The primary goal of weed management is to optimize yields by minimizing competition between the weeds and the crop. Weeds reduce yields by competing with the crop for water, light, and nutrients. Weeds also harbor insects and diseases and encourage vertebrate pests. Timely cultivation, wise use of herbicides, and never permitting weeds to go to seed are integral parts of a good weed management system. Many of the weeds found in these fields are difficult-to-control perennial weeds that are not common in annual crop culture. New plantings usually have fewer perennial weed problems than older plantings. Annual and biennial weeds can also exist in these fields. Fields should be scouted at least twice a year (spring and fall) to determine specific weed problems. The selection of a weed management tool should be based on specific weeds present in each field. Most annual weeds can be reduced with mulches that are free of weed seeds and placed thickly, but perennial weed may require additional management. Several herbicides are labeled for use in this crop. A list of herbicides and their recommended uses is presented in Table 58 below.
Herbicides can be broadcast or applied as a directed spray to the base of the crop. With a band treatment, only 1 to 2 feet on either side of the rows is treated. The area between the crop rows is usually maintained with a mowed cover of sod, clover, weeds, or a combination of these. This cover is used primarily for erosion control and to improve trafficability in the field. With banding, less herbicide is needed in each acre. For example, a 3 foot band (1.5 feet on either side of the row) where rows are spaced 9 feet apart will require only one third the amount of herbicide normally required for a broadcast treatment.
Weeds can develop resistance to herbicides. The Weed Science Society of America (WSSA) developed a grouping system based on the mode of action of different herbicides. WSSA Group numbers can be used as a tool to choose herbicides in different mode of action groups so mixtures or rotations of active ingredients can be planned to better manage weeds and reduce the potential for resistant species.
Cultivation and mulching are sometimes used as weed management tools. All cultivations should be timely and shallow to minimize crop root injury, to minimize loss of soil moisture, and to avoid repositioning new weed seeds to the soil surface. Mulches that are free of weed seeds and placed thickly enough can be very effective at reducing or eliminating most annual weeds from the crop row. They are seldom effective on perennial weeds. If mulches are used in combination with herbicides, use the lowest recommended herbicide rate to avoid crop injury.
| Preemergence | |||
|---|---|---|---|
| Weed Problem | Material | Rate/Acre (phi) | Comments and Limitations |
| Annual and perennial grasses and broadleaves | (dichlobenil) Casoron CS Casoron 4G Group 29 |
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Perennial weeds: Apply from Nov. 15 to Feb. 15 as a soil surface application. Can also be applied in late fall or early spring before May 1 and incorporated immediately. Annual Weeds: Apply in early spring after cultivation before weeds emerge. Rain or irrigation is needed for activation. A shallow incorporation is recommended. Apply 4 weeks after transplanting after soil has completely settled. |
| Annual grasses and broadleaf weeds | (indaziflam) Alion 1.67 Group 29 |
3.5-5 oz |
Use Alion only in established vineyards at least 5 years after planting and exhibiting normal growth and good vigor. Apply as a directed spray to the base of the plants. Ensure that the grapes have been planted at least 12 inches deep and that there is 12 inches of soil barrier between the soil surface and the major portion of the root system priot to using or injury may occur. Do not use on grapes grown on sand or on soils with more than 20% gravel content. More than one application can be made but do not exceed 5 oz/acre and allow a minimum of 90 days between applications. Ideally use this product in the fall or in the spring prior to weed emergence. Does not control perennial weeds. See label for specific rates. |
| Annual broadleaves and suppression of grasses | (flumioxazin) Chateau SW Group 14 |
