By: Bryan Hed, Plant Pathology Research Technologist, Erie County
At this time of year, it’s so important to continue scouting leaves for the distinctive white ‘downy’ sporulation of downy mildew. Growers of susceptible varieties need to keep closely monitoring their vineyards for active sporulation and use that information in combination with the DMCast model on NEWA.
The presence of active white sporulation on the undersides of leaves means the downy mildew pathogen is capable of spreading quickly under wet conditions and can spiral out of control, strip vines of their leaves and effectively end the season (and the ripening of canes for next year’s crop).
If you find yourself trying to control this disease well into the ripening period, be aware that your list of chemical control options will start to become shorter as we get within 30 (Ranman, Reason), then 21 (Ziram, Presidio (only older stocks; can’t purchase new material anymore)), then 14 (Revus, Revus Top, Zampro) days of harvest, until in the end you’ll be left with some formulations of Captan, copper, and phosphorous acid products (0 day pre-harvest interval).
Its also important to remember that materials like Ranman, Reason, Revus/Revus Top, and Zampro contain chemistries that are prone to the development of resistance. These materials should not be used to put down an epidemic, which will speed up the resistance development process. And, although phosphorous acid products are less prone to resistance development, you will enhance the chances of losing this technology to resistance as well, by using these materials on a heavily diseased vineyard.
Also, limit your use of phosphorous acid products to three applications per season. On the other hand, fungicides like Captan or copper formulations would be least risky in terms of the development of resistance and can be an effective means of controlling downy mildew late into the growing season.
Just be mindful of varieties that may be injured by copper applications, and that copper injury will be exacerbated by application under slow drying conditions and application to wet canopies (for example, don’t make applications to dew covered canopies in the early morning). If you are protecting a non-bearing, young vineyard from downy mildew (you’re not selling/harvesting a crop), you can continue to use mancozeb products past the 66-day pre-harvest interval.
In this week’s blog, you will find updates and information from several of our authors with an emphasis on disease and insect management and vine nutrient status.
Bloom and early fruit set disease management
By Bryan Hed, Department of Plant Pathology and Environmental Microbiology, Penn State Extension
Well, the 2018 season has gone from 0 to 100 mph over the past four weeks, and grapevine shoots are currently growing at a rate of at least an inch a day. Trying to keep grape tissue protected with pesticide sprays can be a bit of a challenge when canopies double or triple in size each week. However, now it’s time for the most critical fungicide applications of the season; the immediate pre and post-bloom sprays. This is your annual reminder. Fruit ($$) of all grape varieties are most vulnerable to infection from all the major fungal diseases at this time (black rot, Phomopsis, powdery and downy mildew), and in many places across Pennsylvania the previous 4 weeks have been warmer and wetter than average; the perfect setup for fungal disease development on fruit. There’s no more critical time to “spare no expense” than immediately before bloom to about 2 weeks (juice grapes) to 4 weeks (wine grapes) after bloom. Use best materials, apply for best coverage, and allow no more than 10-14 days between these next 2 to 3 sprays. At this time, do not rely on materials that we know are slipping in efficacy, or have already slipped in efficacy, due to the development of resistance in many parts of the East (ie, strobilurins and sterol inhibitors).
When I hear from growers that have experienced problems with fungal fruit infection in the past, breaches in disease control are most often traced to the period of grapevine development around bloom. Some common mistakes include: i) use of the wrong materials (there was resistance to what they used, their mix didn’t cover all diseases, their choice of materials wasn’t very effective, etc), ii) stretching of spray intervals (more than 10-14 days between the immediate pre and post bloom spray), iii) less than optimal coverage (canopies were too dense, canopy management was lacking, sprayers weren’t adjusted for maximum coverage, etc), iv) taking a vacation from farming during this period of time (all of the above?).
If you’re growing bunch rot susceptible wine varieties, fruit-zone leaf removal around or shortly after bloom, can improve coverage and create a fruit-zone environment that is less favorable for the growth of fungal pathogens (For more detailed information see: Early season grapevine canopy management, Part II: Early leaf removal). Strict pre-bloom sucker control can delay the rise of diseases like downy mildew and black rot that emanate from the vineyard floor. Pre-bloom shoot thinning, while shoots can be easily removed by hand, will not only balance canopies with yield but also improve the efficacy and value of fruit protection sprays. Proper weed control/maintenance of row middles and cover crop height can reduce humidity in the vineyard and improve drying time of plant surfaces after rainfall. Integrating these cultural practices into your pre-bloom crop management plan will greatly assist your fungicide applications toward maximizing fruit disease control during bloom.
