A Conversation with Dr. Mizuho Nita
[On July 27, 2023, I had an extended conversation with Dr. Mizuho Nita at the Virginia Tech Extension Center south of Winchester. I did not electronically record the conversation. This post is a paraphrase of the conversation using my notes of the visit, supplemented from public sources where indicated. A full listing of references is at the end of the piece. I have tried as much as possible to be faithful to what was said and the tone in which it was conveyed. We are thankful to Dr, Nita for his time and candor.]
July 27, 2023. Here we are near the end of July 2023, what has turned out to be the hottest month in recorded history (see, Reuters). Rogue wildfires ravage Greece; two-thirds of all Americans are under heat advisories (see, NewsNation); coral reefs in the Florida Keys are bleaching to death in waters over 100 degrees (see, CNN), Canadian wildfires. The list goes on. It is clear that Global Warming is here. You may debate what causes it, but farmers are the most practical people on the planet. They don’t ask who is to “blame.” They don’t have the time. They have crops to grow and get to market and they need strategies to deal with climate change now and for the future. Of course, vineyard owners are farmers. Their crop may have more cachet than soybeans, but their vineyards are subject to the same challenges. Their future is subject to the same concerns.
With all of this in mind, I chose the hottest day of the hottest month to visit Virginia’s top grape pathologist to explore what is being done to handle climate change and prepare for a warmer future.
Dr. Mizuho Nita is Associate Professor and Extension Specialist for Grape Disease Management with the Virginia Tech Extension Center, School of Plant and Environmental Science. He is Virginia’s lead grape expert at Virginia Tech’s experimental vineyard growing at the Alson H. Smith, Jr., Agricultural Research and Extension Center (AREC) in Winchester.
Professor Nita was born in central Japan and attended Nagoya University with an undergraduate focus in Geography. He entered an intensive English language program and was able to take enter the exchange program with Southern Illinois University-Carbondale. Even though he did not grow up in an agricultural family (his father worked for an electronics manufacturer), he has an interest in the use of natural resources and attained his Bachelor’s degree from Southern Illinois University in 1994 in that area. He returned to Japan to work for several years. Not finding the work there particularly rewarding, he was able to enter the Master’s program at Ohio State University. Through this program he was introduced almost by chance to the focused study of plant pathology. This really clicked with him and his environmental bent. As a result, he attained his Master’s Degree and his Doctorate from Ohio State in plant pathology. Dr. Nita did post-doctoral research at Penn State and Kansas State before joining the Virginia Tech extension center as its plant pathologist in 2009.
Dr. Nita’s focus both near- and far-term is on the cause and impact of plant diseases on grape and grape vines. He has sponsors, manages, and is involved in several initiatives that are designed help growers plan for vine management and consequently relate to management in this changing environment:
1. Sentinel Vineyards. There are some 12 vineyards throughout the Commonwealth that provide weather conditions and plant disease data to the Alson Smith Center so that there is a state-wide picture of the health of the grapes and potential risks. Dr. Nita briefs Virginia growers at least monthly during the growing season on what diseases are on the rise in different localities and what are the advisable treatments of pesticides or fungicides to address the diseases.
Winchester Sentinel Weather Station
For example, with Climate Change, Dr. Nita has observed more frequent strong rain events followed by heat, including humid nights. This is a perfect environment for Downy Mildew (DM). Therefore, over the past 15 years DM is trending more than Powdery Mildew, and growers need to adapt what treatments to use for the more prevalent disease. Some grapes like the Chardonel hybrid are more resistant to DM than some other cultivars.
2. Grape IPM. Dr. Nita manages an app for grape growers called “Grape IPM.” The app allows growers to input data and develop a plan for pest/disease mitigation for the growing season: what pesticide or fungicide to spray, when to spray, produce spray reports for health regulations and worker protection. Because a grower’s plans for disease management are business confidential in relation to neighboring competitors, Virginia Tech does not share data from this app. Therefore, it is a tool for growers with limited broader use to address climate change.
3. The Virginia Tech research center is not at this time pursuing grape breeding specifically to anticipate Global Warming impacts. However, Dr. Nita believes that the new director for the center will begin a breeding program soon. Meanwhile, the Virginia Wine Board in conjunction with the U.S. Department of Agriculture has commissioned Emily Pelton (Veritas) and Ben Jordan (Lightwell Survey) to look at new developing breeds of grapes for Climate Change impacts. (see, DMV Download). According to that source, this grape breeding work will take at least 10 years to produce a grape that ripens better and is more disease resistant. Dr. Nita said that he consults on this effort but is not involved day-to-day. [We may feature an interview with the principals in that other effort in a later post.]
General Observations and Discussion.
Dr. Nita and I spent quite a bit of time walking the experimental vineyard that grows on the South-facing hillside behind the Center.