6-12 oz (60) | Do not apply after bloom unless with a hooded or shielded application. Apply alone preemergence or tank mix with Roundup or Gramoxone postemergence. Do not incorporate. Do not allow drift to contact foliage or green bark. Always add a crop oil at 1% v/v or nonionic surfactant at 0.25% v/v. Max. rate is 24 oz per season. Min. 30 days between applications. Chateau also has postemergence activity. Age restriction: Do not apply to vines established less than 2 years unless they are trellised at least 3 ft from the ground or are protected by nonporous wraps, grow tubes, or waxed containers. |
| (diuron) Karmex 80DF Group 5 |
2-6 lb (0) | Age restriction: Use on vineyards established at least 3 years and trunks at least 1.5 inches diameter. Apply as a directed spray to soil under trellis in early spring prior to weed germination. Max. 1 application per year. On soils low in organic matter (1-2%), severe injury may result if heavy rainfall occurs soon after treatment. | |
| (simazine) Princep 4L Group 5 |
2-4.8 qt (0) | Age restriction: Apply to soil under trellis between harvest and early spring before weeds emerge. Use on vineyards established at least 3 years. Apply alone to weed-free soil or tank mix with Roundup or Gramoxone. Max 1 application per year. | |
| (rimsulfuron) Matrix FVN Group 2 |
4 oz (14) | Apply as a banded application to the base of the vines. Best results are obtained when the soil is moist at the time of application and 0.5 inch of rainfall or sprinkler irrigation occurs within 2 weeks after application. Age restriction: Do not apply to vines established less than one year. PHI=14 days. |
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| Annual broadleaves and suppression of grasses cont. | (oxyfluorfen) Goal 2XL Group 14 |
5-8 pt (b) | Dormant application only: effective both preemergence and postemergence as a directed spray on weeds less than 4 inches. Do not apply from bud swell to harvest. Can be mixed with other preemergence herbicides, or with Roundup or Gramoxone. Max rate is 8 pt/A/year. Age restriction: Do not apply to grapes established less than 3 years unless vines are on a trellis wire a minimum of 3 ft above ground. |
| Most broadleaves | (isoxaben) Gallery 75DF Group 29 |
0.66-1.33 lb (1yr) | Non-bearing only: May only be used on crops that will not be harvested within one year of application. Apply in late summer to early fall; or in early spring prior to weed germination or anytime immediately after cultivation. Do not apply to new transplants until soil has settled with no cracks present. Rainfall or irrigation of 0.5 inch is needed within 21 days of application. Not effective on germinated weeds. Min. 60 days between applications. Max rate is 4 lb/A. |
| Annual and perennial grasses and certain broadleaves | (pronamide) *Kerb 50WP Group 3 |
2-8 lb (c) | Apply as a directed spray in the fall after harvest prior to soil freeze-up, or early winter when temperatures are below 55˚F. Rainfall or irrigation are required to activate. Max. 1 application per year and 8 lb/A/year. Kerb also has early postemergence activity. Rate depends on soil texture. |
| Annual grasses and certain broadleaves | (pendimethalin) Prowl 3.3EC Prowl H2O Group 3 |
2.4 qt (1 yr) | Non-bearing only: May only be used on crops that will not be harvested within one year of application. Do not apply if buds have started to swell . May be applied preplant incorporated, preplant surface, or preemergence. For best results, rain or irrigation is needed within 21 days of application. Not effective on germinated weeds. Do not allow spray to contact leaves, shoots, or buds. For new plantings, do not apply until soil has settled and no cracks are present. |
| (napropamide) Devrinol 50DF Group 0 |
8 lb (35) | Apply from late fall (prior to soil freeze-up), to early spring (prior to weed emergence). If no rainfall of 1 inch or more occurs within 24 hours after treatment, cultivate or irrigate to activate. Apply alone to weed-free soil or in tank mix with Roundup or Gramoxone. Do not allow spray to contact fruit or foliage. | |
| (oryzalin) Surflan 4AS Group 3 |
