Looking Back at the 2017 Growing Season

By Michela Centinari, Bryan Hed, Kathy Kelley, and Jody Timer

The 2017 growing season was a rewarding one for many Pennsylvania (PA) grape growers; crop quality and yields generally met or exceeded expectations. However, this season was not without its challenges. Before we start planning for next year, let’s review this past season and discuss the important issues and concerns PA growers faced in 2017. In November a link to a 10-minute Internet survey was sent via email to 110 members of a PA wine grape grower extension mailing list. The survey was designed to solicit their feedback with regards to the 2017 growing and harvest season. Fifty participants completed the survey* and their responses form the basis of this blog article. So that we have a complete accounting for growers throughout the Commonwealth, we encourage PA wine grape growers who may not have received the email to contact us (Michela Centinari; Bryan Hed) and provide their contact information so that they can be included in future surveys.

First, some information about participant demographics

Of those who provided the region where they grew grapes (44 participants), the majority (16) were located in the Southeast region, followed by South Central (9), Northwest (8), Northeast (5), North Central (3), and Southwest (3) regions.  Species of grapes survey participants grew are listed in Table 1.

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What did we ask the survey participants?

Participants were asked to indicate the average yield of the grapes they grew in 2017 by selecting the appropriate category: “poor,” “below average,” “average,” “above average,” or “record crop.” Although growers often adjust crop load to meet a desired level, environmental or other unexpected factors may cause final yield to differ from expected, “average” values.

Participants were also asked to rank the overall quality of the fruit from “poor” to “excellent,” and the insect and disease pressure from “below average” to “above average.”  Respondents were then directed to open-ended questions where they indicated what cultivars performed “below,” “average,” or “above average” and why.

Weather conditions during the growing season

A look at the weather conditions throughout the growing season can help to explain participants’ answers.  In Figures 1 and 2, we reported monthly, seasonal (April 1 through October 31) growing degree days (GDD; index of heat accumulation), and precipitation collected by weather stations (http://newa.cornell.edu/) at two locations: Lake Erie Regional Grape Research and Extension center (LERGREC) in North East (Erie County, northwestern PA) and in Reading (Berks County, southeast PA). We compared the 2017 data to the previous 18-year (1999-2016) average.

Screenshot 2017-11-30 15.00.21

We recognize that weather conditions might vary greatly from site to site, but some general trends were observed. For example, April GDDs were above-average in many regions of the Commonwealth. On the other hand, May was slightly cooler than the average in both the Southeast and Northwest (Figure 1). Additionally, below freezing temperatures were recorded during the early morning hours of May 8 and May 9 at the agricultural experiment station located near the Penn State main campus in State College. Some of the grape cultivars grown at this research farm, especially those that typically break bud early like Marquette and Concord, sustained crop loss due to frost damage. Fortunately, spring frost affected relatively few growers in PA and only two survey participants, one from the Southwest and another from the Northeast, reported reduced crop yield due to early May frost damage.

Growing degree day accumulations were slightly above the long-term average in June and July. However, August was noticeably cooler than the average in the Southeast and many other regions of the state, but not in Erie which remained warmer than average nearly all season (Figure 1). As the season came to a close, temperatures in September and especially October were warmer than average at both locations (Figure 1).

In most regions of the state, precipitation was abundant, particularly in June, July, and August (Figure 2 and Table 2). The one exception to this trend was in the far Northwest corner of the state where rainfall along the Lake Erie shore was well below average in July and August. September was relatively dry statewide, which was a big relief for many growers after facing a wet summer.  As the season came to an end, October saw a return to higher amounts of rainfall in some areas of the state.

Screenshot 2017-11-30 15.07.18

Survey participants’ responses 

Yield: Twenty-two respondents (44% of the participants) indicated that overall crop yield was “average,” which was close to the target values (Figure 3). Sixteen percent of the participants indicated that overall yield was “above average,” or “record crop,” while for 40% was “below average” or “poor.”

Screenshot 2017-11-30 15.01.39

“Poor” or “below average” yield was attributed to several factors, including poor or reduced fruit set, herbicide drift damage from a nearby field (for more information please refer to the newsletter article: Growth regulator herbicides negatively affect grapevine development) and/or disease issues (e.g., downy mildew, bunch rot). Two participants reported crop yield losses due to late spring freeze damage.  One respondent indicated that “above average” yield was likely related to bigger berry size.

Fruit quality: Participants were asked to rate fruit quality, with the majority of the respondents (82%) rating fruit quality as “average,” “above average” or “excellent.”  Only 18% of the respondents indicated that overall quality was “below average” or “poor,” although in some cases the rating varied depending on the cultivars grown as specified in a follow-up question.

Screenshot 2017-11-30 15.02.00

With the exception of the Northwest region, several participants across the state pointed out that despite the wet summer conditions the warm and dry fall weather favorably influenced fruit ripening, especially for late ripening cultivars.

For example, some of them commented:

  • Early cultivars were of lower quality than later cultivars due to the cold, wet weather in the August and early September time frame. The warm and dry later half of September and most of October benefited the later.”
  • Pinot Gris, Sauvignon Blanc, Viognier, Chardonnay all had excellent sugar levels and good pH and acidity. Flavors were well concentrated. Reds were average to good. Some like Merlot had low sugar levels while later varieties had better sugars like Cabernet franc and Cabernet sauvignon.  The late reds seemed to ripen more quickly than normal.”
  • “Later varieties were above average due to smaller crop size and better weather conditions.”

Disease pressure: Half of the growers who participated in the survey experienced “above average” disease pressure during the 2017 growing season, while 41% reported “average” disease pressure and only 9% reported that the disease pressure was “below average.” This contrasts markedly with results obtained in 2016 when 47% of survey participants experienced “below average” disease pressure (Looking back at the 2016 season).

