Weed Management. K u r t J. H e m b r e e. Herbicide susceptibility and performance charts are on pages 150 and 152.

Transcription

1 Weed Management K u r t J. H e m b r e e Herbicide susceptibility and performance charts are on pages 150 and 152. Grapes for raisin production are grown under a wide variety of soil types, management methods, and irrigation systems. In order to maintain profitable production, weed management must be an integral part of the total program throughout the life of the vineyard. Weed control is especially important in the first few years after planting, since heavy weed competition can reduce vine vigor and delay fruit production (late 20.1). Besides competing for essential water and nutrients, weeds can host diseases, insects, and nematodes, and provide a favorable environment for rodent pests. In vineyards irrigated with low-volume emitters, weeds interfere with water distribution, reducing irrigation efficiency and water availability. Weeds growing within the vine rows can also increase production costs and reduce harvest efficiency (late 20.2). To achieve cost-effective weed control, one must be familiar with the tools available and must understand their proper use. Weed identification, monitoring, field selection, sanitation, and mechanical and chemical control are all essential components of an effective, economical weed management program. Weed Identification roper weed identification is essential for any weed management program. If you know which weeds are present in your vineyard, you can learn about their growth habits (prostrate vs. erect), life cycles (annual, biennial, or perennial), and competitiveness for water and nutrients. Furthermore, knowledge of the type of weeds present (broadleaf vs. grasses) and when they germinate, grow, and reproduce has a direct influence on how to choose mechanical and chemical control tools. Depending on the species, a single mature weed may produce several thousand seeds. Over time, proper weed management can significantly reduce their populations (late 20.3). Many weed species commonly infest raisin vineyards. Some of the more important weeds are listed in Table Table 20.1 Weeds commonly found in raisin vineyards Summer annuals Winter annuals erennials Barnyardgrass Annual bluegrass Bermudagrass Flaxleaved fleabane hickweed Dallisgrass Horseweed ommon groundsel Field bindweed Lambsquarters Fiddleneck Johnsongrass Large crabgrass Filaree spp. Yellow nutsedge Mullein spp. Mustard spp. Nightshade spp. udweed rickly lettuce Shepherdspurse Sowthistle Sprangletop Several publications listed in References at the end of this chapter can help you identify weeds: The Grower s Weed Identification Handbook, U IM est Management Guidelines: Grapes, Weeds of alifornia, and Weeds of the West. Local farm advisors, specialists, and consultants can also help you identify weeds. Weed samples that you collect for identification should be stored under cool conditions and transported in a sealed plastic bag to maintain sample integrity. Accurate Weed Records The maintenance of accurate weed infestation records is important in tracking the progress of weeds within a field and selecting the most appropriate methods of control. The exact method used to collect weed data and the number of times you should monitor a field in a year may vary. It is best to monitor a vineyard at least three times per year, in winter, spring, and summer. If you maintain records on computer files or in a field notebook they will be readily available when you gather new information or need to review the vineyard history. Weed records should include the timing of mechanical operations, timing and rates for any herbicide applications, stage of weed growth at time of chemical or mechanical treatment, degree of

2 1 4 6 e s t Management control obtained, and exact locations of infestations within the field. A vineyard map may also be useful. A sample weed monitoring record is shown in Figure A single weed species left uncontrolled can become the field s dominant weed species in as few as three years. To prevent this kind of shift, growers often rotate herbicide, tillage, and mowing control methods. Accurate weed infestation records will help you make appropriate decisions to avoid weed shifts. An overall understanding of how your weed management efforts are progressing will help you maintain long-term cost-effective control. Field Sanitation Along the borders of a field, timely disking, mowing, burning, and herbicide applications can help eliminate weed seed production and dissemination into previously uninfested fields. Many times a grower will achieve excellent weed control in the field but fail to clean the surrounding areas. Reducing this potential seed source can go a long way toward preventing new weed infestations. year can successfully destroy weeds growing between the vine rows (Figure 20.2). Unless you cross-disk (as in new vineyards), however, weeds are not eliminated within the vine row; there they must be controlled with specialized equipment (i.e., French plow [Figure 20.3], Bezzerides, power-driven rotovators equipped with tripping mechanisms, and other