Looking Back at the 2015 Season

By: Michela Centinari and Bryan Hed

As harvest ends it is a good practice to review the season carefully, before getting busy with winter pruning and preparation for the next growing season. In the fall issue of Grape Press, the quarterly newsletter of the Virginia Vineyards Association edited by Bob and Chris Garsson, you can find some good examples of regional reports of the growing season written by wine grape growers across Virginia. It is interesting and informative to read growers stories and learn what they experienced in the vineyard and their perception of the current vintage. In addition, Drs. Tony Wolf and Mizuho Nita (Viticulture and Grape Pathology Extension Specialists, respectively, at Virginia Tech University) contributed to the quarterly publication. The final seasonal issue of Veraison to Harvest, electronic newsletter of the Cornell viticulture and enology Extension personnel, also provided a comprehensive overview of the grape and wine season in New York state, which was written by Chris Gerling [1].

With this short article we will provide a succinct overview of the season in Pennsylvania (PA) and we will share some of the data collected during the season for the research project NE-1020 “multi-state evaluation of wine grape cultivars and clones.”  Our observations are based on the data we collected and on feedback we received from some of the PA wine grape growers throughout the state. We welcome more PA wine grape growers to share their stories with us by adding a “comment” on this blog post.

Let’s start once again with the winter:

It was a cold winter in many regions of Pennsylvania, but in the Lake Erie region, it was extremely cold. At the Penn State Lake Erie Regional Grape Research and Extension Center (LERGREC) temperatures bottomed out at about -21 °F (-30 °C) on February 16, 2015. Unfortunately more cold events (-13, -14 and -15°F) were recorded over the following ten days.  As expected, extensive freeze injury was observed in the Erie region not only on Vitis vinifera cultivars, but also on inter-specific hybrids and native wine grape cultivars. Among the inter-specific hybrids Traminette, Cayuga White, Vidal and Valvin Muscat were some of cultivars that experienced extensive damage as reported by growers. Even Concord and Niagara sustained bud and trunk injuries [2]. Luke Haggerty and Kevin Martin reported that many Concord growers retained more buds than they typically do to compensate for observed winter bud injury. Large berries and more buds helped Concord growers to maintain crop levels near average [2].

After budbreak bud mortality data were collected on 10 hybrid cultivars established in the cultivar evaluation vineyard at the LERGREC (Figure 1). The vines were planted in 2008 as part of the NE-1020 project. Bud mortality was not evaluated in the V. vinifera cultivars due to the extensive level of winter injury (e.g., 100% bud mortality, and trunk injury in some of the cultivars). On a positive note, only 20% or lower bud mortality was recorded in Marquette, La Crescent, and MN1235, cold-hardy cultivars developed by the breeding program of the University of Minnesota (Figure 1). However, other hybrid cultivars, such as Vidal, Chambourcin, and NY 81.0315.17 (Cayuga White X Riesling) sustained 60% or higher bud mortality. Trunk injury was observed mostly in Noiret, NY81.0315.17 and Traminette.  Fifty, 17, and 8% of the Noiret, NY81.0315.17 and Traminette vines, respectively, collapsed during the summer.

The last two winters are a reminder of the importance of cultivar and site selection, and how crop diversification can help growers to maintain sustainable yields in cold climate regions.

Figure 1. Bud mortality assessed as percentage of dead buds over the total number of buds left with pruning. Data were collected at the Penn State Lake Erie Regional Grape Research and Extension Center.

Figure 1. Bud mortality assessed as percentage of dead buds over the total number of buds left with pruning. Data were collected at the Penn State Lake Erie Regional Grape Research and Extension Center.

The yield data collected at harvest from the cultivar evaluation trial established at LERGREC are shown in Figure 2. For the second consecutive year no crop was harvested from the V. vinifera cultivars. Within the hybrid cultivars, crop level varied from 1.8 tons/acre in Norton to 5.3 tons/acre in Chambourcin. The only cultivar that needed crop adjustment was Chancellor. The lower than average yield recorded in Marquette was attributed mostly to high levels of bird damage to the fruit. Due to its early fruit ripening, earlier than the nearby Concord that seems to work greatly as bird repellent, Marquette seems to be the preferred bird target.

Figure 2. Yield data (tons/acre) of the 15 winegrape cultivars in the NE-1020 cultivar evaluation trial established at the Penn State Lake Erie Regional Grape Research and Extension Center. Vines spacing is 6’ between vines and 9’ between rows.

Figure 2. Yield data (tons/acre) of the 15 winegrape cultivars in the NE-1020 cultivar evaluation trial established at the Penn State Lake Erie Regional Grape Research and Extension Center. Vines spacing is 6’ between vines and 9’ between rows.

