By: Maria Smith and Dr. Michela Centinari, Dept. of Plant Science
This is the first of two posts on grapevine canopy management in the early growing season from bud burst to bloom. The second in the series will be post in two weeks and will focus on pre- or trace-bloom leaf removal for crop level and disease pressure control.
This week, our blog post will focus on shoot thinning, the first canopy management practice of the growing season. As seen in the pictures below, we spent last week shoot thinning Grüner Veltliner (V. vinifera) vines in a central Pennsylvania vineyard (Figure 1).
In the following sections, we will highlight the benefits and costs associated with shoot thinning while providing a few general shoot thinning guidelines for both V. vinifera and hybrid cultivars in the Mid-Atlantic region.
Benefits of Shoot Thinning Grapevines
While dormant pruning (https://psuwineandgrapes.wordpress.com/tag/dormant-pruning/) is the primary tool used by grape growers to maintain vine structure, canopy architecture and regulate crop level, shoot thinning provides an additional canopy management tool to bring vines into vegetative and fruiting balance by reducing shoot density and the number of clusters per vine. Cluster thinning later in the season may be needed in order to balance highly-fruitful vines.
In addition to improving balance between vegetative growth and fruit biomass, other benefits of shoot thinning include:
- Reduction of canopy density and fruit shading: through removal of selected shoots, shoot thinning reduces overcrowding of shoots in the canopy thus reducing the number of leaf layers and improving sunlight exposure to fruit (1).
- Reduction of disease pressure: reducing canopy density improves air circulation and sunlight penetration that promotes quicker drying of leaves and fruit, as well as increases spray penetration.
Timing of Shoot Thinning
Shoot thinning should be done early in the growing season, when shoots are approximately 5-6 inches long and not more than 10-12 inches long. Shoot thinning should be timed after the date of last ‘expected’ frost, such that secondary or non-damaged primary shoots can be retained in the event of a late spring frost.
When shoot thinning is performed before inflorescences are visible (shoots 0.8 inch to 4 inches), increased vigor of the remaining shoots and lateral shoot growth may occur as a response, negating the benefits of shade reduction (1). When performed too late (shoot longer than 10 inches), shoots become lignified at the base and difficult to remove. If performing late thinning, pruning shears should be used if there is risk of damaging the arm of the vine. It also takes longer to thin longer shoots, potentially decreasing the cost-effectiveness of this practice.
Shoot Spacing and Density Recommendations
Generally, shoot thinning on cane-pruned vines is easier, faster, and more straight-forward than spur-pruned vines, which require substantially more decisions regarding what shoots to retain or remove, and where shoots should be spaced along the cordon (2; Figure 2).
Plant genotype, soil, and climate are all factors influencing vine vigor potential and capacity to fully ripen a crop. Therefore, these factors indirectly affect the appropriate number of shoots to retain at thinning. Many Cooperative Extension websites provide recommendations on range of optimal shoot density based on cultivars grown in their region. [Author’s note: for the eastern US see the additional resources section at the bottom of the post.]
Shoot density targets for Pennsylvania regions:
- For vinifera cultivars it is recommended to leave 3 to 5 shoots per linear foot of canopy (3, 4; Figure 3). The general rule of thumb is to retain fewer shoots in red varieties and more in white varieties. However, other factors (i.e., cultivar disease susceptibility) must be taken into consideration.
- For most of the hybrid cultivars it is recommended to leave 4 to 6 shoots per linear foot of canopy (5).
- For Concord and other native cultivars, as many as 15 shoots per linear foot of canopy can be retained (4).
- In divided canopies trellis systems, the same shoot density along each cordon should be retained (Figure 4).
In addition to the number, the position of the shoots along the cordon is important. Ideally, the shoots retained should be equally spaced to promote a uniform, balanced canopy.
What types of shoots should you remove?
- Weak, non-fruitful shoots especially if they grow in crowded areas of the canopy.
- Secondary and tertiary shoots, if a primary healthy shoot has emerged.
- Shoots arising from the trunk that are not retained for renewal wood (e., new trunks and canes or cordons).
Does shoot thinning improve fruit composition and wine sensory perception?
The associated costs with manual labor and labor shortages are reasonable considerations before implementing vineyard management practices. This is also true for implementing shoot thinning techniques into a vineyard. Nonetheless, it is also important to consider the potential benefits from implementing a new practice.
The effects of shoot thinning practices on hybrid varieties are a bit unclear. A previous study on shoot thinning found that shoot thinned Marechal Foch (red interspecific hybrid of Vitis) vines exhibited higher total soluble solids (ᵒBrix) and berry anthocyanin concentrations as compared to un-thinned vines (6). The increase in berry anthocyanin, however, did not translate into higher anthocyanin concentration in the final wine, and furthermore, shoot thinning did not impact the sensory perception of “fruitiness” of the wines (6). In contrast, a study focusing on Corot noir (red interspecific hybrid of Vitis) implementation of shoot thinning provided inconsistent results in grape and wine quality across a two-year (2008-2009) evaluation, which was determined by ᵒBrix, pH, titratable acidity (TA), wine anthocyanin, berry and wine tannin content (7). Shoot thinning increased berry ᵒBrix, wine alcohol concentration and anthocyanin content only in second year of this study. While berry TA at harvest was lower (e.g., 2008, un-thinned = 8.6 g/L, shoot thinned = 7.6 g/L), there were no differences in the TA of wine in either year (7). Shoot thinning also decreased berry seed tannin in 2008 and berry skin and wine tannin in 2009, which could have negative implications for final wine, considering generally low tannin concentrations in hybrid red wines (7). In an effort to compensate for costs associated with shoot thinning and yield loss, this study on Corot Noir suggested growers increase the price of grapes by 11 to 20% per ton, depending on the average annual market price and yield loss (7).
A study in Fayetteville (Arkansas) on three highly-fruitful French-American hybrid cultivars (Aurore, Chancellor, and Villard noir) found that shoot thinning increased fruit sugar accumulation (ᵒBrix) only in Chancellor and without changes in pH or TA, while a more intense juice color was associated with shoot thinned vines of both red cultivars (Chancellor and Villard noir; 8). In addition, shoot thinning favorably decreased the Ravaz index (yield to pruning weight ratio) for all three cultivars, improving vine balance (8).
The results of these studies suggest that in some situations the costs of shoot thinning may not outweigh the benefits, especially for hybrids that do not command a high market value (Finger Lakes Grape Prices 2016). However, none of these studies account for potential reduction in disease infections, which may help justify the implementation of shoot thinning in a given vineyard. For example, it has been found that higher shoot density may contribute to the increased incidence of Botrytis rot infections in susceptible cultivars such as Seyval Blanc (9) and Vignoles (4).
In other cases, shoot thinning improved fruit composition in Pinot Noir and Cabernet Franc for two consecutive vintages (1), and also increased color intensity, phenolic content, and total anthocyanins of Cabernet Franc berries (1). Benefits of shoot thinning on fruit quality and wine sensory perception have been reported for other vinifera cultivars, such us Barbera (10) and Sauvginon blanc (11).
Unless your vineyard is located in a low or moderate vigor site, shoot thinning is strongly recommended for vinifera cultivars growing in the Mid-Atlantic region.
If you want to assess the effects of shoot thinning on fruit composition, plan to leave half of a row of vines un-thinned and thin the remaining half to a consistent number of shoots per foot (e.g., 4 shoots per foot). Alternatively, use two rows (of the same variety and cultivar) to assess the impact of shoot thinning in your vineyard: one row thinned and the adjacent row un-thinned. These two methods should help evaluate the effect of shoot thinning on berry composition at harvest and if possible, on wine chemistry and sensory perception assuming that the lots of berries can stay separated through wine production.
