Professor of Botany and Plant Pathology and Extension Plant Pathology Specialist, Oregon State University
The sky is falling!
(Well, maybe not.)
Jay W. Pscheidt, Ph.D.
Professor of Botany and Plant Pathology and Extension Plant Pathology Specialist, Oregon State University
The new Compendium of Grape Diseases, Disorders and Pests (Wilcox et al 2015) points out the multitude of problems that can beset grapes. Oregon’s grape industry has done well to avoid many of these troubles using geographic isolation, unique climate conditions and planting stock quarantines. Grapes are still susceptible to all these problems, which could arrive and cause havoc on any growing season. When one of these problems does come along, we may sound a lot like “Chicken Little” declaring that the sky is falling. Several disease issues have fallen onto our doorstep that need to be discussed. Although some are very serious and not unexpected, all can be dealt with. These issues include Xylella, sterilizing pruners, fungicide resistance and climate change, which we will address throughout the season.
In October, 2015, the presence of the bacterium Xylella fastidiosa was confirmed by the Oregon Department of Agriculture (ODA) in several pear trees growing in the field germplasm collection at the USDA Repository in Corvallis. Grape growers may be alarmed knowing that Pierce’s Disease is caused by Xylella fastidiosa subsp. fastidiosa. Pierce’s Disease has been a high-profile and rapidly increasing disease in California and other southern states but has not been known to be in the Pacific Northwest. At this time, the preliminary DNA sequence data suggests the bacterium on pear is X. fastidiosa subsp. multiplex, which can cause a chronic leaf-scorching disease in many different species of woody landscape shrubs and shade trees, including oak, elm, and other trees – but not grape. (Whooh!)
There are still a ton of questions that need to be answered in the coming months and years about this find. Keep half an ear open on this problem.
Why don’t find Pierce’s Disease in the Pacific Northwest? Our climate may be too cold for the pathogen to survive. Infected grapevines do not retain the pathogen after a cold dormant season typical of continental climates. Also the majority of leaf hoppers (xylem feeding insects that vector the bacterium) found in PNW surveys are Western grape leafhopper which are not efficient vectors of Xylella. The Blue-green sharpshooter will vector Xylella and has been found in the Willamette Valley, Columbia Gorge, Medford and Milton-Freewater areas of Oregon. This leafhopper is usually found in surrounding vegetation but less in vineyards. The glassy winged sharpshooter, a very efficient vector, has not been found in or around Oregon vineyards nor is it abundant in the PNW.
If you are still worried, you can keep an eye out for various symptoms. Pierce’s Disease first appears as water stress in midsummer and gradually gets worse. Leaves become slightly yellow or red along margins in white and red varieties, respectively, and eventually leaf margins dry or die in concentric zones. Fruit clusters shrivel or raisin. Dried leaves fall, leaving the petiole attached to the cane. Wood on new canes matures irregularly, producing patches of green, surrounded by mature brown bark. ‘Pinot Noir’ and ‘Cabernet Sauvignon’ have highly regular zones of progressive marginal discoloration and drying on blades. Unfortunately, any other problem that blocks, inhibits or limits water from getting to the leaves will produce similar symptoms. Fungal cankers, damaged trunks, girdling roots, gopher damage, herbicide injury and root rots also can produce similar symptoms.
Bottom Line: Finding Xylella on pears in Oregon is not, at this time, a worry for grape growers.
Reference: Wilcox, W. F., Gubler, W. D. and Uyemoto, J. K. 2015. Compendium of grape diseases, disorders, and pests. Second edition. St. Paul, MN: APS Press.
The December Vine to Wine is now available to read. It contains the OWRI Picture Newseletter, a timely warning on cutworm, a summary of the webinar Dr. Patty Skinkis gave in early December, and relevant information from our archives. To view, click here.
Clive Kaiser, Extension Tree Fruit Specialist
Oregon State University, Umatilla County
On July 21, 2015, a dedicated group of growers from Oregon and Washington gathered in the Walla Walla Valley to listen to renowned experts about how to minimize cold damage to grapevines and fruit trees.