For more details on the various diseases and how to deal with them during this critical fruit protection period, you may find it convenient to check out previous posts from April 7 and June 16, 2017:
Insect updates on Grape Berry Moth and Spotted Lanternfly
By Jody Timer, Entomology, Lake Erie Grape Research and Extension Station
Grape Berry Moth (GBM): The first grape berry moth for the season usually appear at about 150 degree days from January 1st. This year, in the Lake Erie Grape growing region, we had a late spring which resulted in a later-than-usual emergence of GBM (around May 15th). The emergence occurred much earlier for the growers in the Southeastern portion of the state. The research we have done in the past indicates that spraying for GBM prior to the first full generation (not this emerging generation) is more effective and will not adversely affect yields at harvest. So this generation, which starts to peak at wild grape bloom and continues for about 10 days, does not in most cases need to be sprayed. Wild grape bloom in the Lake Erie Grape growing region occurred around May 30th, it was as early as May 13th in the southeastern regions of PA. Wild grape bloom is used as the biofix for the NEWA system to start accumulating degree days. This system uses the GBM phenology model to recommend optimal spray timings for GBM http://newa.cornell.edu. It is important that you keep track of when wild bloom occurred in your area to allow the model to precisely track the GBM phenology. If you missed the wild bloom date, the NEWA system will calculate wild bloom for your area based on historical data. The best way to determine infestation of your vineyard is to scout for damage. This generation of GBM produces webbing on the flowers and clusters. This webbing, although harder to scout for than later berry damage, is a good indication of severity in the ensuing generations. If your vineyard has high GBM consider spraying more often during the upcoming generations. Grape berry moth can cause considerable damage to vineyards through berry damage and late season rots.
Spotted Lanternfly (Lycorma delicatula): This new invasive insect was first discovered in Bucks County in 2014, the affected area was placed under quarantine to prevent the movement of the insect and its egg masses. Prior to its discovery in the fall of 2014, the spotted lanternfly had not been found in the United States. This fall, when the adults were flying and laying eggs, the quarantine area saw considerable increases and movements of the population. As a result, the quarantine area has been expanded to include all of the counties in southeastern PA. There has also been a colony found in Virginia. Spotted lanternfly host plants including fruit trees, ornamentals, hardwood trees, and grapevines. These insects are exhibiting a preference for tree of heaven (Ailanthus altissima) and vines including grapevines. Spotted lanternfly has the potential to cause substantial damage. Some have estimated potential crop losses, which includes Pennsylvania apples, grapes, and hardwoods, at $18 billion dollars. While feeding on and damaging their host plants, spotted lanternfly also ejects a liquid called honeydew which causes sooty mold and attracts secondary insect pests. Spotted lanternfly overwinter as egg masses, which are small (about 1-4”) and greyish white. They somewhat resemble a dirt splatter.
The first nymphs began to hatch in late April or May and complete four instars. These nymphs are 4-9 mm long and wingless with black with white spots. The fourth instar develops red patches, and then emerge into adults in late summer. This time of the season it is important to scout for egg masses, which although hatched, would indicate an infestation in your area. The black and white nymph stage will be present now.
There is a team of state, federal, and local public officials, academic researchers, and extension personnel working on the problems dealing with this insect. It is important to report findings of spotted lanternfly is you are not in the quarantine area. The website: https://extension.psu.edu/spotted-lanternfly as well as the PDA website has important information on this insect and includes numbers to call if you find insects outside of the quarantine area.
Assessing vine nutrient status
By Dr. Michela Centinari, Assistant Professor of Viticulture, Department of Plant Science
Proper vine nutrient management is crucial for the vineyard longevity, as it helps ensure adequate vegetative growth, fruit set and growth, and optimum wine quality. While some nutrients up-taken by the vine are recycled through fallen-leaves decomposition, the majority of nutrients leave the vineyard in harvested fruit, pruned-wood material (if the brushes are not chopped and left in the vineyard), or through leaching and runoff. Assessing vine nutrient status should be a routine practice and used not just to confirm a suspected nutrient deficiency.
To determine vine nutrient status in an established vineyard, plant tissue nutrient concentration should be analyzed at bloom and/or later in the season around véraison. A soil test is useful and can provide clarification, but has limited benefit. It will indicate relative nutrient availability, but it does not tell what and how much the vines absorb.
What type of tissue to collect for nutrient analyses
There is a long-standing debate about what leaf tissue (blade, petiole, or the whole leaf) best reflects vine nutrient status and correlates to nutrient requirements for optimum vine growth, yield, and fruit composition. However, in the eastern US, the sufficiency range (or target value) of each nutrient concentration is only defined for petiole tissue.