Effects of shoot thinning on vine physiology
Impacts of shoot thinning on vine physiology and performance are complex. A study conducted in Italy evaluated the whole-canopy photosynthetic response to shoot thinning using spur-pruned Barbera vines (V. vinifera; 10). Vines were thinned to 5 shoots per foot, reducing the total shoot number by 50% as compared to un-thinned control. In this study (10) shoot thinning significantly improved grape sugar content, color, and phenolics. Despite the benefits provided by shoot thinning on fruit composition, which has been already reported by other studies, what makes this study unique and interesting it that they investigated the mechanisms behind the improvement in grape quality through the measurement of whole-canopy net carbon assimilation. Although the shoot-thinned vines had initially lower photosynthesis (carbon assimilation) than un-thinned vines due to the removal of photosynthetic source (leaf), they had regained photosynthetic capacity to levels similar to the un-thinned vines within 17 days of treatment. This occurred as a result of a substantial increase in both main leaf size and amount of lateral leaves as a result of shoot thinning (10). Therefore, individual shoots of thinned-vines had a higher supply of assimilates (e.g., sugar) per unit of crop, which can increase sugar accumulation during ripening. This may explain why shoot thinning improved grape composition in Barbera under these growing conditions.
Additional Shoot Thinning Resources
- Cornell Cooperative Extension (CCE) video tutorial on shoot thinning: https://www.youtube.com/watch?v=5wyFolawc-s
- Fiola, J. 2017. Canopy Management – Shoot thinning and positioning. “Timely Vit” from UMD Extension. https://extension.umd.edu/sites/extension.umd.edu/files/_docs/programs/viticulture/TVCanopyMgmtShootThinPos.pdf
- Martinson, T and Vanden Heuvel, J. Shoot density and canopy management for hybrids. http://www.fruit.cornell.edu/grape/pdfs/Canopy%20Management%20for%20Hybrids%20-2007.pdf
- Reynolds AG., et al. 2005. Timing of shoot thinning in Vitis vinifera: impacts on yield and fruit composition variables. 56, 343-356.
- Intrieri, C and Poni, S. Integrated evolution of trellis training systems and machines to improve grape and vintage quality of mechanized Italian vineyards. AJEV. 46, 116-127.
- Fiola, J. 2017. Canopy Management – Shoot thinning and positioning. “Timely Vit” from UMD Extension.
- Walter-Peterson, H. 2013. Shoot thinning: Good for the vines, but good for the wines? Finger Lakes Vineyard Notes.
- Martinson, T and Vanden Heuvel, J. Shoot density and canopy management for hybrids. CCE. http://www.fruit.cornell.edu/grape/pdfs/Canopy%20Management%20for%20Hybrids%20-2007.pdf
- Sun Q., et al. 2011. Impact of shoot thinning and harvest date on yield components, fruit composition, and wine quality of Marechal Foch. AJEV. 62:1, 32-41.
- Sun Q., et al. 2012. Impact of shoot and cluster thinning on yield, fruit composition, and wine quality of Corot noir. AJEV. 63:1, 49-56.
- Morris, JR. et al. 2004. Flower cluster and shoot thinning for crop control in French-American hybrid grapes. AJEV. 55:4, 423-426.
- Reynolds, AG et al. 1986. Effect of shoot density and crop control on growth, yield, fruit composition, and wine quality of ‘Seyval blanc’. J. Amer. Soc. Hort. Sci. 111, 55-63.
- Bernizzoni, F. et al. 2011. Shoot thinning effects on seasonal whole-canopy photosynthesis and vine performance in Vitis vinifera L. cv. Barbera. Aus. J. Grape Wine Res. 17, 351-357.
- Naor et al. 2002. Shoot and cluster thining influence vegetative growth, fruit yield, and wine quality of ‘Sauvignon blanc’ grapevines. J. Amer. Soc. Hort. Sci. 127(4), 628-634.
Maria Smith is a viticulture PhD candidate with Dr. Michela Centinari in the Department of Plant Science. She specializes in cold stress physiology of wine grapes. She was the previous recipient of the John H. and Timothy R. Crouch Program Support Endowment, an endowment founded and funded by the Crouch brothers, original owners of Allegro Winery in Brogue, PA. She is currently funded by the Northeast Sustainable Agriculture Research and Education (NE-SARE) program, a program from the USDA National Institute of Food and Agriculture (NIFA).
By: Jody Timer, Entomology at LERGR & EC
In the colder parts of this state, we are always looking for new berries to make into wine.
Ideally, we are on a search to find berries that will stand cold winters and late frosts. As an end to this means, three years ago at Lake Erie Regional Grape Research and Extension Center (LERGR & EC) we planted an experimental patch of Haskap bushes (Lonicera caerulea).
Haskap or blue honeysuckle, is an extremely cold hardy, edible berry producing plant, resisting temperatures as low as -46°C (-50.8°F) (Thompson 2008). Even flowers can be exposed to temperatures of -7°C (19.4°F) with no detriment to fruit set. Haskap is also tolerant of a wide range of soil pH (5.5-7.5) (Retamales and Hancock 2012) allowing for production in many different soils. The bushes will survive in the wild in swamp-like conditions, but they thrive in well drained soils. The fruit development period for Haskap starts very early in spring and is very short; 6-8 weeks from bloom to harvest (Thompson 2006). In our climate, Haskap will produce fruit as early as mid-June, coinciding somewhat with the strawberry market. The small blue fruits have a fresh, somewhat tart, raspberry/blueberry to cranberry flavor. They should be purple all the way through before they are fully ripe. These plants do not sucker, need little pruning, and tend to fruit when very young. A Haskap bush can be productive for 30 years. Haskaps are native to Siberia and northeastern Asia (Bors et al. 2012), and were recently introduced to the North American market being advertised for its many claimed health benefits. Some researchers (Bors et al. 2012) believe that haskap could replace blueberries as the new ‘super fruit’. Lonicera have been used widely in folk medicine in northern Russia, China and Japan since ancient times. In recent years, phenolic compounds present in fruit crops, especially berries, have gained much attention due to the accumulating scientific evidence of their potential health benefits. Its juice has 10 to 15 times more concentrated color than cranberry juice. The fruit is high in Vitamin C, Vitamin A, fiber, and potassium.
Antioxidant levels are measured using the ORAC (oxygen radical absorbance capacity) method. A wide variety of food has been tested using this methodology, with the Haskap Berry being rated very highly in comparison with other berries. The berries’ extremely high ORAC value indicates a high anthocyanin, poly phenol, and bioflavonoid content.
In addition to fresh market potential, Haskap can be used in processed products including pastries, jams, juice, ice cream, yogurt, sauces, and candies. These berries also make a nice dark red or burgundy colored wine. The Canadian market is receives about $13.00 per pound, while the Japanese market is about $30.00 per pound of berries (LaHave Forests’ Haskap Day).
Haskap fruits obtain almost full size 4 weeks after blooming and begin to turn purple. The dark skin of the fruit is covered by a waxy coating (bloom) and resembles the outer covering of blueberries and concord grapes. At 5 weeks old they are fully purple but at 6 or 7 weeks old they are fully ripe and tasty. That is for a normal year. But some varieties do develop slower especially if not pruned to let in enough light. Though Haskap is touted as having few disease and insect pest problems, the plant can be negatively impacted by sunburn, mildew and birds.
Bob Bors of University of Saskatchewan has been the primary researcher of Haskap varieties. The following is from the research at the University of Saskatchewan (www.usask.ca/agriculture/dom_fruit/index.html):
Like many other fruit crops, haskap requires pollen from an unrelated variety in order to set fruit. Haskap does not have separate male and female plants. When two compatible haskap varieties are planted close to each other, both bushes will set fruit. But it is not enough to have compatible pollen. To pollinate each other both plants must bloom at the same time and be genetically compatible. There is overlap between nearby groups but peak bloom is usually five days different between categories. Blooming times are dependent on where the Haskap are located.