Dr. Glenn McGourty, viticulture and plant science advisor, University of California Cooperative Extension in Mendocino and Lake counties, outlined the basics of frost protection, offering practical examples of passive and active frost protection techniques and the role of ice nucleating bacteria and how to control them. He also discussed remediation of frost-damaged vines and differentiated between winter injury, when temperatures drop below -12°F and frost events when temperatures drop below 32°F. During the latter, ice crystals form between the cells and disrupt the cell membranes. With cell membrane integrity gone, the cell contents desiccate and the cells fail. The foliage turns black in spring and brown in fall. Glenn also distinguished between radiation frosts- when inversions occur- versus advective frosts, when a large, cold air mass is usually accompanied by wind and low humidity.
Measures to avoid frost exposure include:
- Careful site selection; uplands are best if you have the choice. Glenn cited the age old Latin saying “Bacchus amat colle” which translates to “Bacchus loves the hillock” and further suggested south and west facing slopes tend to be the warmest – one upside to other aspects is that bud break may be delayed in spring, thus helping to avoid early spring frosts.
- Manage brush, trees and other air dams that trap cold air in the vineyard.
- Soil water management: bare, packed soils offer the most protection but present risk of erosion, loss of soil organic matter, destruction of soil structure, and poor footing for early spring spraying.
- Maintain the soil moisture near field capacity: wet the top 12 inches of the soil surface 2-3 days in advance of a predicted frost event. It is not necessary to wet the entire profile as the top layer provides insulation and protects soil lower in the profile from losing heat. Glenn also compared different types of vineyard floor management systems ranging from bare, firm, moist ground (being the warmest) to tall cover crops with restricted air drainage, which can be6-8°F cooler.
- Delay pruning where practical: consider double pruning by leaving long spurs (6-10 buds), which can be cut back to two spurs later in spring. This will result in delayed bud break and can avoid frost damage by gaining a week of delay.
- Mow cover crop as close to the ground as possible in late winter before bud break and the first spring frost.
- If available, utilize overhead sprinklers as frost protection, especially where cover crops are present.
Glenn discussed ice nucleating bacteria, which are ubiquitous in nature. Common examples include Pseudomonas syringae, Pseudomonas flourescens, Psuedomonas viridflava, Erwinia herbicola and Xanthamonas campestris var. vesicatoria. The presence of these bacteria will lead to increased freezing. For example, snow-blowing freeze-dried Pseudomonas syringae, which will produce snow at 27°F versus water at 15°F, is an obvious effect of these pathogens, therefore controlling the bacteria will help prevent ice nucleation. Applying up to three copper hydroxide sprays one week apart in spring, after bud break but before a frost event, will have a beneficial effect of protecting foliage against frost damage as long as temperatures do not drop below 25°F.
Glenn also discussed his regeneration pruning work on damaged vines. This research indicated that comparing no pruning to breaking damaged shoots, cutting out spurs, or cutting damaged shoots, yields mixed results and is cultivar dependent. Positive impacts of pruning were seen in Chardonnay but not Cabernet Sauvignon. Pruning did not impact fruit quality on either cultivar, however, significant differences occurred in shoot emergence of spurs which may result in lower pruning costs in future years.
Dr. Imed Dami, research and extension viticulturist at Ohio State University discussed his research using vegetable oil to delay bud break. He discovered that an application of eight percent vegetable oil (v/v) with an emulsifier applied mid-winter can delay bud break by seven to ten days without affecting yield or fruit quality. He also discussed other practices such as “hilling up” (burying graft unions with soil) the vines to protect the stems against cold damage. When temperatures dropped below 15°F in Ohio, the best pruning technique as found to be give-bud hedging. When regrowth from the ground took place, training and pulling the new shoots immediately resulted in the best recovery over time. Bull canes (vigorous canes greater than pencil thickness) must be removed since they often do not harden off properly resulting in more cold damage the next winter.
