Wine Grape Recommendations as Harvest Approaches

In the case of downy mildew (DM), I had conversations with Andrew Landers and Han Peterson, both from Cornell University, recently and they highlighted a variety of fungicides that are available for DM control including Revus, Presidio and Ranman, that can be tank-mixed with a phosphorus acid product to give good protection. The NY-PA Pest Management Guidelines end with mid-summer recommendations but there is so much season still to go, so please review Alice Wise’s Late Season Disease Management suggestions (especially for vinifera varieties) from Cornell Cooperative Extension on Long Island.  Hopefully the vines have been given one final hedge pass before nets were applied, which tends to bunch and compress leaves,improving the environment for the mildews.  The wet conditions cause two main problems for growers – the vines continue to produce new laterals and these are very susceptible, especially new growth on top to DM.  On a 6 to 7 ft canopy, it can be very difficult to maintain good spray coverage to the leaves, so calibrate your sprayer to emphasize the best possible coverage of the tops of canopies.  Fruit zones also need excellent coverage so sprayers should be calibrated to wash clusters thoroughly (see Andrew Landers article).  Tower sprayers are favored for late season spray applications.

I would say that everywhere in the Eastern US that bird control measures should be fully operational now.  If damp conditions persist, any damage birds cause will exacerbate fruit rots.  With Hans we talked a lot about birds and there are widely differing opinions about all the various tactics and equipment that are available other than nets, and even those need spacers to provide adequate protection.  PermaNet will provide some yellow jacket control, which can be a big benefit if they become a pest.

We do not know whether brown marmorated stink bug (BMSB) and/or spotted wing drosophila (SWD) will be a problem this year.  Suffice to say that both are around and, in a conversation with Kathy Demchak, Penn State small fruits extension specialist, have been a major nuisance in berry crops this year, especially raspberries and blackberries.  Note that SWD behaves like grape berry moth (GBM) and lays eggs in the fruit, so it can cause direct damage to fruit. As for BMSB, I have yet to hear a report of direct damage to grape clusters.  As they mainly get into the wine processing stream and can taint wines, they should be monitored as harvest approaches.

Of course, we cannot forget about GBM, which due to the warm weather (degree day accumulation) will almost certainly add an additional flight or two to the season, the latter arriving right at harvest-time. With each successive flight, the emergence peak flattens making it more difficult to monitor and treat later flights.  At this time of the year, Andy Muza, Penn State horticulture educator in Erie, suggests that high value grapes be protected on a 7 to 10 day schedule in hot spots around the vineyard.  His threshold for treatment is 15% of clusters affected by GBM, but he feels this may be low.  In Erie, they are anticipating a fourth generation in early September. There is a linger stench of sour rot from the Susquehanna basin and east, a reminder that the fruit zone is oh-so vulnerable at this time of year.  Anything you can do to open it up for air, sun and spray, loosen clusters and maintain cluster isolation will help to reduce the threat of fruit rots.  So we have arrived at crunch time, where the wine quality rubber meets the road (and any other clichés you can think of).  Make your last crop adjustment passes now, particularly on the less ripe red varieties, focusing on green to pink berries and clusters that are touching/bunching or growing into the wire or leaves on short shoots.  At Blair Vineyard, Rich has taken Bryan Hed’s (Penn State grape research pathologist in Erie) work on early leaf removal to heart – over three varieties (Pinot Gris, Pinot Noir and Chardonnay) he removed the leaf opposite clusters on every other row of a significant portion of his vineyard.  He reports seeing the best cluster loosening effect on the Pinot Noir and will monitor fruit rots and make wines in separate lots to check juice/wine quality differences.  This is the kind of in-house viticulture research that makes me smile and, in the end, makes better wines.

The season is divided into three parts – budbreak to bloom, fruit set to veraison and post-veraison, and as a grower I always felt that this was the most important third. It would be so nice to just sit back and enjoy the fruits of the hard work of the past four months but with the rain and all the threats to the crop, it’s a maddening time of year.  For more information, please visit the Pennsylvania Wine Grape website.