‘Tundra’ may be the variety best suited for commercial production at this time (2007).Tundra’s fruits were firm enough to withstand commercial harvesting and sorting at the University of Saskatchewan, yet tender enough to melt in the mouth. Firmness is a rather rare trait especially for large fruited blue honeysuckles. Ranking at almost the top for flavor and fruit size the shape of its fruit was deemed acceptable for the Japanese market. Its fruit is at least 50% larger than blue honeysuckles currently available in Canada and the US. Its firmness and the fact that this variety does not ‘bleed’ from the stem end when picked could make this variety especially suited for Individually Quick Frozen (IQF) processing.
‘Borealis’ has the distinction of having the best testing and largest fruit size in our breeding program as of 2007. (However, there were many good tasting haskap varieties and it was hard to decide) Its fruits were usually twice the size of any of the 35 Russian varieties in our collection of similar age. (Most varieties of haskap/blue honeysuckles seem to have larger fruit as the bushes get older). Unfortunately, this variety does not have the firmness of ‘Tundra’ and it is not suitable for IQF. It tends to get a bit mushy when handled with equipment. It may be best for home gardeners or U-pick operations who can hand pick the delicate fruit. Or if shake harvesting the fruit, the berries will be damaged and will need to be quickly processed. Not only did the breeder and a University panel choose it as having the best flavor, but its top rating for flavor was also verified by a Japanese Company that chose it as the best tasting of 43 samples!”
The Tundra is by far the hardiest and best growing of the four varieties we have planted at the research station in Erie County (PA). The Indigo Treat is also doing well. Indigo Gem and Berry Blue have both developed black leaves. We are going to determine this year if the black leaves are from sunburn, mildew, or early dominancy. Haskap can go dormant as early as mid-August which may be the cause of brown leaves.
Haskapa of Nova Scotia at www.Haskapa.com has a wide variety of products made from Haskaps. They include syrup, wine, gin, jelly, soap, dried berries, and oils to name a few. This new crop could be grown alongside existing fruit tree orchards, blueberries, raspberries, strawberries, and juice and wine grape vineyards that currently dominate the landscape. If successful, these new crops may serve to supplement the growers’ income, especially in adverse years.
- Bors, B., Thomson, J., Sawchuk, E., Reimer, P., Sawatzky, R., and Sander, T. Haskap breeding and production-final report (pp. 1-142). Saskatchewan Agriculture: Regina.
- Retamales, J.B., and Hancock, J.F. 2012. Nutrition. In J.B. Retamales and J.F. Hancock (eds.), Blueberries (pp. 103-142). Wallingford: CABI.
- Thompson, M.M. 2006. Introducing haskap, Japanese blue honeysuckle. Journal of American Pomological Society 60:4:164-168.
- Thompson, M.M. 2008. Caprifoliaceae. In J. Janick and R.E. Pauli (eds.), The Encyclopedia of fruit and nuts (pp. 232-235). Wallingford: CABI.
By: Denise M. Gardner
The use of oak in the winery offers many options from winemakers. With today’s availability of various oak products (i.e., chips, staves, powders), winemakers have more choices than ever before to integrate a wood component into their product. However, the use of oak barrels remains an intrinsic part of most winery operations. During the aging process, oak barrels have the potential to:
- integrate new aromas and flavors into the wine.
- add mouthfeel and/or aromatic complexity to the wine.
- change the wine’s style.
- add options and variation for future wine blends.
Additionally, the barrel room is often romantically viewed upon by consumers, and it is not uncommon for visitors to find barrel show cases in many tasting rooms, private tasting rooms, or while on a guided winery tour.
Nonetheless, barrels also offer challenges to wineries. One of the most inherent challenges associated with a barrel program is maintaining a sanitation program.
The growth of spoilage yeast, Brettanomyces, is often discussed amongst wineries that utilize barrel aging programs. However, additional spoilage yeast species such as Candida and Pichia have also been associated as potential contaminants in the interior of wine barrels (Guzzon et al. 2011). Brettanomyces, commonly abbreviated as Brett, was first isolated from the vineyard in 2006 (Renouf and Lonvaud-Funel 2007) and until that point had most commonly been associated with the use of oak in the winery. The growth of Brett in wine has the potential to impart several aromas as a result of volatile phenol [especially 4-ethylphenol (4-EP) and 4-ethylguaiacol (4EG)] formation in the wine. Descriptors used to describe a Bretty wine include: barnyard, horse, leather, tobacco, tar, medicinal, Band-Aid, wet dog, and smoky, amongst others. It should be noted that the presence of these aromas does not necessarily confirm that Brett is in the wine; there are other microflora, situations (e.g., smoke taint) or oak chars that can impart some of these aromas, as well.
When barrels are filled with wine, it’s important to monitor the wine regularly for off-flavors while it is aging. Wines should be regularly topped up with fresh wine to avoid surface yeast or acetic acid bacteria growth that can contribute to the volatile acidity (VA). We usually recommend topping barrels up every-other-month. Keep in mind that free sulfur dioxide concentrations can drop quicker in a barrel compared to a tank or wine bottle (MoreFlavor 2012) and free sulfur dioxide contractions should be checked (in conjunction with the wine’s pH) and altered as necessary to avoid spoilage. Finally, when using a wine thief, both the internal and external part of the thief need cleaned and sanitized in between its use for each and every barrel to avoid cross contamination. Dunking and filling the thief in a small bucket filled with cold acidulated water and potassium metabisulfite (acidulated sulfur dioxide solution) is a helpful quick-rinse sanitizer.
Barrels offer a perfect environment for microflora to flourish. Wine barrels are produced from a natural substance (wood), which has its own inherent microflora from the point of production; obviously, barrels are not a sterile environment when purchased. However, the structure of wood is rigid and porous, which provides nooks and crevices for yeast and bacteria to harbor within. The porosity of the wood also makes it difficult to clean and sanitize, especially when compared to cleaning and sanitation recommendations associated with other equipment like stainless steel tanks. Guzzon et al. (2011) found that barrels used over 3 years in production had a 1-log higher yeast concentration rate retained in the barrel compared to new and unused oak barrels. This demonstrates the ideal environment within the barrel for retaining microflora over time, even when adequate cleaning and sanitation procedures are utilized in the cellar.
Common barrel sanitizers include ozone (both gas and aqueous), steam, hot water, acidulated sulfur dioxide, and peroxyacetic acid (PAA). A study conducted by Cornell University on wine barrels used in California wineries found the use of sulfur discs, PAA at a 200 mg/L concentration, steam (5 and 10 minute treatments) to be effective sanitation treatments for wine barrels (Lourdes Alejandra Aguilar Solis et al. 2013). In this same study (Lourdes Alejandra Aguilar Solis et al. 2013) ozone (1 mg/L at a 5 and 10 minute treatment) was also evaluated and found effective in most barrels tested, but a few barrels that did not show adequate reduction with the ozone treatment. While the research conducted by Cornell indicated the potential lack of cleaning the barrel thoroughly before the ozone sanitation treatment, Guzzon et al. (2011) cited ozone’s efficacy is most likely caused by its concentration. Both are important considerations for wineries.
Barrels should always be effectively cleaned of any debris and or tartrate build up before applying a sanitation agent. This is essential to allow for maximum efficacy during the sanitation step. High pressure washers, a barrel cleaning nozzle, and the use of steam are some options available to wineries in terms of physically cleaning the interior of barrel. Additionally, some wineries use sodium carbonate (soda ash) to clean some of the debris (Knox Barrels 2016, MoreFlavor 2012) in addition to the use of a high pressure wash. Always remember to neutralize the sodium carbonate with an acidulate sulfur dioxide rinse prior to filling with wine.
Dr. Molly Kelly from Virginia Tech University has previously recommended a 3-cycle repeat of a high-pressure cold water rinse, followed by high pressure steam before re-filling a used barrel and assuming the wine that came out of that barrel was not contaminated with spoilage off-flavors (Kelly 2013). If the barrel is hot by the end of this cycle, it may be advantageous to rinse with a cold, acidulated sulfur dioxide solution before filling the barrel with new wine. If there isn’t wine available to refill the barrel, it can be stored wet with an acidulated sulfur dioxide solution or using sulfur discs (Kelly 2013).
