Category: Current Issue

By: Judit Monis, Ph.D.

This year I was invited to do a presentation at the Southern Interior Horticultural Show in Penticton, British Columbia (Canada).  The growers in British Columbia are experiencing problems due to diseases and need to replant their vineyards. I was so glad that my audience was interested in plant health and procuring material that is not infected with pathogens (disease causing agents). There are so many articles and books that focus on planting a new vineyard.  These describe soil preparation, setting up irrigation, trellis systems, etc. but rarely focus on plant health.  The best way to avoid disease in a vineyard is prevention.  It is known that diseased plants are more susceptible to environmental stress such as heat, cold, drought.  Further, once infected vines are planted, it is too late to fix the problem.  In this article, I will describe guidelines and best practices to assure that the vineyard planting material is healthy and remains healthy during its lifetime.

Available Nursery Material

  In the spring. Nurseries are busy grafting the cuttings of rootstock and scion varieties that were collected in the winter.  Most nurseries in California propagate and grow material from the California Certification and Registration (R&C) program.  This R&C program was revised in 2010 to include testing for specific pathogens (mainly viruses and Xylella fastidiosa, the causal agent of Pierce’s disease).  After the discovery of Grapevine red blotch virus (GRBV), the regulations were revised once more in 2016 to include the exclusion of this detrimental virus in the certification program.  Canadian growers procure plants from the Canadian Certification program but also purchase plants from California nurseries.

  Some growers and winemakers already have a favorite nursery they have worked with and have had good success with the planting material. Others may had had a bad experience and likely will avoid working with that nursery.  In every case, it is important to develop a good working relationship with the nursery that will produce the grafted vines to be purchased. Prior to placing an order, there is important information to request from the nursery that will help determine the quality and health of the plants they produce. 

  Most growers will be interested in purchasing certified grafted vines as they have an extra level of assurance (the foundation mother blocks are tested regularly for certain pathogens).  However, growers must be aware that grapevine plants are still being propagated in nurseries from the old California R&C program (material from the early 1980s Since many diseases are transmitted and spread in the vineyard you can expect that the older the block the higher the chances of being infected with one or more pathogens!).  It is also important to know when was the nursery increase block planted. As starting in 2017, the new U. C. Davis foundation block was found to be progressively infected with GRBV to the point that it had to be abandoned and replaced with plants grown in greenhouses.

  Even if the nursery propagates material from the certification program you should ask if the nursery has a disease testing and sanitation plan.  The nursery personnel can provide their quality assurance protocol.  Questions to ask include the following: how old are the mother blocks? how many vines are tested in each block? Does the nursery perform random testing or do they have a plan and test all vines on a rotation basis?  Which pathogens are tested for, how often, and why do they not test for others?  Do they test single vines or composites of many vines?  What do they do when a composite sample tests positive for a detrimental virus (i.e., Grapevine leafroll, fanleaf, or red blotch)?  Would they allow you or your consultant to take samples of the varieties or clones of interest and base your purchase on the laboratory results? The answers to these questions will reflect the seriousness of the nursery operation and give some idea of the overall health of the increase blocks and nursery rows.   In addition, I strongly recommend to request reports of the analyzed vines to learn about testing schedules and health history of the nursery’s increase blocks. If the reports are not clear, talk to the nursery personnel or a plant pathologist to help you understand the testing schedule and/or results. It is important to visit the grafting and propagation facilities to perform your own inspection. Finaly, inspecting the plant material and performing a random test prior to delivery and planting will avoid planting material infected with trunk disease causing fungi and Allorhizobium vitis (previously known as Agrobacterium vitis, the causal agent of grapevine crown gall).  If you do not have the required knowledge to understand what to look for, I recommend you hire an expert who can help. 

Testing Requirements of Plant Material

  To increase the assurance of freedom of disease, representative samples from blocks of the rootstock and scion material should collected and submitted to a testing laboratory to determine their health status.  If the vines are field finished (i.e., not potted), testing after growing in the nursery rows or after cold storage is recommended to assure freedom of disease-causing agents.  Is it possible to develop a testing plan depending on the number of vines to be produced, either by testing individual mother plants or using statistical sampling.  The more samples that are submitted for testing, the better confidence in results.

  The grower may decide to propagate and graft material from their own or a neighbor’s vineyard. This choice can be based on early performance of the specific variety or clone in the winery.  However, caution must be taken to assure that the field selection is not infected with detrimental pathogens.  A field selection that performs well in one vineyard may not perform the same way in a newly planted vineyard.   For example, it is known that some pathogens may not display symptoms until a stress factor is present.  Also, some varieties display more symptoms when grafted to a specific rootstock.  In summary, regardless of where the plants originate, it is a good practice to test the mother vines for the presence of pathogens.