Dr. Mark Battany, University of California Cooperative Extension farm advisory in San Luis Obispo County and a self-confessed gizmologist, presented his findings on active versus passive control of frost. He highlighted the importance of managing cover crops and delaying bud break in spring, as well as the importance of knowing the temperature at both five and 35 feet above ground level. Wind machines only work when an inversion exists due to radiant conditions. In fact, when an advective freeze (polar express) occurs you can cause more damage by running a wind machine, as the air temperature at 35 feet can be substantially colder than at five feet. He also explained that for a wind machine to work well the temperature difference between the two different heights needs to be at least 8°F for the wind machine to have an effect. Mixing the air from the warmer layer will result in averaging of the two temperatures and a 4°F gain temperatures can be expected. He also presented work showing that wind machines which blow warm air down are far more effective that those that blow cold air up. He suggested using black float ball modified sensors rather than standard shielded air temperature readings as the latter are not accurate measures of plant tissue temperatures at night because objects exposed to the sky are subject to radiation heat losses. Consequently, the leaf temperatures are actually colder that those in the standard shielded sensors.
Finally, Dr. Kevin Kerr of Brock University provided an overview of the cold management techniques utilized around the Niagara peninsula in Canada. The focus of Kevin’s work is to understand and predict when freezing temperatures are going cause issues. His team has developed an extensive network of differential thermal analysis (DTA) using programmable freezers and measure cold hardiness of buds throughout the region. This is presented to participants through a novel VineAlert system. This includes both rates of acclimation and de-acclimation of bud. This information is being used by the growers to determine precisely when the wind machines will be required to help protect buds and as a result has saved their industry more than $13.8 million in lost grape revenue as well as saving another $1 million in operating costs of the wind machines. Lessons learned include: – early shutting down of vines in fall result in hardier buds; a wet harvest season results in slower vine acclimation; excessive crop load result in less hardy vines; too little crop leads to excess vigor which results in less hardy vines; de-acclimation begins in late January with a very rapid rate of de-acclimation during March; once the vine de-acclimates, there is no going back to maximum hardiness vines need 72 hours of sub-32°F re-exposure to stop de-acclimation from continuing.; maximum hardiness is achieved by prolonged exposure at 32°F or colder but does NOT require extremely cold temperatures (<20°F) to reach maximum cold hardiness.
All in all, the volume of information imparted by the speakers was vast. Both theoretical knowledge and practical applications were abundant and useful to all the participants, who expressed their sincere thanks to all the speakers for making the trek to the Walla Walla Valley.
If you have any additional questions about this workshop, please contact me at: email@example.com.
Preparing for the Upcoming Harvest
Dr. James Osborne, Enology Extension Specialist and Associate Professor
Harvest is here and in the winery there are many things to prepare for before the fruit starts arriving. One key area to prepare for is yeast and nutrient management. While yeast and nutrient management are always key factors in conducting successful fermentations, extra care is needed in years like this where grape composition may lend itself to more problematic fermentations. Because of the warm and dry growing season fruit may contain high °Brix and lower than optimal nutrients. This fruit chemistry can cause problem alcoholic fermentations as yeast need to metabolize a greater amount of sugar with a lower amount of nutrients in an increasingly high alcohol environment. The end result is often a very slow/sluggish fermentation or fermentations that do not complete fermentation but rather stall out with a few Brix still remaining. One key factor in preventing stuck/sluggish fermentations is ensuring there is sufficient yeast nutrients present during the fermentation. Yeast assimilable nitrogen (YAN) is one of these key nutrients and insufficient amounts can result in stuck fermentations as well as increased production of hydrogen sulfide. YAN is composed of nitrogen from ammonia (inorganic nitrogen) and nitrogen from primary amino acids (organic nitrogen). Luckily, we have a number of tools at our disposal to supplement YAN but how and when to perform this supplementation is a little more complicate.