Overall, we did not receive many inquiries from growers in the other regions of the state concerning cold injury as we did last season.  Although it was a cold winter, fewer temperature fluctuations were recorded in 2014-2015 as compared to the previous winter (2013-2014). The long stretch of cold temperatures may have provided a positive, reinforcing maintenance of the vines’ mid-winter cold hardiness.  Freeze damage was observed in Northeastern Pennsylvania in some of the V. vinifera cultivars, such as Pinot Grigio and Dornfelder. Growers attributed part of the damage (i.e., crown gall) to the previous winter (2013-2014) low temperatures. No above-average winter damage was observed in the southern part of the state.

Please note that these are general observations. The level of winter injury varies greatly with genotype, along with other factors. So these observations may not match what you experienced if, for instance, you grow tender V. vinifera cultivars (i.e., Tannat, Malbec, Syrah,  etc.) in a cool/cold climate region. For example, we harvested only 0.4 tons/ acre of Tannat and Malbec grapes at the Penn State Fruit Research and Extension Center in Biglerville (South Central PA). Those extremely low crop levels were due to bud and trunk injuries sustained by those cultivars in the last two winters.

The vast range of varietal winter hardiness expressed in the NE-1020 vineyards over the past two brutal winters has left us with many good lessons for grape growing in the Northeastern U.S., and will serve as a rich source of science based information toward more sustainable grape production in PA.

Weather during the growing season:

In Figures 3 and 4 we reported the cumulative precipitation and growing degree days (GDDs) recorded at the two Penn State research stations located in the South Central (Biglerville) and Northwest (North East) part of the state. We also included the 2013 and 2014 data, so you can compare this season’s heat accumulation (GDD) and precipitation’s pattern and amount with those of the two previous seasons.

Precipitation: June will be definitely remembered as the wettest month of the season in 2015 (Figure 3). For instance, in Biglerville (South Central, PA) around 10 inches of rain were recorded in June. High precipitation level during bloom may negatively affect the rate of fruit set (Fruit Set in Grapevines 101). Although some clusters with reduced fruit set level were observed, growers did not report reduced crop level. In the Northwest region of PA, 6 and 5 inches of rain were recorded in June and July, respectively.

Figure 3.  Monthly precipitation recorded in Biglerville (South central, PA) and North East (Northwest PA).

Figure 3. Monthly precipitation recorded in Biglerville (South central, PA) and North East (Northwest PA).

The best note of the summer was the warm and dry weather conditions observed in August and September in a majority of the state. In Biglerville the cumulative precipitation recorded from April to October was lower than that of the two previous seasons (Figure 3). However, in late September heavy rainstorms came through several areas of PA, raising concerns about bunch rot infections. Indeed some of the white cultivars and most of the reds were still hanging in Central and North PA. Despite the heavy rain, wine grape growers were mostly happy about the health of their grapes. Tony Wolf (Professor of Viticulture and Extension specialist at Virginia Tech University) offered some thoughtful advice on the dilemma: “Should I pick or wait out the rain?” which you can find on Grape Press, page 7 “How to Assess When Rain Threatens” [3].

Temperatures: High (or above-average) heat accumulation was recorded in many areas of PA in 2015. In Biglerville (South Central PA) GDD accumulation from April 1 to October 30 was 3500 in 2015, compared to 3089 in 2014 and 3270 in 2013 (Figure 4C). Specifically May, August and September 2015 were warmer than in 2013 and 2014 (Figure 4A). In the Northwest GDD accumulation in 2015 (2800) was similar to that of 2013 (2760), but higher than in 2014 (2590) (Figure 4 B). The greatest difference in heat accumulation among the three seasons was recorded in September (Figure 4D). Indeed both white and red wine grapes harvested at the LERGREC in 2015 reached a good level of ripeness.

Figure 4. Monthly growing degree-days (GDD) (A; B), and cumulative seasonal GDD (C; D) in Bigerville (South Central, PA) and North East (Northwest, PA).

Figure 4. Monthly growing degree-days (GDD) (A; B), and cumulative seasonal GDD (C; D) in Bigerville (South Central, PA) and North East (Northwest, PA).


Insects: Several growers reported problems with Japanese Beetles. Damage was worse than average, and in many cases required extra sprays (for more information please check: What’s Bugging your Vines?). In the Lake Erie region, the severe cold of the past two winters appears to have had no negative impact on populations of the grape berry moth, according to entomologist Jody Timer.  Her research has indicated that this insect continues to cause heavy damage in vineyards, particularly in rows bordering wooded areas, and has in some cases made inroads deeper into vineyards over the past two years. It’s imperative to remember that brutal winter temperatures do NOT necessarily reduce the threat of this grape insect pest; grape berry moth is well adapted to life in Pennsylvania and growers will need to continue to be vigilant with regard to timely insecticide applications, regardless of the winter cold.