When to collect grapevine petiole samples for nutrient analyses
Collecting a petiole sample at both bloom and véraison and having it analyzed will provide meaningful insight when developing a nutrient management plan. For example, if you noticed visual symptoms of nutrient deficiency in the previous growing season (Figure 1), a nutrient test at bloom will help determine if there is an actual deficiency, and you will be able to correct it in a timely manner (1). Nutrient concentrations in leaf tissue tend to be more stable as the season progresses, so taking a sample at véraison is typically recommended compared to taking samples at bloom, especially for routine analysis (1).
How to collect grape leaf tissues for nutrient analyses
A comprehensive and illustrated guideline on how to collect whole leaf samples (which can also be used for petiole sampling) is on page 12 of the Vineyard nutrient management in Washington State extension bulletin. Be sure to sample each variety separately and to collect 50 large petioles or 100 small ones per variety.
Where to send the samples
Use a reliable lab in your area that has experience in vineyard tissue testing, and use the same lab each year so that the analysis is consistent. If you are in Pennsylvania you can send your plant tissue sample to the Penn State Agricultural Analytical Services Lab. Please be sure to provide all the information required to interpret the lab results (e.g., type of tissue, time of the year the sample was collected). Lab results will report the concentration of each nutrient analyzed and if its level is low/deficient, sufficient, or too high/excessive. If you need assistance with interpreting your report, contact your local extension for further assistance. You can find the contact information for your local Penn State Country Office by entering your zip code in the search field on this site: bit.ly/2J9yCPr
- Moyer M., Singer S., Hoheisel G., and Davenport J. – Vineyard Nutrient Management in Washington State, EM111e (Bulletin) Washington State University
Comments concerning insect and disease management at this time of the season (Immediate Prebloom – Early Postbloom period)
By Andy Muza, Penn State Extension – Erie County
I’ll begin by stating that every commercial grape grower in Pennsylvania should have a copy of the 2018 New York and Pennsylvania Pest Management Guidelines for Grapes: https://store.cornell.edu/p-201631-2018-new-york-and-pennsylvania-pest-management-guidelines-for-grapes.aspx This guideline provides a wealth of information on insect, disease and weed management with pesticide options, rates, and schedules, as well as, a chapter on sprayer technology.
Also, monitoring your vineyard(s) at least weekly throughout the season is critical for managing pests. Frequent scouting will alert you to problems developing in the vineyard and provide the information needed to make informed decisions concerning pesticide applications. (You won’t know what’s out there if you’re not).
Diseases – When thinking about disease management the first thing that commonly comes to mind are fungicide applications. However, cultural practices (e.g. shoot thinning, leaf removal in the fruit zone, etc.) are integral components of a disease management strategy and should be used whenever applicable.
As Bryan Hed mentions and deserves repeating, The Immediate Prebloom (just before blossoms open) through early post-bloom/fruit set period is a critical time for managing fruit infections caused by phomopsis, black rot, powdery mildew and downy mildew. Fungicide protection for botrytis on tight – clustered varieties at bloom (when 80 – 90% of caps have fallen) can also be important in wet seasons.
Insects – Two important insect pests that Jody Timer is covering are grape berry moth and spotted lanternfly. (For additional information on grape berry moth see: Three Phases to Managing Grape Berry Moth https://psuwineandgrapes.wordpress.com/2017/04/28/three-phases-to-managing-grape-berry-moth/ and Grape Berry Moth: Answers to questions you should be asking about this native pest https://psuwineandgrapes.wordpress.com/2015/05/15/grape-berry-moth-answers-to-questions-you-should-be-asking-about-this-native-pest/ ).
I will briefly mention 2 of the more widespread, leaf-feeding pests that you are likely to see sometime this season which are grape leafhopper and Japanese beetle.
Grape Leafhopper – There are several species of leafhoppers in the genus Erythroneura that feed on grape foliage. Regardless of which of these species is prevalent, their life cycles are similar and the injury caused by these leafhoppers and their management is the same. The greatest risk for economic losses due to grape leafhopper feeding occurs during hot, dry years in vineyards with heavy crop loads and high leafhopper populations. In most years, the majority of vineyards in Pennsylvania should not require an insecticide treatment specifically for management of grape leafhopper. However, the decision to apply an insecticide should be based on scouting information and threshold levels. (For more detailed information see: Grape Leafhoppers https://psuwineandgrapes.wordpress.com/2017/06/09/grape-leafhoppers/ ).