The first step is measuring how much YAN is present in the juice/must. While you want to add enough YAN for a complete and clean fermentation, you do not want to add excessive nutrients as this can also cause problems. Large additions of YAN early in the ferment may lead to over vigorous fermentations and alter the aroma compounds produced by the yeast. In addition, residual nutrients in the wine may contribute to microbial spoilage during aging. So how much YAN do you need? Well, it depends. The general recommendation is between 150-250 mg/L for a 21-23°Brix must. If you have higher °Brix must or are using a high nutrient demand yeast strain then you may want to consider higher YAN levels. These are not hard and fast rules as many people may have no problems fermenting juice with much lower YAN levels then these. But these YAN levels have been found by researchers to result in fermentations with good kinetics. Aside from nitrogen, the other nutrients that are essential factors for yeast growth are the micronutrients such as the vitamins biotin, pantothenic acid, and thiamin. A simple method for analyzing these compounds does not exist so the general rule is that if your grapes are low in nitrogen they are probably also low in micronutrients. If you just want to increase YAN then DAP is an efficient way to do this. However, DAP does not contain any micronutrients so in addition to DAP you also should use a complex yeast nutrient that contains a blend of organic nitrogen (amino acids, peptides) and micronutrients. A balanced approach of both DAP and complex nutrients works best if you need to significantly increase your YAN levels.
The timing of nutrient additions is important for successful fermentations. Yeast preferentially up-take ammonia (DAP) before amino acids. Therefore, one large addition of DAP at the beginning of fermentation may delay/inhibit uptake of amino acids and cause problems later in fermentation. It is therefore recommended that you do multiple additions of nutrients during the early to mid-fermentation stage. For example, add half the nutrients 12-24 hours after inoculation followed by the remainder of the nutrients around 1/3 sugar depletion. Adding nutrient supplements all at once can lead to too fast a fermentation rate, and an imbalance in uptake and usage of nitrogen compounds. Alternatively, supplements added too late in the fermentation (after mid-fermentation) may not be utilized by the yeasts. This is because as the fermentation proceeds ethanol concentrations reach a point it impacts the yeast membrane and reduces the ability of the yeast to uptake nutrients. In addition, adding nutrients to a stuck fermentation seldom does any good at all and may add to the problem by ‘feeding’ spoilage bacteria that may have caused the issue.
Aside from YAN, the other yeast nutrient that can play a critical role in conducting successful alcoholic fermentations is oxygen. During the early stages of alcoholic fermentation Saccharomyces can use O2 for the production of sterols. These sterols are a key component of the yeast cell membrane and will help the yeast resist osmotic stress at the beginning of fermentation and ethanol toxicity near the end of fermentation. There are two times during the fermentation where oxygen addition has been shown to be beneficial. First, once the fermentation has become active and a 1-3 0Brix drop has occurred. The second time is at about 1/3 0Brix drop. Addition of oxygen to the ferment after this time is not recommended. Pumping over or racking and returning can supply some oxygen to the ferment but using a macro-oxygenator or micro-oxygenator at a high rate is a more reliable way to provide air to the ferment.
Warmer years also typically present us with fruit containing lower acidity. If acid additions are to be performed it is important to measure a few different components of acidity. The typical measurements of acidity are pH and titratable acidity (TA). These two measurements are not interchangeable and provide different information about acidity. pH is a measure of acid strength (hydrogen ions concentration) while TA is a measure of titratable groups. Often we consider pH a parameter for microbial stability and SO2 effectiveness while TA is often related more to taste. The pH and TA of your juice/grapes will be impacted primarily by the concentrations of tartaric and malic acid. These acids have different strengths and so a different ratio of these acids will impact both pH and TA independently. For example, you can have two juices with very similar TAs but quite different pH values if their tartaric and malic acid concentrations differ. pH is also impacted by the buffering capacity of the juice/must. The major component of grapes that impacts buffering capacity is potassium. Grapes with high potassium concentrations can be resistant to pH change from acid additions because of this buffering capacity. For example, you may make an acid addition to a set TA level but not see the expected decrease in pH if the juice/must contains high amounts of potassium. Bench-top trials for acid adjustments are recommended so that you can an accurately determine how much acid will be needed to achieve a certain pH and what the resulting TA will be. Knowing your malic acid concentration can also impact pre-fermentation acid additions. Malic acid will be converted to lactic acid during malolactic fermentation (MLF) and so this needs to be considered when making pre-fermentation acid additions. If your juice/must is high in malic acid then a larger pre-fermentation acid addition may be required than your juice/must TA values would initially indicate. On the other hand, if your juice/must contains very little malic acid (as is typically the case in warmer seasons) then your TA values pre-fermentation will be a little more predictive of what the wines TA will be post-MLF.
