News: Find all the blog content here!

Applying Fertilizer to Vineyards After Harvest

Authors: Annie Klodd and Anne Sawyer, University of Minnesota Extension

Key Points:

  1. Minimize the amount of nitrogen applied in the fall; save it for the spring.
  2. Granular fertilizer is best applied as a broadcast directed to the vine rows
  3. If possible, avoid fertilizer application to the grassy aisles unless groundcover renovation is the intent
  4. Fertilizer application rates should be calculated based on soil and foliar tests. Use test reports from the current year or recent years.

During the growing season, grapevines allocate significant amounts of sugars and nutrients to the fruit, which is then removed from the vineyard when the fruit is harvested. If the soils are limited in nutrients like phosphorus (P), potassium (K), nitrogen (N) and magnesium (Mg), adding these nutrients back into the soil periodically is important to the continued productivity of the vineyard. Fertilizer amounts (rates) applied should be calculated based on soil and foliar test results, rather than applying an arbitrary rate.

Reasons to Consider Post-Harvest Fertilization

Other vineyard tasks are done for the year, and it is too early to begin dormant pruning. Therefore, growers likely have more spare time now than they do in the spring.

In terms of nutrients, grapes are in one of their most depleted states immediately following harvest, and in the early spring.

It is logistically easier to apply fertilizer in the fall when the ground is dry but not yet frozen, compared to the early spring when the vineyard may be impassable due to melting snow.

While applying fertilizer in the fall may not necessarily decrease the chance of vine winter injury, it will help the vines get off to a healthy start in the spring.

How to Apply Fall Fertilizers

As stated before, fertilizer rates should be determined based on soil tests, as well as foliar (petiole) tests if possible. Applying fertilizers without considering test data can cause growers to waste money and fuel on excess inputs, and can even cause soil nutrient toxicities, in which nutrient levels are so high that they negatively impact plant growth. Excess fertilizers are also tough on the environment.

The most effective and efficient method of vineyard fertilization is to apply it as a targeted broadcast directly underneath the vine rows. While many fertilizer spreaders broadcast the product over the whole area, it is generally unnecessary to apply fertilizer to the row middles (grassy strips) unless you specifically intend to improve the growth of the grass. Most grapevine roots grow within the vine rows (also called “herbicide strips”) rather than under the grass, so fertilizer applied to the grass has little impact on the grapevines.

Broadcast fertilizer spreaders vs. targeted broadcast spreaders

As mentioned above, most common fertilizer spreaders used in agriculture will broadcast the fertilizer in a certain radius behind the machine, which will of course apply the product to both the grass and vine rows. While this is not necessarily harmful, it is less efficient and more costly than using a targeted spreader (as explained above).

Specialized vineyard or orchard fertilizer spreaders can be purchased that are designed to direct the fertilizer under the vine rows.

General use broadcast spreaders can also be retrofitted to target vine rows, for those who do not wish to purchase a vineyard-specific spreader. This can be done by attaching a V-shaped bar on the back, or otherwise engineering a way to redirect the fertilizer at an angle so that it only hits the ground beneath the vines. One grower I spoke to recommended making and attaching a wooden V onto the back of a plastic spreader (such as those from Fleet Farm). He uses wood because he has found that frequent use can cause metal spreaders to rust. Of course, the methods of retrofitting a spreader will depend on the spreader you have and what tools are available to you.

Why not apply fall nitrogen?

For cold climate grapes, it is very important to eliminate or minimize nitrogen applications in the fall, especially while the leaves are still on the vines.

1) Nitrogen application in the fall can significantly increase the vines’ chances of severe winter injury.

After harvest, grapevines need to begin shutting down (senescing) in preparation for the winter. They stop growing, harden off green tissue, and move their energy and nutrients from the canopy down to the roots for winter storage. If nitrogen is applied in the fall, it encourages the vines to form new leaves, which is not a good thing. This interrupts the senescence process, which makes them unprepared for winter and therefore more vulnerable to winter injury.