Japanese Beetle – Adult beetles feed on over 300 species of plants including grape. They prefer smooth, thinner types of grape leaves which are characteristic of many wine grape varieties (e.g., Chardonnay, Traminette, and Vidal Blanc). Feeding injury, depending on severity, can result in leaves having a skeletonized appearance due to consumption of the soft leaf tissues between veins. Research has shown that grapevines can tolerate a fair amount of leaf area loss without detrimental effects. However, no economic threshold level has been established for leaf injury on grapes caused by Japanese beetle. Since young vineyard blocks, vines in grow tubes and many wine varieties are vulnerable to serious leaf loss by Japanese beetle feeding consistent monitoring is important. (For more detailed information see: Japanese Beetle: A Common Pest in the Vineyard https://psuwineandgrapes.wordpress.com/2016/07/09/japanese-beetle-a-common-pest-in-the-vineyard/).
By Dr. Michela Centinari, Assistant Professor of Viticulture, Department of Plant Science
Grape growers across Pennsylvania would agree that grapevines are breaking bud later this spring compared to the past few years. Some of you might be relieved and are hoping that a late bud break will reduce the likelihood of spring frost injury, particularly for those cultivars that tend to break buds early, while others might wonder if a late bud break will mean a shorter growing season and what impact this might have on fruit and wine chemistry.
This might be a good opportunity for a short review on bud break (or bud burst if you prefer) and some of the major factors that influence it.
What is bud break?
Bud break is one of the grapevine’s key growth or phenological stages. Phenology is defined as “the study of the timing of natural phenomena that take place periodically in plants and animals1.” Many vineyard operations related to canopy, nutrient, disease and insect management are conducted at specific phenological stages, so it is important for growers to record dates for bud break and other important growth stages.
Bud break is commonly described as “the appearance of green tissue through the bud scales2” or “the emergence of a new shoot from a bud during the spring3.” There are several systems used to precisely identify bud break and other key phenological stages. One of the systems most widely used today is the modified Eichhorn Lorenz (E-L) system, which was developed by Eichhorn and Lorenz in 1977, modified by Coombe in 19954, and later revised by Coombe and Dry in 20043. A primary reason why the E-L system was revised multiple times was that the visual characteristics during the early stages of bud growth might vary among cultivars. For example, in some cultivars buds “emerge as hair-covered cone from between the scale without any sign of green tissues” while in other cultivars buds can have “green tips visible early through the hairs1.” To avoid, or at least reduce confusion, the latest E-L system modification (2004) defines grapevine bud break when leaf tips are visible (Figure 1).
Although there might be slight differences in how growers or scientists define bud break, using a consistent method across years and cultivars is important in order to make comparisons. Photos of the modified E-L system and information on how to use grapevine phenology to improve vineyard management can be found by clicking on these hyperlinks: modified E-L system by The Australian Wine Research Institute and Grapevine Phenology Revisitedby Fritz Westover5.
Why was bud break late this year in Pennsylvania?
Grapevine phenology is strongly tied to air temperature. Once buds fulfill their chilling requirements they are in a state of eco-dormancy, which means they are dormant only because of cool or cold weather. In temperate regions, buds tend to reach this state by early winter, therefore, warm weather in late winter or early spring might result in early bud break and consequently increase the risk of spring frost injury.
An air temperature of 10 °C (50 °F) has traditionally been used as the base temperature for grapevines, as it is the temperature threshold below which grapevines will not grow. Hence, mean daily temperatures above approximately 50 °F (or, more specifically, 46 to 50 °F) induce bud break and shoot growth6. Grapevine base temperature is higher than that reported for fruit trees, such as apple, peach, cherry, and apricot (the base temperature ranges from approximately 39 to 41 °F)7. Base temperature for bud development varies between grapevine species and cultivars, and the physiological basis of this thresholds is still unclear2.
Over the years, many models have tried to use temperature data to predict bud break and other key phenological stages. Some models are based on the accumulation of temperatures above the mean daily temperature of 50 °F, for example, Growing Degree Days (GDD), while others use temperature averages rather than summations8. However, there is not(at least to my knowledge) a solid and simple formula that we can use to predict when bud break will happen.
GDD calculated from January 1 to bud break may not be a very good way to answer the question: Are we going to have an early bud break? Hans Walter-Peterson, Finger Lakes Grape Program, Cornell University, used data collected over many years in the Lake Erie region to show that the date of bud break for Concord was not well correlated with GDD (base 50 °F) accumulated from January 1 to bud break. Using the total GDD for this period, however, does not take into consideration when GDD accumulates. For example, having seven consecutive days with mean temperature above 50 °F might not be the same of having seven days with the same temperature but interspaced by a long period of cool/cold weather with mean temperatures below 50 °F.