Screenshot 2017-11-30 15.02.51

The major disease problem identified by the growers was downy mildew followed by bunch rot. A few respondents indicated that downy mildew pressure was particularly high in August. This is not surprising; downy mildew pressure is very dependent on rainfall and the threat of this disease would be particularly high in areas where recorded rainfall had been above average for most of the season (for example, Berks County).

It is important to note that areas of the state that experienced “above average” disease pressure may have a relatively high overwintering population of the pathogen(s), particularly if a fair amount of disease was actually observed in the vineyard. This can easily translate into higher disease pressure in 2018, especially if conditions remain wet.

In contrast to the majority of grape growing areas in PA, growers in the Lake Erie region experienced a second consecutive dry season, and disease development in many of the region’s vineyards was limited to powdery mildew in 2017. Therefore vineyards in the Lake Erie region will generally carry relatively low overwintering pathogen levels into 2018, with the exception of powdery mildew (a disease that is only dependent on rainfall for the first primary infections in early spring).

Despite the above-average wet conditions, respondents pointed out that fruit was clean from major diseases: “low fruit disease despite wet season,” and “given the weather conditions during the growing season overall our grapes were kept almost disease free.”

Several of them attributed their ability to keep disease pressure under control to a “persistent spray program,” “solid spray program and very good protective materials available,” and that “rainy season required that growers stay on top of their disease management program.  Botrytis, downy and powdery mildew could have been rampant.”

A respondent pointed out that in addition to a solid spray program new canopy management implemented likely helped to reduce Botrytis infection in susceptible varieties:  “I also started to leaf pull pre-bloom which I believe has loosened our clusters up and has allowed for better spray penetration and overall less rot.

Insect pressure: Twenty-two participants (45% of the respondents) experienced “average” insect pressure during the 2017 growing season, while 31% answered “above average” and 24 % “below average.”

Screenshot 2017-11-30 15.03.11

The majority of the growers who experienced “average” or “above average” insect pressure indicated problems with late-season insect pests, such as Spotted Wing Drosophila (SWD), wasps and hornets (for more information on those insect pests and how to manage them please refer to: Is Spotted Wing Drosophila a problem in my wine grapes?; Late season insect management)

Some of them commented:

SWD seems to be more present at the end of the season,” “Drosophila was the primary insect,” “SWD was above normal.”

Japanese Beetles were also named, although answers were divided: some respondents indicated “Japanese beetle pressure was lower than in previous years” while others answered that “Japanese beetles were the most prevalent insect” and they were “very aggressive in the vineyard.”  A respondent observed a new insect in the vineyard, the grape leafhopper.  Grapevines can tolerate fairly high populations of leaf hoppers and Japanese beetles without harm to the crop. Populations of fewer than 20 leafhopper nymphs/leaf usually does not require spraying (Japanese Beetle: A common pest in the vineyard).

In the Lake Erie region the grape berry moth was once again the most destructive insect present.  The unusually dry summer kept a potentially large population to average numbers.  Brown Marmorated stink bug damage is beginning to be noticeable in some Lake Erie vineyards (Will the Brown Marmorated stink bug be a problem in wine and juice?)

Unfortunately, the insect who made its big entry this season into southeastern PA vineyards was the Spotted Lanternfly (Lycorma delicatula).  Spotted Lanternfly (SLF) is an invasive insect first discovered in Berks County in 2014 and is now threatening parts of southeastern PA and Southern New York (Invasive insect confirmed in New York). Half of the respondents from the Southeast region (8 participants) observed the Spotted Lanternfly in their vineyards, and this was the first year for many of them.

Some of them commented:

  • At the end of the season I started seeing Spotted Lanternfly.”
  • “Lantern fly moved into my vineyard this year. Some of us believe honeydew from lantern fly is attracting yellow jackets and other bees, which were really bad.”
  • The Spotted Lanternfly in our vineyard continues to put pressure on the crop; we estimated that we killed 1/2 million adults in September.”
  • The significant increase in the adult Spotted Lantern Fly population this season in our area causes significant concern for our vineyard longevity. While many of the sprays were able to knock the populations back quickly only so many applications could be made. Within a few days of spraying and killing the adults, new adults migrated into the vineyards.”

The quarantined area for SLF at the beginning of the season included three counties of southeastern PA, but by the end of the season, SLF populations had decidedly increased causing the quarantine area to be markedly expanded.  The PA Department of Agriculture does not have the quarantine map completely updated at this time, however, they do have a search quarantine map where you can put in your location to check to see if you are included in the quarantine. (https://www.agriculture.pa.gov/spottedlanternfly; http://www.agriculture.pa.gov/plants_land_water/plantindustry/entomology/spotted_lanternfly/pages/default.aspx)

Information on SLF and measures that can be taken to stop its spread can be found at: https://extension.psu.edu/spotted-lanternfly, additional resources are listed on the Penn State Extension website. As stated in the article: “Penn State is at the forefront of education and research aimed at stopping the spread of this exotic species.” Penn State is seeking to hire an entomologist extension associate to coordinate outreach and response efforts for the SLF.

We are also planning to discuss Spotted Lanternfly management options at the Penn State Grape Disease & Insect Management Workshop, soon to be announced through the Penn State extension website and our listserv.

We would like to thank all the growers who participated in the survey. Their time spent responding to these questions provides us with valuable information that research and extension personnel can utilize to customize efforts to help the industry grow and improve. The more responses we receive, the more accurately our efforts can target the needs of our stakeholders statewide.  Despite some challenges, it was a rewarding growing season for many PA wine grape growers. We are looking forward to tasting this season’s wines!

Notes

* 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.

 

 

 

 

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