storms were probably long enough for downy mildew pathogen to cause infection. So, just a reminder.  If you have seen downy mildew, and you have not applied any protective material (captan, Revus, even phosphorous acid products) in the past 10 days or so, you may want to consider a rescue application of a phosphorous acid product to reduce the risk of infection that might have happened in the past two days of rains.  (Note: If you are considering harvest in a few days, I would wait until harvest....

Dr. Wayne Wilcox at Cornell University wrote an article on sour rot management on " Finger Lakes Vineyard Notes ". (The link will open a pdf file)  Please check it out.  Results from his research group is showing that 1) good canopy management matters, and 2) management of insect (fruit flies) seems to have a big impact on the development of sour rot.  Since their regions do not have issues with spotted wing Drosophila (aka SWD), even regular fruit flies, which cannot damage grape skin, can still aid transmission of sour rot pathogens.  I know some of us in VA have been managing SDW in the past few years. If you have managed SWD and have seen lower level of sour rot, please let me know.

Now the season is wrapping up, and one of questions I get often is “when to spray what to protect your crop at the last stretch”.    Unfortunately (as with everything else), my answer to the question is “it depends.”   But it won’t help anybody, so, let’s go over several potential scenarios and see one of them makes sense to you. Case 1: you are expecting harvest in 2-3 weeks I think many of Chardonnay and other early white cultivars are about to be harvested.   Luckily, around Winchester area, we have had a good stretch of relatively dry weather.   We had rain showers came in several times, but only two of them, one at 8/4 and another one on 8/20 were long enough to initiate major late season diseases, such as Botrytis.   We have three Botrytis trials, but we have not seen evidence of Botrytis outbreak.   Moreover, at Winchester area, a forecast of next rain is on next Tuesday, and it looks like a case of another thunderstorm. ...

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 acti...

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 c...