One additional note when it comes to calculating pre-fermentation adjustments (YAN and acid). When taking grape and juice samples for analysis, the more closely these samples represent the grape/juice in the tank the better. When assessing red grapes I would recommend taking the grape samples and crushing them by hand in a zip lock bag and letting the juice soak on the skins for a few hours (in the fridge). This will give you a more accurate pH value because the grape skins contain a significant amount of potassium that will soak out during this time. If you analyze the juice immediately after crushing the grapes then you will not account for this potassium. Grape skins also contain some YAN and so soaking the grapes will give a better estimation of the YAN content of the grapes.
I wish you all many clean and complete fermentations this coming harvest. If you have additional questions please contact me at 541-737-6494 or email firstname.lastname@example.org
I am a Research Plant Pathologist with the USDA-ARS Horticultural Crops Research Unit working on viruses of berry crops and grapes, and the Research Leader for the Horticultural Crops Research Unit (read paper pusher). I am also a Courtesy Professor in the Department of Botany and Plant Pathology at OSU and core faculty member of OWRI.
- What do you enjoy most about your work?
Technically, at the USDA-ARS our job descriptions are 100% research, though to be successful and responsive to stakeholders we do carry out extension activities. My position is unique in several ways in that we are the only laboratory in the U.S. that focuses entirely on viruses of berries and grapes. This provides an opportunity to be involved in virus issues on these crops across the U.S. and overseas, and work with a wide range of stakeholders and colleagues. As a USDA-ARS researcher located on campus I have many advantages of regular OSU faculty, such as mentoring graduate and undergraduate students, access to a wide range of seminars, central laboratory services, computing services, and many colleagues to discuss research ideas. I have a fantastic group of colleagues to collaborate with and a great job, what’s not to like?
- When you’re not working, how do you enjoy spending your time?
I enjoy spending time with family, I have five brothers and five sisters and we try to get together at least once a year, thus usually includes a trip to Wisconsin each year. Now with four grandchildren, going on five, my wife and I very much enjoy being grandparents. I also enjoy woodworking, hiking, backpacking, making wine and cheese, wine tasting, cooking and reading. Each of these activities provides gratification on a short time frame compared to research, where timeframes from developing a project to implementation in the field can take several years.
- What inspired you to choose your career path?
I grew up on a family dairy farm in central Wisconsin and as a teenager I knew there were certain areas we planted clover instead of alfalfa, experienced grain harvests where I was covered with a red dust and there was very little grain to be had, saw cherry trees oozing with slime and the impact of Dutch Elm Disease on native stands. I had seen crop failure due to diseases, insects and frosts in July. The idea of trying to avoid losses due to diseases and insects was something that intrigued me from an early age. Summer frosts – well that I can’t change, but at least it was rare.
- What’s the best advice you’ve ever received?
Trust that people will do their best until they prove you wrong. With this philosophy, people will usually do much better than you expect. Only micromanage once someone demonstrates that they need it.
- Which three people (living or dead) would you invite to dinner? Jesus, Muhammad, and Marx, I would like to get their views on how their teachings have been used and abused in the world. I would like to get their input on how they would change their messages now that there has been time to see the impact they have had on the world.
- What is your vision for the future of your research?
I would like to see the results of our research on viruses of grapevines and berry crops lead to management tools that growers can implement to reduce production costs, improve fruit quality and extend the life of plantings. I would like to use plant viruses as tools to develop sustainable tools for insect and disease control. I know this will require overcoming the concerns about the use of genetically modified organisms, but I do believe there are situations where this will be an effective technology. Publications are nice and often the primary factor in evaluating research programs, but having an impact for the grower’s is much more important to me. If one finishes a research project when the publication is completed, they are only doing part of the job. As a researchers we should be accountable to stakeholders and taxpayers.