mechanical equipment). While this specialized equipment is effective in killing young weeds within the planted row, the repeated use of heavy equipment can lead to increased erosion, soil compaction, dust, reduced water infiltration, and mechanical damage to the vines. Some weeds are difficult to control (e.g., Johnsongrass growing from rhizomes). However, by using a French plow during the dormant season you can bring the rhizomes to the middles and then disk them at least twice. This breaks the rhizomes up into smaller sections. Additional diskings during the spring and summer destroy the individual plants as they begin to grow. re-emergence herbicides like trifluralin can also be sprayed on the soil ahead of the disk to provide pre-emergence weed control and reduce root growth of perennial weeds. lanning a Weed ontrol rogram It would be ideal if one method of management or control could be used in all vineyards, but this is not possible. Many local conditions such as topography, soil structure and texture, permeability, type of irrigation, availability of equipment, the cost of labor and herbicides, and accessibility of the vineyard during wet periods can influence a weed management program. The best specific methods of control vary from site to site, and often include combinations of mechanical and chemical control. Tillage vs. Nontillage Weed control can be accomplished in a raisin vineyard with or without herbicides. Mechanical disking or power mulching of vineyards three or more times per Figure 20.2 Repeated disking of middles provides effective control of undersirable vegetation. hoto: Kurt Hembree. Field Date rop Herbicides/Rates Other ontrol Weeds resent % ontrol Notes Figure 20.1 Weed record for field monitoring Figure 20.3 A French plow provides a means of controlling weeds within the row of mature staked vines. hoto: Bill Fischer.

3 h a p t e r 20: Weed Management Mechanical control is most appropriate when weeds are small and easy to kill or dislodge from the soil. Timing is therefore important. ower-driven mulchers provide shallow (1- to 2-inch) cultivation, so weeds must be in the seedling stage to be effectively controlled. Another limiting factor for mechanical control is that the equipment cannot be used under wet conditions. are should also be taken to prevent mechanical injury to the vines. The practice of nontillage in the middles is also an option where resident vegetation or cover crops are maintained between vine rows. Repeated mowings with a flail or rotary mower during the year can help maintain lowgrowing vegetation to allow better field access during wet periods, reduce erosion and compaction, and increase water infiltration. However, since most alifornia raisins are sun-dried, the middles need to be disked, harrowed, and sloped prior to harvest to promote uniform drying. A well-established cover crop can outcompete weeds in some instances. The degree of weed suppression varies with cover crop type, time of year, and management to reduce the amount of exposed soil. In general, a fastgrowing cover crop is best suited to outcompete weeds. Most cover crops used in raisin production are planted in the fall after harvest and mulched or disked-in the following spring to prepare the field for harvest. Which cover crop is the most appropriate depends on several factors, including soil type, climate, water requirement, nutrient value, management, and cost. Refer to the U Sustainable Agriculture Research and Education rogram (U SARE) Worldwide Web page ( sarep. ucdavis.edu) to determine the appropriate cover crop for a given management strategy and location. Where Do Herbicides Fit? Herbicides, when properly used, can be effective tools for controlling weeds in vineyards, especially within the vine row. In order to select the most appropriate and effective herbicide or combination of herbicides, or the sequence of application for multiple herbicides, one must first properly identify the weeds present in the vineyard and know their susceptibility to the various herbicides. Local conditions such as soil type, irrigation method and frequency, and availability of application equipment may influence the selection of herbicides and their ultimate performance. Soil residual herbicides sprayed onto the soil surface and incorporated mechanically or with rainfall control germinating weed seeds. These herbicides are degraded primarily by photodecomposition, hydrolysis, and microbiological activity. Local environmental conditions may influence herbicide persistence and efficacy. For greatest effectiveness, spray them on the soil surface free of leaves and other debris. The effectiveness of postemergence herbicide control varies depending on the weed species, size, and vigor, and the uniformity of application. Weeds that are droughty or water-stressed at the time of application will not be effectively controlled. Several soil residual and postemergence herbicides are available for use in alifornia vineyards. The weed susceptibility charts at the end of this chapter and in the U IM est Management Guidelines: Grapes (available from U ooperative Extension county offices or via the