It is not usually recommended to store used barrels dry for long periods of time, and wineries can use an acidulated sulfur dioxide solution (top off as if it had wine in it) for long-term storage. However, wineries that store their barrels dry need to rehydrate the barrels prior to filling with wine. Check the cooperage for leaks, air bubbles, and a good vacuum seal on the bung. Steam or clean water (hot or cold, overnight) are adequate rehydrating agents (Pambianchi 2002). Barrels that leak wine offer harboring sites for potential yeast, bacteria, and mold growth, which can all act as contaminants to the wine itself.
It should be noted that contaminated barrels (barrels that produce a wine with off-flavors) may need extra cleaning and sanitation steps to avoid future contamination when the barrel is refilled. It is typically recommended to discard barrels that have a recorded Brett contamination. If the barrel has picked up any other off-flavors, especially during storage, it should probably be discarded from future wine fillings.
Barrels undoubtedly offer several challenges for wineries, including proper maintenance, cleaning and sanitation. Nonetheless, engaging in good standard operating procedures for maintaining the barrel’s cleanliness can help enhance the longevity of the barrel and minimize risk of spoilage for several wine vintages.
Guzzon, R., G. Widmann, M. Malacarne, T. Nardin, G. Nicolini, and R. Larcher. 2011. Survey of the yeast population inside wine barrels and the effects of certain techniques in preventing microbiological spoilage. Eur. Food Res. Technol. 233:285-291.
Kelly, M. 2013. Winery Sanitation. Presentation at Craft Beverages Unlimited, 2013.
Knox Barrels. 2016. Barrel Maintenance.
de Lourdes Alejandra Aguilar Solis, M., C. Gerling, and R. Worobo. 2013. Sanitation of Wine Cooperage using Five Different Treatment Methods: an In Vivo Study. Appellation Cornell. Vol. 3.
MoreFlavor. 2012. Oak Barrel Care Guide.
Pambianchi, D. 2002. Barrel Care: Techniques. WineMaker Magazine. Feb/Mar 2002 edition.
Renouf, V. and A. Lonvaud-Funnel. 2007. Development of an enrichment medium to detect Dekkera/Brettanomyces bruxellensis, a spoilage wine yeast, on the surface of grape berries. Microbiol. Res. 162(2): 154-167.
By: Andy Muza, Penn State Extension – Erie County
As the season begins, growers should be prepared to manage a serious pest which can cause substantial economic losses. The grape berry moth (GBM) is a prevalent pest of grapes throughout Pennsylvania and the eastern United States. The larval stage feeds on berries and causes yield losses due to consumption and shelling of berries and by providing entry sites for fungi that can cause cluster rots.
I consider management of this pest to be a three phase process which includes: 1) PRE –TREATMENT Phase; 2) TREATMENT Phase; 3) POST – TREATMENT Phase.
1) PRE-TREATMENT PHASE
Follow maintenance procedures outlined in your sprayer manual. Check pump, hoses, filters, nozzles, etc. to be sure that everything is in good working order before your first pesticide application. Also practice routine sprayer maintenance during the season such as lubrication of bearings and cleaning and flushing of the sprayer after each use.
Calibration of Sprayer
Sprayers should be calibrated early in the season well before any insecticide or fungicide spraying is required. Calibration of sprayers ensures that the appropriate amount of spray material is being applied where it is needed to manage pests. The sprayer should be calibrated in the vineyard under conditions in which the sprayer will be operated. Ideally, sprayers should be calibrated 2-3 times during the season as canopy growth increases.
Classifying a Vineyard Using the GBM Risk Assessment Program
The GBM Risk Assessment Program was developed by Hoffman and Dennehy (Cornell University), (“Bulletin 138, Risk Assessment of Grape Berry Moth and Guidelines for Management of the Eastern Grape Leafhopper” – http://nysipm.cornell.edu/publications/grapeman/files/risk.pdf). It is a method of classifying vineyard blocks for risk (e.g., High, Low or Intermediate) of receiving damage from grape berry moth. The criteria used for assigning risk include: Value of the varieties being grown; Surrounding Vineyard Habitat; History of GBM injury; Climatic factors related to the region where grapes are being grown.
High Risk Classification
Value of the varieties being grown – if higher value varieties such as Vitis vinifera, many hybrids, or table grapes are being grown then these vineyards should automatically be assigned a High Risk Classification. Therefore most vineyards in Pennsylvania, outside of the Lake Erie Region, should initially be classified as High Risk. This classification can be adjusted later if scouting history reveals that GBM injury is consistently low at your vineyard site.
Surrounding Vineyard Habitat – if wooded edges or hedgerows/weedy areas are present around vineyards.
History of GBM injury – if scouting reveals that damage is often above 6% cluster damage in July and /or above 15 % cluster damage (2% berry damage) at harvest. These injury levels were developed with processed juice grape varieties in mind and injury levels may be lower for varieties that command a higher value/ton.
Climatic factors related to the region – if a region has prolonged winter snow cover or mild winter temperatures.
Low Risk Classification
Value of the varieties being grown – if lower value varieties (e.g., juice grapes) are being grown.
Surrounding Vineyard Habitat – if no wooded edges or hedgerows/weedy areas are present around vineyards.
History of GBM injury – if vineyards seldom have problems with GBM. The history of GBM injury for each site is acquired by maintaining scouting records of vineyards over the years.
Climatic factors related to the region – if permanent snow cover is rare and site is prone to severe winter temperatures.
Intermediate Risk Classification – is a catch all classification. If it isn’t High or Low risk then site is classified as Intermediate risk.
Life cycle and description of GBM
Knowledge about the life cycle and ability to identify the pest and injury caused is important for successful management. Moths emerge from the overwintering pupal stage in spring. Emergence in Erie County, Pa. occurs in late May but in other areas of the state this may occur 2 -3 weeks earlier. These moths are small (about 6 mm), brownish with grey-blue coloration at the base of wings (Figure 1). Unless pheromone traps are used it is unlikely that moths will be observed. Adults are active around dusk and have a distinctive zig zag pattern in flight. Mated females lay eggs singly on flower clusters or berries. Eggs are very small (< 1mm), scale-like and whitish, opaque (Figure 2). Due to their size, eggs are difficult to observe without a hand lens. Early in the season larvae hatching from eggs will web together small berries to feed. However, when berries reach about 5 – 7 mm in size, larvae will bore directly into berries to feed. Newly hatched larvae are tiny with white bodies and black head capsules. Later stages are brownish to purple in coloration (Figure 3). Upon completing development larvae exit berries and either drop to the ground to pupate in leaf litter or some will pupate in the canopy in a semicircular leaf flap. Pupae which are encased in leaf sections are light brown to greenish in coloration (5 mm). Leaves with pupae will remain underneath the trellis if there is poor weed control or will be moved by the wind and collect along wood edges, or in brushy areas. Adults will emerge from pupae to begin the next generation. There are usually 3 – 4 generations of GBM per year in Pennsylvania, depending on temperatures during the growing season.
Regular scouting throughout the season (at least weekly) is critical in determining if and where applications should be applied for GBM. A scouting protocol for GBM is described in “Bulletin 138, Risk Assessment of Grape Berry Moth and Guidelines for Management of the Eastern Grape Leafhopper” .
This protocol recommends selecting four different areas in your vineyard to be sampled during each scouting event. Two different areas should be checked in the interior of the vineyard and two different areas along the exterior (border) portions of the vineyard. At each of the four sampling sites, randomly select 5 vines and examine 10 clusters/vine for GBM injury. Determine separate injury levels (# injured clusters/100 clusters = % injured clusters) for the interior and exterior portions of the vineyard. It is important to keep separate injury levels for the interior and exterior areas because border areas near woodlines/hedgerows will usually have higher levels of injury. Therefore, border areas may need an insecticide application while interior areas may not.
