Looking back at the 2016 season

By Michela Centinari, Bryan Hed, and Kathy Kelley

The 2016 growing season was a rewarding one for many Pennsylvania (PA) wine grape growers. But before we move on with plans for next year, let’s review this past season using some interesting data we gathered from PA grape growers. In November 2016, we sent out a 5-min Internet survey developed by our team and housed on SurveyMonkey.com. A link to the survey was sent to 90 members of a PA wine grape grower extension electronic mailing list. Thirty-seven participants clicked the link and responded to questions related to the 2016 harvest and growing season.

All procedures were approved by the Office of Research Protections at The Pennsylvania State University (University Park, PA). Upon completion of the survey, each participant was entered into a raffle to win one of three $25 gift certificates that could be redeemed toward any Penn State Extension wine or grape program fee.

This article is based on our observations and feedback we received from survey participants. We welcome more PA wine grape growers to share their stories and to send us (Michela Centinari; Bryan Hed) their contact information so they can be included in future surveys (where else do you have a chance to win a gift card for a Penn State Extension event?).

First, some information about the respondents

Thirty-three survey participants (89%) indicated the region where they grew grapes. The majority of the respondents (11) were from the Southeast region, followed by Northwest (7), Northeast (6), South Central (4), North Central (3), and Southwest (2) regions.

Data that described what species of grapes survey participants grew were: Vitis vinifera (e.g., Riesling, Cabernet Franc, Chardonnay), Vitis interspecific hybrid (e.g., Chambourcin, Traminette, Vidal Blanc), abbreviated in Table 1 as vinifera and hybrid, respectively, and native (e.g., Concord, Niagara) cultivars (Table 1).

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What did we ask the survey participants?

Participants were asked to rank the average yield of the grapes they grew in 2016 from “poor” to “record crop.” They were also asked to rank the average quality of the fruit from “poor” to “excellent,” and the insect and disease pressure experienced from “below average” to “above average.”  Respondents were then directed to open-ended questions where they indicated what cultivars performed below or above average and why.

 Survey participant responses  

  • Yield: The majority of the respondents (88%) indicated that average crop yield was “average” “above average,” or “record crop” (Figure 1). Only four participants (12%) indicated that average yield was “below average” or “poor.”screenshot-2016-12-14-15-41-31

Of those four respondents, two attributed “poor” or “below average” yield to disease issues (e.g., powdery mildew, black rot). One survey participant from the Southeast region indicated problems with freeze injury as the vines were approaching bud burst.  Specifically, the participant wrote: “My whites especially Chardonnay were light (lower crop yield than average) this year. I believe the whites were hit hard with the early April freezes when we had three nights in a row dip down into the 20’s. I believe many of the primary buds froze. Most of the white grape clusters were much smaller than usual.”

An unusually warm March was indeed followed by a very cold start to the month of April. Between April 3 and 10, there were several nights in the 20’s ºF in many regions of PA. While there was no sign of bud burst, as far as we are aware, for grapevines grown in central or north PA, some were approaching bud burst in several areas of south central and southeast PA.

The fourth respondent from northwest PA commented that “Vines are still recovering from 2014 winter injury, and that is too expensive to replant large percentage.” Despite long-term issues with winter injury recovery, finally, after two harsh winters (2013-2014; 2014-2015) PA grape growers were able to enjoy the winter without having to worry about their vines. In many regions of PA, winter temperatures did not reach critical low values that tend to injure many of the cultivars grown in the Commonwealth. However, on February 14 temperatures reached -10°F and below in northeast PA.  The lowest temperature recorded (-19°F) was in Potter County. Despite this isolated event, we did not receive inquires of growers concerned about winter injury.

  • Fruit quality: The majority of the respondents (83%) ranked fruit quality as “above average” or “excellent,” which was consistent across cultivars and regions. Only one grower rated fruit quality as “below average” as a consequence of high disease pressure.

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A few survey participants from southeast PA who rated fruit quality from “above average” to “excellent” commented:

“Early veraison and high heat degree days in September allowed the early varietal to ripen in almost perfect condition. The Bordeaux reds .. in late September and early October soaked up a lot of rain and didn’t recover completely from this. I harvested Merlot clusters bigger than I have ever seen them”

“Bordeaux varieties (Cabs, Merlot, Petit Verdot) were at least 23ºBrix with a high of 25. Nice and ripe with good flavors”

“Grüner, Riesling, Merlot, Chambourcin, and Cabernet Franc achieved mature ripe flavor. Acids were in ideal range”

Other survey participants from across the state also indicated that in 2016 the grapes reached “Optimal ripeness and acidity level,” “Good acid balance,” “Berry size, color, acids, pH, and sugars were the best ever,” “Excellent cultivar character.”

Several respondents pointed out that “Hot and dry weather played an important role in the quality this year” and commented that fruit was clean from major diseases.

