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Herbicide Injury to Grapes from 2, 4-D, and Dicamba: Awareness and Prevention

Andy Muza, Penn State Extension – Erie County

In 2017, members of Penn State’s Grape Team received a number of reports from extension educators and grape growers around Pennsylvania concerning herbicide injury in their vineyards from drift. From pictures of injury symptoms, we concluded that the causes were mainly due to 2, 4-D and possibly also Dicamba, in one case.

In efforts to educate farmers concerning this problem for the upcoming season, members of Penn State’s  Grape and Field Crops Teams have been conducting presentations at meetings and writing articles concerning growth regulator herbicides and the potential for phytotoxicity from drift to crops sensitive to these herbicides.

Therefore, this article is going to concentrate on the growth regulator herbicides 2, 4-D, and Dicamba since these herbicides are the most likely to be implicated in spray drift cases.

However, also keep in mind that even herbicides registered for grapes have the potential to cause herbicide injury in vineyards if applied carelessly or if not applied according to the pesticide label.

Over the years, I have observed phytotoxicity in vineyards due to improper applications of simazine (Princep), diuron (Karmex), paraquat (Gramoxone) and most notably, glyphosate products (Roundup, Touchdown, etc.).  Of these herbicides registered for grapes, the most extensive injury has been due to misapplication of glyphosate products by grape growers themselves.

However, of much greater concern for grape growers are growth regulator (GR) type herbicides, which are not registered for grapes but are applied to other crops/non crop areas in proximity to vineyards. The concerns about these products are due to the fact that grapes are extremely sensitive to very low concentrations of GR herbicides and the potential for injury from drift.

Drift – is defined as the movement of a pesticide from the intended application site to an unintended site (i.e., off target movement). Spray drift results when fine spray droplets move in wind currents to non-target areas. Vapor drift occurs when spray material volatilizes from the application site and vapors are moved to off target areas. The risk of volatilization is directly related to air temperatures. Vapor may be generated under high temperatures during and after application.

Growth Regulator Herbicides                                                                                                                                      Grapes are extremely sensitive to growth regulator herbicides including the phenoxy, benzoic and pyridine classes of compounds. Herbicide concentrations of 100 times below the label rate have been reported to cause injury. The most common GR herbicides used are those containing 2,4–D or Dicamba. But others, which have been documented as causing injury to grapes, include: picloram (e.g.,Tordon), triclopyr (e.g., Garlon), and clopyralid (e.g. Stinger). All of the GR herbicides should be considered to have the potential to cause injury to grapes. Therefore, their use around vineyards should be discouraged.

GR herbicides are commonly applied to lawns, turf, pasture, agronomic crops (e.g., corn, cereals, sorghum) and noncropland (e.g., roadsides, right of ways). There is a wide variety of GR herbicides and for a partial listing of product trade names refer to Reference 1. Also, be aware that many prepackaged mixes may contain a GR herbicide.

Growth Regulator Herbicides – How they Work                                                                                                                                                      Auxins are plant hormones which regulate growth and development in the plant and are in the highest concentrations in the growing tips. Growth regulator (GR) herbicides mimic the action of these plant growth hormones. The herbicide molecules bind to auxin receptors and abnormal growth results due to disruption in the hormonal balance of the plant. These herbicides are systemic and translocate from absorption sites (i.e., leaves or roots) to areas of rapid growth. The youngest terminal growth is most severely affected.

2,4-D                                                                                                                                                                                     The most severe and most common cases of injury to grapevines due to growth regulator herbicides, that I have seen, have been caused by herbicides which contain 2,4-D. There are numerous products on the market with various trade names and these are available for both homeowner and commercial use.                                                                                                   Grape is considered one of the crops most susceptible to injury. Other crops sensitive to injury include: tomatoes, potatoes, peppers, melons, squash, soybeans & other legumes.

2,4–D Formulations – products are formulated as both esters and amines.

Ester formulations – most ester formulations available today are much less volatile than previous products. However, there is still a greater risk of vapor drift with ester formulations than with amine formulations.

Amine salt formulations – are safer to use, especially at temperatures greater than 80 degrees Fahrenheit

2, 4–D & Dicamba – have been reported to occur 1 miles or more downwind of where herbicide applications were applied. However, the most extensively injured vineyards are usually within closer proximity of the herbicide application.

Factors Affecting the Severity of Injury include:

Growth Stage of the vines at time of exposure – grapes are always sensitive BUT most extensive injury occurs if exposed during the period of rapid shoot growth (bud break – fruit set).

Vine Age – young vines are more likely to suffer greater injury or death than mature vines.

Level of Exposure – exposure to higher concentrations of GR herbicides or repeated exposures result in more severe injury.

Variety – all varieties are susceptible to GR herbicides but there are differences among cultivars (refer to Reference 2 ).

Symptoms of GR herbicide Injury

2,4-D Injury on Leaves – a variety of leaf distortions may occur such as: fan shaped, puckered leaves with pointed leaf margins (Fig. 1); small, narrow leaves with numerous, thick white veins and pointy leaf margins (Fig.2).

Screenshot 2018-03-29 12.45.56Screenshot 2018-03-29 12.46.01

Dicamba Injury on Leaves – Downward or upward cupping of leaves with a distinct marginal band of restricted growth and pointy leaf margins (Figures 3 and 4).

Screenshot 2018-03-29 12.59.00

2,4-D Injury on Shoots – Shoots may exhibit zigzag growth with shortened

internodes (Fig. 5). Shoot tips may stop growing or exhibit twisted growth with deformed leaves (Fig. 6).                                    Screenshot 2018-03-29 13.01.26

 

2,4-D Injury on Flowers/ Clusters – Injury to clusters can include: flower abortion; fruit set reduction;

reduction of fruit size (shot berries intermingled with normal size berries); delayed ripening; and reduction in fruit quality (Fig.7).

Screenshot 2018-03-29 12.46.51

Proactive Approach for Grape Growers to Minimize Problems

Grape growers need to take a proactive approach to minimize potential problems due to drift from 2,4-D, dicamba and other GR herbicides.

  • Inform your neighbors about your vineyard location – contact farmers, pesticide dealers, homeowners, commercial applicators (e.g., lawn care companies, county/state highway departments), if possible, within a mile of your vineyard. Your neighbors may not be aware that a vineyard is in close proximity or that commonly used GR herbicides can cause serious injury to grapevines.
  • Aerial maps – provide aerial maps of vineyard locations to farmers/applicators/homeowners.
  • Post Signs – post signs around the vineyard indicating crop sensitivity.

Applicator Practices to Reduce Risk of Growth Regulator Herbicide Injury                                                         

The Applicator Practices and References listed below can be used to educate farmers and commercial applicators about the hazards of using GR herbicides near vineyards.

  • Be aware of vineyards in close proximity of herbicide applications.
  • Read the herbicide label and follow precautions concerning spray drift.
  • Avoid application of growth regulator herbicides near vineyards from bud break through fruit set.
  • Use less volatile Amine formulations of GR herbicides.
  • Monitor weather conditions (wind speed and direction, temperature). Avoid spraying when wind speed is likely to cause spray droplets to drift. Spray when wind direction is moving away from vineyard. Avoid applications if a temperature inversion exists. Remember, high temperatures during and a few days after application increase the risk of vapor drift.
  • Use nozzles (e.g., air induction nozzles) that reduce drift by increasing droplet size.
  • Keep spray pressure at lower end of pressure range and boom height as close as possible to target.
  • Use a drift reducing additive.