Although further studies are needed to clarify the relationship between bud break and temperature, air temperature still remains the dominating factor affecting bud break. The number of GDD accumulated from January 1 through April 30 in 2018 across Pennsylvania was definitely lower than the accumulated GDD during the same months in 2017 (Table 1). This indeed had an influence on grapevine bud break occurring later in 2018 compared to 2017.
Time versus rate of bud break
While the number of GDD accumulated from January 1 through April 30, 2018, was lower than the same period in 2017, the number of GDD accumulated during the first week of May 2018 was, however, much higher than the number accumulated during the same period in 2017 (Table 2). Although bud development started later this year, you might have noticed a greater rate of bud break or higher speed of bud development due to consecutive days of high, above average daily temperatures at the beginning of May. The rate of bud break increases as the air temperature rises above 50 ℉ up to approximately 86 ℉ (30 °C). However, at higher temperatures, the rate of bud break might start to decline6.
Other factors to consider:
Species and cultivars: The base temperature requirements vary amongst grape species (e.g., V. berlandieri > V. rupestris > V. vinifera > V. riparia) and cultivars (for example, Riesling > Chardonnay)6. Regardless of the seasonal weather conditions, the order of bud break across different species and cultivars tends to be consistent. Those with a lower base temperature threshold will break buds earlier than those with a higher base temperature. For example, Chardonnay always bursts earlier than Cabernet Sauvignon.
Soil and root temperature: There is contradictory evidence about the role of soil and root temperature on the timing of bud break. Studies conducted in California9,10found that Cabernet Sauvignon bud break was positively correlated with soil temperature: bud break occurred several days earlier when soil temperature increased from 52 ℉ to approximately 77 °F. In a more recent study, however, soil temperature did not influence the timing of Shiraz bud break11.
Number of buds left at pruning: The number of buds (or nodes) retained at pruning (24 to 72 per vine) had little influence on bud break and other phenological stages of Sauvignon Blanc vines up to veraison12.
Bud position along the cane: When dormant canes are left upright, the more distal buds generally tend to break first and suppress the growth of the buds at the base of the cane (closer to the cordon) (Figure 2). This phenomenon is called apical dominance or, more precisely, correlative inhibition. In frost prone areas, to delay bud break of cordon trained vines, canes can be pruned back to 2-bud spurs when the distal buds reach bud break. For more information please refer to a past blog post: How does delaying spur pruning to the onset or after bud burst impact vine performance?
In some cultivars, for example, Cabernet Franc, correlative inhibition may cause inconsistent bud break in cane-pruned vines. Meaning that buds located in the central part of the cane might not open or they might develop shorter, weaker shoots than those positioned at the beginning or at the end of the cane. There are, however, practices that can be used to promote uniform bud break along the canes, these include bending or arching (Figure 3), and partial cracking of canes6.
Age of the vine: Within the same cultivar, the timing of bud break and other key phenological stages may vary between young vines that are not in full production yet (3rd leaf or younger) and mature, established vines (4th leaf or older)5.
- Iland P, Dry P, Proffitt T, Tyerman S. 2011. The grapevine: From the science to the practice of growing vines for wine. Patrick Iland Wine Promotions.
- Creasy GL and Creasy LL. 2009. Grapes. Wallingford, UK; Cambridge, MA: CABI.
- Coombe BG and Dry P. 2004. Viticulture 1 – Resources. 2nd edition. Winetitle
- Coombe BG. 1995. Adoption of a system for identifying grapevine growth stages. Aust J Grape Wine Res 1:104–
- Westover F. 2018. Grapevine phenology revisited. Wines and Vines.
- Keller M. 2010. The science of grapevines: Anatomy and physiology. Academic Press.
- Moncur MW, Rattigan K, Mackenzie DH, and McIntyre GN. 1989. Base temperatures for budbreak and leaf appearance of grapevines. Am J Enol Vitic 40:21–26.
- Malheiro AC, Campos R, Fraga H, Eiras-Dias J, Silvestre J, and Santos JA. 2013. Winegrape phenology and temperature relationships in the Lisbon wine region, Portugal. J Int Sci Vigne Vin47: 287–299.
- Kliewer WM. 1975. Effect of root temperature on budbreak, shoot growth, and fruit-set of ‘Cabernet Sauvignon’ grapevines. Am J Enol Vitic 26:82–
- Zelleke A and Kliewer WM. 1979. Influence of root temperature and rootstock on budbreak, shoot growth, and fruit composition of Cabernet Sauvignon grapevines grown under controlled conditions. Am J Enol Vitic 30:312–317.