2) Nitrogen applied in the fall may vanish before the spring

Nitrogen is highly mobile in the soil, meaning that it can be easily lost to the environment with water movement through the soil. Nitrogen can also be lost through volatilization (gaseous loss to the atmosphere). When water carries nitrogen down below the root zone (where the roots grow), the plant can no longer reach it and the N is lost to groundwater. This process is called “leaching.” If nitrogen is applied in the fall, it’s more likely to be lost to the environment than to be taken up by the plant. However, during the active growth season in the spring, the roots are actively growing and nutrients are in high demand by the plants. Therefore, fall-applied nitrogen is likely to be gone before the 2020 growing season starts.

What about other nutrients, like P and K?

Unlike N, P and K are immobile in the soil and are less likely to be lost to the environment with fall applications. Therefore, applying P and K in the fall will give vines a ready source of nutrients in the spring.

Some P and K fertilizers are available that do not contain N; read more at this link. However, many other fertilizers (like "N-P-K") and micronutrient sources contain some level of nitrogen. Therefore, it may be challenging to completely avoid fall nitrogen application if other nutrients are also being applied, particularly if using organic fertilizers. If this is the case, select a fertilizer product with very low N concentrations relative  to the P and K concentrations, such as a 10-20-20 or 5-10-10 and wait until the leaves have fallen off the vines before applying it.

About the authors: Annie Klodd and Anne Sawyer are University of Minnesota Extension Educators for fruit and vegetable crops. Annie’s position focuses on assisting fruit farmers with topics involving fruit crop production, including grapes. Anne holds a PhD in soil science from UMN, and her position focuses on assisting farmers with soil health and farm food safety topics.

Publish Date: 
Wednesday, October 23, 2019 - 2:00pm

Cold Climate Conference: Save the Date

Cold Climate ConferenceMinnesota Grape Growers Association

Cold Climate Conference 

Rochester, MN February 20-22, 2020

 

Publish Date: 
Wednesday, October 23, 2019 - 8:00am

Itasca Wine Making: New report

Sensory Analysis of Itasca Wines

preliminary findings of industry sensory evaluation of Itasca winemaking practices

September 11, 2019

Presented by Matthew Clark and Andrew Horton

‘Itasca’ is a new wine grape variety developed at the University of Minnesota and released in 2017.  This grape variety demonstrates vineyard sustainability traits like cold hardiness, powdery mildew resistance, and low incidence of foliar phylloxera. Furthermore, the juice of the wine is about 30% lower in total acidity than its parent ‘Frontenac Gris’, making it suitable for dry wine production or for use in blending. The novelty of this variety means that few winemakers have had an opportunity to trial different winemaking practices.  In 2017 and 2018 we made experimental ‘Itasca’ wines in order to provide some initial insight to winemakers who may be making ‘Itasca’ wines for the first time. We conducted 2 different experiments, and then conducted sensory analysis of the wines during the Cold Climate Conference in 2018 and 2019. Here we describe the preliminary results of this research. 

Click here to open the .pdf file

Publish Date: 
Wednesday, September 11, 2019 - 9:15am

2019 Fall Open House

Join in celebrating the fall grape harvest with an open house hosted by the University of Minnesota Grape Breeding and Enology project.  

This annual event is a great time to meet other grape growers and enthusiasts. You will get to taste about 50 different grape varieties and learn about research being conducted on enology, viticulture, and grape genetics.

The open house will be from 10 am - noon on Saturday, September 14, 2019 at the Horticultural Research Center, 600 Arboretum Blvd., Chaska, MN 55331.  

*note this is one week later than normal

Publish Date: 
Wednesday, September 4, 2019 - 9:30am

2019 ICCWC Winners

 ICCWC

The 2019 ICCWC Winners are announced.

Click here to see the full list of winning wines

 

Minnesota Governor's Cup

Blue La Crescent (2017) The Winery Sovereign Estate, Waconia Minnesota

Winery of the Year

Dancing Dragonfly Winery, Saint Croix Falls, WI

Best of Show White Wine

St. Pepin (2017) Parallel 44 Vineyard and Winery, Kewaunee, WI

Best of Show Rosé Wine

You Betcha Blush (2018) Carols Creek Winery, Alexandria, MN

Best of Show Red Wine

Marquette (2018) Vintage Escapes Winery, Kilkenny, MN

Best of Show Speciality/Fortified Wine

Lindy (2017) Dancing Dragonfly Winery, Saint Croix Falls, WI

Many thanks to the sponsors! You can find the list here.