What if Drift occurs or is suspected

  • Identify area affected.
  • Document the date and growth stage of the grapes.
  • Contact crop insurer as soon as possible (if applicable).
  • Identify the source of drift, if possible, and make a determination if you want to settle the problem amongst your neighbors. Severe injury settlements should be delayed until after next season’s harvest.
  • Flag both affected and unaffected plants. Take high reso­lution pictures weekly until symptoms subside. Document yields of affected and unaffected vines by variety. NOTE: A Leaf Index and Severity Rating and Verified Report and Loss Form by Washington State University (http://feql.wsu.edu/eb/), Reference 3, provides valuable information on documentation procedures.
  • Contact your state department of agriculture (e.g., Pennsylvania Department of Agriculture), as soon as possible, if you cannot determine the source of the drift and/or you want to formalize the complaint.

 

References

  1. Preventing Herbicide Drift and Injury to Grapes https://catalog.extension.oregonstate.edu/files/project/pdf/em8860.pdf
  2. Questions and Answers about Vineyard Injury from Herbicide Drift http://www.bookstore.ksre.ksu.edu/Item.aspx?catId=237&pubId=1105
  3. Leaf Index and Severity Rating & Leaf Index Report (Washington State University) http://feql.wsu.edu/eb/
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Winter Cold Damage Revisited

By Bryan Hed

Since the new year was ushered in we have had several scary moments when Mother Nature unleashed an “excess of personality.” I’m referring to the cold weather events we experienced around January 1, 7, and 14, when temperatures slipped down below zero in many places across Pennsylvania, even in some south central parts of the state. As many of you might remember, the last time we saw below zero temperatures that far south (February from hell, 2015) primary bud damage was widespread and grapevine trunks in vineyards all over Pennsylvania (and certainly other parts of the Northeast) exploded in crown gall the following spring. This generated a two-year trunk renewal process that we’ve only just recovered from. Therefore, this may be a good time to review grapevine winter hardiness and the factors that affect it, as well as how we can prepare for possible remediation pruning and renewal this spring.

Now I don’t want to raise alarm bells just yet, as the conditions we’ve experienced this January haven’t been as horrific as February of 2015. But it’s always good to be prepared for any potential consequences, like bud loss and trunk damage, so we can anticipate altering our winter pruning plans and production practices this season.

Let’s start with a review of the temperature stats available to everyone on the NEWA website (newa.cornell.edu) and see just how cold it got in various places across the state during the first half of January. In the table below, I’ve listed low temperatures for January 1, 7, and 14 for many of the NEWA locations. Starting at northeastern PA and moving counterclockwise to swing back up into northern New Jersey and finally western New York, we get the following data (Table 1).

Screenshot 2018-01-20 07.11.38

Areas of southeastern and northwestern Pennsylvania, at opposite corners of the state, appear to have escaped the below-zero temperatures for the most part, but some areas of south central Pennsylvania took a hit (look at York Springs). Areas of southwestern Pennsylvania experienced some of the most extended periods of below-zero weather, and parts of northeastern and central Pennsylvania also got quite cold. The temperature low is the most important bit to consider when sizing up vine bud damage, but the duration of those lows can affect the extent of trunk damage, especially in big old trunks where it may take longer for the core to reach ambient temperatures. Up in the northwestern corner of the state, the buffering effect of Lake Erie probably played a role in our relatively mild temperatures during that period, and we expect little to no damage to most of our vines as our wine industry there is heavily invested in tougher hybrids. The Erie area was also blessed (?) with a heap of snow (10 feet!) before the cold snap that provided added protection to bud unions of grafted vines.

If you’re anticipating primary bud damage, here’s a review of the ranges of temperatures for the LT50 (low temperature at which 50% of primary buds fail to survive) for the cultivars you’re growing. For Vitis vinifera, the LT50 range of the most winter sensitive cultivars falls between 5o and -5oF. This includes cultivars like Merlot and Syrah. But for most cultivars of V. vinifera, LT50 values fall more in the 0o to -8oF range (Chardonnay, Cabernet Sauvignon, Pinot gris, Pinot noir, Gewurztraminer). And finally, there’s the tougher V. vinifera and sensitive hybrids that have buds with LT50 values of -5o to -10oF. This includes cultivars like Riesling, Cabernet franc, Lemberger, and Chambourcin. On the flip side, most hybrids fall into the -10o to -15oF range (which is why Northeastern U.S. vineyards are perhaps still more invested in hybrids than V. vinifera). Then there are the V. labrusca (Concord) and the Minnesota hybrids that range from -15o down to -30oF for cultivars like Frontenac and LaCrescent. Unfortunately, we don’t have such helpful ranges for determining trunk damage, which often comes with more profound consequences and is costlier to address.

Rapid temperature drops are often the most devastating in terms of the extent of damage. Fortunately, December temperatures this winter descended very gradually giving vines time to fully acclimate to cold weather extremes. In fact, recent data from the Cornell research group in the Finger Lakes region of New York shows that LT50 values for primary buds of several cultivars were close to, or at, maximum hardiness. Therefore, it is hoped that many Northeastern U.S. vineyards were well prepped and close to their hardiest when these cold events occurred. On the other hand, any given cultivar in central New York is likely to be a bit more cold hardy than that same cultivar growing in southern Pennsylvania, simply because vines farther north will have accumulated more cooling units than those farther south. So there is the possibility of bud and—worse yet—trunk damage in parts of PA, to the more sensitive cultivars of V. vinifera.

We also had a balmy warm period during the second week in January that pumped temperatures up into the 60s in some places before plunging back down into single digits. However, it’s unlikely the brief warm period was long enough to cause any deacclimation of vines before cold temperatures resumed, and little, if any harm, is expected from that event.

The capacity for cold hardiness is mostly determined by genetics. As I alluded to above, V. vinifera cultivars are generally the most sensitive to cold winter temperature extremes, French hybrids are generally hardier, and native V. labrusca cultivars are often the toughest. Nevertheless, other site specific factors can come into play to affect cold hardiness, and this is often the reason for the range in the LT50 values. For example, there’s vine health to consider; vines that finished the season with relatively disease-free canopies and balanced crop levels can be expected to be hardier (within their genetic range) than vines that were over-cropped and/or heavily diseased. At times like these, we can’t emphasize enough how important it is to maintain your vines and production strategy with a view to optimizing their chances of surviving every winter. Other stresses like drought or flooded soils (during the growing season) that we can’t do much to control, and infection by leafroll viruses, can also play a significant role in reducing vine cold hardiness.

If you suspect damage, you should delay winter pruning of your vines, according to Dr. Michela Centinari. Feel free to revisit her previous blog posts and others at psuwineandgrapes.wordpress.com. Type “cold hardiness” or “winter injury” into the search box, and you’ll quickly and easily gain access to several timely blogs.

Bud damage can be estimated from 100 nodes collected from each potentially compromised vineyard block. Typically, gather ten, 10-node canes from each area, but do not sample from blocks randomly, unless the block is relatively uniform. If a block is made up of pronounced low and high areas (or some other site feature that would affect vine health and bud survival) make sure you sample from those areas separately as they will likely have experienced different temperature lows (Zabadal et al. 2007). You may find that vines in high areas need no or less special pruning consideration than vines in low areas that suffered more primary bud damage and will require increased remediation.