- What is your position at Oregon State University/OWRI?
I am the Viticulture Extension Specialist and an associate professor in the Department of Horticulture. My Extension program encompasses outreach statewide.
- What do you enjoy most about your work?
My position entails duties in the three mission areas of the land grant university: Extension, research and teaching. I truly enjoy being able to work in these areas and with the different groups that these missions serve, including industry, students and the scientific community. By having this tripartite position, I have been able to develop programs that integrate rather than segregate research from extension and education.
- When you’re not working, how do you enjoy spending your time?
I spend most of my non-work time with my family. We enjoy gardening and landscape design; I constantly am improving my home landscape while my turf-fanatic husband manicures our lawn. I particularly enjoy finding and growing different herbaceous perennials and woody ornamentals. Those who know me well know that I dislike shopping, but I love visiting nurseries in search of new and interesting plants. I also enjoy vegetable gardening, cooking, and sewing. More recently, these hobbies have been replaced with chasing around my endearing 1 year old son.
- What inspired you to choose your career path?
I grew up on my family’s dairy farm outside of Green Bay, Wisconsin, where I enjoyed being a part of agricultural production. Over time, I had a greater interest in crop production than dairy cattle, and chose to pursue plant sciences in college. I initially thought about studying botany but quickly realized that horticulture was the better route to go if I wanted to work with agricultural production. I also found horticultural plants far more interesting than the corn, soybeans and forages that I was more familiar with. Therefore, I studied Professional Horticulture at the University of Wisconsin-River Falls. While learning about different horticulture production systems, I became most interested in vegetable and fruit production. It was during an internship at the University of Wisconsin Peninsular Ag Research Station in Sturgeon Bay, WI that I had my first exposure to cold hardy grapevines. There were many interesting research questions and production challenges to be tackled for grape production in the Midwest, so I chose to focus my graduate studies in viticulture. I chose a graduate program where I could get exposure to both applied research and Extension. I studied viticulture under Dr. Bruce Bordelon at Purdue University where I earned my PhD in Horticulture. In growing up on a farm, I saw firsthand how Extension provided information to producers, and the great impact it had on farming practices; I wanted to be able to serve in this capacity through my career.
- What’s the best advice you’ve ever received?
Be honest and hard-working. It may not lead to great success nor be popular, but at least you will be able to sleep at night.
- Which three people (living or dead) would you invite to dinner?
Andy Rooney – I always enjoyed his short weekly broadcasts on 60 Minutes that often provided an enlightening and humorous view of everyday occurrences and current events.
Mother Teresa – It would be a distinct honor to be in the presence of someone who spent her entire life giving so much to those who had so little.
Vince Lombardi – Yes, he is considered the #1 coach of all time (ESPN), and he served as coach for the best football team in the US. However, that is not the only reason I chose him. I have great respect for his ability to lead a team from spoils to swift success. He was hard-working and had strong standards, two qualities I strive for in my life.
- What is your vision for the future of your research?
I want the research that I conduct to have true impact and lead to change not only in how things are done in industry but how they view viticulture and vineyard production. This requires long-term studies that integrate industry with the research process, much like the Statewide Crop Load Project. I hope that results of my research program will lead to sound and applicable metrics and guidelines that can actually be used by the industry and have an impact on how they do business, not just be filed away in a scientific journal for students or other academics to read in the future.
I have some more basic scientific interests, but what motivates me as an Extension specialist and applied research is integrating science and asking questions of applied research that others before me had not considered. Sometimes looking at things from a slightly different perspective creates a minor shift in our operational paradigm that can mean big changes. The question often on my mind in applied research is whether outcomes of our production practices are real or perceived. Viticulture researchers who work with winegrapes have the distinct challenge of considering the art-science divide more than any other cropping system. How to approach design of impactful research studies must consider more facets than just horticulture science.
Rust Mites Can Cause Damage Shortly After Budbreak
Dr. Patty Skinkis, Viticulture Extension Specialist & Associate Professor
Grape rust mites have been a nuisance pest in vineyards of western Oregon for years. They can be found living on grape tissues from early spring through summer. Grape rust mite has been known to cause shoot deformity early in the growing season with most notable damage in years when vines have delayed growth under cool conditions.