Click here to see the full list of winning wines

 

Publish Date: 
Friday, August 16, 2019 - 1:45pm

2019 ICCWC

ICCWC Header

August 15, 2019
 

The MGGA in partnership with the University of Minnesota is 
happy to announce the 11th Annual International Cold Climate Wine 
Competition. As the only competition dedicated to cold climate grape
varietals, registration will be open to any commercial winemaker
producing wine using cold-hardy grape varieties (as defined in the rules)
may enter.

REGISTRATION IS NOW OPEN! 

IMPORTANT DATES:

Registration closes August 2, 2019 at 11:00 p.m. CDT.

Early Bird discount ends midnight July 10, 2019.

Delivery of wines no later than August 9, 2019, at 4:30 p.m. CDT.
     a. Entered wines must be postmarked or delivered in-person
         no later than August 9, 2019 at 4:30 p.m. CDT, with registration
         form.

FEES:

$55 per entry.

Early Bird discount is $15 per bottle or $40 per entry (if registered
by midnight July 10, 2019).

Fees are non-refundable and required for each wine entered in
the competition.

Publish Date: 
Tuesday, July 9, 2019 - 7:45am

Renewing Grapevines from Suckers Following Severe Winter Injury

Annie Klodd, University of Minnesota Extension, kloddann@umn.edu

Grapevine suckers with old trunk removedMany vineyards across Minnesota have been severely affected by winter injury, while others survived the winter well. For the vineyards reporting winter damage, many are reporting partial or entire blocks of one variety to have died to the ground, often leaving behind multiple suckers per vine. So far, more damage has been reported on lower sites with higher water tables or more wet, humid environments; while sites on higher ground seem to have faired better overall. Damage also varies by variety. It is also likely that vines that were less healthy going into last winter suffered more extensive damage, although more data must be collected in order to make that conclusion. A formal multi-state survey will be conducted to determine which varieties, site types, and geographic areas were most affected.

Rejuvenating Grapevines Following Severe Winter Damage

If a vine is dead to the ground but has several healthy suckers growing from the base of the trunk, leave roughly five suckers on the vine and select one to train up to become a replacement trunk. If the vine has more than about five suckers, trim the rest off; or if you have less than five, leave as many as you can. Choose a healthy, strong sucker to be your new trunk, but avoid selecting a bull cane (a bull cane is more than pinky-finger diameter, with wide bud spacing). The reason to leave extra suckers is to distribute some of the excess energy that is in the vine's root system and reduce the risk of the vine developing bull canes. Once you have chosen your new "trunk" shoot, use tapener tape or other fasteners to secure it vertically upward onto a fresh bamboo pole or rebar.

In order to spray herbicides, treat these as you would new vines; apply grow tubes so that you can safely spray herbicide around the vines without injuring the suckers. Try to maneuver the suckers into the grow tube. If the suckers are running along the ground and are very thick, it may be too late to get them all into the grow tube without breaking some. At that point, you may consider leaving the weeds, weed-whacking around the vines instead of spraying, or removing the shoots that are causing problems. Leaving the weeds may take away excess vigor from the vines, if that is an issue on the particular site. Therefore, these decisions depend on the needs and goals of the particular vineyard to some extent.

Remove the grow tubes no later than October, or whenever you are done with your last herbicide spray of the season. Leaving them on past mid-fall could lead to poor winter acclimation and further winter damage the next year. During winter pruning, prune off the excess suckers and consider training up one of them as a second "insurance" trunk.A vineyard with Frontenac blanc on the left and Marquette on the right, following winter injury

When to remove the dead trunk

You can remove the dead trunk now (June) if it is not producing anything, using loppers or a saw. If the trunk is partially alive and producing a few clusters, it is acceptable to leave it there for the season and cut it down during winter pruning. The fruit may not be high quality if the vine is unhealthy, but it will help distribute some of the excess energy in the roots. 

Is Grapevine Trunk Disease Contributing to Vineyard Die-back?

There has been much discussion about the role of grapevine trunk disease (GTD) in vine die-back in the Midwest. At this point, it is not known how much GTD is contributing to winter die-back in the Midwest. Laboratory analyses are currently underway at the University of Minnesota to help determine this, but at this point it is not possible to say how much it is contributing, and it likely varies depending on the vineyard and on the overall health of the vines. Dispite contradictory claims online, trunk disease species cannot be reliably diagnosed without the help of trained plant pathologists, of whom we are currently working with on this issue. 