Once you have your sample, bring the canes inside to warm up a bit and make cuts (with a razor blade) through the cross section of the bud to reveal the health (bright green) or death (brown) of primary, secondary, and tertiary buds. You’ll need a magnifying glass to make this determination as you examine each bud. You should figure that primaries will contribute two thirds of your crop and secondaries, one third when considering how many “extra” buds to leave during pruning. And remember that some bud damage, up to 15% or so, is normal. If you’ve lost a third of your primaries, leave a third more nodes as you do your dormant pruning. If you’ve lost half your primaries, double the nodes you leave, and so on. However, when bud mortality is very high (more than half the primary buds are dead), it may not be cost effective to do any dormant pruning as it is likely there are more sinister consequences afoot, like severe trunk damage that is much harder to quantify. A “wait and see” strategy, or at least very minimal pruning, may be best for severely injured vines (Figure 1) and trunk damage will manifest itself in spring by generating excessive sucker growth (Figure 2). And one more thing: Secondary buds are often more hardy than primaries, may have survived to a larger extent, and in some cultivars, can be incredibly fruitful. This is especially true of some hybrid varieties like DeChaunac. So, to make more informed decisions when winter damage is suspected, you have to know the fruitful potential of your cultivar; and in cases where primary bud mortality is high, it’s therefore important to also assess the mortality of secondary buds.

Screenshot 2018-01-20 07.07.06.png

Another great fear is the appearance of crown gall, mainly at the base of trunks. This disease is caused by a bacterium that lives in the vine. However, the bacterium generally doesn’t cause gall formation on trunks until some injury occurs, usually from severe winter cold damage near the soil line or just above grafts on grafted vines (if you hilled over the grafts last fall). Another search at psuwineandgrapes.wordpress.com will bring up information on how to deal with this disease.  You can also visit What we have learned about crown gall for an update on research into this disease from Dr. Tom Burr and his research group at Cornell University. Tom has devoted a lifetime to researching grape crown gall and many advances have been made over the years. But it’s still a huge problem for Northeastern U.S. grape growers; and crown gall problems will likely increase as our industry becomes more and more heavily invested in the most susceptible cultivars of V. vinifera.

With more sensitive detection methods, Tom’s group is getting us closer and closer to crown gall-free mother vines and planting stock, but they’re also discovering that the crown gall bacterium is everywhere grapevines are located. Not restricted to internal grapevine tissues; it’s also found on external surfaces of cultivated and wild grapevines. So, clean planting stock may still acquire the pathogen internally down the road and management of crown gall, once vines are infected, will continue to be an important part of life in any vineyard that experiences cold winter temperature extremes. However, there is potential for a commercial product that inhibits gall formation, which can be applied to infected vines. The product is actually a non-gall-forming, non-root-necrotizing version of the crown gall bacterium that is applied to grape wounds and inhibits the gall-forming characteristic of the pathogenic strains of the bacterium. This product is still under development in lab and greenhouse tests, awaiting field nursery trials soon.

If you do happen to meet up with some crown gall development this spring, galled trunks can be nursed through the 2018 season to produce at least a partial crop while you train up suckers (from below the galls) as renewal trunks. When our Chancellor vineyard was struck with widespread crown gall in the 2015 season, we were able to harvest a couple of decent sized crops while trunk renewal was taking place (Figure 2), and we never went a single season without some crop. There’s also the issue of crop insurance to think of; adjusters may want you to leave damaged trunks in place so they can more accurately document the economic damage from winter cold.

Screenshot 2018-01-20 07.07.34

Lastly, a great guide to grapevine winter cold damage was published about 10 years ago by several experts. In fact, information from that guide was used in composing large parts of this blog and I highly recommend you read it. It’s an excellent publication, the result of many years of outstanding research by a number of leading scientists and extension specialists from all over the Northeastern U.S. The details of that publication are found below and you can purchase a hard copy for 15 bucksby clicking here: Winter Injury to Grapevines and Methods of Protection (E2930).

For those of you who can spend hours reading off of a computer screen without going blind, you can also access a web version of the document at msue.anr.msu.edu/uploads/files/e2930.pdf.

Zabadal, TJ, Dami, IE, Goiffinet, MC, Martinson, TE, and Chien, ML. 2007. Winter injury to grapevines and methods of protection. Extension Bulletin E2930. Michigan University Extension

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.

Screenshot 2017-11-30 14.59.03

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.

 

 

 

 

Winemaking in Austria: An introduction and comments from an 8th generation winemaker

By Dr. Helene Hopfer

Since starting to work at Penn State last year, I am excited about all these local wines made of Austrian varieties. As a native Austrian, Grüner Veltliner, Zeigelt, and Blaufränkisch (called Lemburger in Germany and Kékfrankos in Hungary) and in particular, the (even) lesser known Rotgipfler, Zierfandler and St. Laurent, are near and dear to my heart (and my palate).

Screenshot 2017-10-23 10.40.41

The more I learn about viticulture in Pennsylvania, the more similarities I discover: Similar to Pennsylvania, Austrian growers worry about late spring frosts, fungal pressure and fruit rot, wet summers, and damaging hail events [1]. So it is only fitting to provide some details and insight to Austrian winegrowing and winemaking through this blog post.

Located in the heart of Middle Europe, the Austrian climate is influenced by a continental Pannonian climate from the East, a moderate Atlantic climate from the West, cooler air from the north and an Illyrian Mediterranean climate from the South. Over the past decades, the number of very hot and dry summers is increasing, leading to more interest in irrigation systems, as on average the annual average temperature in Austrian wine growing areas increased between 0.3 to 1˚C since 1990 [2].

 

Austrian wine growers also see a move towards larger operations: Similar to other wine regions in Europe, the average vineyard area per producer is increasing, from 1.28 ha / 3.16 acres in 1987 to 3.22 ha / 7.96 acres per producer in 2015. Many very small producers who often run their operations besides full-time jobs are now selling grapes or leasing their vineyards to larger wineries. A similar trend is true for wineries [2].

 

Different to other countries where widely known varieties like Chardonnay or Pinot noir make up the majority of plantings, the most commonly planted grape varieties in Austria are the indigenous Grüner Veltiner (nearly 50% of all whites) and Zweigelt (42% of all reds), followed by the white Welschriesling and the red Blaufränkisch (Lemburger).  Another interesting fact is that over 80% of all planted vines are 10 years or older, with 30% of all vines being more than 30+ years old [2].

 
The Austrian wine market is very small on a global scale, with just over 45,000 hectares / ~ 112,000 acres of planted and producing vineyards by around 14,000 producers nation-wide [2]. Nevertheless, Austrian wine exports are steadily increasing, particularly into countries outside of the European Union, such as the USA, Canada, and Hongkong, indicating a strong interest in this small wine-producing country. Austrian wines are considered high quality, attributable to one of the strictest wine law in the world, the result of the infamous wine scandal of 1985 [3]. Today, the law regulates enological treatments (e.g., chaptalization, deacidification, and blending), levels and definitions of wine quality (e.g., the “Qualitätswein” designation requires a federal evaluation of chemical and sensory compliance), and viticultural parameters such as maximum permitted yield of 9 tons/ha or 67.5 hL/ha and permitted grape cultivars (currently 36 different varieties) [4].

