Preemergence herbicides should be applied prior to weed seed germination AND prior to bud break. If applied to weeds that are already out of the ground, most of these products will not control them. Keep in mind that these herbicides should receive at least ½” rainfall or irrigation one to seven days after application (depending on herbicides) to incorporate the herbicide into the soil (usually called “activation”).

In order to reduce the potential of selecting for herbicide-resistant weeds, it is highly recommended to mix two residual herbicides with different Modes of Action (MOA) whenever you apply preemergence herbicides. Make sure the herbicides you plan to apply will be effective at controlling the weed species in your field by checking the herbicide label. Usually, residual herbicides will suppress weeds for 6 to 8 weeks depending on irrigation as well as soil and weather conditions. Roundup (glyphosate), Rely 280 (glufosinate), and Gramoxone (paraquat) are postemergence herbicides that may be applied with preemergence herbicides before bud break with little risk of crop injury.

• MOA 2: Matrix FNV or Solida (rimsulfuron) are ALS (acetolactate synthase) inhibitors with both preemergence and postemergence activity. These herbicides will control most annual broadleaves and help suppress yellow nutsedge. However, they are weak on common groundsel, common lambsquarters, eastern black nightshade, and will not control ALS resistant weeds (horseweed, ragweed) already widespread in New Jersey. Thus, these herbicides should always be tank mixed with a partner effective at controlling these weeds.
• MOA 3: Kerb (pronamide), Prowl H2O (pendimethalin) and Surflan (oryzalin) are mitosis inhibitors that will be effective at controlling many annual grass species for 4 to 6 weeks after application. Kerb can also help control perennial quackgrass. If applied to warm soils (> 55°F), Kerb persistence (and weed control) is much reduced; therefore, reserve Kerb for fall or winter application. Prowl H2O and Surflan are labeled for use in bearing and non-bearing grapes, whereas Kerb can only be used in vineyards that have been established for a minimum of 6 months. We strongly recommend applying Prowl H20 before bud swell in order to avoid any phytotoxicity injury later in the season.
• MOA 5 and 7: The photosynthesis inhibitors (PS II inhibitors) have a broad spectrum of control and will be effective against many broadleaves (including common chickweed, common lambsquarters, common groundsel, henbit, nightshade, redroot pigweed, pineappleweed, shepherd’s-purse, smartweed, and some mustards) when applied in spring. Princep will also control most of the annual grasses and help suppressing quackgrass. Karmex (diuron) and Princep (simazine) have relatively low solubility and have been very safe on grape. Both herbicides are labeled only for use in vineyards established at least 3 years.
• MOA 12: Solicam (norflurazon) is a pigment inhibitor that may be applied in fall or early spring primarily for annual grass control and quackgrass suppression. Solicam may also provide partial control of many broadleaf weeds as well as of yellow nutsedge. Use Solicam only in vineyards that have been established for a minimum of 6 months.
• MOA 14: Chateau (flumioxazin), Goal 2XL (oxyfluorfen), Zeus XC (sulfentrazone), and Zeus Prime XC (sulfentrazone plus carfentrazone) are PPO(Protoporphyrinogen oxidase) inhibitors with activity against many broadleaves (including pigweeds, common groundsel, common mallow, common lambsquarters, ladysthumb, wild mustard, shepherd’s-purse, nightshades, morning glories) when applied preemergence in spring. Chateau, Goal 2XL and Zeus Prime XC also have some postemergence activity on newly emerged seedlings of annual weeds. Zeus products may also provide some suppression of yellow nutsedge. Vineyards must have been established at least two years (Chateau) or three years (Goal 2XL, Zeus products) prior to use of these herbicides.
• MOA 15: Devrinol (napropamide) is a long-chain fatty acid inhibitor. Devrinol will provide good control of annual grasses and should therefore be tank mixed with a PSII or a PPO inhibitor for controlling broadleaf weeds. Devrinol is rapidly degraded if left exposed on the soil surface, so it should be applied less than 24 hours before a rain event to incorporate the herbicide in the soil. Devrinol is labelled for use on bearing and non-bearing vineyards.
• MOA 20: Casoron (dichlobenil) is a cellulose synthesis inhibitor recommended for fall application to control many annual and perennial broadleaves, grasses and yellow nutsedge. If left on the soil surface or if applied to warm soil > 55°F for Casoron 4G or 70°F for Casoron CS, this herbicide can lose much of its activity. So, reserve this herbicide ONLY for fall or winter applications. Casoron CS is labelled ONLY for use in vineyards established at least 3 years.
• MOA 21: Trellis SC (isoxaben) is a cell wall synthesis inhibitor currently registered for use on bearing and non-bearing grape. Trellis SC primarily controls annual broadleaf weeds, such as horseweed, common lambsquarters, wild mustards, shepherd’s- purse, purslane, and common chickweed; higher rates may also suppress field bindweed and curly dock. However, Trellis SC will have to be mixed with a Group 3 residual herbicide for controlling annual grasses.
• MOA 29: Alion (indaziflam) is a cellulose-biosynthesis inhibitor that works by affecting cell wall formation, as well as cell elongation and division. Alion provides long-lasting residual control of a wide range of annual broadleaf weeds and grasses but will not be effective at controlling emerged weeds or providing residual control of sedges and perennial weeds. Research conducted by Rutgers University has shown improved weed control with Alion applied in fall rather than in spring. Grapes must have a 6” barrier between the soil surface and a major portion of the vine’s root system. Be aware that Alion CANNOT be used on sandy soil as well as on soils with 20% or more gravel content.