Prevention of Infection in the Newly Planted Vineyard

  Procuring certified and/or disease-free tested vines, is just the start.    The newly planted vines have the potential to become infected during their life span. This is especially possible if a diseased vineyard block was removed and replaced with “clean planting stock” or nearby blocks are infected with a virus that is able to spread (e.g., some Grapevine leafroll associated virus species are transmitted by mealybugs; Grapevine fanleaf virus is specifically transmitted by nematodes).

  The new blocks and adjacent vineyards should be monitored for insect vectors and/or suspicious symptoms.  It is always a good idea to determine the cause for suspicious symptoms as viruses and other pathogens can spread from adjacent vineyards.   The knowledge of a positive finding of a virus that is transmissible and the presence of the insect that transmits it will turn on a warning sign.  For example: Grapevine leafroll associated virus-3 or other related Ampeloviruses (GLRaV-1, or -4) and the mealybugs that can transmit these viruses should alert the vineyard manager of a disease prevention strategy that will help avoid the spread of these viruses. I have observed instances in which a vineyard owner removes (and replaces with tested vines) only half of the infected vineyard block to avoid production losses.

A new vineyard planted with vines infected with Allorhizobium vitis (cluse up)

  The other half of the infected vines are removed after the newly planted vineyard block starts to produce grapes.  This is not recommended.   In these cases, I have seen that by the time the infected older plants are removed, the newer plants have become infected with the same pathogens that were present in the original block.

  Some important fungal and bacterial pathogens are soil-born and can be transmitted to the new planting after the infected vines were removed.  But it is also possible to bring these pathogens with the new planting material.  In many cases, a simple visual inspection can indicate that the planting material is infected with A. vitis. Either way, with no symptoms present, sophisticated tests are available to test the vineyard soil and planting material to allow the grower to make informed decisions on planting and disease management.

Conclusions

  In summary, new vineyard development is a critical task that should be taken seriously.  My recommendation is not to hurry.  Do not just purchase the only material left at the nursery or propagate your next-door neighbor’s budwood because you made last minute decisions.  Take the time to make sure that the planting material will meet the quality standards that will produce the best grapes for optimal wine or table production.  You probably heard me say many times that the only way to avoid disease in the vineyard is to prevent the introduction of harmful pathogens.

   By far the most efficient way of pathogen introduction in a vineyard is by planting material that is already infected (one infected mother plant can produce 200-300 infected daughter plants!).   Currently there is no cure for graft-transmissible diseases once established in the vineyard.     This urges you to apply special care when selecting planting material prior to developing a new block.   With these simple guidelines, it is my hope that you will develop a vineyard that will be healthy and productive. 

  Judit Monis, Ph.D. provides specialized services to help growers, vineyard managers, and nursery personnel avoid the propagation and transmission of disease caused by bacteria, fungi, and viruses in their vineyard blocks.   Judit (based in California) is fluent in Spanish and is available to consult in all wine grape growing regions of the word.  Please visit juditmonis.com for information or contact juditmonis@yahoo.com to request a consulting session at your vineyard.

By: Michael Cook and Justin Scheiner, Ph.D. – Texas A&M AgriLife Extension Service

As grape growers, we know how important water is for profitable production. Water is involved in pretty much every physiological activity inside a grapevine. We also realize that water is a precious resource and no matter how you slice it, it costs us money. It is not only expensive to apply, but the indirect costs of over or under watering can lead to negative impacts on our bottom line.

  Most climate models predict future growing seasons will be warmer, which will increase water use by grapevines and vegetation in vineyards. This may be good for our friends in Canada, “eh”, but for growers and grapevines in more arid and hot areas on the West Coast as well as in the warm continental and humid climates east of the Rockies, it would spell trouble. These trends mean that it’s increasingly important for commercial producers to adopt data driven technology to monitor water in the soil and in the vine to help guide our decisions. Long gone are the days when the small producer could say there are no sensors in their price range.

  Thanks to advances in technology and manufacturing, there are sensors of all shapes and prices available to today’s grape grower. Having accurate, intuitive data about water use can save a grower serious money. Soil moisture sensors can be very useful in determining when to start irrigating and when to stop. Those that dry farm often irrigate the first few years of vineyard establishment and soil sensors can even be useful in these more temporary situations. Here we’ll briefly discuss soil sensor types and how even the smallest grower can benefit by adopting this technology as part of their irrigation management plan. In a future article, we’ll discuss monitoring vine water status directly and weather-based modelling for irrigation scheduling.