Screenshot 2017-10-23 10.39.40

One of the leading figures in developing the now well-established Austrian wine law was Johann Stadlmann, then president of the Austrian Wine Growers’ Association. During his 5-year tenure starting in 1985 at the peak of the wine scandal, he made sure that the wine law could be implemented in every winery and ensured strict standards; Johann Stadlmann could be called the father of the Austrian ‘Weinwunder’ (=’wine miracle’), the conversion of Austria as a mass-producing wine country to one with an emphasis on high quality.

 

Weingut Stadlmann – an estate with a very long history

If you ever visit Austria, you most likely fly into Vienna, the country’s capital. Vienna is one of the few cities in the world that also has producing vineyards located within city limits. Just outside of the city limits to the South, lies another important wine region in Austria, the so-called ‘Thermenregion’, named after thermal springs in the region. The region has a long wine history, dating back to the ancient Romans, and later Burgundian monks in the Middle Ages. The region is characterized by hot summers and dry falls, with a continuous breeze that reduces fungal pressure. One of the leading producers within the region is the Weingut Stadlmann, dating back to 1778 and now run by the eighth generation, Bernhard Stadlmann. He is the latest in a line of highly skilled winemakers that combine innovation with a conservative approach. His grandfather, Johann Stadlmann (yes, the same guy of the Austrian wine law), was one of the first ones in Austria to use single vineyard designations on his wine labels. Bernhard’s father, Johann Stadlmann VII, a master in creating wines from varieties only grown in this region, and named ‘winemaker of the year’ in 1994, is known for his careful approach and is now working alongside his son, Bernhard. In 2007, Bernhard started the conversion of the family-owned vineyards to certified organic. The family cultivates some of the best vineyards in Austria, including the single vineyard designations ‘Mandel-Höh’, ‘Tagelsteiner’, ‘Igeln’, and ‘Höfen’, planted with the indigenous varieties Zierfandler and Rotgipfler only grown here in the region. Wines from these vineyards are among the very best Austria can offer!

 

The vineyards cultivated by the Stadlmann family also differ quite dramatically in soil composition: While the ‘Mandel-Höh’ vineyard is highly permeable to water and nutrients, with lots of ‘Muschelkalk’ (limestone soil formed of fossilized mussels shells), is the ‘Taglsteiner’ vineyard characterized by more fertile and heavier ‘Braunerde’ soil, capable of retaining more water.

Screenshot 2017-10-23 10.39.07

The long winemaking history becomes apparent once one steps into the wine cellar, full of large barrels, made of local oak: Some of these barrels have hand-carved fronts, depicting their vineyards and Johann Stadlmann senior. All of these barrels are in use, and part of the Stadlmann philosophy of combining tradition with innovation.

Screenshot 2017-10-23 10.38.32

Another increasing threat is the spotted wing Drosophila, Drosophila suzukii, damaging ripening grape berries from véraison onwards. Bernhard sees some varieties more affected by Drosophila suzukii than others. There is intensive research on pest control, including shielding nets, fly traps, and insecticide strategies, and the Stadlmanns currently run experiments within their organic program: They blow finest rock flour (Kaolin and Dolomite rock) into the leaf canopy and fruit zone to create unfavorable conditions for different insects, including Drosophila, wasps, which pierce sweet berries, earwigs and Asian lady beetle, both leafing residuals causing off-flavors in the wine once they’re crushed.  Drosophila suzukii was first discovered in Austria a few years ago and is also an issue in the US (see also Jody Timer’s blog post).

 
During a recent visit at the Stadlmann estate, I had the chance to chat with Bernhard about the challenges of Austrian winegrowing and winemaking. I was interested in a young winemaker’s perspective, especially as Bernhard has been trained all around the world, including Burgundy, Germany, and California. This year, spring frost in late April threatened vineyards in many winegrowing regions in Austria, requiring the use of straw bales and paraffin torches to produce protective and warming smoke. Luckily, not too much damage was done to the Stadlmann’s vineyards, however, it caused some sleepless nights for Bernhard and his family, and shows also the importance of developing effective spring frost prevention alternatives (see also Michela Centinari’s blog post).

 
We also talked quite a bit about wine quality: while the Austrian ‘Qualitätswein’ designation ensures basic chemical (e.g., ethanol content, titratable and volatile acidity, residual sugar, total and free SO2, malvidin-3-glucoside content (for reds), etc.) and sensory (i.e., wine defects like volatile acidity, Brettanomyces, atypical aging, mousiness and other microbial defects) quality, this only ensures a lower limit of quality. In the recent years, the Austrian governing bodies added another layer of wine quality, based on the Romanic system of regional typicity and origin: The so-called DAC (Districtus Austriae Controllatus) wines are quality wines typical for a region, made from varieties that are best suited for that region. DAC wine producers adhere to viticultural, enological, and marketing standards, with the goal to establish themselves as famous wines of origin (think Chablis, Cote de Nuits, Barolo, Rioja or Vouvray).  As this is a relatively new system for Austria, we will see how successful these DAC regions will be. Their success will also depend on the regional producers, and how stringent they set the criteria for the DAC designation, as they have to walk a fine line between establishing a recognizable regional typical wine without losing individual character that each producer brings to their wines.

 

Screenshot 2017-10-23 10.37.51

If you are interested in learning more about Austrian wines, and Bernhard and his family’s wines, they were recently highlighted in a couple of US wine publications, including a great podcast episode on ‘I’ll drink to that!’ and an article in the SOMM journal about Zierfandler. Zierfandler is one of Stadlmann’s signature varieties, indigenous to the region, but tricky to grow, as it requires long and dry ripening periods and has a very thin skin, prone to botrytis. However, when done well (like the Stadlmanns do), it produces extraordinary wines with fruity, floral, and sometimes nutty notes that have a long aging potential. If you are able to get your hand on these Zierfandler wines get them while you can!

Last, a big Thank You to Bernhard Stadlmann for his help with this blog post: He took time out of his super busy harvest schedule to show me around, never getting tired of answering my questions. He also graciously provided all but one of the pictures.

References

[1] Huber K (2017) Durchschnittliche Weinernte 2017 erwartet. LKOnline. Available at (in German): https://noe.lko.at/weinbau+2500++2455141

[2] Austrian Wine Marketing Board (2017) Austrian Wine Statistics Report 2015. Available at (in German): http://www.austrianwine.com/facts-figures/austrian-wine-statistics-report/

[3] New York Times (1985) Austria’s Wine Laws Tightened in Scandal. Available at: http://www.nytimes.com/1985/08/30/world/austria-s-wine-laws-tightened-in-scandal.html

[4] Austrian Wine (2017) Wine Law. Available at: http://www.austrianwine.com/our-wine/wine-law/

Is it Possible to Control These Insect Pests?

By: Jody Timer, Entomology & Lake Erie Regional Grape Research and Extension Center

Over the last ten years there have been an inpouring of newcomers to the insect community of Pennsylvania’s grape vineyards. These pest, combined with the numerous indigenous pest, have created an ever evolving challenge for the area’s grape growers. In this blog, I will briefly review the grape pest which I feel are becoming ever increasingly problematic for grape growers to control.