- Field SK, Smith JP, Holzapfel BP, Hardie WJ, and Emery RJN. 2009. Grapevine response to soil temperature: xylem cytokinins and carbohydrate reserve mobilization from budbreak to anthesis. Am J Enol Vitic 60: 164–172.
- Greven MM, Neal SM, Hall AJ, and Bennett JS. 2015. Influence of retained node number on Sauvignon Blanc grapevine phenology in a cool climate. Aust J Grape Wine Res21, 290–301.
Bryan Hed, Department of Plant Pathology and Environmental Microbiology, Penn State Extension
As the new grape growing season commences, this is a good time to revisit some of the fungicide updates that were discussed at grower meetings earlier this year. While these materials are available to growers in most states, some of them have not yet cleared the extra hurdles required for legal use in New York, and in those instances, I make specific mention of that. I hope this blog will be useful for growers in the 2018 season.
FUNGICIDE CHANGES, NEWS, & REVIEWS
First, Aprovia/Aprovia Top. The active ingredient in Aprovia is solatenol (benzovindiflupyr), and while it does not represent a new chemical class for us grape growers (succinate dehydrogenase inhibitor or SDHI) it is a new and improved chemistry. The SDHI fungicides belong to FRAC Group 7, which also includes chemistries in products like Endura and Pristine (boscalid) and Luna Experience (fluopyram). Aprovia was available for use in most states last year but has now been labeled for use in New York as well. As a solo product, Aprovia is very effective for the control of powdery mildew as trials in NY over several years have shown. Trials at Penn State over the past couple of seasons have also revealed some efficacy on black rot, but I would consider it more in line with “suppression” of this disease and I cannot recommend it for black rot control, especially on susceptible varieties. Also, it should not be relied on for significant control of Botrytis, unlike other SDHIs. The label also lists control of Phomopsis and anthracnose, but I have not seen any real proof of that. Penn State has tested this product over two years on Concord, to examine it for any potential crop injury issues to that variety. in comparison to Revus Top, a standard spray program, and an untreated check, there were was no injury to Concord grape from Aprovia, while, as expected, Revus Top caused severe damage to leaves developing at the time of application.
Aprovia Top, on the other hand, is a mixture of two active ingredients: i) solatenol, the active ingredient in Aprovia and ii) difenoconazole, a DMI fungicide with very good to excellent activity against powdery mildew, black rot, and anthracnose. Aprovia Top is also labeled for control of Phomopsis, but again, local experience and published results of trials with Phomopsis is lacking. The label rate for Aprovia Top is 8.5 to 13.5 fl oz/A; 13.5 fl oz of Aprovia Top provides about the same amount of solatenol as 10.5 fl oz of Aprovia; it also provides about the same amount of difenoconazole as 18 fl oz of Inspire Super, but falls a little short of that found in 7 fl oz of Revus Top. Aprovia and Aprovia Top have a 12 hr REI and a 21-day PHI. As with all the products containing difenoconazole, Aprovia Top should not be applied to Concord grape and other varieties on which difenoconazole injury has been reported. This includes Brianna, Canadice, Concord Seedless, Frontenac (minor), Glenora, Noiret (minor), Skujinsh 675, St. Croix (minor), and Thomcord.
Intuity. The active ingredient in Intuity is mandestrobin, and if that sort of sounds familiar, it’s because this is another strobilurin fungicide (FRAC group 11). Intuity offers protectant and antisporulant activity against Botrytis, for which it is exclusively recommended, though it will provide suppression of powdery mildew, at least where strobilurin resistance has not yet developed. In limited NY and PA trials, Intuity has provided good to fair control of Botrytis equivalent to current standards like Elevate, Vangard, Scala, and Switch. The label rate is 6 fl. oz/A with a maximum number of three applications (two is recommended) and 18 fl oz per season. Do not make sequential applications; rotate with non-FRAC 11 materials (Elevate, Endura, Fracture, Inspire super, Rovral, Scala, Switch, Vangard) and allow at least 20 days between Intuity applications. Intuity is at risk for resistance development by the Botrytis fungus and it is essential that its use is limited to rotations with other, unrelated Botrytis fungicides both within and between seasons to reduce the development of resistance. Intuity is rainfast within 2 hours of application, has an REI of 12 hours and PHI of 10 days. Do not use Intuity on V. labrusca, V. labruscahybrids or other non-viniferahybrids. Avoid mixing with organosilicone surfactants. Intuity has not yet been cleared for use in New York.
