By Jim Kamas (February 2018)

Grapevines vary in their ability to withstand cold winter temperatures, but in Texas, weather conditions preceding any freeze event typically have more to do with bud and vine survival than the cold hardiness of the variety itself. The process of vine acclimation for the next winter actually starts with the shortening of day length after the summer solstice. As the days shorten, vines start to form periderm on current season’s growth and decelerate the rate of vegetative growth.  In late summer and fall, healthy vines continue to photosynthesize and store carbohydrates in buds, roots, trunks and canes. This late season carbohydrate loading is important in maximizing the hardiness of grapevines. This is why it is important that water not be cut off following harvest as it is needed to maintain the canopy and photosynthetic action necessary for this carbohydrate formation. As temperatures cool through autumn, leaves begin to senesce and fall with the first hard frost or freeze.

With the onset of winter and falling temperatures, vines go deeper into rest and reach their ultimate hardiness where they are capable of withstanding temperatures into the teens and even single digits. Not all grape varieties enter dormancy at the same time. ‘Cabernet-Sauvignon’, for example, is a late acclimater and can be injured by early hard freezes in autumn when other varieties receive no injury at all. There are relative degrees of ultimate hardiness among varieties, so in some locations, that hardiness or lack of hardiness needs to be a part of the decision whether a variety gets planted or not.

Grapevines acclimate very slowly, but they deacclimate very rapidly. Unseasonably warm periods in January and February can cause vines to quickly begin to deacclimate making them susceptible to injury at temperatures they could have withstood before the warm weather. Whether it’s very low temperatures themselves or a hard freeze after vines have deacclimated, cold injury can occur on buds, canes, cordons and trunks. Identifying this injury early can help a grower take appropriate measures to minimize the financial impact and take appropriate corrective measures.

Acute winter injury can be observed early in the season when buds fail to force and vines respond with a flush of suckers from the trunk or ground. At this point a grower should realize that the crop has been badly damaged and even if some primary or secondary buds were not killed, the vascular tissue of the vine has been so badly harmed that it cannot support a canopy through the high transpiration of rates of mid-summer.

Internal inspection of the vascular tissue can confirm that vines have been damaged, but the browning of internal tissue may only be visible after a period of warming temperatures after the freeze event. If vines have been severely damaged, growers should consider retaining three or four suckers and train them up and on to the cordon wire to replace the existing trunk and cordons.  Only leaving one or two will most likely result in replacement canes with excessive vigor (bull canes) that will have limited fruitfulness and most likely be cold tender in the following winter.

Severely damaged grapevine forcing suckers in mid-spring

More subtle injury in some ways is much more difficult to identify and manage. Buds may force, but stunted vegetative growth typically means there is damage to the “plumbing” somewhere, either on the cordon or trunk. In other cases, vines appear to force and set fruit normally, but collapse during the heat of summer when the compromised vascular system can no longer transport enough water to support the canopy it has produced.  In these cases, growers thinking that there was no problem commonly remove suckers in spring which will limit the ability to generate new shoots for vine reconstruction.

In some situations, stunted shoot growth can signify cold injury

In years like this one where mid-January temperatures were in single digits in much of the state, cold injury may have ocurred in some vineyards. Even though temperatures preceding this cold spell were not warm and vines should have been well acclimated, growers might consider pealing back small patches of bark to look at the vascular tissue.

In some seasons, damage to vascular tissue can only be seen after vines collapse in the heat of summer

Brown or grey coloration indicates injury while healthy tissue is bright green. Because of preferential heating of tissue by direct sunlight, southern and western parts of vines can be more quickly deacclimated and are commonly more prone to injury than the north side of the vine. With serious trunk and cordon injury, re-training vines is a necessary task to return the vineyard to productive status. There is really no hurry to cut out freeze injured tissue on injured trunks. Let the vines force and reveal exactly how profound the injury is. If there are a dozen or more competing shoots, selectively thin them out in summer, but remember summer pruning is a dwarfing action and removing a third or more of the vines vegetative tissue will most likely stunt the vine and stop growth.

Winter injury can also cause trunk splitting and can provide entry wounds for crown gall or trigger gall formation in vines already infected with Agrobacterium.