The Spotted wing drosophila has become a progressively severe problem in blueberries raspberries, and grapes. Recent research has shown that they are attracted to all cultivars of grapes that we tested. Spotted wing Drosophila, Drosophila suzukii, Matsumura (Diptera: Drosophilae) (SWD) is an invasive vinegar fly of East Asian origin, that was recently introduced into the United States. It was first found in California in 2008 and is now found in all major fruit-growing regions of the country including Pennsylvania. It was first discovered in Pennsylvania’s Lake Erie grape growing region in the late fall of 2011. The potential infestation rate of spotted wing Drosophila differs from other vinegar flies because the female possess a serrated ovipositor that cuts into healthy fruit to lay eggs. Consequently, spotted wing Drosophila (SWD) larvae can be found in fruit that is just ripening: https://youtu.be/dPr61VC2gyo

During egg-laying, it is believed that sour rot and fungal disease can also be introduced, further affecting the fruit quality. During peak temperatures, a female can lay more than 100 eggs a day. Such a high reproduction rate indicates the SWDs’ high potential for fruit infestation and their potential for spreading rapidly through a field or a vineyard. Because of this prolificity it has become increasing important to protect wine grapes starting at veraison.  A good YouTube video on how to identify SWD damage is: https://youtu.be/DLNDnMMfWfs

In our research we have seen SWD showing up earlier in the spring each season and their numbers increasing yearly. SWD do attack injured grapes before non-injured, they tend to wait till veraison before attacking grapes, and they will reproduce in fallen berries.  For this reason it is important to keep your vineyards as clean as possible and to maintain coverage of these wine grapes through harvest. Trapping and forecasting can lead to improvements in grower’s capability to optimally time pest management decisions which should reduce both the direct cost of pesticide treatments and the indirect cost to wineries.  Information can also be found at:
http://extension.psu.edu/pests/ipm/agriculture/fruits/spotted-wing-drosophila

The brown marmorated stink bug (BMSB) is currently a very serious pest in tree fruits and vegetables, and can be a nuisance when they overwinter in houses. Although BMSB prefer other fruits and vegetables to grapes, they do feed on grapes. Their damage can cause ugly scars on table grapes and grapes grown for sale at fruit stands. This type of damage is not important to wine grape and juice grape growers, however, the holes open pathways for fungal and bacteria late season infections. This season, in the Lake Erie region, we have begun to see a small number of BMSB damaged grapes. BMSB may also be easily harvest with the grapes. The insects tend to move to the interior of the cluster when disturbed and are hard to see. When they are killed they give off a foul odor – which is how they got their name. Our research has shown that this odor and resulting taste do survive the pasteurization of juice grapes, but disappears after being stored for longer periods of time. There is conflicting research on whether this taint transfers to wine, more research is ongoing. There are traps commercially available to trap these insect, but their efficacy is very low. BMSB have been found in both grape foliage and grape clusters; they seek the moisture, sugar, and warmth on the inside the clusters (especially overnight) and they often migrate to the cluster’s interior close to harvest. This makes the possibility of BMSB inside the cluster very likely when these grapes are mechanically harvested and transported to the processor.

Brown Marmorated Stink Bug in a Grape Cluster

With the yearly increase of numbers of BMSB in the Pennsylvania vineyards, it is very important for growers to scout for the adults and the presence of the eggs on the underside of grape leaves. There are one to two generations in Pennsylvania. A compilation of research can be accessed at www.STOPBMSB.org

Life stags of the Brown Marmorated Stink Bug. Photo from: http://www.mda.state.mn.us/plants/insects/stinkbug.aspx

 

The newest invasive poised to become a major problem to grape growers, the spotted lanternfly (SLF), Lycorma delicatula, (Hemiptera: Fulgoridae) is native to China, India, Japan, and Vietnam and has been detected for the first time in the United States in northeastern Berks County, Pennsylvania. This approximately one inch long insect with piercing-sucking mouthparts has the potential to impact the green industry, grape growers, tree fruit growers, and the forests and wood products industries in Pennsylvania as well as the United States. The host plants of the SLF in its native habitat include grapes, pines, stone fruits, and up to 50 other hosts. Early detection of the SLF is critical for effective control and protection of Pennsylvania’s agriculture and its related businesses. SLF group feeds on grapevines in numbers great enough to cause destruction of the entire grapevine. Grapes are listed as a primary host in its native regions. To date this insect has been confined to areas of Berks and Bucks counties in Pennsylvania. The PDA has issued a general order of quarantine for these areas over the past few years, however this insect is slowly increasing its range.

The following is a link to the PDA’s information on the SLF: www.pda.state.pa.us/spottedlanternfly. You may find a link to a pdf copy of the SLF Order of Quarantine, a PowerPoint on Lycorma Inspection Tips, and the SLF Pest Alert at this website.

What to do if you:

  • See eggs: Scrape them off the tree or smooth surface and place the eggs in a tightly sealed container with 70% alcohol or hand sanitizer to kill them.
  • Collect a specimen: Send the adult/nymph specimen or egg mass to the PDA Entomology Lab for verification. The mailing address for the lab is: PDA, Entomology Room-111, 2301 N. Cameron St., Harrisburg, PA 17110. First, place the sample collected in 70% rubbing alcohol or hand sanitizer in a leak proof container. Complete the PDA Entomology Program Sample Submission Form. This sample form can be found in the PDA SLF website www.pda.state.pa.us/spottedlanternfly.
  • Report a site: Call the Bad Bug hotline at 1-866-253-7189 with details of the sighting and your contact information.

The most destructive insect pest in the Lake Erie region remains the native Grape Berry Moth (GBM), Paralobesia viteana.  This insect is becoming increasingly harder to control as result of shorter residual time of insecticides, resistance to insecticides, and abandoned vineyards. GBM larval burrow into the grape berry soon after hatching, making precise timing of spray applications a critical component of control.  This insect has four generations per year.  Each generation increases in number exponentially if control measures are not applied to the early generations. Spray timings can be calculated by following the NEWA model recommendations (see earlier posts). Growing seasons with large populations of GBM, will require a second spray in July and/or August to control the populations, and to prevent them from moving farther into the vineyards. Scouting for GBM damage often during the season is a critical component of control, as the pheromone traps capture only the males and are not a good indicator of infestation after the first generation.  More information can be found on extension pages and on the LERGP Podcasts on Youtube.

Grapevine leafroll associated virus; A brief introduction to an old disease. Should Pennsylvania grape growers be concerned?

By: Bryan Hed, Michela Centinari, and Cristina Rosa

As if wine grape growers don’t have enough challenges in this day and age, the effects of grapevine viruses have been taking on greater importance in eastern vineyards over the past several years. Studies examining grapevine leafroll-associated viruses are developing a growing body of information that will be essential for vineyard managers to continue moving the eastern wine grape industry forward. Grape growers in the eastern United States need not feel they are the only ones with this disease management challenge (as is the case with many fungal diseases of grapes); grapevine leafroll-associated viruses (GLRaVs) are found in vineyards all over the world (Compendium of Grape Diseases). This group of viruses causes a disease known as grapevine leafroll disease, and the association of symptoms with grapevine leafroll viruses was recognized over 80 years ago. As is the case with so many plant pathogens, the worldwide distribution of these viruses occurred as a result of increased movement of plant material/goods across the globe; the ever widening dissemination of infected planting stock (Compendium of grape diseases). The effects of these leafroll viruses is most severe on – you guessed it – cultivars of V. vinifera, where the disease is known to greatly reduce yield, vine vegetative growth or vigor, and cold hardiness; a factor of critical importance for these cultivars grown in the northeastern United States. Grapevine leafroll disease can also delay fruit maturity, reduce color development in red grapes, and fruit quality (decreased soluble solids, increased titratable acidity) of V. vinifera grapes (Fuchs et al. 2009), which can negatively impact perceived wine quality. The severity of the effects of leafroll viruses is dependent on a great number of factors such as grapevine cultivar, virus strain, climate, soil, cultural practices, stress factors, etc. So naturally, the severity of symptoms can vary from one season to the next (Compendium of Grape Diseases). With respect to cultivar, the effects of these viruses on Vitis interspecific hybrids and Vitis labrusca are generally considered to be less serious, but are also less well defined and studied.