Worldwide Web at provide information on the registration status and use recommendations for herbicides. Herbicide erformance and Irrigation Method Most vineyards in alifornia are irrigated by furrow, basin-flood, and low-volume drip emitter systems. Unlike flood or basin-flood irrigation, low-volume systems improve uniformity in irrigation application and efficiency and ensure that the water needs of the vines are met. However, irrigation water applied too frequently in this manner, especially on lighter soil types, can significantly influence the leaching of herbicides, their selectivity, and their persistence in the zone where weed seeds germinate. You must consider the herbicides behavior under various soil and irrigation regimes when you select a weed-control chemical. onsult the herbicide label for recommendations on any particular soil type. In a drip-irrigated vineyard, weeds tend to grow more vigorously in the area wetted by the emitters, and consequently the vineyards require repeated, timely applications of postemergence herbicides when preemergence herbicides break down. Weeds may also interfere with the uniform distribution of water so that the monitoring of the irrigation system becomes more costly and time consuming. How wet the emitters get the area beneath them also influences weed growth and the types of weeds present. For example, yperus esculentus (yellow nutsedge) prefers wet, sandy soils. Frequent applications of low-volume irrigation will increase the risk that, once introduced into a field, this weed will survive. By adjusting the frequency and duration of irrigation to minimize excess watering, you may be able to reduce infestations. When soil residual herbicides are applied to a trash-free berm and activated by rainfall, irrigation, or mechanical incorporation, their performance is enhanced. As mentioned previously, herbicide performance is influenced by the length and frequency of irrigation. While oxyfluorfen appears to persist for several months under high water regimes, herbicides like napropamide may only last a third as long. Other herbicides, like norflurazon, may be leached into the vine s root zone and produce veinal chlorosis of the

4 1 4 8 e s t Management grape leaves, especially in sandy soils. Therefore, you may want to reduce the frequency of irrigation, use herbicides like these in fields where furrow or basin-flood irrigation is used, or use mechanical cultivation. ostemergence herbicide activity can also be influenced by the frequency of irrigation. Weeds growing in the wetted area tend to be vigorous, and thus susceptible to foliar herbicides like glyphosate, paraquat, and sethoxydim; you have to apply these herbicides before the weeds get too large for effective control. On the other hand, weeds like onyza canadensis (horseweed),. bonariensis (flaxleaved fleabane), and Gnaphalium spp. (cudweed) growing on the perimeter of the wetted area may be droughty and difficult to control. Yellow nutsedge growing in these wetted areas can produce new vegetative propagules (tubers) as soon as three weeks after emergence, making timely control essential. Management of weeds requires special attention for effective control in low-volume irrigated vineyards. Selecting an Effective Herbicide rogram lanning for an effective weed control program that includes herbicides should be based on the weeds that are present or are anticipated in the vineyard. The best time to start a weed management program is before the vines are planted. Unless you keep the rows weed-free during establishment, weed competition can greatly reduce vine growth and make subsequent control difficult. Metham sodium (a preplant soil fumigant) applied to the rows can provide effective control of weed seeds as well as some plant pathogens and nematodes. Trifluralin (a dinitroanaline herbicide) is also commonly applied to the soil as a strip or broadcast treatment before vine planting for early weed control. Once treated, the field should be disked immediately in two directions, 3 to 4 inches deep for thorough incorporation and to prevent loss by volatilization. The vines are planted with their roots below the treated zone to avoid injury. While trifluralin does not control all weeds common to raisin vineyards, it controls several important annual grass and broadleaf species, such as annual bluegrass, barnyardgrass, and pigweed. One of the most common herbicide programs for vineyards is a tank mix of oryzalin and oxyfluorfen or simazine and diuron during the dormant period (fall, winter, or both). Such a tank mix controls a broad spectrum of annual grass and broadleaf weeds. Because some herbicides, like oryzalin, can adhere to organic matter on the soil surface, burning, blowing, or raking debris from the treated area ensures proper soil contact and performance while minimizing potential losses from off-site movement of the herbicides with wind-blown debris. Where you expect a need to control horseweed and flaxleaf fleabane, a low-rate tank mix of diuron and simazine would be a desirable combination as a winter application. This combination provides cost-effective control of numerous weed