Consult the Commercial Grape Pest Control Recommendations for New Jersey available at https://njaes.rutgers.edu for rates and additional information on weed control, tank mixing partners and restrictions. The information above is correct to the best of our knowledge. Other formulations with the same active ingredient as some of the products listed above may exist that may or not may be labeled for the same uses. Always consult the label before making pesticide applications. Information was current as of February 25, 2020.

Source: https://njvines.rutgers.edu/what-herbicide-should-i-use-in-spring-2020-for-preemergence-control-in-new-jersey-vineyards/

Fall or early winter is the best time to consider the application of a residual herbicide that will help maintaining the ground clean in early spring and allow for delayed herbicide applications in spring. Most residual herbicides primarily control annual grasses or annual broadleaf weeds.  A combination of an annual grass herbicide and an annual broadleaf weed 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.

Post-harvest application of a residual herbicide should be done 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. Weed residues from last season should also be removed as much as possible before considering application of a residual herbicide in fall. Too many leftover residues will prevent the residual herbicide to penetrate into the soil (the “activation” process), and the herbicide will lose efficacy at controlling the emergence of weed seedlings. If you plan hilling-up the vine, be aware that the de-hilling operations will break the residual herbicide coverage. Thus, hilling may not compatible with the use of residual herbicide in fall.

• Casoron (dichlobenil), applied in late fall, followed by a spring application of a residual annual grass herbicide is a very effective residual weed control program.  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 until 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.
• 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 be 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 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 herbicide(s) a different herbicide mode of action.  Use Chateau or Tuscany (flumioxazin) at 0.19 to 0.38 lb of active ingredient per acre or Goal 2XL (oxyfluorfen) at 1.0 to 2.0 lb of active ingredient per acre in late fall or late winter. 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.
• Alion (indaziflam) is a relatively new (2012) herbicide labeled for use in stone and pome fruit orchards, and in vineyards.  Alion is very effective at controlling a broad range of annual grasses and broadleaf weeds. Alion does not provide control of sedges or established perennial weeds. Alion is ideally applied in late fall at 0.045 to 0.065lb of active ingredient per acre in late fall. The most compelling characteristic of Alion is its VERY long weed control period (up to 6 months). However, the use restrictions for Alion are stricter in vineyards than in orchards:

1. 1. Alion can only be applied in vigorous grapes that have been established for a minimum of three years after transplanting.
   2. Alion can only be used in grapes that have at least 6 inches of soil barrier between the soil surface and the major portion of the root system.
   3. Alion cannot be used on soils with 20% or more gravel content or on sand or loamy-sand soil.
   4. Do not apply Alion prior to any type of soil disturbance, including hilling/dehilling operations, and only apply the herbicide after the soil settles.
   5. Do not allow spray or spray drift to contact crop foliage, green bark, roots or fruit of the crop being treated as it may cause localized crop injury or death
   6. Maximum use rate per application now has a restriction based on soil organic matter (OM) content: if soil contains less than 1% OM, maximum rate is 3.5 oz/A (0.045 lb ai) and if over 1% maximum rate is 5 oz/A (0.065 lb ai). In any case, maximum use rate cannot exceed 5 oz/A (0.065 lb ai) per year or in a 12 month period.
   7. No irrigation can be applied within 48 hours following Allion application. This is designed to ensure crop safety by giving the herbicide enough time to bind to surface soils before rainfall or irrigation to ensure proper activation of Alion by allowing weed seeds or seedlings to come into contact with the herbicide.

The Alion label also lists some guidelines that will ensure efficient weed control:

• Soil should be free of debris, clumps or cracks at application time to ensure best weed control performance and prevent the herbicide from reaching the grape roots (this is true for best performance of ANY of our PRE herbicides).
• For best weed control, dry soil surface for 48 hours followed by rainfall or sprinkler irrigation within 3 weeks is ideal. If irrigation is used to activate, 0.5 inch of water is ideal (the idea is to incorporate the herbicide into the surface an inch or so, where the weeds germinate, but not go too deeply.  This is also true for all PRE herbicides.

Consult the New Jersey Commercial Blueberry Pest Control Recommendations for rates and additional information https://njaes.rutgers.edu/pubs/publication.php?pid=E283.

As with all herbicides,always  read and follow all label instructions and precautions.