Infection by leafroll viruses results in the degeneration of primary phloem tissues in grapevine shoots, leaves and clusters (Compendium of Grape Diseases). As one can imagine, this can have profound effects on all parts of the vine. Symptoms of the disease, which are generally most observable on V. vinifera, consist of cupping and discoloration of older leaves in late summer and fall. On red fruited varieties, leaves of infected vines can display a distinct red coloration of the interveinal tissue, while veins remain green (Figure 1). On white fruited varieties of V. vinifera, symptoms are less striking and leaves tend to look yellowish (chlorotic) and cupped (Figure 2). Leaf discoloration generally affects older leaves first, but these symptoms are not diagnostic of the disease, as they may be due to other causes such as nutrient deficiencies, water stress, and even crown gall. Analysis of grapevine tissues in the laboratory is the only way to confirm the presence (or absence) of these viruses.

Figure 1. Grapevine Leafroll Disease on red fruited Vitis vinifera. The infected vine is on the left (Courtesy: Dr. Wendy McFadden, OMAFRA)

 

Figure 2. Symptoms of leafroll virus on white Vitis vinifera. Note the more subtle yellowing of the leaves and cupping of leaf margins. (Courtesy: Dr. Wendy McFadden, OMAFRA)

Currently, there are about seven GLRaVs found in cultivated grapes, the most common being GLRaV-3. These viruses are easily spread over long distances through the movement of infected nursery stock, but can be spread (vectored) within the vineyard by mealybugs (Compendium of Grape Diseases). Unfortunately, there are no known sources of resistance to GLRaVs among Vitis species and they have been found in many cultivated grape varieties, including V. labrusca, Vitis interspecific hybrids, and V. vinifera. Interest in grapevine leafroll disease and the extent of its effects has been growing in the eastern United States over the past ten years or so. Surveys conducted in New York, Ohio, and Virginia (Fuchs et al. 2009, Jones et al. 2015, Han et al. 2014), have provided confirmation of the presence of GLRaVs in commercial vineyards and have yielded important information necessary to the management of grapevine leafroll disease. For example, infection by GLRaVs is permanent and infected vines must be destroyed to reduce the incidence of grapevine leafroll disease. Therefore, management of the disease would naturally include planting only stock that is free of GLRaVs. Insecticides that target mealybugs and soft scales can prevent vine to vine spread (within the vineyard) of GLRaVs that are known to be vectored by these insects (Compendium of Grape Diseases). Indeed, studies have shown that applications of insecticides like dinotefuran (Scorpion) and spirotetramat (Movento) can significantly reduce mealybug counts and result in a slowing of the progress of the disease in vineyards. One study from New York (Fuchs et al. 2015) showed that insecticide applications should target overwintered and second instar mealybug crawlers from bud swell to bloom and summer generation crawlers later in mid-summer. A study with grape phylloxera as a potential vector of these viruses showed that phylloxera can acquire the virus through phloem feeding on infected vines, but there was no evidence that phylloxera can transmit it (Wistrom et al. 2017).

As was mentioned earlier, cultivars of Vitis labrusca (Concord, Niagara) can also become infected with GLRaVs, but the infections appear to remain latent or dormant (Bahder et al. 2012) and have not been shown to result in visual symptoms of the disease (Wilcox et al. 1998). On the other hand, cultivars of V. vinifera are severely affected by GLRaVs and make up a very important and growing sector of the PA wine grape industry. Surveys conducted in New York, Ohio, and Virginia (Fuchs et al. 2009, Jones et al. 2015, Han et al. 2014) have revealed the presence of GLRaVs in commercial vineyards to the north, west, and south of Pennsylvania and have led to the development of some important guidelines for management of grapevine leafroll disease.

Given the fact that grapevine leafroll disease is common worldwide and that grapevine leafroll disease can profoundly impact wine quality and grapevine health, researchers at Penn State University are initiating a project to look for GLRaVs in Pennsylvania vineyards.  As in other states, the study is targeted to help growers recognize the impact that the disease may be having on the Pennsylvania wine industry and help them to address the effects of these viruses on productivity and fruit quality, reduce their spread and impact, and thereby grow and improve the wine grape industry in Pennsylvania.

The short term, initial objectives of this project will focus on the development of an online survey to collect information from growers with regard to the presence of symptoms of grapevine leafroll disease in Pennsylvania vineyards and their interest in participating in the project. The project will then follow up with tissue sampling from participating, symptomatic and non-symptomatic vineyards throughout the state and serological analysis to determine the presence of Grapevine leafroll virus-1 and Grapevine leafroll virus-3 – the most common of the leafroll viruses – in commercial vineyards in Pennsylvania. The collection of vineyard samples across the state will map the incidence and geographical distribution of these viruses on cultivars of Vitis vinifera and Vitis interspecific hybrid grapevines. The project will also determine and compare the impact of grapevine cultivar and age on infection by Grapevine leafroll virus-1 and -3 in Pennsylvania. Once infected vines have been identified in Pennsylvania vineyards, future objectives will focus on studying the impacts of grapevine leafroll disease on grape quality and productivity in Pennsylvania, and management techniques to mitigate the economic impact of the disease on the Pennsylvania wine industry.

Vineyards will be selected from all parts of Pennsylvania, but the number of locations will favor northwestern and southeastern PA, where the majority of vineyards are located. The study will be expanded as new findings are made and the results will be made available to growers at various meetings throughout the next several years.

 

Literature cited:

Bahder, B., Alabi, O., Poojari, S., Walsh, D., and Naidu, R. 2013. A Survey for Grapevine Viruses in Washington State ‘Concord’ (Vitis x labruscana L.) Vineyards. Plant Health Progress, August 5, 2013. American Phytopathological Society (online).

Compendium of Grape Diseases, Disorders, and Pests. 2nd edition, 2015. Editors Wayne F. Wilcox, Walter D. Gubler, and Jerry K. Uyemoto. The American Phytopathological Society. Pp. 118-119.

Fuchs, M.Martinson, T. E.Loeb, G. M.Hoch, H. C. 2009. Survey for the three major leafroll disease-associated viruses in Finger Lakes vineyards in New York. Plant Disease 93:395-401.

Fuchs, M.Marsella-Herrick, P.Hesler, S.Martinson, T.Loeb, G. M. 2015. Seasonal pattern of virus acquisition by the grape mealybug, Pseudococcus maritimus, in a leafroll-diseased vineyard. Journal of Plant Pathology Vol.97 No.3 pp.503-510

Han, J.Ellis, M. A.Qu, F. 2014. First report of Grapevine leaf roll-associated virus-2 and –3 in Ohio vineyards. Plant Disease Vol.98 No.2 pp.284-285

Jones, T. J.Rayapati, N. A.Nita, M. 2015. Occurrence of Grapevine leafroll associated virus-2, -3 and Grapevine fleck virus in Virginia, U.S.A., and factors affecting virus infected vines. European Journal of Plant Pathology 142:209-222.