Being aware of the first signs and symptoms of rust mite infestation in early spring is important to determine if there is a problem. However, visual symptoms are not enough for action. It is critical to determine presence of grape rust mites before considering application of miticide sprays. The presence of high numbers of rust mites have been found to cause severe stunting of emerging buds and young shoots. For examples of these symptoms, see the grape rust mite section of the PNW Insect Management Handbook. There can be numerous other causes of stunted shoots, but with the hype of rust mite concerns, many growers blamed rust mites as the cause of all stunted shoots. As a result, there have been potentially unnecessary applications of miticides (sulfur, lime sulfur, stylet oil, or other miticide products) early in the season.
Grape rust mites are impossible to see with the naked eye, so tissue collection and viewing under magnification is required. A user-friendly method was recently developed by a team at the OWRI to monitor grape rust mites on vine tissues. This method has since been employed by growers in Oregon to determine presence of rust mites. The protocol is available for use and links provided below:
Using this method, we were able to determine a strong correlation of rust mite presence on stunted shoots early in the season. Damaged shoots often had hundreds of mites; there were over 100 mites found on shoots <10 cm in length using the rinse in bag protocol and up to 500 mites when evaluated upon subsequent extractions (Schreiner et al. 2014). Since there can be great variability in mite numbers and rapid growth of tissues early season, it is difficult to determine clear action thresholds. However, action is warranted if there is significant shoot stunting, deformity and confirmed high populations of rust mites. In-season sulfur sprays that are applied as a means to prevent powdery mildew has been found to keep rust mite populations in check (Schreiner et al. 2014). Current recommendations exist for early season rust mite control, and those can be found in the 2015 Pest Management Guide for Wine Grapes in Oregon.
For more information about monitoring for rust mites and management, see the following publications and resources:
Schreiner, R.P., P.A. Skinkis, and A.J. Dreves. 2014. A rapid method to assess grape rust mites on leaves and observations from case studies in Western Oregon vineyards. HortTechnology. 24: 38-47.
Skinkis, P.A., J.W. Pscheidt, E. Peachey, A.J. Dreves, V.M. Walton, I. Zasada, R. Martin, D. Sanchez, and C. Kaiser. 2015. 2015 Pest Management Guide for Wine Grapes in Oregon. OSU Extension Publishing. https://catalog.extension.oregonstate.edu/sites/catalog.extension.oregonstate.edu/files/project/pdf/em8413_0.pdf
Skinkis, P. 2014. Grape Rust Mites, eXtension/eViticulture.org. http://www.extension.org/pages/33107/grape-rust-mite#.U_yZCHcXOVo
Skinkis, P., J. DeFrancesco, and V. Walton. 2015. Grape Rust Mite, PNW Insect Management Handbook. http://insect.pnwhandbooks.org/small-fruit/grape/grape-grape-rust-mite
Dr. Vaughn Walton, Associate Professor, Department of Horticulture, Dr. Nik Wiman, Assistant Professor Sr. Research, Department of Horticulture, OSU, Daniel Dalton, Faculty Research Assistant, Department of Horticulture, OSU
Brown Marmorated Stink Bug, (BMSB) is an invasive pest that has spread significantly throughout Oregon’s Willamette Valley. Since 2012, BMSB has increasingly been encountered by growers and can be found in wine grape vineyards of the Willamette Valley during the harvest period (Wiman et al. 2014), and established populations of BMSB are now found within the boundaries of nearly all Oregon AVAs. The highest risk areas include the Chehalem Mountains, Dundee Hills, Eola-Amity Hills, and McMinnville AVAs, although the risk is also increasing in AVAs located in southern Oregon and the Columbia Gorge. BMSB feed on vegetative tissues and grape berries, potentially causing contamination of wine grapes and wine quality losses. BMSB may be moving into wine grapes late in the season because other food sources become unavailable and population levels are at their peak. BMSB also display “hilltopping” behavior in the fall, where they may aggregate at relatively high elevations for overwintering. Unfortunately, this means they will encounter vineyards and wineries. Winemakers have reported infestation of winery buildings and finding dead BMSB in fermenting wines.