As a precaution, when growers cut down trunks to re-train new trunks, they may spray each pruning cut with Rally or Topsin, or apply latex paint. I recommend bringing a small backpack sprayer or handheld sprayer with these products while cutting down trunks in order to make this process more efficient. 

Photos: (top) A vine that died to the ground, with the trunk removed. One sucker should be chosen as the new trunk and trained up on a pole. (bottom) Healthy Frontenac blanc on the left and a dead block of Marquette on the right (photo credit Annie Klodd, 6/12/2019).

Publish Date: 
Tuesday, June 18, 2019 - 9:15am

Free Workshop Series: Managing and Trouble-Shooting Young Grapevines

 

 

 

 

Author: Aimee Foster. A warm gentle breeze cSovereign Estate's vineyard overlooking a lakearries the chatter and laughter of happy wine-sipping visitors and cools us off in the miraculous 80 degree heat. We are sitting under the beautiful pavilion at Sovereign Estate Wine, a vineyard and winery in Waconia, Minnesota, where new and experienced Minnesota grape growers from near and far are gathered to learn about managing and trouble-shooting young grapevines. This is the second workshop and tour in a free series put on by the grape and enology team at the University of Minnesota.

Matt Clark talking to a crowd at a field day on May 30, 2019

Photo: Dr. Matt Clark, PI of the grape and enology team at UMN, introducing us to the workshop. Photo: Aimee Foster

After an introduction by Dr. Matt Clark, we walk across the lawn to visit some older Marquette vines. This picturesque block slopes gently downhill towards Lake Waconia where jet skis rip across the open water, soaking in the warm sunshine. Sheep graze the weeds in the next block over - nature’s herbicide. Here we listen to Isaac Savaryn, the vineyard manager at Sovereign Estate, talk about his pruning methods. We also discuss how bud break and shoot growth varies from region to region in Minnesota.

Next, we load up a caravan and drive to the next vineyard block. This is a newer site, planted in 2018. Annie Klodd, UMN Extension Educator, demonstrates how to shoot thin a second year vine that has been winter injured. She also demonstrates how to train two trunks on second year vines and goes into detail about the importance of training two (or more) trunks, especially in a cold climate such as Minnesota. We ask a lot out of our vines in the winter! We also discuss new site preparation, weed management for young vines, and soil and foliar testing.

Thinning and pruning up a young grapevine

Photo: Annie Klodd, UMN Extension Educator, demonstrating shoot thinning on second year vines. Photo credit: Laise Moreira

Once again, we load up and caravan over to yet another new planting from 2018. Sovereign Estate is now up to about 25 acres of vineyard, one of the largest in the state. Here we discuss disease management and trellising systems.

Our last stop, quite naturally, is the tasting room. Isaac shares generous pours of the winery’s Marquette, La Crescent, and Frontenac Blanc wines as we sit at round tables and share our stories.

Sovereign Estate wine in tasting glasses

Photo credit: Sovereign Estate Wine’s Instagram

Thank you to all the growers who attended this workshop and added to our lively discussions. We hope to see you again!

A huge thank you to our partner, Sovereign Estate Wine, for helping to lead and organize this particular workshop and to North Central SARE for support and funding of this project.

The UMN team is partnering with Smiley Vineyard in Cannon Falls, MN for the next workshop on Saturday, June 8. They will discuss canopy management techniques and sustainable pest control. Stay tuned for a recap in a few weeks!

Publish Date: 
Monday, June 10, 2019 - 4:00pm

Practical Tips for Managing Grape Phylloxera in Minnesota

Bill Hutchison1, Eric Burkness1, Lu Yin2 & Matt Clark3

1Dept. of Entomology, Extension IPM Program, 2Graduate Student, Dept. of Horticultural Science, & 3Dept. of Horticultural Science & UMN Extension, University of Minnesota

The foliar form of Grape Phylloxera (GP) is quite common throughout Minnesota and most eastern grape growing regions of the U.S. Although we have experienced a late spring so far this year, the first grape leaves for most hybrids have started to appear; this is a good time to begin monitoring for the “yellow crawler” stage of GP, as the crawlers hatch from their “mother” galls (including a female with several eggs, Fig. 1).