Galling of grapevine trunks from Crown Gall infection

In some years, cold temperatures may not be low enough to cause injury to the vine’s primary structure, but primary fruiting buds may have been killed or injured.  Purists would object to the use of the term “bud”, because on grapevines, everywhere a leaf is attached on a shoot is actually called a node, which has three buds. The primary bud is the most fruitful and is why growers refer to leaving a given number of buds per vine after pruning. In addition, each node has a secondary bud which can be somewhat fruitful and a tertiary bud which is not fruitful. Growers typically depend on surviving primary buds to produce the coming season’s crop and plan their pruning programs to leave the appropriate number of nodes to produce a crop at a target tonnage. Cold events that cause primary bud loss commonly affect yield the following growing season. If growers know an approximate level of damage, they can adjust their pruning practices to compensate for the loss. With a very damaging freeze, or after a spring frost takes out primary shoots, secondary buds can force and produce a partial crop. In years with potential damaging events, growers should consider cutting dormant canes of each variety for examination. Bright green coloration indicates healthy buds while killed or injured buds take on a brown or blackish hue. Knowledge of bud survival can help growers make final pruning decisions that may include leaving more “buds” up than average to compensate for primary bud loss due to freeze.

Using a razor blade or other sharp knife, growers can cut and examine grape buds to assess damage

By Jim Kamas (February 2018)

Among perennial deciduous fruit crops, grapevines are the most heavily pruned. Unlike many other perennial crops, measurements of one year old growth removed after dormant pruning is a common way to measure vine vigor and a vineyard’s ability to produce a crop the following season. In many vineyard experiments such as fertilizer or rootstock trials, this parameter is a vital part of the information gathered that can describe how a given treatment affects vines.

Commercial growers can use this technique to measure how a vine has fared given the previous season’s crop load and environmental conditions to help achieve a balanced and uniform block of grapevines. We have witnessed vineyards cropped at say six tons per acre per year progressively decline in vine vigor while the grower was unaware that the annual yield and the decline in vine size were related. While in experiments, pruning weights are collected from every vine, that practice is certainly not practical for commercial growers. Many experienced growers do, however mark “sentinel” vines in every block of grapes to prune, weigh and record weights on every year. Alternatively, the best means of getting a picture of what is happening in an entire block is to do a random sample of vines for a whole block comparison. The difficulty is that in order for this technique to work properly, it is essential that the selection of vines from one year to the next actually be random, a process that can be confounding for people not accustomed to this type of measurement. Either way, vines on the ends of rows, or vines that are not typical for environmental or cultural reasons should be avoided. By actually weighing vine pruning weights every year, this exercise helps calibrate a grower’s eye to discern subtle differences between varieties or sections of vineyards. A practical rule of thumb is that vineyards with less than 0.125 pounds of annual prunings per linear foot of row are considered to have undesirably low vigor while vines exceeding 0.4 pounds of prunings are considered to have excessive vigor.

Water Relations in Viticulture

Other Metabolic Functions of Water in Grapevines

Irrigation Water Quality

Irrigation Budgeting

Monitoring Soil Moisture

Drip Irrigation Operation and Management

Monitoring Vine Water Status

The Concept of Terroir in Viticulture

Terroir

Grapevine Rootstocks & Emerging Varieties

Grapevine Canopy Management

Grapevine Canopy Selection

Understanding Your Soil Report

Understanding Tissue Testing

Fertilizers

Wine Grape Soil Nutrient Management for Yield and Quality

By Jacy Lewis (April 2017)

It is common that growers may feel powerless when it comes to preventing herbicide drift into their vineyards, however there are actually a number of ways that winegrape growers can be proactive in protecting their vineyards from the effects of herbicide drift.

First and foremost start with your own pesticide program. This not only means in your vineyard but also on any property that you own surrounding your vineyard including your home, winery, or adjacent crops. Be certain that everyone who may care for any of these areas understands that there is a zero use policy for all synthetic auxin herbicides. This includes lawn and garden maintenance contractors. It is your responsibility to educate everyone working on your property about the dangers these synthetic auxin herbicides pose to your vineyard. It is surprising how many vineyards have experienced injury when the target plants were weeds on their own property, often applied by well meaning grounds keepers. This is the type of non-target injury that you have complete control over.

Another way to avoid injury is by networking and building relationships with anyone in your area who may be applying herbicides or interacts with individuals who do. If you have homes nearby, get to know your neighbors and let them know how dangerous these chemicals are for your vineyard. Because many homeowners are not fully aware of the nature of the herbicides they use in their lawn, provide them with a list of chemical and brand names to watch out for.