Brown Marmorated Stink Bug can develop on a wide range of host plants, meaning that it can find refuge or reproduce on non-crop hosts and then spread to cultivated crops such as wine grapes. Often, BMSB can be found along vineyard borders that have host plants such as bigleaf maple, Himalayan blackberry, Oregon ash, or other species that produce abundant seeds or fruits. Fruit feeding by adult BMSB may cause direct crop loss due to berry necrosis (VMW, SCRI CAP grant report 2013). Contamination of grape clusters and taint because of BMSB defense chemicals is also concern. These taints can be persistent, and may result in market losses. Work conducted on Pinot noir has shown that trans-2-decenal, a defense compound produced by BMSB, is a contaminant present in wine that is processed with BMSB.
Populations of BMSB have continued to grow unabated, with major increases over the past two seasons because of increased distribution and long growing seasons. The extra heat units during the growing season allow more of the nymphs to reach the adult stage and then fly to overwintering sites. Furthermore, lack of cold temperatures in winter has limited mortality. BMSB pressure is predicted to increase in 2015 over levels seen during 2014. Growers are encouraged to learn to recognize BMSB to be aware of potential damage or contamination risk during the harvest season. BMSB can be scouted by visual observation of clusters with efforts concentrated on borders. Despite availability of commercial products, traps are not encouraged at this time because of lack standard monitoring protocols and inability to link trap captures to meaningful damage thresholds.
Spotted Wing Drosophila, Drosophila suzukii (SWD), is firmly established in most Oregon vineyards (Loriatti et al. 2015). D. suzukii contributes to spoilage of wine grapes, but only under certain conditions. Our studies have shown that wine grapes are less suitable than fresh berry crops as a reproductive host for SWD. Wine grapes damaged by pre-harvest rains, birds or fungal infection are attractive to SWD, and when high population levels coincide with split grapes, SWD can affect quality of wine grapes by acting as a vector of Acetobacter spoilage bacteria.
The lack of winterkill and seasonal population models indicate that SWD will be present at high levels during harvest in 2015. Growers should be aware that conditions suitable for vectoring of spoilage bacteria may result in an economic impact by SWD during harvest of 2015.
Ioriatti C., V. Walton, D. Dalton, G. Anfora, A. Grassi, S. Maistri and V. Mazzoni. 2015. Drosophila suzukii (Diptera: Drosophilidae) and its potential impact to wine grapes during harvest in two cool climate wine grape production regions. Economic Entomology, 10.1093/jee/tov042.
Wiman N.G., V. M. Walton, P. W. Shearer and S. I. Rondon. 2014. Electronically monitored labial dabbing and stylet ‘probing’ behaviors of brown marmorated stink bug, Halyomorpha halys, in simulated environments. PLoS ONE 9(12): e113514 doi:10.1371/journal.pone.0113514.
1. What is your position at Oregon State University/OWRI?
I am an Associate professor and Horticultural Entomologist at Oregon State University in the Department of Horticulture, and a Core member of the Oregon Wine Research Institute.
2. What do you enjoy most about your work?
Working with growers, and students and being able to solve problems through discovery.
3. When you’re not working, how do you enjoy spending your time?
Spending time with my family. We try to get out as often as possible in order to enjoy the mountains and hiking trials. When I get the opportunity I love to do some mountain biking.
4. What inspired you to choose your career path?
I grew up in a farming family. I’ve always had the desire to be involved in farming because of this. Farming is of course problem solving and multidimensional. My current job is very similar.
5. What’s the best advice you’ve ever received?
When doing any job it is about serving people, not yourself. Excellence is important when serving.
6. Which three people (living or dead) would you invite to dinner?
Nelson Mandela, Ernest Shackleton, Erica Walton, my wife.
7. What is your vision for the future of your research?
To serve the industry and help them solve problems and improve their daily life.