Grape Phylloxera Life Cycle

In brief, the GP life cycle is quite complex, with galls formed on both root and foliar portions of the vine. However, given the genetic background of the cold-hardy grape hybrids in the Midwest region, the primary potential for damage is the presence of foliar galls formed by GP. Much of this information is taken from a recent publication by one of our graduate students in Horticultural Science, Lu Yin (Yin et al. 2019; see full citation below).

Close up view of a grapevine leaf with phylloxera eggs and adults in it

Figure 1: Mature grape phylloxera female and eggs (indicated by red arrow) and crawler (blue arrow) on a young grape leaf (Hannah Burrack, NC State).

Following the hatch of overwintered eggs (on trunk of vine), typically in early May (though later this year), the first-generation nymphs, or “crawlers” move to the grape shoots to feed on 1st to 3rd expanding terminal leaves. The leaf forms a gall around each crawler; at this time the crawlers will form less than 5 galls/leaf.  During May-June, each crawler matures within the gall (Fig. 1) and will produce 100-300 yellow, oblong eggs.  The subsequent emergence of young 2nd generation crawlers (Fig. 1) will begin, and crawlers will move out from the “mother gall”, to establish new galls on new leaves during the summer months (Fig. 2 and 3). 

Phylloxera galls in beginning stages on a grapevine leaf

Figure 2: Fig. 2. Early pin-sized galls (open), and mature foliar galls (closed), Grape Phylloxera, MN (Lu Yin, Univ. of Minnesota).

Phylloxera galls covering a grapevine leaf

Figure 3: Mature foliar galls formed by Grape Phylloxera crawlers (E. Burkness, Univ. of Minnesota).

Scouting and Management

The crawlers that hatch from the mother eggs, are the most critical generation for timing a 1st insecticide application, early summer. These crawlers will walk up the plants to 5-6th open leaves, and generate 40-50 galls per leaf, common on susceptible varieties. Three or more generations can occur in MN depending on the year, with additional galls being formed throughout summer.

For timing, growers can use a degree-day (DD) or “heat unit” model to track the initial infestation rates of crawlers. Degree-days for GP are calculated from the bio-fix date (time at which 1st leaves unfurl) by the following: DD = Average daily temperature – 43F, and accumulate DDs each day. The 2nd generation crawler emergence period occurs at 500-800 DDs; in MN we recommend to start scouting at 450 DDs, and twice weekly when possible.

Regarding insecticidal control, the two most common options used in MN have been Danitol (pyrethroid) and Movento (systemic).  To minimize the risk of resistance, these can be alternated (via different modes of action). In most years, only one spray for GP is necessary, or a maximum of 2 sprays.

With Movento, on recent on-farm trials, we have found that one application is often sufficient. After the first spray, check again for any additional gall formation instead of assuming an automatic 2nd spray is needed. As with other crops, sprays should ideally be applied during the evening hours to minimize the risk of direct contact, and mortality to bees and pollinators. Prior to any insecticide use, the label should be reviewed carefully to follow all application safety and use requirements. For more information, review the 2019 Fruit Pest Management Guide (cited below). Finally, in recent years, for some MN vineyards, we have noticed that once GP has been controlled (1 or 2 sprays), it may take up to 2 additional years for the pest population to re-establish, at least at high levels. Bottom-line: to monitor vineyards each spring/summer to verify low or high infestations via the presence of early galls.

More Information

For more information on insecticide options for managing GP, see the 2019-2020 Midwest Fruit Pest Management Guide, at: https://ag.purdue.edu/hla/Hort/Documents/ID-465.pdf

For more information on the history and biology of grape Phylloxera in the U.S., click here for the open access article by Lu Yin et al. (2019), https://academic.oup.com/jipm/article/10/1/16/5490144

For additional Fruit Insect IPM updates, see: www.fruitedge.umn.edu

Publish Date: 
Monday, June 3, 2019 - 1:00pm

Herbicide Recommendations for New Grapevine Plantings

Author: Annie Klodd, Extension Educator. kloddann@umn.edu.