Altogether, the Center occupies around 124 acres, of which most is taken-up with apple trees. Grape vines currently cover only around two acres. Dr. Nita largely manages the vineyard himself, doing the spraying, pruning, and harvesting, in addition to the analysis, reporting, and the collection of data from this and other locations to inform his larger advisory role to the wine industry. He also assists some chemical companies that are trying new solutions at the experimental vineyard. Dr. Nita has occasional help from graduate students, however, policies at Virginia Tech have reduced the student workforce he can rely on to be available to work the vineyard. This is quite a workload for one man.
Tony Wolf, the recently retired
Virginia Tech viticulturist, began the vineyard ten years ago, and Dr. Nita is
considering a major replanting in the next year or two. When starting a new vineyard, growers are
normally advised that it takes three seasons for vines to produce their first
fruits. But in an established vineyard,
when a vine is diseased and needs to be replaced, the new planting may take
five years or more to be productive.
That is because the new vine is in competition with the established
vines for water and resources. Dr. Nita will be considering all of this in the near future.
Dr. Nita noted that grapes in tight clusters, like Chardonnay, are more prone to mildew. Chardonnay and Pinot Noir grapes have thin skins that crack early in Virginia heat. The popularity of Chardonnay to consumers has to be tempered by its susceptibility to disease and damage in heat. Understandably, Pinot Noir is little grown in Virginia.
One virus showing up in the vineyard more frequently is the Grape Leaf-roll Virus, which can delay ripening, alter the chemistry of the grapes, and reduce yield by up to 50%. This virus spreads by insects. A number of vines in the experimental vineyard had the telltale red leaves and curled edges. The most effective response is to remove the infected vine, but then you have the replanting dilemma of an extended time of lost productivity noted above.
Another example of milder winters promoting more warm-weather disease, according to Dr. Nita, is the increasing incidence of Pierce’s Disease, which is spread by treehopper insects in warm wet weather. To kill-off the treehoppers, temperatures need to get below 49 degrees (9.6̊º C) for three nights. Unfortunately, in some parts of Virginia, nighttime temperatures haven’t gotten that cold in recent winters.
One approach that Dr. Nita is testing is a practice adapted from his native Japan. Biodegradable plastic sheeting is rolled out between the grape canopy and the grape clusters.
In this way, rain, that promotes many kinds of mildew and rot, is kept off of the grapes themselves. This also reduces the number to times vineyards have to be sprayed, reducing the cost of sprays and manpower to apply them.
Dr. Nita observed another consequence of mild winters is in the ability of grape vines to react to cold snaps. Vines need to store carbohydrates as they enter winter dormancy in order to be able to tolerate cold snaps. Mild Autumns fail to trigger a vine to store energy for the Winter. When a cold snap happens, the vine has insufficient resources to respond, leaving the vine injured for the coming season, or dead. Just like people, vines need their rest. Older vines are better at storing carbohydrates than younger vines. And some grape varieties, like Cabernet Sauvignon and Cabernet Franc do better at bouncing back than some other reds. In whites, Chardonel does better than Chardonnay in this respect. This is one factor that growers may think about in their planting strategies as warm winters may continue.
Dr. Nita noted candidly that Virginia is not the best environment for growing grapes. We do not have the consistent weather that blesses California and the Pacific Northwest. Growers in Virginia have to intervene constantly to prevent disease in the vines. This generally involves application of chemicals and arduous work with vines. Letting nature run its course is not really an option. In fact, Dr. Nita noted that Virginia has only one winery that is certified as “organic” (Loving Cup). But he strongly applauds the determination and resourcefulness of Virginia’s vintners to be able consistently to produce good crops and great wine in an environment that is trending warmer and wetter. Our long experience with temperature fluctuations, humidity, and intense rain or wind at inopportune times means that Virginia growers probably will be able to adapt to an environment that is only getting more challenging.
References.
July 2023 set to be world's hottest month on record, by Gloria Dickie, Reuters, July 27, 20233:51 PM EDT at https://www.reuters.com/business/environment/july-2023-set-be-worlds-hottest-month-record-scientists-2023-07-27/ accessed July 28, 2023.
Florida ocean temps surge to 100 degrees as mass coral bleaching event is found in some reefs by Eric Zerkel, CNN updated 9:56 AM EDT, Wed July 26, 2023 at https://www.cnn.com/2023/07/25/us/florida-ocean-heat-coral-bleaching-climate/index.html, accessed July 28, 2023.
Heat wave puts two-thirds of US population under alerts, NewsNation at https://www.newsnationnow.com/weather/heat-wave-northeast-plains-south-severe-weather/, accessed July 28, 2023.
Climate change pushes Virginia wine makers to experiment with heartier grapes, by DMV Download, October 14, 2022 at https://dmvdownload.wtop.com/climate-change-pushes-virginia-wine-makers-to-experiment-with-heartier-grapes/ accessed July 23, 2023.
Loving Cup Vineyard and Winery, North Garden, VA, at https://lovingcupwine.com/, accessed on July 29, 2023.
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