When scouting early in the season look for webbing in the clusters (Figure 4). Until berries are large enough to enter, larvae will web together multiple berries and feed from inside webbing sites. Some varieties (e.g., Concord) may exhibit a distinct reddening of portions of the berry if injury occurs before veraison (Figure 5) while other varieties do not (Figure 6). Later in the season look for holes, splits, webbing or dark tunneling underneath berry skin (Figure 7). If injured berries are broken open then larvae may be found.
Map vineyards and keep scouting records – Develop detailed maps of your vineyards and surrounding topography. Keep records of GBM injury levels for each scouting date and vineyard sections checked. These records will provide a GBM history per site.
Pheromone Traps – GBM flight periods can be monitored using commercially available pheromone traps (Figure 8). Traps and pheromone caps can be purchased from a number of sources such as at Great Lakes IPM, Inc. and Scentry Biologicals, Inc. Monitoring traps are baited with small rubber lures impregnated with GBM female sex pheromone for attracting male moths. Pheromone traps may provide an idea of population levels at your vineyard site and can be used as a scouting tool to indicate flight periods. However, trap data are not used for timing of spray applications due to ambiguity concerning correlation of capture numbers and berry injury levels.
Cultural practices are integral for any integrated pest management program. Therefore, maintain good weed control under the trellis. Poor weed management resulting in excessive vegetation under the vines can harbor grape berry moth (GBM) pupae.
Viticultural practices that promote a more open, less dense canopy resulting in better exposure of clusters to sunlight (e.g., shoot thinning, leaf removal, judicious use of nitrogen) will not only improve quality of fruit but will enable better spray coverage.
Vineyard area maintenance such as preventing overgrown, weedy areas around the vineyard will reduce overwintering sites for GBM pupae. If possible, removal of wild grapevines near the vineyard will decrease potential reservoir sites.
2) TREATMENT PHASE
To accurately time insecticide applications it is recommended that the Grape Berry Moth Degree-Day Model be used. The GBM DD Model is a temperature-driven developmental model developed by Tobin and Saunders at Penn State. This model is incorporated into Cornell’s Network for Environmental and Weather Applications (NEWA). Collaborative research at Penn State, Cornell and Michigan State Universities has shown that use of this developmental model can improve GBM management. For a comprehensive explanation concerning the development and use of this forecasting model consult “Focus on Females Provides New Insights for Grape Berry Moth Management” , Issue 14, May 2013.
Use of the GBM DD Model:
- CHECK the NEWA weather station closest to your vineyard. There are a number of NEWA weather stations located throughout Pennsylvania. However, the majority of vineyards outside Erie County, PA will probably not be close enough (i.e., within a few miles) to a NEWA station for this option to be useful. But you can still use the GBM DD Model by recording daily maximum and minimum temperature data on your own. Options include either purchasing a max/min thermometer or weather station for your site. The RainWise AgroMET & IP-100 Package http://www.rainwise.com/ is the authorized choice for participation into the NEWA network.
- MONITOR and RECORD the date of wild grape bloom (i.e., when approximately 50% of flowers open) for each vineyard site. Research has shown that egg laying by females that emerge in the spring (first generation) is closely associated with bloom of wild grapevines. Therefore, the majority of eggs from this generation are laid on wild grape clusters and not in cultivated vineyards. NOTE: If using a NEWA site then enter the date of wild grape bloom into the model. If you do not record a wild grape bloom date for your site then the model does provide an estimated date for the weather station that is used.
- TRACK GBM degree days using a NEWA station closest to your vineyard site OR keep a running total throughout the season of GBM degree days [(Daily MAX + MIN Temperatures)/2) – 47.14 F] starting on the recorded date of wild grape bloom.
- SCOUT to determine injury levels.
- SPRAY (if needed) as close to the designated degree day timings as possible.
The model recommends an insecticide treatment in high and possibly intermediate risk sites when: 810 GBM degree days are accumulated for the second generation; 1620 GBM degree days for the third generation; and 2430 GBM degree days (if harvest has not yet occurred) in years that a fourth generation occurs. Insecticides such as Intrepid, Altacor, and Delegate are suggested for these timings.
If using broad spectrum contact insecticides (e.g., pyrethroids) then applications should be delayed about 100 GBM degree days for each generation (i.e., 910, 1720, 2530 GBM degree days).
Insecticide Choices/Application Practices
There are numerous insecticides effective for GBM which are registered for use in Pennsylvania. Consult the 2017 New York and Pennsylvania Pest Management Guidelines for Grapes (https://store.cornell.edu/p-197039-2017-new-york-and-pennsylvania-pest-management-guidelines-for-grapes.aspx).
Rotate insecticides with different modes of action into your GBM spray program to prevent/delay insecticide resistance. Read the label to determine if a spray adjuvant and/or pH adjustment to spray water is required. Also, incorporate more selective insecticides (e.g., Intrepid, Altacor, Delegate) into your spray program which will aid in conserving natural enemies.
Good spray coverage on clusters is critical. Therefore, spray every row and use appropriate gallonage, speed, pressure, and nozzles for good cluster coverage as the size of the canopy increases throughout the season.
3) POST-TREATMENT PHASE
Evaluate efficacy of applications
Don’t assume that because an insecticide was applied that GBM was controlled. After an insecticide application check areas that were sprayed to determine the effectiveness of the application. High Risk sites in Erie County, PA have benefited from back to back applications (about 10 days apart) per generation due to extremely high population levels at these sites.
Continue to Scout
Monitoring your vineyard(s) not only for GBM but also for other insects, diseases and weeds should continue through harvest.
Keep Accurate Records
Accurate records should be kept each season for: scouting (e.g., dates, pests observed, vineyard location where observed, injury levels); pesticide applications (e.g., pesticides used, rates/acre, gallons/acre applied, etc.) and weather data.
Re – examine management practices
At the end of the season, especially if GBM was not adequately controlled, re – examine management practices by reviewing your records. A few factors to consider that contribute to poor control include: Inadequate Spray Coverage; Inaccurate Spray Timing; Too Few Applications; and Choice of Insecticides.
Change/Fine Tune management practices
The results of re-examining your practices may reveal flaws in your management strategy. If flaws are identified then be prepared to make the necessary changes in the future. Fine tuning your pest management strategy is an ongoing process which should evolve as long as you continue to farm.
By: Denise M. Gardner
At the recent Sparkling Wine Production workshop in PA, our speakers talked a lot about various production methods used to incorporate carbonation into [grape] wine. But what about for a sparkling hard cider?
For base cider production, the objectives are similar to that of sparkling wine: create a fresh and fruity alcoholic product with high acid, good apple flavor, and a clean nose and palate. Nutrient strategies during primary fermentation should be considered by the cider maker, as flaws like hydrogen sulfide (H2S) or general reduction (sulfur-containing off-odors) will diminish the enjoyability of the product. Carbonation has the tendency to enhance the perception of flaws. Therefore, it goes without saying that sanitation is generally very important during this process in order to obtain a clean product suitable for carbonation.
For producers that struggle with obtaining high-tannin apple varieties, sparkling [hard] cider may offer an alternative to the establishment’s product portfolio. In sparkling wine production, low tannin concentrations and perceptions are often preferred, as too much tannin may create a harsh mouthfeel with the additional sensory contribution from the carbonation. This concept may also be applied to sparkling hard ciders.
Malolactic fermentation, MLF, or partial-MLF is determined stylistically by the cider maker. Stabilization including protein stabilization and clarification should be completed prior to carbonation. Dependent on the method of carbonation, sulfur dioxide additions may be required at this step, too.
Dependent on the size and capabilities of the cidery, most sparkling wine production techniques can be utilized by hard cider producers to enhance the carbonation of a hard cider product.