When planting new grapevines, a strong weed management plan is essential to growing healthy, vigorous, and productive vines. Young vines do not compete well with weeds. Dense weeds in the establishment year will dramatically stunt the growth of the vines and have long term effects like making them weaker, slower to produce a crop, and more susceptible to winter injury. 

A well-planned herbicide program allows strong weed control without disturbing the soil and tender grapevine roots. Mechanical weeders such as a weed badger around the vines can cause extreme stress on the young vines, since most grapevine roots are in the top few inches of the soil and are damaged by mechanical weeders. Mowing or weed wacking is a good weed control option for established vineyards, but still allows a high risk of root competition with young vines, especially if perennial grasses are present. Therefore, it is good practice to use an herbicide program on first-year vines unless the vineyard is organic (stay tuned for another article on recommendations on organic weed control for vineyards).

The basic steps to herbicide management in the year of planting include:

  1. Making the rows weed-free before planting, with post-emergent herbicide (and pre-emergent herbicide when appropriate)
  2. Placing grow tubes around the vines in order to spray without injuring the vines
  3. Applying a pre-emergent herbicide after planting to suppress weed germination
  4. Applying post-emergent herbicides as needed to maintain weed-free rows the entire season

Herbicides should be selected based on the weeds in the field. Apply them only to the ground with a directed or shielded sprayer to minimize drift onto the vines, and always follow label instructions.

Before planting, clear all vegetation from the rows in a 2 foot wide strip where the vines will be planted. This can be done either with post-emergent herbicides, or by tilling in strips. 

After planting, the vine rows must be kept free of weeds during the whole season. Put grow tubes on the vines after planting, in order to protect the vines from in-season herbicide sprays.

Controlling weeds before planting

Post-emergent (POST) herbicides are the most common form of weed control prior to planting. Apply the POST herbicide once the grass is actively growing (more than 4 inches of green growth). POST herbicides are not effective on dormant weeds. A pre-emergent product may sometimes be used following the POST, if timing safely allows. 

Allow a few days between POST herbicide application and vine planting, in order to avoid herbicide injury to the vines. In order to determine how much time to allocate between application and planting, check the herbicide product restrictions and re-entry intervals (REI) on the label, and in the Midwest Fruit Pest Management Guide. As always, the label is the law.

Selecting pre-plant POST herbicides: Often, the natural vegetation growing in the field before planting will be a mix of perennial and annual grasses, with some broadleaf weeds. In these cases, it is very important to use full rates of herbicides that have strong activity on perennial grass. Beyond that, select herbicides based on what types of weeds are in the field. 

Example 1: If a fallow field has a large amount of perennial grass and broadleaf weeds (such as pigweed and lambsquarter), use an herbicide that has good activity on both grasses and broadleaves or apply multiple herbicides to meet your needs (options below). Example 2: If the field has been in an annual grass cover crop and no broadleaf weeds are present, it is not as necessary to use a product with broadleaf effectiveness. If the field has little to no perennial grass, a product with strong activity on annual grasses can be used even if its activity on perennial grass is weak.

Post-emergent (POST) herbicides to use before planting 

Below is a selection of herbicides with strong effectiveness against grasses, and many have broadleaf effectivness as well. For more details on how to apply these products, refer to the Midwest Fruit Pest Management Guide and the product label.

  • Glyphosate (i.e. Roundup WeatherMax 5.5EC): Effective on a broad range of perennial and annual grass, and broadleaves. Use a high rate for perennial weeds, within the label restrictions. Can be tank mixed with labeled pre-emergent herbicides.
  • Fusilade DX 2EC (fluazifop): Effective on most annual and perennial grasses. Do not exceed 24 fl. oz. per application per acre, or 72 fl. oz. per acre per year. Allow 14 days between applications. This product is best to apply early in the season, as it has a 50 day pre-harvest interval (PHI).
  • Select Max (clethodim): Effective on most annual and perennial grasses, but no activity on broadleaves. This product can only be used on non-bearing vines, meaning those that will not be harvested within one year of application. If broadleaf weeds are present, combine Select Max with another herbicide with broadleaf activity such as Aim 2EC or Goal 2XL.
  • Scythe 4.2E (pelargonic acid): Effective on a broad range of annual grasses and broadleaves, with some activity on perennial grasses. Use a high rate for perennial grasses or winter annual weeds, and a lower rate for summer annual weeds.
  • Rely 280 (glufosinate): Effective on annual and perennial grasses and broadleaves. Use care when applying this product, making sure to direct the spray to the ground and to not spray during windy conditions; if glufosinate drifts on to the grapevine foliage it may cause significant injury. 
  • Gramoxone: Effective against annual grasses and broadleaves, but not perennial grasses. Will not kill perennial grasses, only burn the tops. This is a Restricted Use Pesticide and therefore requires the applicator to have a Private Pesticide Applicator’s License. 
  • This information is based on the Midwest Fruit Pest Management Guide