species, limiting the need for follow-up postemergence sprays. Although napropamide controls some winter grasses and some species better than oryzalin, it is less effective against many summer annual weeds under low-volume frequent irrigation. Oxyfluorfen complements both napropamide and oryzalin and controls a wide spectrum of winter and summer annuals, including Malva parviflora (little mallow), Erodium spp. (filaree), and some clovers. Oxyfluorfen may also be used postemergence at low rates to control vigorously growing seedling weeds. If cudweed or grasses are the only weeds you expect, napropamide might be your herbicide of choice. Other herbicides are also effective for specific weeds; be sure to follow label instructions. Regardless of which soil residual herbicide you select, timely incorporation is required for maximum control. The period of time required for herbicide incorporation is shown on individual herbicide labels and in Table If weeds are present at the time of application, you can add postemergence herbicides like glyphosate or paraquat to the tank mix for burn-down control. When using postemergence herbicides, it is important that you time the application to the stage of weed growth. In general, weeds less than 4 to 6 inches tall are easiest to control. As the weeds mature, many become mealy, hairy, and woody, making control difficult. Horseweed and flaxleaved fleabane, for example, become very hairy and woody as they mature, so the spray solution comes to rest on leaf hairs above the actual leaf surface, reducing absorption and subsequent control. Horseweed and flaxleaved fleabane are controlled most easily with postemergence herbicides if applied before the 8- to 10-leaf stage. Table 20.2 Time required for incorporation of soil residual herbicides ommon Brand Maximum time to name name incorporate with water Diuron Karmex < 4 weeks Isoxaben Gallery < 21 days Napropamide Devrinol < 21 days Norflurazon Solicam < 4 weeks Oryzalin Surflan < 21 days Oxyfluorfen Goal < 3 to 4 weeks endimethalin rowl < 7 days* or < 21 days ronamide Kerb < 24 hours Simazine rincep < 4 weeks Trifluralin Treflan < 24 hours *Mechanical incorporation

5 h a p t e r 20: Weed Management Effective weed control is difficult if you rely solely on postemergence herbicides, especially once canes and foliage reach the soil surface. Trimming the canes during the season will facilitate spraying, although hooded sprayers are recommended to reduce the risk of injury. Sethoxydim, fluazifop-butyl, or clethodim applied postemergent in combination with a non-phytotoxic crop oil concentrate will control most established annual and perennial grasses when they are growing vigorously and have not yet tillered. erennial grasses will require multiple applications for complete control. Because perennial grasses (like bermudagrass and Johnsongrass) are often distributed in clumps within a field, spot treatment is often practical. Spot treatment involves a smaller herbicide input than strip treatment. Fescue and brome species are not effectively controlled by these herbicides. Of the grass herbicides, only clethodim is effective against oa annua (annual bluegrass), and then only if it is sprayed early, when the weeds have fewer than 4 or 5 leaves. Yellow nutsedge (and to a lesser extent purple nutsedge) can become troublesome in vineyards. Nutsedge infestation generally begins in limited areas of the field (especially under drip emitters), but if not controlled they can spread throughout the entire vineyard and become very difficult to manage. Because nutsedge reproduces primarily by underground tubers, you should apply postemergence herbicides before new tubers form. Spray nutsedge with a postemergence herbicide when the weeds have four to five leaves and before the onset of tuber formation. This program can be effective, but if you miss a single application or apply postemergence herbicides too late you may lose any previous gains against the weed. When nutsedge first appears, manage it immediately to prevent it from spreading into other areas of the field. Norflurazon can also provide control as a pre-emergence treatment. While cultivation can effectively control new nutsedge plants, it is also likely to result in spread of nutsedge tubers. For this reason, control is generally limited to timely postemergence treatments during the spring and summer months when the weed is actively growing. Nonselective herbicides like paraquat or glyphosate can cause significant crop injury when they contact immature bark or green foliage, whether by direct spraying or as spray drift. To avoid vine injury, use hooded or shielded sprayers to protect the canes and foliage from the spray pattern. Mechanical trimming of the canes also facilitates spraying within the vine row. Never spray weeds in newly planted vineyards unless the vines are adequately protected. Sprayers are available that can spray green vegetation without treating bare soil. This smart sprayer uses a light source to activate solenoid valves and spray nozzles when the sprayer sees green at the soil surface. With these sprayers, growers can achieve control while reducing the