Chemical Weed Control in Vineyards

Grapes October 20, 2015 Print Friendly and PDF

Highly Erodible Vineyards       Plan Ahead       Sod       Cultural Control       Chemical Control       More Info

David Lockwood, University of Tennessee / University of Georgia

Vineyard Floor Management

As has been previously pointed out in the article Overview of Vineyard Floor Management, several factors, including vine age, vineyard design, soil type, and growing region need to be taken into consideration when deciding how best to manage the vineyard floor.

Highly Erodible Vineyards

In areas with

  • high rainfall
  • heavy thunderstorms
  • highly erodible soils, and
  • sloping ground,

clean cultivation and trashy cultivation are not options for the vineyard floor. Instead,

  • orient rows across the slope, and
  • use a continuous strip devoid of vegetation under the vines and permanent sod cover between the rows.

This offers a way to make vineyards accessible for necessary operations while lessening soil erosion problems.

The weed and grass-free strip under the vines should be about three feet wide (18 inches each side of the centerline of the row) to lessen competition for water and nutrients, to avoid trunk damage from mowers used in row middles, to facilitate good air circulation around the vine canopy, and to aid in controlling certain pests such as grape root borer in eastern vineyards. From an economic and efficiency standpoint, consider making the sod strip wide enough to be mowed with one pass of the mower.

Permanent sod between rows serves several important roles in vineyards located on sloping fields and in areas receiving substantial rainfall throughout the year. Where rows are oriented across slopes, the sod middles serve as deceleration and diffusion strips for runoff water, thus lessening erosion problems. In areas that experience high rainfall during the growing season, vineyard operations such as spraying will need to be carried out at times when soil conditions are far from ideal. A good sod will support equipment travel and lessen rutting and compaction.

Plan Ahead

Establishment of a desirable vineyard floor begins prior to vine planting. At this time, eliminate noxious, persistent weeds by mechanical or chemical means. Summer fallowing involves tilling the soil to destroy existing grasses and weeds. When regrowth occurs, till again to lessen weed and grass pressure. If soil amendments such as lime and/or fertilizer are needed based on soil test results, you can till to incorporate the recommended materials in the upper portions of the soil before planting. There are numerous highly effective herbicides for use on non-cropland, whereas very few of them are labeled for use in newly established vineyards. Select non-persistent herbicides to eliminate the potential for damage to new vines. Always read and follow directions on herbicide labels as the labels are legally binding and have precedence over any other recommendations.

Sod

The ideal sod for the vineyard floor will vary among different regions of the country. It should be relatively easy to establish, thick enough to suppress weeds, and capable of withstanding considerable travel without much damage. It should not compete too strongly with vines and be relatively easily controlled by the use of herbicides. Check with your local Extension office to see what grasses are best adapted to your area.

Cultural Weed Control

Weed control under the trellis may be accomplished by mechanical or chemical means. Mechanical methods include the use of implements such as weed hoes and rotary disks. These may also be used for mounding around the base of vines to protect graft unions during the winter or to control insect pests such as grape root borer. Take care to avoid damaging the trunks of vines with equipment. Tillage should be shallow to prevent damaging grapevine roots near the soil surface.

Chemical Weed Control

You can use herbicides to control vegetation under the trellis. The types of herbicides labeled for use in vineyards fall into one of two broad categories:

  • pre-emergence herbicides
  • post-emergence herbicides

Pre-emergence herbicides should be applied to the soil surface before weed and grass emergence and growth have begun. They work by killing emerging weed seedlings or by preventing weed seed germination. Pre-emergence herbicide rates usually vary according to soil type and should be applied at the rate recommended on the herbicide label.