Contact your county commissioner or city and be certain they know that use of these chemicals in right of ways pose a serious threat to your vineyard operation, even when used according to label instructions. If you see someone spraying near your vineyard, don’t be afraid to politely ask them what they are spraying, if injury occurs this will arm you with needed information and they may even be willing to stop.

Get to know the chemical salesmen in your area. Be certain they are educated on the dangers these chemicals pose to your operation and ask them to please help you by educating buyers about these dangers as well. Having a congenial relationship with these salesmen can go a long way towards making them partners with you in educating consumers. Particularly in areas where winegrapes are not an established crop, many chemical applicators continue to be unaware of this danger and unaware that there are vineyards in their area.

Additionally, get to know the commercial applicators operating in your area. This includes landscape contractors as well as aerial applicators. Let them know the location of your vineyard as well as the damage that can be done to it from inadvertent drift. Be certain they are educated with regard to the volatility of some compounds and the distances from which they can pose a threat under certain weather conditions.

Finally, two new programs in Texas are designed to work in conjunction with one another to assist applicators in protecting non-target  crops from accidental drift.

Flag the technology uses a system of colored flags to help applicators to visualize both resistant and susceptible crops both from the road and from above. Red flags are used to signify Extreme Caution; conventional varieties with no herbicidal resistance as well as apiaries, orchards, vineyards, vegetable fields, and organic crops. We recommend that as a precaution all growers participate in this system by marking their vineyards with these flags.

Red Flags are used to indicate highly sensitive crops like grapes. Photo courtesy of U. Missouri Extension

In conjunction with the Flag the technology program, the Hit the Target program that is replacing the Texas Crop Registry allows growers to register their sensitive crop acreages to be included in maps available to applicators. This program was advertised to go into effect on May 1st 2017.

The app can be found under the title “Flag the Technology” in your app store. It is available for both IPhone and Android devices.

While some growers are questioning the utility of the program, we feel it is important for growers to be proactive in taking all possible cautionary measures to protect their vineyards. Doing so might not only prevent accidental drift injury to your vineyards but may be important in showing regulators and courts that a grower has taken all possible protective action should an incident occur.

 

By Justin Scheiner (April 2017)

Damage from herbicide drift is not something that any grape grower wants to think about, but it’s a good idea to have a plan in case it happens to your vineyard. As discussed in Jim Kamas’ article Understanding and Recognizing Synthetic Auxin Damage in Grapes, plants immediately begin to metabolize herbicides upon absorption, and herbicides begin to degrade so action should be taken without delay to preserve evidence. Likewise, if you intend to file a formal complaint with the Texas Department of Agriculture (TDA), it should be initiated  soon after the damage is noticed while the evidence is most apparent.

The TDA employs just over twenty agriculture inspectors that are tasked with  investigating complaints of herbicide drift or misuse. These  are also the folks that inspect your spray records if you get audited. If you file a formal drift complaint, one of these inspectors will be assigned to investigate your case. The investigation will include a series of interviews, beginning with you, to determine if a violation occurred and who the perpetrator is.

Upon arriving at your property, the inspector will begin with checking your spray records to rule out the most obvious culprit, you. That  means your pesticide program had better be in compliance and your spray records better be up to date. There have been cases where growers that filed complaints ended up paying a fine for noncompliance. This is a good time to remind growers that it is a violation to use product brands not specifically labeled for use in grapes, even if the same formulation of the chemical is labeled for grapes under another brand name. Products not labeled for use on any crops on your farm have no place in your pesticide shed.

The inspector may photograph the damaged area of your vineyard and surrounding area. He or she may also collect samples for herbicide residue analysis. This decision is made by the inspector, and is not required during an investigation. The inspection may then proceed to neighboring properties. TDA does not esti- mate monetary loses that may have occurred, nor will they indicate suspected guilt until the investigation is finalized.