Soil-Based Approaches

  Getting the most out of soil sensors requires some basic knowledge of soil water dynamics. A thorough treatment of these principles is beyond the scope of this article, but we’ll highlight a couple of key concepts here. The foundation for using soil-based water availability measurements, which are ultimately an indirect method of monitoring vine water status, is that we want to maintain some level (e.g., 50-80%) of plant available water (PAW) to vines throughout the growing season. Plant available water is the amount of the water in the soil that vines can actually take up versus the total amount present. While it can be represented as a percentage, we can also express PAW as a volumetric measurement (e.g., inches per acre). Once the soil begins to dry out and the moisture content decreases below a threshold, typically 40-50% of PAW, vines experience drought stress. The specific minimum depletion level that a grower may allow, often called the management or maximum allowable depletion (MAD), may be fine-tuned where a water deficit is allowed to persist over key phenological stages. However, once the soil moisture level approaches 50% most growers will opt to turn the irrigation on.

  Plant available water for a given site or vineyard block can be easily estimated based on soil type, texture, and depth (Table 1). These soil qualities can be investigated by consulting USDA Natural Resources Conservation Service soil maps, collecting soil samples for soil texture and chemical analysis and by simply digging soil pits with an excavator to observe soil horizons, potential rooting depth for new vineyards, and actual rooting depth for mature vineyards.

  Although we still need to get out and scout our vineyard blocks for visual cues throughout the season, soil sensors provide actual data about what is happening in the plant’s root zone. These sensors can be categorized by their function, including those that measure soil tension (qualitative) and those that measure soil moisture content or volume (quantitative).

  There are a number of things to consider when choosing a soil sensor. One is determining the number of sensors to utilize as many can only provide a single point of measurement. Even when using multi-depth sensors, vineyard sites or individual blocks with higher soil variability and with greater topographical changes will require more sensors to accurately determine irrigation needs. The tradeoff for this is higher data resolution leading to more informed decision making. The viticulturist should also consider installing soil sensors at multiple depths in the soil profile so that water infiltration through the soil can be monitored (Image 1). This is also useful for determining if deep soil moisture is available during periods when irrigation may not be routinely applied such as near bud break. With so many soil sensor options available, cost, convenience and accuracy should be weighed to identify the best option.

  No matter which soil sensor you choose, pay particular attention to the placement, installation, and maintenance protocol as each soil sensor type has different requirements. No soil sensor will provide accurate data if it is installed and maintained improperly. Sensors must maintain constant contact with the soil and should be located under the trellis in an area that would normally be wetted by the irrigation system but not immediately underneath an emitter. Make sure to flag soil sensors in the field, secure any cabling, and map locations for future reference as they can easily become lost or damaged.

Qualitative-Based Soil Sensors

Qualitative-based soil sensors, also called water potential sensors, matric potential sensors, or water suction sensors, measure how tightly moisture is bound to soil particles. These measurements are described in tension units (often as centibars, or cbars). Data can reflect suction or negative pressure as with a tensiometer or electrical conductance/resistance as with electrical resistance blocks. Water potential readings are higher (less negative) in fully saturated soil and become more negative as soil begins to dry due to the increase in soil water tension. In other words, there is still water in the soil, but the plant can’t use it because the soil won’t give it up. Soil tension sensors are generally soil-specific and can be inaccurate if the correct model, calibration and installation instructions are not followed.

  These sensors are useful to indicate when to irrigate, but it typically requires some time to understand roughly how much water to apply to bring soil moisture up to an appropriate level.

Quantitative-Based Soil Sensors

  Quantitative-based soil sensors, also called volumetric water content (VWC) sensors are the most used sensors in commercial vineyards. Based on a calibration, they measure how much water in liquid form is present relative to the amount of soil (i.e. volumetric). Measurements are generally in units like percent volume of water to volume of soil or cubic inches of water per cubic inches of soil. For example, a sensor giving a reading of 25% volumetric water content is the same as 0.25 cubic inches of water per cubic inch of soil. When compared to the water content at field capacity, VWC deficits can be used to drive irrigation scheduling decisions. Although the information provided by VWC sensors can be highly valuable, it does not provide any insight into other pertinent information such as water adherence to the soil or ease of extractability by the vine.

  Two classes of quantitative-based soil sensors include Neutron probes and dielectric sensors. Neutron probes are primarily used by researchers and irrigation specialists, requiring bulky and expensive equipment and licensing. Dielectric sensors include Time Domain Reflectometry (TDR) and Frequency Domain Reflectometry (FDR), often referred to as capacitance sensors (Image 2). Of all the soil sensors currently on the market, FDR sensors are the newest and fastest developing area of technology. They can be cost effective, accurate, reliable, low maintenance, and easily integrated into other sensor-based modules like weather stations (Table 2). As with all sensor types, consult the manufacturers recommended installation and maintenance protocol for proper placement, density and depth per block.

