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Current Situation 6-29

Current Situation June 29, 2012

Thanks to Coyote Moon Vineyards for hosting the June 25th Field Day.

Vine Development:  Fruit should be past fruit set and (for tight clustered varieties such as marquette) toward ‘bunch closure’.  This is the time to consider additional canopy management options.

Leaf Removal. For VSP (vertical shoot position):  Early leaf removal in the cluster zone allows grapes (while still ‘hard and green’) to adjust to sunlight exposure and heat.  Some growers ‘leaf pull’ on one side (generally E side of North/South rows or N side of East/west rows) to promote air movement, while also protecting clusters on more ‘sun exposed’ sides of canopy against potential for sunburn.  Others pull on both sides.  Disease management is a big reason to do so (exposed clusters can get better spray coverage and dry off faster), but need is dependent upon vine vigor (small vines with slow shoot growth might not need it) and in general ‘reds’ benefit more than ‘whites’ – at least for ‘vegetal flavors’ associated with compounds in the skinds.  If you have vines on Top Wire or Umbrella, cluster-zone leaf removal is also possible, though a little more difficult because the ‘cluster zone’ is less defined.

Hedging or shoot-tipping:  Too early, in general.  For VSP, shoot tip removal often done when tips start bending over and starting to shade the fruiting zone.  Shoot tipping generally done at least 1 FT above top wire, leaving at least 3 ft of canopy, and leaves with 12-15 shoots below.  Hold off as long as possible, to prevent early lateral growth.  Shoot tipping is generally NOT effective in High Wire-trained vines.  Too easy to leave some shoots ‘too short’.  Skirting cuts at bottom are sometimes done when shoot tips get close to the ground.

Growing Degree-Days At Watertown: Growing degree-days are calculated by adding up the average of daily minimum and maximum temperatures and subtracting a ‘minimum’ threshold (50 degrees F in this case) below which vine growth does not occur.  Degree-days are more accurate than calendar date for predicting dates of bloom, veraison, and insect development.
Access GDD at Network for Weather Awareness, for more weather data and disease/insect forecasting models.

Current GDD at Watertown: June 28, 2012: 897 growing degree-days

Last year:  June 28, 2011: 717 growing degree-days

Date in 2011 at which 897 growing degree-days were accumulated:  July 8, 2011

Heat Unit accumulations are 9 days ahead of last year’s at this date.

Disease Management: Two to three weeks past bloom.  Clusters should be gradually getting more resistant to powdery mildew(PM), downy mildew (DM), and black rot (BR).  Most growers should be ready for the 2nd postbloom spray, still critical to keep your grapes clean and disease free.  In another two weeks, grapes will be highly resistant to new PM and DM infections, and Black Rot (BR) will be DONE for the season. 

AnthracnoseWe are seeing some early and recent infections in basal leaves and shoots that look like Anthracnose. We’ll try to confirm next week, but materials you are putting on for other diseases should control anthracnose as well. NY PA Pest management Guidelines don’t say much about anthracnose beyond this:  Early-season sprays of mancozeb, captan, or ziram targeted against Phomopsis also provide significant control of anthracnose, although this latter disease is not listed as a target on most labels. Some DMI fungicides, e.g., difenoconazole (Revus Top, Quadris Top, and Inspire Super), and myclobutanil (Rally) are labeled for anthracnose control as well.

Botryticides – Botryticides are probably not necessary at bunch closure on MN and Swenson hybrids, though some (eg. Marquette) might benefit from a single application at veraison. Save your money for then!

For specific information on materials and options, consult 2012 NY/PA Pest Management Guidelines or Wayne Wilcox’s annual Disease Management Guidelines – 2012 version posted online as of last week.

Insect Management: 

Grape Berry Moth (GBM)The grape berry moth model for watertown (pasted below) shows that the first generation should be starting to pupate, and the next generation won’t start laying eggs until sometime after July 6 or 7.  Should reach 810 (grape berrymoth GDD) past wild bloom sometime the following week.  The week of July 9-13 will be a good ‘spray window’ for 2nd generation GBM.    See previous post, Spray Timing for Grape Berry Moth for more information

Grape Phylloxera: Foliar phylloxera is out in several vineyards, but not yet ‘severe’ in any.   Examine shoot tips (unfolded leaves at the very tip) for new galls – and use their presence in significant numbers as a ‘signal’ on when to start insecticide treatments if needed.  If you don’t see any there is no point in applying an insecticide to control them. If you do see some?  Your call – many vines have the 12 -14 functional leaves they will need to ripen the crop, so injury out at the shoot tips may have less impact on the (already grown) vine than if the phylloxera showed up earlier.

Japanese Beetle:  Adults are out in several vineyards scouted this week.  Look for continued emergence over the next several weeks.  High populations can defoliate vineyards – and small backyard plantings are more prone to defoliation than larger commercial blocks. Young vines in grow tubes are also targets. One to two insecticide applications generally are enough to prevent economic injury.

Fertility:  Post-bloom is an excellent time to apply modest amounts of N to your vineyard.  Typical rate for wine grapes tends to be 30 lb actual N per acre or less.  Most soils with 2-3% organic matter can supply a lot of nitrogen as well.  Clay (assuming well-drained) to loamy soils will have and hold more N than will sandy soils.

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