amount of postemergence herbicides they apply by 70 percent or more in fields with sparse weed populations. Raisin producers have many mechanical and chemical tools available for weed control, and with these they can develop weed management programs that meet their individual needs. Effective weed control in the vineyard is possible with or without the use of herbicides. One cannot overemphasize that, where herbicides are used, proper weed identification and accurate application are imperative for effective, economical control. By being familiar with all of the weed control tools available and by properly identifying the problem weeds, any grower can produce raisin grapes relatively free of competing weeds in a manner that is both economically and environmentally sound. R e f e r e n c e s Anderson, W Weed science principles. 3rd ed. St. aul: West ublishing o. alifornia Weed onference rinciples of weed control in alifornia. 2nd ed. Fresno: Thompson ublications. Elmore,., H. S. Agamalian, D. Donaldson, and B. B. Fischer Grapes. In U IM pest management guidelines: Grapes. Oakland: University of alifornia Division of Agriculture and Natural Resources publication Fischer, B. B., et al Grower s weed identification handbook. Oakland: University of alifornia Division of Agriculture and Natural Resources publication Harrington, M. D., and L. W. Durrell How to identify plants. Denver: Sage Books. Hopkins, W. L Global herbicide directory. 1st ed. Indianapolis: Agricultural hemicals Information Services. Kempen, H. M Growers weed management guide. Fresno: Thompson ublications. Lanini, W. T., W. E. Bendixen, H. S. Agamalian, A. S. Lange, H. M. Kempen, B. B. Fischer, and D. Donaldson Grape pest management, 2nd ed. Oakland: University of alifornia Division of Agriculture and Natural Resources publication Munz,. A A alifornia flora and supplement. Berkeley and Los Angeles: University of alifornia ress. Robbins, W. W., K. Margaret, K. Bellue, and W. S. Ball Weeds of alifornia. Sacramento: alifornia Department of Agriculture. Whitson, T. D., ed Weeds of the West. Newark, A: Western Society of Weed Science and Western U.S. Land Grant Universities ooperative Extension Services.

6 1 5 0 e s t Management Susceptibility of Weeds to Herbicides Evaluated for Use in Vineyards in alifornia heeseweed hickweed ocklebur udweed lovers Fiddleneck Filaree Flaxleaf fleabane Goosefoot Groundcherry Groundsel Henbit Horseweed Knotweed Lambsquarters London rocket Miners lettuce Mustard Nettle Nightshade igweed ineappleweed rickly lettuce uncturevine urslane Red maids Russian thistle Shepherdspurse Sowthistle Spurge Speedwell Wild radish Broadleaves Soil-applied residual *Nonbearing only Foliar applied Diuron (Karmex) endimethalin (rowl)* Napropamide (Devrinol) MSMA* (Various trade names) araquat (Gramoxone Extra) Glyphosate (Roundup) Oryzalin (Surflan) Norflurazon (Solicam) Simazine (rincep) ronamide (Kerb) Sethoxydim (oast) Oxyfluorfen (Goal) Fluazifop-p-butyl (Fusilade DX)* Trifluralin (Treflan) Isoxaben (Gallery)* ontrolled No control or no information artial control lethodim (rism)* Dichlobenil (asoron) 2,4-D amine (Dri-lean) *Nonbearing only This chart is not a recommendation for the use of herbicides. lease check the herbicide label for recommendations on it use and rates of application. roper weed identification, timing, and accuratre application of herbicides are imperative for effective control. The information in this chart is tentative; additional information may warrant changes.

7 1 5 1 h a p t e r 20: Weed Management Johnsongrass (S) Johnsongrass (E) urple nutsedge Yellow nutsedge erennials Annual bluegrass Barnyardgrass Bromegrass anarygrass rabgrass Fescue Foxtail Jungle rice Lovegrass Rabbitfootgrass Ryegrass Sandbur Wild barley Wild oats Witchgrass Annual grasses (S) = seedling, (E) = established *Nonbearing only This chart is not a recommendation for the use of herbicides. lease check the herbicide label for recommendations on its use and rates of application. roper weed identification, timing, and accurate application of herbicides are imperative for effective control. The information in this chart is tentative; additional information may warrant changes. Foliar applied Soil-applied residual Susceptibility of Weeds to Herbicides Evaluated for Use in Vineyards in alifornia (continued) Dichlobenil (asoron) Diuron (Karmex) Simazine (rincep) Trifluralin (Treflan) Oxyfluorfen (Goal) endimethalin (rowl)* ronamide (Kerb) Oryzalin (Surflan) Norflurazon (Solicam) Napropamide (Devrinol) Isoxaben (Gallery)* MSMA (Various trade names)* Sethoxydim (oast) araquat (Gramoxone Extra) Glyphosate (Roundup) lethodim (rism)* Fluazifop-p-butyl (Fusilade DX)* ontrolled artial control No control or no information 2,4-D amine (Dri-lean) (S) = seedling, (E) = established *Nonbearing only This chart is not a recommendation for the use of herbicides. lease check the herbicide label for recommendations on it use and rates of application. roper weed identification, timing, and accuratre application of herbicides are imperative for effective control. The information in this chart is tentative; additional information may warrant changes.