Applying pre-emergent (PRE) residual herbicides before planting

First, what is a pre-emergent herbicide? As opposed to post-emergent (POST) herbicides, which kill actively growing weeds, pre-emergent (PRE) herbicides are applied to bare soil to stop new weed seeds from germinating. 

Applying a PRE product before planting is an optional step, and may not be logistically possible in all years depending on weather and time constraints. When possible, the advantage of applying a PRE herbicide before planting is to prevent new weed emergence for several weeks, reducing the need for frequent POST applications later on. 

Why is a pre-plant PRE herbicide logistically difficult? First, most of the PRE herbicides for vineyards have age restrictions and cannot be applied before planting or to vines less than a year old. Some have age restrictions of several years. Prowl H2O is one of the only PRE herbicides that can be safely applied before planting vines. Additionally, most PRE herbicides must be applied to bare ground only; the ground should not have vegetative cover in the form of turf or weeds, or the product will have trouble reaching the soil where it is effective. This means the grower can only apply a PRE after they have applied the POST, and the weeds have died down completely. Because it sometimes takes days for weeds to die down after a POST, a grower may not have time to apply both a POST and PRE herbicide before planting.   

How and when to apply Prowl H2O (pendimethalin) before planting: Before applying Prowl, apply a POST herbicide to the rows to kill existing weeds. Wait until the weeds have died to the ground, and then apply Prowl. Following the range of allowable rates on the label, apply a high rate to ensure good weed control. It may be either incorporated with tillage or applied to the surface. Rain or watering is needed within 21 days in order to activate the compound. Do not allow the spray to touch nearby vines that have broken bud.

Weed management after planting

After planting, maintain weed control throughout the season in order to prevent competition with the newly established vines. This should be done with a combination of PRE and POST herbicides in the rows (two-foot strip), and mowing between the rows. A good PRE application early in the season will decrease the number of POST applications that are necessary, because fewer weeds will emerge from the soil. 

Grow tubes: In order to apply herbicides without injuring or killing the young vines, secure grow tubes around the vines and keep them there for the entire first season.

Pre-emergent herbicide application after planting

Pre-emergent herbicide options are limited for newly planted vines, but there are several products that can be applied after planting, as long as a grow tube is used to protect the vine. Many products specify that they can only be applied to dormant vines, which means they cannot be applied after bud swell. However, if the vines are protected by a grow tube, the PRE can be sprayed later in the season without damaging the buds.

The timing of PRE applications is important. The ground should be as weed-free as possible when PRE herbicides are applied, and the soil should have settled after planting and have no cracks. The chemical needs to reach the soil in order to work. Weeds growing there will intercept some of the product before it can reach the soil, decreasing the product’s effectiveness. Therefore, if many weeds are growing, apply a POST product to clear the soil before applying a PRE. 

Additionally, wait to apply a PRE until the soil has settled after planting. If cracks remain in the soil from planting, PRE application could injure the grapevine roots. In the meantime, apply a POST product to remove any early season weeds that have emerged.

PRE options for the establishment year, after planting, include: 