2-6 qt (0) | Make a single band or broadcast spplication to the ground beneath vines before weeds emerge. Apply alone to weed-free soil or postemergence mixed with Roundup or Gramoxone. Min 0.5 inch of rainfall or irrigation is required for activation. Min 2.5 month between applications. Max rate is 12 qt per year. | |
| Annual grasses and broadleaves and suppression of yellow nutsedge | (norflurazon) Solicam DF Group 12 |
1.25-5 lb (60) | Apply as a directed spray to settled and firm soil from fall to early spring before weeds emerge. Rainfall or irrigation is needed within 4 weeks of application. Do not contact fruit of foliage. Do not apply after bud break on sandy loam soils. Check label for maximum amount allowed per year depending on soil type. Age restriction: Allow a minimum of 24 months after planting before first application. |
| Postemergence | |||
| Weed Problem | Material | Rate/Acre (phi) | Comments and Limitations |
| Annual broadleaves | (carfentrazone) Aim 2EC Group 14 |
1-2 oz (3) | Apply any time during the season. Always add nonionic surfactant at 0.5% v/v or crop oil at 1% v/v. Mix with Roundup or Gramoxone or labeled preemergence herbicides for broader weed control. Max. 7.9 oz/A/year. Min. 14 days between applications. Sucker management: Apply when suckers are green. Do not allow spray to contact desirable fruit, foliage, or green bark. |
|
(pyraflufen ethyl) |
1 - 4 oz (0) |
Apply as a directed spray to the base of the vines. Can be used in-season, postharvest, dormant, or pre-bloom. Provides contact burn down of existing broadleaf weeds. Do not make more than 2 applications or exceed 6.8 oz/acre during the growing season. Do not make more than 2 applications or exceed 6.8 oz/acre during the off-season. Non-ionic surfactant at 0.5 to 2% is recommended. Larger weeds will require the highter rate. Avoid contact with green, uncallused bark of young vines established less than one year. See label for other precautions. |
|
| (oxyfluorfen) Goal 2XL Group 14 |
5-8 pt (b) | See “Preemergence” section of this table for details. | |
| Most annual and perennial grasses | (fluazifop) Fusilade DX Group 1 |
16-24 oz (1yr) | Non-bearing only: May only be used on crops that will not be harvested within one year of application. Apply as a directed spray to actively growing grasses before tillering. Always add crop oil at 1% v/v or nonionic surfactant at 0.25% v/v. Avoid contact with foliage. Rainfast in 1 hour. Max rate is 72 oz/A/year. Min. 5 days between applications. |
| (clethodim) Select Max Group 1 |
9-16 oz (1yr) | Non-bearing only: May only be used on crops that will not be harvested within one year of application. Apply as a directed spray to actively growing grasses before tillering. Do not use if rain is expected within 1 hour. Always add nonionic surfactant at 0.25% v/v. Do not use crop oil. May be applied as a spot treatment at 0.32-0.64 oz per gallon. Max rate is 32 oz/A/year. | |
| (sethoxydim) Poast 1.5EC Group 1 |
1.5-2.5 pt (50) | Apply as directed spray to actively growing grasses before tillering. Always add crop oil at 1% v/v. Max 2.5 pt per application and 5 pt/A/year. | |
| Annual and perennial grasses and broadleaves | (glufosinate) Rely 1L Group 10 |
3-6 qt (14) | Age restriction: Do not apply within 1 year of transplanting. Apply as a directed spray to actively growing weeds. Do not apply on desirable foliage or drift on foliage, green, or uncallused bark of vines. Max 18 qt/A/yr for bearing and 12 qt/A/yr for non-bearing vines. For spot applications, mix 1.5-4 oz per gallon. Sucker control: a split application approximately 4 weeks apart at 4 qt/A is recommended or spot spray with 3 oz/gallon of water. Suckers should not exceed 12 inches long. |
| (pelargonic acid) Scythe 4.2E Fatty acid, Group 0 |
3-10% solution (0) | For contact nonselective control or burndown of a broad spectrum of actively growing weeds. Use low rate for annual weed control and high rate for maximum vegetative burndown. Use as a directed spray or shielded spray. Can be mixed with Roundup. | |
| Most annual grasses and broadleaves and top kill of perennial weeds | (paraquat) *Gramoxone SL 2.0 *Firestorm 3SC Group 22 |
2.5-4 pt (0) 1.3-2.7 pt |