8 1 5 2 e s t Management erformance of Soil-Applied Residual Herbicides Evaluated in Vineyards in alifornia Herbicide Dichlobenil (asoron) Diuron (Karmex) onditions resulting in effective control Incorporated into the soil on the berms in furrow or basin flood-irrigated vineyards. rovides effective control of some perennials. Applied on berms where no irrigation water is applied. Apply at low rates in combination with other herbicides for broad-spectrum weed control. onditions resulting in poor control or crop injury Applied on the soil surface without incorporation. Symptoms of phytotoxicity observed where irrigation water applied over treated area. Selectivity is reduced when irrigation water is applied over the treated area. When common groundsel, Russian thistle, spotted spurge, or turkey mullein present. Isoxaben (Gallery) For use in nonbearing vinyards only. Applied prior to weed seed germination or emergence. Rainfall or irrigation water applied shortly after application. When grasses are the primary weeds present. Susceptible weeds emerged at time of application. No rainfall or irrigation water applied within 21 days of treatment. Napropamide (Devrinol) Norflurazon (Solicam) Oryzalin (Surflan) When rainfall or irrigation occurs within 14 to 21 days of application or when incorporated into the soil soon after application. Most effective and longest residual control obtained on berms or where irrigation water is not applied over the treated area. rovides effective control of nutsedge. When applied in combination with simazine or oxyfluorfen. When rainfall occurs within 14 to 21 days following application on areas free of trash. Incorporated into the soil with tillers soon after application. Not leached or incorporated into the soil within 14 to 21 days after application. rovides short-lived control under low-volume frequent irrigation. Weeds are emerged at the time of application. Trashy conditions. Readily leached by irrigation water. Short-lived control under low-volume frequent irrigation. Symptoms observed in orchards where irrigation water is applied over the treated area. If rainfall does not occur or no irrigation water applied over the treated area or not incorporated within 14 to 21 days after application. Vineyard floor covered with leaves or other trash. Oxyfluorfen (Goal) endimethalin (rowl) ronamide (Kerb) Simazine (rincep) Trifluralin (Treflan) Most persistent herbicide under low-volume frequent irrigation. rovides pre- and postemergence control of susceptible weeds. In nonbearing vineyards only. When rainfall occurs or irrigation water is applied within 7 to 10 days of chemical application. rovides good preemergence control of susceptible weeds. Effectively controls emerged seedlings if irrigated soon after application. Best when used in combination with other herbicides. Applied on the berms. Applied at very low rates (0.5 to 1.0 lb active ingredient per acre in combination with other herbicides. Incorporated into the soil to a depth of 1 to 2 inches within 2 to 3 hours of application. Most effectively used prior to planting vineyards. Soil disturbed following application. an cause foliar symptoms on lower leaves when applied in early spring or following bud swell. Rainfall does not occur or irrigation water not applied within two weeks of treatment. Weeds are emerged at the time of treatment. Residual effectiveness is short-lived (6 to 8 weeks). Does not control weeds in the sunflower family. Weeds are already emerged. Injury can occur if spray contacts fruit, foliage, or stems or if applied within 3 years of planting. Not incorporated within a short time of application. Deep incorporation may temporarily retard growth of newly planted vines. Numerous factors factors influence influence the performance the performance of herbicides. of The herbicides. observations The and observations comments in this and chart comments assume accurate in this and chart timely assume application. accurate onsult and the timely weed susceptibilitry application. charts onsult (pages the 150 weed and 151) susceptibility for the effectiveness charts (pages of the herbicides 150 and to 151) control for specific the effectiveness weeds. This chart of is the not herbicides a recommendation to control for the specific use of herbicides. weeds. lease check the herbicide label for recommendations on its use and rates of application. roper weed identification, timing, and accurate application of herbicides are This chart is not a recommendation for the use of herbicides. lease check the herbicide label for recommendations on its use and rates of imperative for effective control. The information in this chart is tentative; additional information may warrant changes. application. roper weed identification, timing, and accurate application of herbicides are imperative for effective control. The information in this chart is tentative; additional information may warrant changes.