Wilcox, W. F.Jiang, Z. Y.Gonsalves, D. 1998. Leafroll virus is common in cultivated American grapevines in western New York. Plant Disease Vol.82 No.9 pp.1062.

Wistrom, C. M., G. K. Blaisdell, L. R. Wunderlich, M. Botton, Rodrigo P. P. Almeida & K. M. Daane. 2017. No evidence of transmission of grapevine leafroll-associated viruses by phylloxera (Daktulosphaira vitifoliae). European Journal of Plant Pathology. Volume 147, issue 4. pp 937–941.

Growth Regulator Herbicides Negatively Affect Grapevine Development: Identification of Herbicide Drift Damage, How to Prevent it, and What to do if it Occurs in your Vineyard

By: Michela Centinari

The Penn State Extension grape team has been receiving reports on herbicide drift damage in vineyards from a number of Pennsylvania wine grape growers this growing season, definitely many more than in previous years. All herbicides registered for grapes can potentially harm the vines if not applied in accordance to the pesticide label (e.g., glyphosate products) [1]. However, in many of the reported cases through the 2017 growing season the damage was caused by herbicides not registered for grapes, which drifted into the vineyards from nearby fields.

Damage from herbicide drift is, unfortunately, something that grape growers across the country are too familiar with. It represents an economic threat for the grape and wine industry and should not be underestimated. Herbicide drift damage can, indeed, result in significant crop losses which may extend to multiple seasons, and in some cases it also results in vine death. Several extension web resources are available to assist grape growers in preventing and dealing with herbicide drift damage. Some of them are listed at the end of this article, including one from Andy Muza, extension educator at Penn State (Growth Regulator Herbicides and Grapes Don’t Mix).

Due to the increase in reports of herbicide drift damage in Pennsylvania vineyards it seems appropriate to discuss some key points surrounding this issue. This article will review how to identify herbicide drift symptoms, what measures grape growers and pesticide applicators can take to prevent herbicide drift, and what steps to take if the drift occurs.

Plant growth regulators (PGR) herbicides are those most likely to injure grapevines, mainly through drift.

I will only focus on the herbicides which belong to the plant growth regulators (PGR) mode of action group. Common active ingredients of PGR herbicides are 2,4-D (2,4-Dichlorophenoxyacetic acid; phenoxy family), dicamba (benzoic acid), tricolopyr or picloram (pyridine family). A partial list of common PGR herbicides as well as other herbicides that may injure grapevines can be found at Preventing Herbicide Drift and Injury to Grapes, Table 1.

PGR herbicides are widely used for controlling broadleaf weeds in many crops, such as wheat, corn, soybean, pasture, rangeland, etc. They are also frequently utilized to control unwanted broadleaf vegetation in turf, by railroads, road ditches, fence lines, and rights-of-way. These herbicides are not registered for use with grapes. However, when applied to a nearby field, they can drift into the vineyard and cause significant injury to grapevines.

Most of the herbicide drift damage reported this season by Pennsylvania grape growers were caused by drift of PGR herbicides (Figure 1). Physiological symptoms to PGR exposure is not too surprising because grapevines are extremely sensitive to PGR herbicides, including the phenoxy, benzoic, and pyridine classes of compounds [2]. For example, herbicides containing 2,4-D can damage grapes at a concentration 100 times lower than the recommended label rate. Moreover, drift from PGR herbicides can injure grapevines located half a mile or more from the application site.

Figure 1. 2,4-D damage on Grüner Veltliner in Pennsylvania. The leaves are severely distorted, the shoot tip died, and bloom failed.

What is “drift”?

Drift is defined as “the movement of herbicides off the site where they were applied” [3]. Non-target drift can occur either as spray drift or vapor drift. Spray drift occurs during herbicide application when small droplets move off the application site under unfavorable wind conditions. Vapor drift occurs after herbicide application as the spray material volatizes or evaporates and is carried away from the application site by wind or temperature inversions. Some PGR herbicides, such as ester formulations of 2,4-D, readily volatilize, especially when used under high temperatures and low humidity conditions (high vapor pressure) [3].

How PGR damage occurs in grapevines

PGR herbicides mimic auxins, plant hormones that regulate growth and development. Applications of PGR herbicides disrupt plant hormone balance causing growth abnormalities. PGR herbicides can be absorbed by both roots and leaves, however grapevines are usually injured through foliar absorption.

How to tell if the vines have been damaged by PGR herbicide drift

Damage from PGR herbicides typically appears within 2 days of the drift occurrence. Herbicide drift can damage leaves, shoots, flowers, and fruit. Leaf symptoms are often easy to recognize, but sometimes can be mistaken with those of fanleaf degeneration, a viral disease [3]. Growers can send pictures of damaged vines to a local extension specialist for confirmation.

Typical symptoms include:

  • Distorted leaf appearance: Symptoms are typically more severe on the youngest leaves and shoot tips. Affected leaves are “smaller, narrow, deformed, and they have closely packed, thick veins that lack of chlorophyll” [4]. They may also have a distinct fan-shape appearance, and depending on the herbicide’s active ingredient, they can bend downward or cup upward (Figures 2, 3). Leaves may or may not outgrow the symptoms, it largely depends on the severity of the injury and other factors listed in the following section (“Factors affecting the severity of injury”). It is also common to see regrowth of deformed leaves after drift exposure [3].

Figure 2. Leaf cupping caused by improper application of Stinger (PGR-herbicide). Photo credit: Rob Crassweller.

Figure 3. 2,4-D injury on leaves. Photo on the left: A. Muza, Penn State.

  • Shoot growth: Damaged shoot tips rarely resume growth, but lateral shoots can keep growing giving in some cases a “bushy” appearance to the vine resulting in a highly shaded canopy and poor fruit sun exposure.
  • Flower clusters (inflorescences): symptoms can include aborted or failed flowers, and poor fruit set (Figure 4). If the injury is severe enough it can cause reduced yield at harvest and poor fruit quality, in addition to potentially illegal residues of herbicide on the exposed crop.

Figure 4. 2,4-D herbicide drift damage on Grüner Veltliner flower clusters. Photo taken on July 19, 2017 approximately two months after the herbicide drift incident. Notice only two berries developed properly (circled in the photo).

In some cases, depending on the timing and level of drift exposure, floral symptoms may be much more pronounced than those on the leaves making the diagnosis more difficult (i.e., growers may relate poor fruit set or dead flowers to other causes rather than herbicide drift) (Figure 5).

Figure 5. 2,4-D herbicide drift damage on Riesling flower clusters. Photo taken on June 26, 2017. Notice the leaves around the clusters look healthy.

If the damage occurs early in the season, between bud burst and bloom, as it usually does, a significant reduction in healthy leaf area during the period of rapid shoot growth may affect vine photosynthetic capacity, lowering vine ability to fully ripen the crop and possibly its ability to survive cold winters.

Unfortunately there is no guarantee that the vines will fully and rapidly recover from herbicide drift damage. Carry-over effects into the following years, such as reduction in vine vigor, yield, fruit quality, and increased susceptibility to diseases, are common if the damage is extensive and/or the vines have been repeatedly exposed to PGR-herbicide drift. Finally, vines may die as a consequence of their weakened condition [2].

What factors affect the severity of PGR-herbicide drift damage?