- Bottle conditioning
- Traditional method (Méthode Traditionelle, previously referred to as Méthode Champenoise)
- Charmat, or Tank, method
- Forced carbonation
Bottle conditioning is often used by home brewers as a way to incorporate carbonation in each bottle inexpensively. The concept is relatively simple: add yeast and some additional sugar to each bottle so that the yeast will ferment the sugar while in the bottle. Due to the fact the bottle is sealed, the carbon dioxide developed through fermentation will be retained as carbonation in the bottle. While this is often a preferred method for extremely small operations, the results of this technique are often quite variable, which increases inconsistency amongst the product. Additionally, the resultant product is not typically clear and residual yeast will settle at the bottom of the bottle. Sometimes, this noticeable cloudiness and precipitate is not preferred by consumers. For a good explanation on bottle conditioning, please consider reading this document by Northern Brewer: https://www.northernbrewer.com/documentation/AdvancedBottleConditioning.pdf
The Traditional Method (Méthode Traditionelle) is the common practice that is associated with Champagne production. In this case, carbonation is produced in the bottle by a second yeast fermentation. The difference between this method and bottle conditioning is that the residual yeast is removed through disgorgement prior to the addition of a final sugar and stabilization liquid, called the dosage. This production technique has previously been discussed through the blog post: The Bubbles: Basics about Sparkling Wine Production Techniques, which you can access through the link.
Although many wine fermentation suppliers offer various product addition options for hard cider producers, Scott Labs currently offers The Cider Handbook to make addition decisions easier for producers. Their current product portfolio also features encapsulated yeast products, which some sparkling wine producers have had success in using when utilizing the traditional method of production.
Additionally, this style of sparkling hard cider can use similar equipment utilized by sparkling wine producers.
The Charmat Method (Tank Method) is becoming more popular amongst local wineries, and can also be utilized by sparkling hard cider producers. Here, the secondary yeast fermentation occurs inside a sealed tank and then the hard cider is racked off of the lees into a second pressurized tank. The racked cider maintains the carbon dioxide, carbonation, and the second tank it is racked into can contain the final dosage for the whole volume of hard cider in order to manipulate final sweetness and stabilization. The advantage to this system is that it retains the fruitiness associated with the product and requires less labor compared to dealing with hundreds of bottles in the Traditional Method. The downside to this processing option is the initial cost of processing equipment required to retain pressure inside a tank. As with the Traditional Method, details pertaining to the Charmat Process were previously discussed in the blog post: The Bubbles: Basics about Sparkling Wine Production Techniques.
Finally, one of the easiest methods for obtaining carbonation in your product is through the use of forced carbonation. Some hard cider producers have found success in carbonating kegs of hard cider or working with local wineries that offer carbonation services. With this method, the hard cider should be fully produced, stabilized, back sweetened (if applicable) and filtered by the time it is carbonated.
By Bryan Hed
Another season of grape growing is upon us and it’s a good time to review important disease management principles and be aware of some of the tools to consider integrating into your vineyard management programs this spring.
First is your annual reminder to check out the NEWA website (Network for Environment and Weather Applications) found at http://newa.cornell.edu. On the home page is a map of the Northeastern U.S. marked with the locations of hundreds of weather stations where historical and ‘up to the hour’ weather data can be viewed. Although is provided free on the internet, it is funded through the New York State IPM program. Click on a weather station near enough to you (denoted by a leaf/rain drop icon) to get weather, insect pest, and disease information you need to make important management decisions that could save you time and money. Clicking on ‘grapes’ under ‘crop pages’ will give you access to forecasting models for all the major diseases, as well as the grape berry moth degree day model that will improve your timing of grape berry moth insecticide sprays later this summer. Each model forecast is accompanied by helpful disease management messages and explanations.
Next, let’s move our minds into the upcoming pre-bloom disease management season. It’s important to recognize that the threat of disease this spring (pre-bloom) is largely determined by the amount of overwintering inoculum in your blocks. The amount of overwintering inoculum is dependent on the amount of disease that developed in your vineyard last year or in previous years. In other words, if you have kept diseases well under control in the past, especially last year, then there will be relatively little for pathogen populations to build on and cause damage, at least initially, this year. Some very practical research by Wayne Wilcox at Cornell nicely illustrates this point with powdery mildew (pm) development in susceptible wine varieties. In blocks where pm was well controlled all season, fewer overwintering structures of the fungal pathogen (chasmothecia) were available the following spring to jump start disease cycles. Early disease pressure was relatively low and early sprays were less critical to good commercial control than in blocks where disease control was poor the previous year. Where there was poor control the previous year, more of the pathogen overwintered to start disease cycles the following spring and early sprays were critical to maintaining successful commercial control. This is not to say that a bad year of pm will automatically be followed by another bad year. But it certainly tilts the odds in favor of the pathogen, especially if for some reason, you can’t manage the timely application of your early disease control program (stuff happens). It also doesn’t mean you can slack off this year if you had good control last year. Remember, there’s the weather. The weather ALWAYS plays an important role too. A good illustration of this is an experience by an organic grape grower who, in an extremely wet season, developed a serious, economically damaging case of black rot. In conventionally managed vineyards there are several very effective chemistries to control black rot, but in organic production there are no real effective fungicides, and control of this disease in organic vineyards must rely heavily on cultural measures that reduce the pathogen’s overwintering population. Of course, the grower did everything he could to sanitize the trellis of overwintering fruit mummies and bury mummies that had fallen to the ground to reduce overwintering inoculum. But fortunately, the following year was bone dry during the fruit susceptibility period and black rot was not even an issue. Had the previous wet season been followed by another wet one, I’m quite certain, the battle for control of black rot in that organic vineyard would have required ‘the kitchen sink’ to avoid losses. Unfortunately, we have no control over the weather and accurate forecasts, especially long term, are not something to rely on. But, we can (and should) strive to control overwintering inoculum levels every year and the best way to do that is good, practical, season-long disease control.
So, begin to wrap your minds around the campaign ahead. If you had poor disease control in some blocks last season, have you reviewed your spray records where control failed AND where it worked well? Where it failed, did you use the wrong material at a critical time? I’ve had growers discuss their control failures with me only to discover that their timing was fine, but their choice of material did not cover the disease(s) they intended to control. The number of spray materials, what disease each one controls, and how well each one controls each disease, can be bewildering at times…and the list keeps growing and changing. Also, materials that used to be good choices may have become ineffective due to the development of resistance by the pathogens. For example, materials like the strobilurins (Abound, Sovran, Flint, Pristine) are no longer effective at controlling powdery and downy mildew in many parts of the east. In vineyards where this has occurred, using them during the critical fruit protection period (which used to be a great idea!) can now prove disastrous. The sterol inhibitor fungicides (Rally, Elite, Orius, Mettle, Tebusol, Tebustar, Procure, Viticure, etc) are also exhibiting the effects of resistance by the powdery mildew fungus. Though in most cases they still work on powdery to some extent, they are not appropriate for the critical fruit protection period anymore, around and shortly after bloom (products that include the more active difenoconazole are an exception on less susceptible varieties). However, they may be acceptable for maintaining a clean vineyard outside the critical period. Do you have an accurate grasp on that?
Do you have a firm grasp on the critical fruit protection period? The critical period for fruit protection from all diseases generally extends from ‘just before bloom’ to about 4 weeks later. This is the period when you need to be especially vigilant about minimizing spray intervals, using your best materials that cover all the major diseases (Phomopsis, black rot, powdery and downy mildew), focus on good coverage, etc. It is never profitable to try to cut corners during the critical period. However, if you had heavy amounts of black rot in your vineyard the year before, you should assume you have an unhealthy dose of overwintering inoculum in your vineyard this spring, and prevention of leaf lesions in the fruit zone (which would need to be addressed during the first 3-12” of shoot growth, well before the fruit protection period) would also prove to be critical. This goes for other diseases as well (refer back to the previous example with Wayne Wilcox’ powdery mildew experiment). The pre-bloom presence of visible disease in the fruit zone is a big red flag; it means you’ve got potential for serious fruit loss ahead, especially if weather conditions favor the pathogen (wet, warm, humid, calm, cloudy) during the fruit protection period that follows.