Presidio. Presidio has been with us for about 10 years now and is used for downy mildew control, for which it has been very effective. Unfortunately, Valent has pulled the grape use from the Presidio label and any new product will not be legal for use on grapes this year. However, grape growers will be able to legally use up old stock of Presidio with the grape use pattern on the label.
FLINT Extra. A new formulation of an older material, FLINT Extra is a liquid (500SC) formulation that replaces Flint 50WG. The use rate of the new product is the same (in terms of active ingredient) as the old product. In other words, 2 fl oz of FLINT Extra 500SC = 2 oz Flint 50WG. But the new product is labeled to increase the application of active ingredient per acre. For example, for powdery mildew, the new product label lists a 3-3.5 fl oz rate as opposed to the 1.5-2 oz rate on the old product label. This represents a doubling of the amount of active ingredient for powdery mildew control by the new product. For Botrytis, the old 3 oz rate is now 3.8 fl oz, and for black rot, the old 2 oz rate is now almost doubled on the new label to 3.5-3.8 fl oz. Well, what does this mean then in practical terms for grape growers in the northeast? It could mean better disease control with the new product. However, if you already have powdery mildew resistance to the strobilurins in your vineyard, then increasing the amount of active ingredient probably won’t boost efficacy against that disease, and relying on the new formulation for powdery mildew control is risky. The same goes for Botrytis control, as strobilurin resistance among Botrytis isolates becomes more common. For black rot, it could represent improved control of that disease. However, I thought the 2 oz black rot rate for the old material was pretty effective already, and to my knowledge, there have been no cases of black rot resistance to the strobilurins (though I’m not aware anyone has been looking for it). And yes, it is registered for use in New York.
That’s what new. This next section borrows from Wayne Wilcox’ fungicide updates from last year. I have updated that information with new information from some of our research trials as well.
Fracture. According to Wayne’s insights last year, “Fracture is a product whose active ingredient is a fragment of a naturally occurring plant protein, and which has been registered for use on grapes for a couple of years. It has a 4-hr REI and a 1-day PHI, and the residue of its active ingredient is exempt from tolerance by the US-EPA (i. e., it is considered safe enough to humans that there is no limit on the allowable residue level in/on food products)”. We’ve now tested it for powdery mildew control over two years in Concord and Chambourcin and consider its activity against that disease to be modest. New York trial results appear similar. Trial results for bunch rot control I think are a bit more promising; we got fair to good control of bunch rot on Vignoles with this product last year (as good as a standard Botrytis fungicide program), and we’re looking forward to testing it again for that purpose this season. New York trials with Fracture have also shown control of Botrytis as good as standard materials, as well as some activity against sour rot. Fracture is expensive but may appeal to growers looking to reduce reliance on synthetic fungicides for bunch rot control, especially if used in combination with strict sanitation and cultural controls like leaf removal. We’re hoping to look at Fracture again this season, in combination with pre-bloom mechanized leaf removal, for integrated bunch rot control on Vignoles.
Polyoxin D zinc salt. Polyoxin D zinc salt (PZS) is a relatively new fungicide active ingredient with very low mammalian toxicity that has been classified by the U.S. Environmental Protection Agency (USEPA) as a “biochemical-like” pesticide. It degrades rapidly in the environment with a soil half-life of 2-3 days. Production of PZS occurs through a fermentation process using the soil bacterium Streptomyces cacaoi var. asoensis. The active ingredient inhibits chitin synthase, an enzyme essential for the production of chitin, an important component of fungal cell walls. The product is being sold as Tovano and OSO5%SC and is marketed through Certis USA. Over the past two seasons, our results with OSO on Concord and Chambourcin grapes have shown good to modest efficacy against powdery mildew, but no practical level of activity against black rot. For powdery mildew efficacy on fruit, OSO, at the 13 fl oz rate, was equal to or better than BadgeX2 (fixed copper), and equal to a standard rotational program of Quintec/Vivando/Toledo. As with most of the biopesticide type fungicides, cost per application is generally going to be higher than that of the standard synthetic fungicides.
LifeGard. LifeGard is another biopesticide approved for use on grapes in all states. It has provided really good results for the control of downy mildew in New York trials. Our past two years of testing in PA were a bust due to very dry conditions and little to no downy mildew up here in Erie County, PA. However, maybe we’ll get a good test of this product this year. LifeGard works by triggering a plants’ natural defense mechanisms against pathogens so the product may perform best after the vine has been ‘primed’ by an initial spray a few days before it is challenged with the pathogen. The label states that “initial triggering of plant defense response occurs within minutes of application, but 3-5 days are required to attain maximum level of protection”. This may be the reason our greenhouse inoculation trials with LifeGard were largely unsuccessful; we applied the pathogen just a few hours after application of the material instead of allowing ample time for the vine’s natural defense mechanisms to build up. Grapevines do not generally tend to respond to efforts to induce resistance, but the results from New York trials are encouraging and testing should continue.