  Consider incorporating soil sensors in your water management plan to improve your confidence in irrigation decisions.

 Table 1. Plant available water based on soil texture. (Adapted from Goldammer, T. 2018)

Table 2. Major soil sensor types suitable for vineyard use.

¹based off 2025 MSRP for the sensor itself. $ low cost, $$ moderate cost, $$$ high cost.

²maintenance requirement rated from 1-3, with 1 being the lowest maintenance to 3 being highest maintenance.

Image 1. A single soil sensor monitoring moisture placed in the topsoil and another installed in the sub-soil at the same location.

Image 2. A capacitance type sensor being installed in a vineyard.

By: Alyssa L. Ochs, Staff Writer

Animals of all sizes and types can have devastating impacts on grapes growing in a vineyard. There are direct economic impacts when animals eat, trample or otherwise damage grapes, which leads to yield losses and additional expenditures for pest control measures.

It is essential for vineyard owners to find a balance between the costs and labor involved in wildlife control and the benefits of a healthy harvest. We connected with leading vineyard wildlife control companies to learn more about the effects of wildlife and how to manage grapevine damage caused by wild animals.

How Wildlife Affects Vineyards

  There are many ways in which animals can affect grapevines in a vineyard. For example, they can cause direct crop damage by eating grapes, especially when grapes mature right before harvest. Wildlife can contaminate grapes by leaving behind fungus and bacteria from their fecal matter. This residue often leads to off-flavors and bunch rot.

Vine damage occurs when animals gnaw on vines’ bark or dig around the base of plants, impacting current and future grape growth. There is also the possibility of soil erosion caused by wildlife trampling through the vines and damage to irrigation systems.

  Some vineyards are faced with increasing costs for pest control because they need to address the damage already caused and then take more effective action to protect future crops. Changing weather conditions and increasing extreme weather events may also impact pests’ natural behaviors, requiring shifts in vineyard pest control strategies to accommodate new patterns of infestation.

Factors Affecting Wildlife Damage

  A vineyard’s geographic location matters regarding wildlife damage to grapes. Some areas are more prone to animal activity, so it is important to understand the prevalence of wildlife populations and their feeding patterns where you are. You may experience more or less wildlife due to the availability of food and shelter, as well as your vineyard’s terrain and proximity to wild habitats and urban areas.

  The type of wildlife present in your area also determines how much damage is likely to be caused, as some pests cause more harm than others. Fortunately, customized solutions are available to help vineyards improve their management practices and be proactive about minimizing wildlife activity.

Types of Damage Caused by Wildlife

  Birds cause substantial damage by eating copious quantities of grapes, thereby reducing a vineyard’s yield. Starlings, sparrows, and blackbirds are problematic in many vineyards. You may notice pecking damage from birds on grapes, which leaves them susceptible to rot and disease.

  Jon Stone from Avian Enterprises told The Grapevine Magazine, “While grapes that are consumed are a direct loss, pecked grapes may release juice, which can lead to bunch rot and even greater levels of loss. The juice can also attract drosophila flies and wasps, which can spread the rot to otherwise untouched bunches.”

  Based in Sylvan Lake, Michigan, Avian Enterprises offers an EPA-registered solution to eradicate pest birds without causing harm to the birds, other animals, or humans.

  Rodents are common in vineyards, including mice, rats, and voles. These animals are notorious for gnawing on vine roots and bark, which weakens or kills the vines. Rodents can contaminate grapes and vineyard equipment with their fecal droppings, creating risks for food safety and sanitation.

  Deer are known for causing vine damage as they move through vine shoots, leaves and grapes. The movement of deer in vineyard rows reduces the plants’ ability to successfully photosynthesize and produce grapes. Because of their generous size, deer commonly damage vines and soil by trampling through the rows, causing root damage, soil compaction and trellis and fence damage.

  George Horetsky, senior sales representative at Trident Enterprises, told The Grapevine Magazine that bucks also cause damage by rubbing their antlers on young vines, which can kill or weaken them. Based in Waynesboro, Pennsylvania, Trident Enterprises has been a wildlife exclusion expert for over 30 years and is a leading distributor of fence supplies.

  In some areas, wild boars are a problem for vineyard owners. They eat grapes, leading to significant crop loss. Wild boars have rooting behaviors that uproot vines and damage irrigation systems. Predatory animals like coyotes and foxes can also disrupt vineyard operations and scare away beneficial wildlife and insects as they search for food.