  • Insect and disease pressure: Almost half of the growers who participated in the survey (47%) experienced “below average” insect and disease pressure during the 2016 growing season, while 41% answered “average” and only 12 % “above average.”

screenshot-2016-12-14-15-42-34

Of the four participants who reported “above average” disease pressure, one indicated problems with spotted Lanternfly an invasive insect who unfortunately is making its way to some areas of PA (Spotted Lanternfly: A new invasive pest detected in Pennsylvania).  Two respondents reported issues with powdery mildew. Powdery mildew was indeed very much “alive and well” in many vineyards in 2016.  In Erie County, we witnessed flare-ups of this disease on fruit during late June and early July, despite relatively prudent control measures and relatively few primary infection periods. This disease requires rainfall events early in the season for spore release only (minimum of 0.1 inches of rain and temperatures above 50ºF), but once spores are released the pathogen does not require wet plant surfaces to infect susceptible tissue and generate subsequent waves of its parasitic life cycle. This is very much unlike most of the other fungal pathogens we deal with each year. Note that even California growers spend a boatload of time and treasure controlling this disease every year. In short, it is a disease management issue wherever grapes are grown, every year, everywhere. Fortunately, aside from a few horror stories where there were gaps in spray intervals around bloom, most growers managed to get decent commercial control of this disease on their grapes in 2016.

Weather conditions during the growing season

A look at the weather conditions through the online network for environment and weather applications (http://newa.cornell.edu/) can help interpreting survey participant responses. In Figure 4 and 5, we reported data collected by the two new weather stations located nearby the Penn State Fruit Research and Extension center (FREC) in Biglerville (Adams County, south central PA) and at the Lake Erie Regional Grape Research and Extension center (LERGREC) in North East (Erie county, northwestern PA). We compared the 2016 monthly growing degree days (GDD) (index of heat accumulation) and precipitation to the mean values for April through October for a three-year period (2013-2015) (Figures 4, 5).

Temperature: Despite a cool start to the 2016 season (see April and May) the rest of the season was warmer than average in PA and other parts of the eastern U.S. Indeed, the heat accumulated (GDD) from June through October in 2016 was above that of the previous three-year average (Figure 4).

screenshot-2016-12-14-15-43-12

The warm weather led in many cases to great fruit ripening conditions, as indicated by the majority of the respondents, but in a few instances may have hindered fruit sugar accumulation as noticed by one of the participants: “I think that heat in August slowed ripening and resulted in lower Brix than other years but all fruit did achieve ripeness.” High temperatures might increase plant respiration rates to a greater degree than photosynthesis rates, which in other words means lower carbon gain /sugar accumulation for the vine and fruit. A detailed explanation of why this happens can be found in the September issue of Viticulture notes edited by Tony Wolf (Professor and Viticulture Extension Specialist at Virginia Tech).

Precipitation: Rainfall in the spring and early summer was well below average in Erie County (northwestern PA) with 2.1, 1.9, and 2.7 inches of rain in May, June, and July, respectively (Figure 5B). Dry weather often comes hand in hand with a higher number of sunny days and higher temperatures; two additional factors that stymie fungal pathogen growth.

screenshot-2016-12-14-15-43-44

Peak grape disease susceptibility generally occurs during June and early July in PA. Both June and July were drier than average in many parts of the state: see for example Biglerville (south central PA) with only 2.7 and 0.2 inches of rain in June and July, respectively (Figure 5A), or other sites across the state (Table 2: Lewisburg, State College, and Cabot). This helps to explain the large percentage of growers reporting average to below average disease pressure. However, in other parts of the state or near the eastern PA border it was not quite as dry but still warm (Table 2, numbers in bold font).

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In places and months where rainfall amounts were well above average, rainfall was often heavy and punctuated by well defined, often lengthy dry periods in which growers could easily keep up with their protective fungicide sprays. Unfortunately, there were a few locations where diseases like black rot flared out of control, but those were the exceptions rather than the rule (Figure 3).

In summary “dry, sunny, and warm” sums up the weather for the majority of the growing season for many regions of the state, with local and ample variations on precipitation amount. For the most part, these conditions are rather hostile to the fungal or fungal-like pathogens that are responsible for the majority of our grape disease issues every year. This was very fortunate for a number of reasons, not the least of which was the fact that 2016 was following a year that left many vineyards with well above average levels of overwintering inoculum for diseases like black rot and downy mildew. This was especially true in northwestern PA; downy mildew could be found in pretty much every vineyard in Erie County in 2015, despite the fact that the vast majority of the grape acreage is planted to Concord, a variety with relatively low susceptibility to downy mildew. A wet spring and early summer could have left growers really struggling hard to keep those diseases under control on fruit this year. But downy mildew literally “took a vacation” in the Lake Erie region in 2016. It was the most downy mildew-free season Bryan experienced over his 18 seasons of working with grapes. You might say that many PA grape growers got a small taste of what it’s like to grow grapes in California.

When ripening begins, our attention naturally turns toward controlling bunch rots on susceptible varieties. Varieties that produce “tight,” compact clusters are most at risk, and for these control measures are essential. Fortunately, survey participants did not indicate bunch rot issues this season. In Erie, as well as many other locations in PA rainfall resumed by the second week in August (Figure 5), and the ripening period was actually relatively wet through September. As you know, rainfall during ripening leads to bunch rot problems (Late summer/early fall grape disease control) and we did see rot problems develop early in vineyards of Pinot Gris and Pinot Noir with extremely tight clusters despite measures to reduce cluster compactness and a barrage of fungicide applications. In those vineyards, the crop had to be harvested early, before optimum ripeness. However, at LERGREC, rot control was especially good in Vignoles (another cultivar susceptible to bunch rot) where we applied mechanized pre-bloom fruit zone leaf removal in combination with Botrytis specific fungicides at veraison and beyond.

In conclusion, it was a rewarding growing season for many PA wine grape growers. Warm, (mostly) dry conditions favored the production of a high-quality vintage and we are looking forward to tasting this season’s wines!

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