There are several products also worth mentioning that have recently been made available to New York (and hence all) grape growers. Here is a brief recap of those materials.
- Luna Experience: a combination product consisting of two unrelated active ingredients, tebuconazole, (a very familiar sterol-inhibitor (FRAC 3)) and fluopyram, a newer SDHI (FRAC 7). Luna Experience is labeled for powdery mildew control at 6.0–8.6 fl oz/A, and for Botrytis and black rot control at 8.0 – 8.6 fl oz/A. Trials in New York have obtained excellent control of powdery mildew with the 6 fl oz rate. For Botrytis, New York trials suggest the 6 fl oz rate works well from bloom through bunch closure but the 8 fl oz rate would be best by veraison or later, especially if there is any pressure. The higher rate is also recommended for black rot control for the first few weeks after bloom when berries are most susceptible. The fluopyram provides most of the powdery mildew control and all of the Botrytis control, while the tebuconazole provides most of the black rot activity. For resistance management, limit the number of applications of FRAC 7 materials (SDHIs) to two per season.
- Zampro: We tested Zampro a number of years ago and found it to be an excellent material for downy mildew control. More extensive New York trials have gotten similar results. Though it has been approved for use in New York, it still cannot be used on Long Island. Zampro is another combination product of dimethomorph (FRAC 40, same as mandipropamid in Revus) and a new chemistry, ametoctradin.
- Rhyme: The active ingredient in Rhyme is flutriafol (sterol inhibitor, FRAC 3) and extensive powdery mildew trials in New York have shown more consistent results at the 5 fl oz rate rather than the 4 fl oz rate: Rhyme was a little better than Rally (myclobutanil) and tebuconazole, about equal to Mettle (tetraconazole), but not as good as difenoconazole (the newer, more potent sterol inhibitor in Revus Top, Inspire Super, Quadris Top). It received a registration a couple years ago and is also available for use in New York as well (except for Long Island). Rhyme has excellent activity against black rot.
- Topguard EQ: A combination product of flutriafol (just discussed above) and azoxystrobin (the ai in Abound). Obviously, this can’t be used in Erie County, PA, but is available to New York grape growers (except Long Island). The azoxystrobin picks up downy mildew (and Phomopsis?) that the flutriafol won’t, unless of course there is a significant presence of strobilurin resistant isolates of the downy mildew pathogen in your vineyard. For powdery mildew, the azoxystrobin adds a second mode of action against that disease, unless (once again) there is a significant presence of strobilurin resistant isolates of the powdery mildew pathogen in your vineyard. So, if you’re farming grapes in areas where sterol inhibitors and strobilurins have been used for many years and downy/powdery mildew resistance is suspected/likely or known, this product may not provide adequate control of these two important diseases, especially on highly susceptible wine varieties. What this product will definitely control is black rot: the azoxystrobin has excellent protective activity and flutriafol has excellent post-infection activity against this disease.
And finally, what’s new in the pipeline?
Miravis Prime. Miravis Prime is a product with two active ingredients: a new SDHI called adepidyn (FRAC 7) and an older, unrelated active ingredient known as fludioxonil (FRAC 12). This product is not yet registered for use on grapes, but federal registration may occur later this year, which will make it available for growers in most states (New York will probably have to wait at least another year). Our tests with Miravis Prime have shown good to excellent activity on powdery mildew, Botrytis, and black rot. Adepidyn (Miravis) provided excellent control of black rot in our 2015 and 2016 trials on Concord and Niagara fruit. The fludioxonil component in Miravis Prime is an older Botrytis fungicide, (introduced about 25 years ago) that is also found in a registered product called Switch (for Botrytis control in grapes). Having two active ingredients for Botrytis control makes this product effective at controlling Botrytis bunch rot disease in wine grapes.
Part 2 of this blog post will be published next Friday, May 18, 2018.
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).
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).
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).
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).
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.
- Preventing Herbicide Drift and Injury to Grapes https://catalog.extension.oregonstate.edu/files/project/pdf/em8860.pdf
- Questions and Answers about Vineyard Injury from Herbicide Drift http://www.bookstore.ksre.ksu.edu/Item.aspx?catId=237&pubId=1105
- Leaf Index and Severity Rating & Leaf Index Report (Washington State University) http://feql.wsu.edu/eb/
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).
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.
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.
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
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.
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.
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.
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.”
“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.
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).
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.”
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!
* 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.