After the investigation is complete, a final report is written and will be available to you upon written request based on the Texas Public Information Act. You will receive a call from the inspector with the findings of his or her investigation and if a violation is documented, TDA may take one of the following actions: issue a warning; assess an administrative penalty; suspend, modify or revoke a license; or refer the case to another appropriate state or federal agency, county attorney, district attorney or Texas attorney general for further action. In addition to TDA’s investigation and actions, you may conduct a separate, independent investigation, and regardless of the  TDA’s findings, you may pursue civil action. In order to recover losses a civil action is required as TDA does NOT recover losses for injured land owners. We always recommend that a written request via the TPIA of the report be requested in order to eliminate any communication errors between you the grower and TDA when discussing the report. It is also possible the report may contain information not discussed in conversation that will either assist in your case, or aid in preventing problems in the future.

How to File a Complaint

To file a complaint with TDA, you can either call your local TDA office or the state office in Austin (1-800- TELL-TDA). Keep in mind that once a complaint is filed, it cannot be withdrawn without an investigation. Confidential complaints may be filed, but TDA does not guarantee that confidentiality can be maintained through process. After initiating a complaint, the TDA inspector assigned to your case will contact you by phone or mail to initiate a report.

According to TDA, the inspector’s report will contain:

1. the name of the person allegedly responsible for the application of the pesticide, if known;
2. the name of the owner or lessee of the land or structure on which the application was made, if known;
3. the name of the owner or lessee of the land or structure to which adverse effects are alleged to have occurred, if known;
4. the facts of the allegations set forth in detail signed by the complaining

If you have the unfortunate circumstance of herbicide drift and you decide that is worthwhile to file a formal complaint with TDA and/or conduct an independent investigation, don’t wait until it’s too late to collect evidence. Know what the symptoms and signs of herbicide injury look like and be prepared to act. If you have questions regarding herbicide injury contact your viticulture specialist for assistance.

For more information about filing a complaint with TDA visit:

texasagriculture.gov/RegulatoryPrograms/Pesticides/AgriculturalApplicators/AgPesticideComplaintInvestigationProcedures.aspx

By Jim Kamas (April 2017)

A companion article in the linked newsletter outlines the steps growers should take to contact state regulatory agencies responsible for regulating pesticide applications. However, growers who have experience with injured vineyards commonly suggest a parallel course of action. Independent, private laboratories are established around the country that can test for residue in injured grapevine tissue as well as from weeds in and around the vineyard. Procedural recommendations from these laboratories are as follows:

• Find and contact a pesticide testing lab to do business with. A search engine query will come up with several established companies. Contact your local viticultural field agent or specialist for suggestions. When choosing a lab, ask about their detection levels in the plant(s) you will be submitting. Also be certain they are able to test for the exact herbicide that you believe your vines were exposed to. If you are uncertain and are not able to find out which chemical was used, choose a lab that will test for the greatest number of synthetic auxin herbicides. Additionally, choose the lab with the lowest detection levels. If financing permits, sending samples to multiple labs may help in building a stronger legal case. 
• Take samples immediately. These herbicides begin to change and degrade within plants, so time is of the essence. With 2,4-D exposure, while vines may exhibit symptoms for several years, analysis of plant tissue a year or less from exposure commonly fails to confirm any presence of herbicides. Unless you know exactly which metabolite you are looking for, it may not show up.
• Document everything. Take several samples from various parts of the vineyard where contamination is suspected. Record and photograph the relative amounts of injury seen with each sample site. Continue to photograph any continuing symptoms on a regular basis as long as symptoms are present. A photographic timeline may be helpful.
• Use laboratory gloves to take samples, and change them between each sampling site to reduce the possibility of cross-contamination.
• Refrigerate samples after collection and overnight to the lab doing the analysis. Mailing with a cold pack may be beneficial. Contact the lab that you will be using for their specific recommendation.
• Fully document chain of custody with your analytical lab. Having a third party witness that can testify as to the date and location of the sampling is a good idea.

Samples commonly cost $100 or more each, but considering the potential long-term injury, failure to fully document the extent of exposure may leave you without the evidence you may need in settling a legal dispute.

The best prevention and management of herbicide injury is maintaining strong relationships and communication with your neighbors. Human error can occur, but a positive relationship and open lines of communication may not only prevent herbicide damage from occurring but may make legal recourse unnecessary.

Also keep in mind, commercial applicators in Texas must be insured, so odds are that if legal action is required, it may not be against your neighbor of even the applicator directly. The legal fight may well be with the land owner or applicators insurance company. It’s rare for an individual to be completely unsympathetic to damage they have caused to someone else’s property and in many cases land owners are not responsible for application mistakes, so maintaining a positive relationship with them is ultimately in everyone’s best interest.