Did you record the relative levels of disease that developed in years past for each of your blocks? In order to do this, you need to be able to identify the various diseases and then scout regularly for them. This takes up valuable time but you can streamline your scouting efforts in many ways. Do you know when you would expect to first see each disease? Downy mildew doesn’t become active until about the 5-6 leaf stage. So, you know you can’t expect to see it until about that time or shortly after that. In which blocks are diseases most likely to occur first? Your block or rows next to the woods would be a good place to start, or perhaps your most susceptible variety. Blocks with the most disease last year would be a good place to start. On which parts of the vine do you expect to see diseases appear first? Can recent weather data help you to determine where to look for the disease? For example, if a black rot infection period occurred 2 weeks ago (and you can find this out easily by searching the NEWA website), would you examine the newest growth, the oldest growth, or would you look for lesions on leaves that were currently expanding and most susceptible 2 weeks ago? The answers to these questions can help you streamline your scouting efforts, save time, and improve your expertise.
Do you fully comprehend the susceptibilities of all the varieties you’re growing? You cannot spray premium Vitis vinifera like the hybrids or natives and expect the same results. What are you going to change this year to address disease control breaches in your vinifera? If you had good control last year, are you ready to do it again this year? OR, do you feel lucky and plan to back off until close to bloom to apply your first spray? I always plan for the worst when it comes to the weather and assume it’s going to be wet, cloudy, and warm; ideal for fungal disease epidemics. Consider that here in the east we are growing a highly vulnerable, susceptible host (wine grapes) on the pathogen’s ‘turf’ (the wet, humid eastern U.S.). The good news is that disease control during the pre-bloom period is generally easier (good spray coverage not a problem, low initial disease/inoculum levels, etc.) and cheaper (can use lower fungicide rates, lower spray gallonage, less expensive materials, less time, etc) than in the post bloom period, and a well prepared pre-bloom disease management program will provide extra insurance against problems during bloom and early fruit set, when your fruit ($) is most vulnerable. Now let’s review the common diseases with some of these questions and concepts in mind.
Phomopsis cane and leaf spot is often the first disease problem we face in the pre-bloom period, particularly where trellis systems maintain lots of old and/or dead wood. That’s because old and/or dead wood is where the pathogen overwinters. Therefore, the more old wood you have in your trellis, the more inoculum you can expect to be battling with this spring. Conversely, cane pruned systems have fewer problems with Phomopsis, and cane pruning/minimizing older wood is an important cultural control for this disease. Fortunately, many areas of PA and other parts of the east experienced a relatively dry spring in 2016, helping to minimize new overwintering infections on year-old wood. But, older cordons and especially dead wood and pruning stubs, can carry overwintering inoculum into many subsequent springs. So, if there was little opportunity for new Phomopsis infections to occur last year, you can still be carrying a fair amount of overwintering inoculum in old cordons and pruning stubs.
During early spring rains, Phomopsis spores flush from lesions on wood and are splashed about to invade any new shoot, leaf, and inflorescence they land on…provided the wetting period/temperature combination falls within a minimum range for infection. The basal-most (oldest) internodes of new shoots are the most susceptible to shoot infections simply because they are closest to the inoculum source; wood. In every trial where I have rated shoot infection of Phomopsis, the most severe lesion development was ALWAYS found (on average) on the first (oldest) internode region of the shoot. Lesion development typically got less severe as my rating progressed through internodes 2, 3, 4, and 5. However, once these internodes become fully expanded after the first few weeks in the season, they are no longer susceptible to lesion development. I rarely see Phomopsis lesion development beyond the fifth internode region. That’s why this disease is best dealt with preventatively, very early, during the first few inches of shoot growth. Infections that occur on the first few internodes of new shoots are not only the most likely to occur, but also the most critical; infections of inflorescences (generally on nodes 2-5) can lead to crop loss early (parts of the inflorescence may be ‘bitten off’ by the pathogen) or later during ripening (cluster stem infections in spring move into berries and cause fruit rot and shelling after veraison). And, infections that occur on the basal-most internodes, can’t all be eliminated by judicious hand pruning during the dormant season. So, in blocks where you suspect any risk of early Phomopsis infections, applications of a fungicide (mancozeb or captan are good choices) at no later than 3-6” of shoot growth are a good investment, particularly if you are not cane pruning. Following up with fungicides at 8-12” shoots and immediate pre-bloom are also important pre-bloom applications. Below are some pics from last year’s blog (Figures 1, 2) to help you get a handle on the appearance of lesions on year-old canes. Unfortunately, determining the presence of Phomopsis on older wood generally involves more than just a visual assessment.
Figure 1. Dark brown lesions on the first few internodes on these Chancellor canes are from Phomopsis infections that occurred during early shoot growth in the previous year (when these were green shoots). The buds present are just ready to burst open with new shoot growth that will be very vulnerable to infection during subsequent rain periods.
Figure 2. Although the 1” shoot stage can be vulnerable to damage from this pathogen, the more critical stage is at 3-6” shoots, when more shoot, leaf, and cluster tissue is exposed and is highly susceptible (below). Note the inflorescence in the upper right picture from which Phomopsis has “bitten off” whole branches, dramatically limiting yield potential for that cluster.
Pre-bloom fungicide applications for Powdery mildew are also prudent during early shoot growth for Vitis vinifera cultivars and highly susceptible hybrids, especially in vineyards where control of this disease may have slipped last year (again, because of lots of overwintering inoculum). The primary inoculum for this pathogen generally comes from overwintering structures of the fungus that are lodged within cracks in the bark of cordons and trunks. Spring rain periods of at least 0.1” of precipitation and temperatures of 50 F or more, are the requirements for release of primary inoculum (ascospores) from the overwintering structures. The more mildew that was allowed to develop the year before, the larger the release of spores in early spring, the more primary infections that are likely to occur, and the more critical the need to control the disease early. Sulfur, oils, monopotassium phosphate, and potassium bicarbonate materials can be good choices for mildew management early on. All of these materials can eradicate small existing powdery mildew infections on leaves and cluster stems. Most do not generally offer any protection from future infections and therefore work best if applied often. Sulfur is an exception, and has the added benefit of providing a week or more of protection against future infections. Many of the more experienced growers like to utilize a mancozeb/sulfur combination to control all diseases during the pre-bloom period. This combination is relatively inexpensive, there are no resistance issues, and it works. Remember to read labels and be aware that you can’t mix sulfur and oils, or oils and captan. The tebuconazole products can be used during early pre-bloom to control powdery mildew as well, especially at the 8-10” shoot stage. These materials are very inexpensive and generally provide enough powdery mildew control to keep vines healthy until the immediate pre-bloom spray (they will also nicely control early black rot infections). At immediate pre-bloom and first post bloom, you want to apply your best powdery mildew chemistries like quinoxyfen (Quintec), difenoconazole (Revus Top), metrafenone (Vivando), fluopyram/tebuconazol (Luna Experience), etc. For native juice grapes, powdery mildew is rarely a concern during the early shoot growth stages, especially in the cooler Lake Erie region of Pennsylvania.
A note about fungicide resistance management and powdery mildew: It’s important to plan your powdery mildew management choices ahead of time with resistance management in mind. The easiest way to do this is to become familiar with FRAC (fungicide resistance action committee) codes listed prominently on the first page of fungicide labels. Fungicides with the same FRAC group number can be considered similar enough in their mode of action/chemistry that resistance to one is resistance to all others within that group. Therefore when you rotate fungicides for resistance management, you’re essentially rotating FRAC groups. Some good rules to remember are to avoid using the same FRAC group consecutively, or more than twice in a given season. The development of powdery mildew resistance is always a concern when using materials like the strobilurins (FRAC 11), the sterol inhibitors (FRAC 3), Quintec (FRAC 13), Vivando (FRAC U8), Luna Experience (FRAC 7, 3), Torino (FRAC U6), and Endura (FRAC 7) to name a few. Resistance is generally not a concern for uses of sulfur, oils, bicarbonates, and the potassium salts (mentioned above), or copper.