Restricted-use. May be fatal if swallowed or inhaled. Applicators must complete EPA-approved training found at: https://www.epa.gov/pesticide-worker-safety/paraquat-dichloride-training-certified-applicators. Contact burndown with no soil activity. Apply as directed spray to actively growing weeds. Repeat applications are necessary to give sustained control. Avoid contact with desired new whoots, fruit or foliage. Apply as a coarse spray. Always add nonionic surfactant at 0.25% v/v or crop oil at 1% v/v. Best results with flat fan nozzles. Max. 5 applications per year. Sucker management: Apply when suckers are less than 8 inches tall. Do not allow spray to contact desirable fruit, foliage, or green bark. |
| Annuals and some perennial grasses and broadleaves | (glyphosate) Roundup Ultra 4EC Group 9 |
1-5 qt (14) | Rate depends on weed species and stage of growth. See label for details. Apply as preplant broadcast application or in fall for control of roots and rhizomes of perennial weeds or as a directed spray or wiper application (20-100% solution) to actively growing weeds in established plantings. Always add ammonium sulfate 8.5-17 lb/100 gal in hard water or drought conditions (see label). Do not allow spray to contact any part other than mature bark. Does not provide residual control; can be mixed with labeled preemergence herbicides. |
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†Where brand names for chemicals are used, it is for the reader’s information. No endorsement is implied, nor is discrimination intended against products with similar ingredients. Please consult pesticide product labels for rates, application instructions and safety precautions. Users of these products assume all associated risks. OMRI listed for organic production.
NOTES Mission (flazasulfuron) - selective herbicide for preemergence and postemergence control of certain broadleaf weeds. Absorbed through roots and foliage. For preemergence application, rainfall or irrigation is needed for herbicide activation. Length of control depends on environmental factors including soil type, soil moisture, temperature and amount of moisture after the application. Existing weeds or crop residue may reduce the length and level of residual control. Control may also be reduced due to weed stress at application. Weed growth stops within hours after the application, however symptom progress from discoloration or chlorosis to necrosis generally requires from 2 to 4 weeks. Best control is obtained when applied either to weeds just prior to germination or to young, actively growing weeds. Application to a reasonably even bed or soil surface clear of crop and weed residue is optimal for herbicidal activity. Any practices that cause disturbance of soil surface after treatment will decrease herbicidal activity. If rainfall does not occur within 2 weeks of a preemergence application, apply ¼ to ½ inch, but not more than 1 inch, of irrigation water for optimal activity. Zeus/Spartan (sulfentrazone) - a selective soil-applied herbicide for control of susceptible broadleaf, grass and sedge weeds. Adequate moisture of at least 0.5 inch is required within 14 days of application for optimal control. Should be applied as a uniform braodcast soil application to ground or as a uniform band application directed to the base of the trunk. For best control, apply when no weeds are present. If weeds are present, mix with a postemergence herbicide. For flowable forumations, use 8-12 oz/A not to exceed 12 oz/acre per 12-month period. Treflan HFP (trifluralin) - Many formulations are available; read the label of your purchased product to verify specific use rates and recommendations. Target for preemergence control of annual grasses.To reduce loss of herbicidal activity, incorporate into the soil within 24 hours of applications unless specified otherwise. Does not control established weeds. Recommended rate depends on soil type, age of planting, and application method. Please consult label. Suppress EC - nonsystemic, nonselective postemergence foliar burndown herbicide for control of annual and perennial broadleaves and grasses. Best on newly emerged plants, less than 6 inches in height. OMRI-approved product. Axxe - nonsystemic, nonselective postemergence, foliar burndown herbicide. Use higher rates on bigger plants. Very toxic to fish and invertebrates. Do not contaminate water resources during use. Eye irritant. OMRI-approved product. |
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