The program for the control of annual weeds in the vineyard should consider the weed free strip under the trellis and the sod middles between the rows separately. The “Weed Control Season” starts in late fall, after harvest. The program implemented in the spring depends on what herbicides were applied the previous fall. If herbicides were applied in late fall, applications can be delayed until later in the spring. Residual herbicides should be applied in late winter or early spring after the soil is no longer frozen, if no late fall treatment was applied.
Annual weeds are weed species that live for less than one year. Winter annual germinate in the fall or late winter, flower in the spring or early summer, then die. Summer annuals germinate in the spring and early summer flower, and die in late summer or fall. Perennial weeds are weed species that live for more than two years. Control of these weeds must be considered separately.
Emerged annual weeds under the trellis are controlled with a postemergence herbicide. Annual weeds that germinate throughout the remainder of the season are controlled with residual herbicides. Two applications of postemergence herbicide plus residual herbicides are recommended annually in the weed free strip under the trellis. The first application should be applied in late fall, after vines are dormant, but before the soil freezes, or in late winter before the weeds begin to grow in early spring. This application targets the control of winter annuals and provides early season control of summer annual weeds. Most growers are more easily able to apply herbicides to the vineyard in late fall, usually after Thanksgiving in New Jersey. In March, growers find themselves scrambling to apply insecticides and fungicides, and prune. Pruned wood must be removed or chopped before weed spraying can be accomplished after pruning.
The second application of residual herbicides should be applied in late spring, while the late fall application controls early season summer annual weeds. A postemergence herbicide may not be needed to control annual weeds in late spring if residual herbicides were applied in late fall, however, a postemergence herbicide may be included to control certain perennial weeds such as yellow nutsedge, Canada thistle, goldenrod species, or aster species.
Most residual herbicides primarily control annual grasses or annual broadleaf weeds (BLWs). A combination of an annual grass herbicide and an annual BLW herbicide is usually recommended. Rate ranges are recommended for most residual herbicides. Use the lower rates in vineyards with coarse textured (sandy) soil low in organic matter, and the higher rate when soils are fine textured (silt and clay) and have higher organic matter.
Casoron, applied in late fall, followed by a spring application of a residual annual grass herbicide is the most effective residual weed control program recommended. More different species of weeds are controlled than any other residual herbicide combination available. Apply 4.0 lb active ingredient Casoron CS (2.7 gallons per acre) or 4.0 to 6.0 lb active ingredient Casoron 4G (100 to 150 lb per acre) in late fall when soil and air temperatures will remain below 50 degrees Fahrenheit until rainfall moves the herbicide into the soil. The active ingredient in the granular formulation can be lost to volatilization in warm weather. The Casoron CS formulation is encapsulated, which prevents loss due to volatilization. Casoron provides annual broadleaf weed control through harvest and annual grass control till early summer the next year. Certain herbaceous perennials, including goldenrod species, aster species, and yellow nutsedge will also be controlled or suppressed by Casoron applied in late fall. Late winter applications provide less consistent winter annual and perennial weed control. Apply an additional residual annual grass herbicide in the spring to provide late summer annual grass control following the late fall application of Casoron.
If Casoron is not applied in late fall, choose your residual annual grass herbicide for the coming season before the late fall/winter herbicide application. Options include Devrinol, Prowl H2O, Surflan, or Solicam. All four residual annual grass herbicides can be used at the rate of 4.0 lb active ingredient per acre per year. Apply half the yearly labeled rate, 2.0 lb active ingredient per acre, in the late fall or late winter, and the second half, an additional 2.0 lb active ingredient per acre, in late spring.
Your residual BLW herbicides should be chosen considering crop safety, effectiveness, and price. For many years Princep (simazine) was recommended at 1.0 to 2.0 lb active ingredient per acre in the late fall/ winter, and Karmex (diuron) was recommended at 1.0 to 2.0 lb active ingredient per acre in the late spring. Both herbicides have been safe and reliable, and cost effective choices for many years, and continue to good options where their use provides good weed control. Both Princep (simazine) and Karmex (diuron) share the same mode of action, inhibition of the light reaction of in photosynthesis. Unfortunately, triazine resistant weeds, with cross resistance to urea herbicides, including Karmex, are present at some sites.
Where a triazine resistant weed has become established, switch to a BLW herbicide(s) with a different mode of action. Use Chateau at 0.19 to 0.38 lb of active ingredient per acre or Goal (oxyfluorfen) at 1.0 to 2.0 lb of active ingredient per acre in late fall or late winter. Both products should be applied before bud break in early spring to avoid speckling and crinkling the crop’s foliage if spray drift occurs. The activity of both Chateau and Goal occurs at the soil surface as sensitive BLW seedlings emerge. Do not disk, till or otherwise mechanically mix Chateau or Goal into the soil after application, or the effectiveness of the herbicides will be reduced or eliminated.
Matrix controls annual grasses and BLWs, and suppresses yellow nutsedge in stone fruits and pome fruits as well as in grapes. The herbicide has postemergence and residual activity. Matrix is a group 2 herbicide, an ALS inhibitor. Herbicides with this mode of action rely on a single site of action is susceptible weeds, putting herbicides with this mode of action at high risk for weed resistance development. Weed resistance to ALS inhibitor herbicides is already present in the New Jersey and the surrounding mid Atlantic region. Due to resistance management concerns, Matrix is usually recommended for yellow nutsedge control, but not for annual weed control.
Alion is a new herbicide recently labeled for use in stone fruit and pome fruit orchards, and in vineyards. The use restrictions for Alion are more strict in vineyards than in orchards. Grapes must be five years old and the majority of their root system must be 12 or more inches deep. Soils classified as sands and soils with more than 20% gravel are excluded. Phytotoxicity evaluations are currently underway in grapes at two sites in New Jersey, including a study at Rutgers Research and Extension Center, Bridgeton, and at a second site in Atlantic County. No injury to the grapes has been observed at either site to date. Alion recommendations for use in grapes will be finalized at the end of the 2014 growing season.
When annual weeds have emerged before residual herbicides are applied, a postemergence herbicide should be included in the tank. In late fall or winter, add Rely 280 at the rate of 0.9 to 1.5 lb of active ingredient per acre or Gramoxone or other labeled generic paraquat formulations at 0.6 to 1.0 lb active ingredient per acre plus nonionic surfactant at 0.25% of the spray solution to control emerged weeds. Roundup and other labeled generic glyphosate products can also be used to control emerged weeds in well established mature vineyards without low hanging vines, and can be especially useful where susceptible perennial weeds are a problem. The rate depends on the perennial weed targeted.
Grapes are extremely sensitive to 2,4-D during the growing season. Spray or vapor drift from the application 2,4-D during the growing season can cause serious damage grapes and many vegetable and ornamental crops. 2,4-D should not be applied near grapes or other sensitive crops when they are not dormant.
2,4-D amine is labeled and recommended at 1.0 lb of acid equivalent per acre for use in vineyards in late fall to control broadleaf weeds, and is especially useful in sod row middles. Apply ONLY in late fall when the grapes in the vineyard and AND the grapes growing nearby are physiologically dormant, and have dropped ALL their leaves. Grapes that are physiologically dormant will not grow even is subjected to warm weather. Physiological dormancy is broken when the required number of chilling hours is reached in mid to late winter. Grapes become more susceptible to 2,4-D after physiological dormancy is broken. The date dormancy is broken depends on the grape variety and the year, therefore the application of 2,4-D after January 1st is not recommended.
Consult the Commercial Production Recommendations for rates and additional information.