Some of the most important factors affecting the severity of drift damage are:

  • Vine growth stage at the time of exposure. Grapevines are always sensitive to PGR herbicides, but they are most susceptible during the early part of the growing season, from bud burst through bloom. While dependent on the growing season and site, in Pennsylvania this usually occurs around April through June. Early in the growing season shoots are rapidly growing and PGR herbicides are quickly translocated to the shoot tip, where the natural concentration of auxins is greatest inside the grapevine. If exposure occurs later in the season, vines typically outgrow the damage and still produce good yield [5].
  • Vine age: Younger plants are more vulnerable and they have a lower ability to recover from the PGR herbicide damage than mature vines. Young vines may be killed even at low exposures [6].
  • Level of exposure: Higher concentration and/or repeated exposures will result in higher disruption of the vine’s physiology and lower ability of the vines to rapidly and fully recover from the damage [3].
  • Grapevine variety. All grapevine varieties are sensitive to PGR herbicides, but some may show more visual and physiological symptoms than others (see for example Table 1, Questions and Answers about Vineyard Injury from Herbicide Drift)
  • Other factors include herbicide concentration and formulation (for example ester formulations of 2,4-D are more volatile than amine formulations, thus ester formulations of 2,4-D are more prone to move off-target as vapor), weather conditions (temperature, humidity, and most importantly wind speed) at the time of herbicide application.

What is the best strategy to protect vines from herbicide drift injury?

Prevention is undoubtedly the best strategy for grapevine growers to avoid herbicide damage. To reduce the risk of herbicide drifting into their vineyard, vineyard managers and/or owners should be proactive. Some prevention steps both grape growers and nearby growers of other crops can take are listed below:

  • Maintain good relations with neighbors. Vineyard owners and managers should make sure their neighbors within approximately a half-mile to 1 mile radius, are aware that vines are extremely sensitive to PGR herbicides [3]. It is also recommended to encourage neighbors to “use drift-reduction spray nozzles (nozzles that produce large droplets) and to select herbicides that are less likely to injure grapes” [3]. If growers of other crops are unaware of damage to grapevines, collecting information such as this blog post, may be an important educational tool to share. Mike White, viticulture extension specialist at Iowa State University, suggests to share an aerial map of the property showing the vine­yard location with neighbors and commercial pesticide applicators to increase their awareness. It is also recommended to communicate the presence of the vineyard to state and county highway departments.
  • Windbreak (shrubs, trees, physical barriers) and a buffer area between the vineyard and the edge of the field being sprayed are always a good idea. Penn State offers a free publication or pdf print-out regarding windbreaks: http://extension.psu.edu/publications/uh172/view
  • For those states where the service is available, growers can register the location of their vineyard on https://driftwatch.org/. This online service is not available in Pennsylvania, but in many Midwestern states growers and pesticide applica­tors can use this web resource free of charge to report (growers) and locate (applicators) potential drift hazards.

Taking all these steps may not guarantee that herbicide drift will not occur in your vineyard, but increasing pesticide applicators awareness of grape sensitivity to PGR herbicides, the resulting economic loss, and potential litigation risks may very well serve the purpose.

Applicators should always follow all the measures available to minimize the risk of herbicide drift into a nearby vineyard or to other sensitive crops. Legal complaints may result in expensive settlements. In an extreme example, an owner of a 150-acre vineyard in Australia was awarded AUS$ 7M in damages over pesticide drift (Grape grower Awarded $7M in damages over spraying) that occurred from 2013 to 2015.

If PGR herbicides are applied after vine bud burst, applicators should consider eliminating volatile compounds and apply only non-volatile products.

Extension personnel could also facilitate communication between grape and crop field growers as it happens in Long Island, NY. Extension personnel from Cornell University-Long Island, including Alice Wise and Andy Senesac, organized a meeting with local grape and sod growers to tackle the herbicide drift issue which was affecting local grape growers without having to resort to regulatory restrictions. The result of that meeting was a ‘gentleman’s agreement’ not to spray herbicides containing 2,4-D after April 15, around bud burst for the earliest grapevine varieties in Long Island. To keep all parties informed, extension sends out a weekly reminder about this issue.

What to do if the drift occur

Here some key steps Mike White put together on what to do right after a drift incident [7]:

  1. Identify area affected.
  2. Document the date, time and growth stage of the grapes.
  3. If possible, identify the source of the drift and make a determination if you want to settle the problem amongst your neighbors.
  4. Contact your state department of agriculture (Pennsylvania Department of Agriculture, PDA) as soon as possible if you cannot determine the source of the drift and/or you want to formalize the complaint (30 – 45 day deadline in many states).
  5. Flag both affected and unaffected plants, take high reso­lution pictures weekly until symptoms subside and measure final yields per plant.
  6. Severe injury settlements should be delayed until after next season’s harvest. Photo and yield documentation should be continued. Unless the settlement offered seems exceptionally lucrative, I would suggest delaying any settlements until after next season’s harvest to assess for potential carry-over vine damage.

For information on where to find a drift consultant please refer to Need Help? Pesticide Drift Consultants

How to estimate the loss in revenue

Tim Martinson, viticulture extension specialist at Cornell University, provided useful examples on how to estimate the economic loss associated with herbicide drift damage under different scenarios. Scenarios include vine recovery across multiple years, with and without the need of vines replacement. Please refer to: Diagnosis, Economics, Management of Grape Injury from 2,4D and other Growth Regulator Herbicides.

How to manage damaged vines

There is limited information available on best management practices for vines affected by herbicide drift damage. To favor a full and a rapid recovery it is recommended to still implement  good management practices and avoid further stress to damaged vines, as for example over cropping (assuming damaged vines have fruit). Fungicide applications made to protect the fruit should not be necessary if the fruit has been removed [8]. It is also recommended to adjust pruning strategies to smaller vines, with the intent of regaining full vine size [9].

 

Resources

  1. Growth regulator herbicides and grapes don’t mix. Penn State. https://psuwineandgrapes.wordpress.com/2015/10/16/growth-regulator-herbicides-and-grapes-dont-mix/
  2. Watch out for: Grapes. Purdue University. DW-10-W. https://www.extension.purdue.edu/extmedia/ho/dw-10-w.pdf
  3. Preventing herbicide drift and injury to grapes. Oregon State University. EM 8860. http://extension.oregonstate.edu/yamhill/sites/default/files/spray_drift/documents/3-preventing_herbicide_drift_to_grapes_osu_8660.pdf
  4. Avoid phenoxy herbicide damage to grapevines. Texas Cooperative Extension. http://winegrapes.tamu.edu/files/2015/11/phenoxy1.pdf
  5. Avoiding 2,4-D injury to grapevines. Colorado State University. http://webdoc.agsci.colostate.edu/cepep/FactSheets/Avoiding%202,4-D%20Injury%20to%20Grapevines.pdf
  6. Questions and answers about vineyard injury from herbicide drift. Kansas State University. MF-2588. https://www.bookstore.ksre.ksu.edu/pubs/MF2588.pdf
  7. Need Help? Pesticide drift consultant. Northern Grapes Project. http://northerngrapesproject.org/wp-content/uploads/2013/01/11-3-NE-Find-Drift-Consultant.pdf
  8. Top 10 questions about herbicide drift into vineyards. Iowa State University. https://www.extension.iastate.edu/wine/growersnews/243-may-29-2013#Top
  9. The view from New York: Diagnosis, economics, management of grape injury from2,4‐D and other growth regulator herbicides. Northern Grapes Project. http://northerngrapesproject.org/wp-content/uploads/2013/01/Martinson-2-4D-Presentation.pdf