Economic Impacts of Wildlife Damage

  Horetsky from Trident Enterprises explained to us how wildlife damage, especially from deer, can lead to substantial economic losses for vineyards.

“Reduced yields from damaged vines directly impact revenue, while the cost of repairing physical damage and replacing plants adds to the expense,” he said. “In some regions, studies suggest wildlife damage can result in a five to 10 percent loss in total vineyard productivity annually. Beyond crop loss, vineyards may face increased operational costs for pest management and implementing preventative measures. Trident Fence’s wildlife control solutions are designed to help mitigate these losses by offering durable, long-lasting fencing options tailored to vineyard needs.”

  Stone from Avian Enterprises shared with us, “The USDA has estimated that bird damage may result in a loss of up to an average of 40 percent of the crop. In a recently published article, Michigan State University states that losses can be as high as 95 percent and 60 percent in red and white varieties, respectively. Losses of over $100 per acre are possible. Clients who have used Avian Control® Bird Repellent have reported significant reduction in the level of loss, at times less than 10 percent.”

How to Prevent Wildlife in the Vineyard

  According to Horetsky from Trident Enterprises, one of the best ways to control wildlife is to install effective fencing.

  “High-quality fencing is the cornerstone of wildlife prevention,” Horetsky said. “Our fencing solutions, including poly and metal mesh options, are designed to withstand wildlife pressure, providing reliable protection for vines. Customizable features ensure the fencing fits the specific needs of the vineyard, whether it is a large-scale acreage or a boutique operation.”

  Horetsky also recommended creating physical barriers to reinforce vulnerable areas like vineyard perimeters and entry points. He suggested pairing fencing with complementary measures like motion-activated sprinklers or repellents during peak wildlife activity. He also shared that inspecting fencing regularly is essential to identify and repair damage.

  “By investing in durable, scalable fencing solutions and adopting best practices for wildlife deterrence, vineyards can focus on cultivating healthy vines and maximizing their yields, year after year,” Horetsky said.

  Stone from Avian Enterprises explained that rather than trying to manage and repair damage already done, crop loss to foraging birds can be significantly reduced by taking a proactive approach to bird control.

  “Frightening devices like cannons, distress calls and streamers have proven to be somewhat effective, while netting is effective but costly to use and very labor intensive,” Stone said. “Avian Control® Bird Repellent is a non-toxic liquid spray that, when used as directed, irritates birds, teaching the birds to avoid any treated areas.”

  Stone said that Avian Control® has no effect on people, pets, or livestock. Also, it does not affect the taste of grapes and biodegrades rapidly.

“The key to successfully bird control is to begin applying Avian Control® Bird Repellent at the first signs of birds in the vineyard, usually around veraison,” Stone said. “Avian Control® can be used up to the day of harvest.”

Best Practices for Vineyard Wildlife Control

  Stone at Avian Enterprises stressed that growers who have experienced the highest level of success with their company’s products have begun their applications early. 

  “Waiting to see how serious the damage will be allowed the birds to establish themselves in the vineyard, making it more difficult to repel them and ensuring ongoing damage until the birds leave,” Stone said. “Avian Control® works at it best when applied by itself. Tank mixing is discouraged, as the presence of other chemicals has been shown to reduce effectiveness, and a pH that is below 6.5 causes premature breakdown of the product. Properly applied, an application of Avian Control® can last up to two weeks.”

  Meanwhile, Horetsky from Trident Enterprises provided several tips for effectively using his company’s wildlife control solutions in a vineyard. His advice can be broken down into the following: site assessment, proper installation, maintenance, complementary measures, and custom solutions.

  “Conduct a thorough assessment of the vineyard to identify vulnerable areas, such as borders near forests or water sources,” Horetsky recommended. “Ensure fencing is installed at the correct height and depth. For deer, fencing should be at least 7.5 feet tall to prevent jumping.”

  “Regularly inspect fences for damage or wear, especially after storms or during peak wildlife activity,” he continued. “Combine fencing with other deterrents like motion-activated sprinklers or repellents for a multi-layered approach. Finally, utilize fencing systems designed for vineyards, such as those with easy access points for equipment and workers, while maintaining robust protection.”

  Vineyards can preserve their immediate productivity and long-term sustainability by incorporating these measures and investing wisely in wildlife control solutions with the help of trusted companies that understand the industry well.

  “Wildlife pressure can be unpredictable, but proactive measures like high-quality fencing reduce risks and provide peace of mind,” Horetsky said. “Trident Fence is committed to helping vineyard owners find practical, cost-effective solutions tailored to their unique needs, ensuring their vines — and bottom lines — are protected season after season.”