  • Prowl H2O (pendimethalin): Annual grasses and some broadleaves. Apply once the ground has settled post-planting and has no cracks. Needs rain within 21 days to be effective. 
  • Snapshot 2.5TG (isoxaben and trifluralin): Annual grasses and some broadleaves. Apply once the ground has settled and has no cracks. Can only be used on non-bearing vines that will not be harvested within 1 year. Rain or watering (0.5 inches) is needed within 3 days of application. Wait 60 days between applications. Rate is 100-200 lbs/acre.
  • Devrinol 2-XT (napropamide): Annual grasses and broadleaves. Apply in spring or late fall at a rate of 2 gal/acre. It can be tank mixed with a POST herbicide. 
  • Surflan 4AS (oryzalin): Annual grasses and some broadleaves. Apply alone or tank mix with glyphosate or gramoxone, depending on the weeds in the field (see POST table). It will not activate until 0.5 inches of rain has fallen. Wait 2.5 months between applications. Apply 2-6 qts. In 20-40 gallons of water, depending on weed severity, not exceeding 12 qts/year.
  • Treflan HFP 4EC (trifluralin): Annual grasses and broadleaves. Must be incorporated with tillage, which makes this option difficult in many cases. In a new planting, apply 1-4 pts/acre and incorporate within 24 hours. 60-day pre-harvest interval (PHI).
  • Trellis (isoxaben): Annual and perennial broadleaf weeds. Apply between 0.67-1.33 lbs/acre in a minimum of 10 gallons of water. As with others, apply before weeds germinate. 

Post-emergent herbicide application after planting

Post-emergent herbicide options after planting include those listed above as well as those in the below table. Additionally, the Midwest Fruit Pest Management Guide includes an extensive list of herbicide options along with the rates, pre-harvest intervals, re-entry intervals, and relative effectiveness of each product on grasses and broadleaf weeds. 

Use a grow tube on the vines in order to safely apply herbicide to new vines. 

The timing of POST applications is important as well. During the growing season, target weeds with POST herbicide when they are young and growing rapidly. As weeds become more mature, they are more resilient to herbicides. Many weed scientists recommend the “Pop can method” for determining the height at which weeds should be sprayed. For many broadleaf weeds, the rule of thumb is if the weed is taller than a pop can, it may be too tall and strong to be completely killed by herbicides when applied at legal rates. While this is a broad generalization, it seems to hold true for a number of broadleaf species.

POST herbicide options for grapes (taken from the Midwest Fruit Pest Management Guide, pages 153-154)

Grape herbicide table

Publish Date: 
Tuesday, April 23, 2019 - 11:00am

Pages

Registration is now open for the 9th Annual International Cold Climate Wine competition. Click on the logo to learn more.

ICCWC

Winter is Minnesota can be one of the most challenging times for the grape plants.  It's the main reason V. vinifera varieties aren't grown here.  Learn a little bit about whats going on in the vineyard in winter.

Wine making is a rewarding career, but is not free from headaches. A wine maker's nightmare is the re-fermentation of sweet wines and the instability of some wines. This blog entry addresses the topic and offers some strategies to avoid and mitigate a potential devastating re-ferment.

 

Are you curious if your wine is finished with malolactic fermenation? Here is a quick reminder on how to test with paper chromatography

chromatograph

 

 

 

ALERT: September 27, 2016. Spotted Wing Drosophila (SWD) in Grapes: A short memorandom on SWD in Minnesota and associated volatile acidity. Read more here

Fall vineyard managment should focus on managing insects, vertebrate pests, rots, and diseases that will impact the vines in the next growing season.  Making quality wines requires disease intervention and sorting, as infected fruit will impact wine quality. Read more here.

 

International Cold Climate Wine Competition 2016 Results here!

Northern Grapes Project Webinar Registration

“From Vine to Glass: Understanding the Flavors and Aromas of Cold-Hardy Grapes and Wine”
Tuesday, May 17th*, 2016
12:00 Noon Eastern (11:00 am Central)
7:00 pm Eastern (6:00 pm Central)
*Please note this is a date change from the original date of May 10th.

Join Anne Fennell of South Dakota State University, Adrian Hegeman of the University of Minnesota and Somchai Rice of Iowa State University as they discuss their research conducted on Marquette and Frontenac as part of the Northern Grapes Project. 

Mock Winery Inspection

Friday April 29, 2016

 

Savor Minnesota

This Saturday April 16, 2016

 

Itasca Grape Vine Named

The University of Minnesota releases its news wine varieity 'Itasca' on April 4, 2016

 

Intergeneric Grafting

Experimenting with different grafting techniques including grafting Ampelopsis with a hybrid rootstock.

Preliminary Bud Survival Data

Early bud chop counts on cold-hardy cultivars at the HRC

 

Old blog entries

Are you looking for previous blog posts? Search the archived entries