Next, black rot: One of the best ways to reduce overwintering inoculum of black rot is to scout your vineyard for old fruit mummies and eliminate them from the trellis. Black rot infected fruit mummies that have overwintered in the trellis are the most potent source of inoculum for infections the following spring. No matter how cold it gets over the winter, the pathogen survives just beautifully in colonized fruit remaining in the trellis. But, dropping this inoculum source to the soil, allows microbial degradation/weathering to reduce the potential for mummies to release spores the following spring. It also places the inoculum source much farther from new, susceptible plant tissue up in the trellis. The best time to ‘sanitize’ the trellis is during dormant pruning; weathering has already accomplished some of the removal of last season’s infected fruit from the trellis, and what remains is relatively easy to see and remove by hand. Experiments we conducted several years ago clearly showed that the earlier the mummies are knocked to the ground during the dormant period, the more time for decomposition to break them down before the next season, and the fewer spores released from the ground the following spring to start new disease cycles. Nevertheless, some inoculum on the ground will survive to release spores in spring, and burial of mummies with cultivation will go a step further to eliminate the threat. Removal of ALL old cluster material from the trellis before bud break is important to maintaining good control of this disease.
It may not be necessary to apply a fungicide for black rot at early shoot stages IF good control of this disease was achieved the previous year AND conscientious scouting and trellis sanitation has been implemented. However, the importance of early shoot infections should not be underestimated as I mentioned above, especially if they result in leaf lesions in the fruit zone. For example, inoculations we performed from early May to early June (simulating wet weather and an overwintering inoculum source (mummies) in the trellis) resulted in leaf and shoot lesions in the cluster zone (Figure 3). Those lesions went on to release spores during the critical fruit protection period, resulting in crop loss of 47-77% on those shoots with infected leaves!
An application of mancozeb, ziram, or captan for Phomopsis will also provide control of early black rot infections. The sterol inhibitor fungicides and strobilurins are also good materials for black rot that are more rainfast than mancozeb, ziram, and captan. The sterol inhibitors also provide excellent post infection activity that can be very useful at terminating an infection that has already occurred (but not yet manifested itself).
Figure 3. Early (pre-bloom) black rot leaf infections in the cluster zone provide inoculum that can add to problems with controlling fruit infection after capfall. The two small tan lesions on the leaf at node 2 are just inches from the developing inflorescence found at node 3 (picture on the right). These lesions will release spores during rainfall periods that could easily be splashed to highly susceptible cluster stems pre-bloom, and developing fruit after capfall. Resulting fruit infections will lead to crop loss.
Downy mildew and the 5-6 leaf stage: This stage marks the point at which the downy mildew pathogen first becomes active and is capable of releasing primary spores from inoculum sources that have overwintered on the ground (leaves and other plant material that was infected during the previous season). As with all other diseases, vineyards that developed a fair amount of downy mildew leaf/cluster infection last year will be at higher risk this spring than vineyards that were kept clean. However, overwintering structures of the downy mildew pathogen can survive more than one season in the soil.
Periods of rainfall with temperatures of at least 52 F meet the requirements of spore release and the first infections; plant surfaces must be wet for infection to occur. While scouting for this disease, expect to see it first in wetter areas of your acreage and pay close attention to leaves near the ground (sucker growth, grape seedlings that germinated from shelled berries last fall) which are most likely to become infected first. Therefore, keeping such low growth to a minimum in spring is a prudent control measure that can delay the development of the disease. It also suggests that if you’re planning vine trunk renewal from sucker growth, you will need to apply fungicides to protect that growth from the ground up as the pathogen becomes active.
Spring leaf infections are identified by the yellow ‘oil-spots’ seen on the tops of leaves (Figure 4), coinciding with white, downy sporulation of the pathogen on the undersides of leaves. Inflorescences can be blighted and show sporulation as well. Sporulation occurs during darkness under high relative humidity, and can typically be seen during a morning scout of the vineyard following a wet/humid night. Under optimum temperatures (70-75F), only an hour or two of plant surface wetness may be required for infection to occur, and new infections can produce their own spores with just 5 days.
Many parts of the northeast experienced drought conditions last year, which severely inhibited the development of this disease. Up in Erie County PA, the disease basically took a vacation in 2016, and I could barely find a handful of lesions on unsprayed ‘Chancellor’ leaves and fruit near the ground all summer: it was the perfect year to start renewal trunks! It wasn’t until later in August that rains finally returned and we began to see a few more infections, but for the most part the disease literally could not get off the ground in Erie county PA in 2016. What does this mean for 2017? The great lack of downy mildew in drought hit areas last year means that pre-bloom disease cycles this year will have to rely on overwintering inoculum from previous years (although spores of downy mildew can travel long distances between vineyards, the first infections will arise from inoculum within your vineyard). I have not found any detailed information as to how long the pathogen can survive in the soil, but I guarantee that if you’ve had downy mildew before, then it’s still there. Whether your area was wet or dry last spring, the principle described earlier still applies: vineyards devoid of downy mildew last year (whether from drought or just plain good control) will be easier to keep ‘clean’ in the pre-bloom period this year.
Mancozeb products are good options for the first downy mildew, Phomopsis, and black rot sprays in the pre-bloom period. Ziram and Captan have a similar spectrum of control, but Ziram is a little weaker on downy mildew, and Captan a little weak on black rot. However, these may be a viable option if these diseases are not a huge threat early on (that is if you had good control last year). These materials are all surface protectants subject to wash-off by rainfall, which means that under heavy, frequent rainfall conditions, application intervals will need to be minimized (7-10 days?) especially for highly susceptible varieties. For that more critical ‘immediate pre-bloom’ spray (and the first post bloom spray), there are other materials like Presidio, Revus, Revus Top, and Zampro that are quite rainfast, very effective, and will provide longer range protection under wet conditions (when you need the protection most and are least likely to be able to stick to shorter spray intervals). However, products like Presidio also require a second active ingredient (like mancozeb) in a tank mix for resistance management purposes (which isn’t a bad idea at this critical spray timing in any case). Other materials like the phosphonates, Ranman, and the strobies /Reason, are probably best utilized outside the critical two sprays around bloom (especially for V. vinifera and highly susceptible hybrids), unless they’re used as tank mix partners with other effective materials. They’re very good materials, but they’re just not the ‘best of the best’.
Figure 4. Yellow oil-spot symptoms of downy mildew on young spring leaves.
One more time for emphasis: the immediate pre bloom and first post bloom (7-14 days later) fungicide applications are the most important you’ll make all year, regardless of variety grown and disease pressure. These two sprays protect your fruit from all the major fungal diseases (Phomopsis, black rot, downy and powdery mildew). Make sure sprayers are properly calibrated and adjusted for best coverage on a bloom-period canopy, spray every row at full rates and shortest intervals, and NEVER extend the interval between these sprays beyond 14 days.
‘Newer’ Fungicides: Aprovia (solatenol) may be worth a try for powdery mildew control (received federal registration in 2015). The active ingredient is related (same FRAC group) to Boscalid (found in Endura and Pristine) and Fluopyram (found in Luna Experience). It also has activity against black rot, but should not be expected to control this disease under high pressure on a susceptible variety.
***Lastly, to help you with all your grape management decisions this year, you should have…
New York and Pennsylvania Pest Management Guidelines for Grapes. An inexpensive, excellent source of research based information for commercial growers; some information in this blog was gleaned from it and it is revised every year to include the newest information. Copies can be purchased at the Cornell Store at https://store.cornell.edu/c-875-pmep-guidelines.aspx. It sells for about $31.