Fungal disease:  Frequent and sometimes heavy rainfall in June and July was very conducive to the development of downy mildew and black rot on fruit (Figure 5). For example, at the Penn State lab at North East (LERGREC), we recorded 10.7 inches of rainfall from June 7 (immediately before bloom) to July 14 (about 3-4 weeks after bloom), that fell on 22 of those 38 days!!! This time period marks the peak period for fruit susceptibility to downy mildew and black rot for all wine grape varieties, and symptoms of these diseases could be found in many (most?) Lake Erie vineyards. In unsprayed research plots of Concord grape where black rot mummies were hung in the trellis (at LERGREC), almost two thirds of the crop was lost to black rot! So, conditions were nearly ideal for the development of this disease in the growing season of 2015.

However, very few serious problems were reported from commercial growers in the Lake Erie region and growers appeared to have, generally speaking, kept these diseases well under control during this challenging fruit loss period. After fruit became resistant, rainfall thinned out during August and September (even though the rainfall total for September was well above average, rainfall frequency was about half that recorded for the fruit susceptibility period). ‘Seasoned’ growers were watching their vineyards closely, and the potential threat of downy mildew leaf infections during ripening did not materialize to any great extent in most vineyards.

Figure 5. Concord clusters with black rot (A) and Chancellor clusters with downy mildew (B) symptoms.

Figure 5. Concord clusters with black rot (A) and Chancellor clusters with downy mildew (B) symptoms.

Everything we experience in one season is related, to some extent, to what happened in the previous season. For example, when planning your disease control strategy for 2016, keep in mind that inoculum levels for black rot and downy mildew are likely to be starting at higher levels next year, especially if you saw more disease in your vineyard (or your neighbor’s vineyard) than usual in 2015. This means that those first infection periods in spring could be more potent than usual, and if weather is consistently wet, fungicide application timing and frequency, and choice of material, will be more critical. For downy mildew control, be prepared to rotate chemistries to delay the onset of fungicide resistance, especially if you’re using the newer materials (Revus, Revus Top, Presidio, Zampro, any of the strobies, Ranman, Ridomil, and even the phosphorous acid formulations). Be aware that in southern PA there is downy mildew resistance to the strobies in some vineyards already, and that a wet year (and the resulting increased use of strobies to control downy) only serves to exacerbate the problem. On the up-side, we have lots of fungicide options for downy mildew control (as you can see), including the old standards like Captan, copper, Ziram, and any of the mancozeb products that carry a very low risk of resistance development. As for black rot, I know of no resistance problems associated (yet) with our long time ‘heavy hitter’ black rot materials like the sterol inhibitor containing fungicides (Rally, Elite, Mettle, Revus Top, Inspire Super, etc), the strobies, and Captan/Ziram/mancozeb formulations.

So, record your observations of your vineyards from the 2015 season: These are important questions growers should be asking themselves and recording now in order to understand what worked and what didn’t and prepare for the 2016 growing season:

  • How well did your weed and canopy management strategies work this season?
  • How was the overall vine balance?
  • Were there any obvious vine nutrition issues?
  • How well did your disease and pest control program work? How much disease did you observe on your fruit, on your leaves?
  • Any other important observations or notes.

Final notes on the 2015 harvest: Harvest weather was, for the most part, pleasant. Overall, growers are very happy with the quality of the fruit although in some cases crop level was lower than average due to winter injury. The warm and mostly dry conditions recorded in August and September helped the grapes to reach full ripeness within their specific region with good development of flavor and aromas.

As a general reminder, we will taste a series of the 2015 wines produced from various research trials conducted at Penn State University at the 2016 PA Wine Marketing and Research Board Symposium.  We may also feature a few of these wines at various Extension events across the state.  You can review some of the winemaking experiments on Denise’s previous blog post: Reflections: Winemaking at Penn State, and we look forward to sharing these wines with many of you in the months ahead.



[1] Gerling C. (2015) The 2015 Grape & Wine Season: Redefining Normal. Veraison to Harvest issue # 8, pp1-4. Cornell University

[2] Haggerty L., Martin K. (2015) Concord Crop Average Despite Winter Injury; Niagara Crop Reduced. Veraison to Harvest issue # 8, pp5-6. Cornell University.

[3] Wolf T. (2015) How to Assess When Rain Threatens  Grape Press, The quarterly Newsletter of the Virginia Vineyards Association. Vol. 31 No. 3.


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2 responses to “Looking Back at the 2015 Season”

  1. Tim Martinson says :

    Nice article and review, Michela! Enjoyed it.

  2. David Spector says :

    Thank you for the PA harvest review!



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