9 h a p t e r 20: Weed Management erformance of Soil-Applied Residual Herbicides Evaluated in Vineyards in alifornia (continued) Herbicide lethodim (rism) onditions resulting in effective control In nonbearing vineyards only. Applied on vigorously growing annual grasses (except bromes and fescues) and perennial grasses in combination with a paraffinbased adjuvant. Repeated (2 to 3) applications on perennial grasses in newly planted vineyards. Selective on all broadleaf weeds. onditions resulting in poor control or crop injury Applied on grasses stressed for moisture. Repeat applications not made to control perennial grasses. Bromes and fescues the predominant grasses. Adequate paraffinbased adjuvant not used. Fluazifop-p-butyl (Fusilade DX) In nonbearing vineyards only. Applied on vigorously growing annual grasses (except annual bluegrass, bromes, and fescues) and perennial grasses in combination with a paraffin-based adjuvant. Repeated (2 to 3) applications on perennial grasses in newly planted vineyards. Selective on all broadleaf weeds. Applied on grasses stressed for moisture. Repeat applications not made to control perennial grasses. Bromes, fescues, and annual bluegrass are the predominant grasses. Adequate paraffin-based adjuvant not used. Glyphosate (Roundup) Applied on vigorously growing annual and perennial weeds. Used at low rates to arrest the growth of the vegetation without killing it. Applied on nutsedge having 4 to 6 leaves. ombined with soil-persistent herbicides. Repeated applications to control weeds around low-volume emitters. lants droughty or not growing vigorously when treated. If used at low rates can result in rapid shift in population of weed species. areless use under windy conditions can result in drift and injury to crops and desired vegetation. If sprayed on immature, young vines or canes, can cause injury and severe gumming. araquat (Gramoxone Extra) Applied on weeds in their seedling (2- to 6-leaf) stage of growth. ompatible in tank mixes with other herbicides. Applied on plants beyond their seedling stage of growth. lants with waxy, hairy, and mealy surfaces often not killed. Foliage of vines as well as immature bark can be injured. A ategory I pesticide. ermit and protective clothing required. Sethoxydim (oast) Applied on vigorously growing annual grasses (except annual bluegrass, bromes, and fescues) and perennial grasses in combination with a paraffin-based adjuvant. Repeated (2 to 3) applications on perennial grasses. Selective on all broadleaf weeds. Applied on grasses stressed for moisture. Repeat applications not made to control perennial grasses. Annual bluegrass, bromes, and fescues are the predominant grasses. Adequate paraffin-based adjuvant not used. MSMA (Various trade names) In nonbearing vineyards only. Applied repeatedly on vigorously growing johnsongrass. Yellow nutsedge having 4 to 6 leaves and re-growth is treated repeatedly. Treatment was not repeated as needed. Does not control bermudagrass and broadleaf weeds. Injury can result when sprayed onto foliage and immature bark. 2,4-D amine (Dri-lean) Applied on young susceptible broadleaf weeds when growing vigorously. Some weeds are tolerant as they grow beyond their seedling stage. an be used only from October 15 to March 15, and permit is required. Spraying the vines or drift of the herbicide can cause crop injury. Numerous factors influence influence the performance the performance of herbicides. of herbicides. The observations The and observations comments in this and chart comments assume accurate in this chart and timely assume application. accurate onsult and the timely weed application. susceptibilitry onsult charts (pages the 150 weed and susceptibility 151) for the effectiveness charts (pages of the herbicides 150 and to 151) control for specific the effectiveness weeds. This chart of the is not herbicides a recommendation to control for the specific use of weeds. herbicides. This lease chart check is the not herbicide a recommendation label for recommendations for the use on of its herbicides. use and rates lease of application. check roper the herbicide weed identification, label for timing, recommendations and accurate application its use of herbicides and rates are of application. imperative for roper effective weed control. identification, The information timing, in this chart and is accurate tentative; additional application information of herbicides may warrant are imperative changes. for effective control. The information in this chart is tentative; additional information may warrant changes.