Post-emergence herbicides may be selective (they target specific weeds), or non-selective (they kill a wide range of plant species). They may also be referred to as “burn down” herbicides. They should be applied to actively growing weeds and grasses. Depending on the particular herbicide used and the stage of growth of the grasses and weeds to which it is applied, only the aboveground portion of target plants may be killed or the herbicide may be translocated throughout the plants, resulting in destruction of the root systems as well. Weeds under stress from mowing, drought, or cold temperatures may not be adequately controlled by post-emergence herbicides. For better control, wait until the stress has subsided and the weeds have resumed active growth before applying herbicide.

A surfactant may be used to give better coverage on the plant surface by breaking down surface tension and allowing the spray droplet to cover the target more completely. Many post-emergence herbicides require the addition of a surfactant, however, some may already contain a surfactant. Consult the herbicide label for information regarding the use of a surfactant.

Tank mixing involves using two or more herbicides in a spray tank for application at the same time. A tank mix may include a post-emergence herbicide plus one or more pre-emergence herbicides or a combination of pre-emergence herbicides to give better control of a broad spectrum of weed and grass species than may be achieved using a single post-emergence herbicide.

Rate per treated acre refers to the amount of herbicide used on the portion of a field actually being treated, as opposed to the acreage contained in the entire field. For example, if a three-foot-wide strip is to be sprayed in a vineyard where the rows are ten feet apart, only thirty percent of the total acreage in the vineyard will be treated. Therefore, in a ten acre vineyard, only three acres are actually being treated with an herbicide. Failure to take this into account could result in vine injury or death due to application of excessive rates of an herbicide. To achieve the best results from an herbicide application and to prevent damage to the grapevines, use only herbicides labeled for use in vineyards and follow label directions closely with regard to vine age, rates, timing, and application procedures.

Active ingredient (ai) – Several herbicides may contain the same active ingredient, although the formulation and trade names may differ. In selecting herbicides and comparing costs, check labels carefully to be sure the percentage of active ingredient(s) is the same and that the crop to be treated is listed. Follow the label of the product you have purchased for directions on proper usage.

Herbicide resistance management – Continuous use of the same herbicide may result in increased stands of weed species not controlled by that product. In addition, weeds may develop resistance to that class of herbicide over time. Rotating herbicides and including non-chemical controls whenever possible will lessen the potential for build-up of herbicide-resistant weed species.

Concluding Remarks

Success in using herbicides is dependent on using the proper herbicide(s) at the correct rate and timing under favorable weather conditions and using a sprayer that is properly calibrated, in good working order and operated properly. Herbicide sprayers are generally designed to operate at low pressures using nozzles that emit large droplets to reduce the risk of drift or of the spray rebounding from the soil surface and moving up into the crop. Precision in application is dependent on the ability to maintain a constant ground speed, constant pressure and flow rate from the pump and good sprayer maintenance including replacement of worn nozzles. An integrated management system using chemical and non-chemical options is preferable for most vineyard situations.

The information about herbicides contained in this document is general in nature and does not constitute specific instructions for use of specific herbicides. Herbicide regulations vary from state to state, so readers are advised to read and follow product-labeling instructions and check with the manufacturer or supplier for current information and legal usage of these products. Nothing contained in this information should be interpreted as an endorsement expressed or implied of any particular product.

Resources

Southern Region Small Fruits Consortium (SRSFC)
www.smallfruits.org

Wine Grape Production Guide for Eastern North America
Natural Resource, Agriculture, and Engineering Service
Cooperative Extension
PO Box 4557, Ithaca, NY 14582-4557
www.NRAES.ORG

Midwest Small Fruit Pest Management Handbook - Grapes

New York and Pennsylvania Pest Management Guidelines for Grapes

How Herbicides Work

Soil Quality in Vineyards

Overview of Vineyard Floor Management

Grape IPM in the Northeast: Appendix 3 - Weed Management

Vineyard Design

Vineyard Site Selection

Reviewed by Eric Stafne, Mississippi State University and Tim Martinson, Cornell University

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USDA / NIFA

This work is supported by the USDA National Institute of Food and Agriculture, New Technologies for Ag Extension project.