Israel, Trevor D.

Rhodes, G. Neil, Jr.

Steckel, Larry

English

University of Tennessee, Knoxville: Trace

University of Tennessee, KnoxvilleTrace: Tennessee Research and CreativeExchangeField & Commercial Crops UT Extension Publications12-20-2012W291-A Preventing Off-target Herbicide Problemsin Cotton FieldsG. Neil Rhodes Jr.Trevor D. IsraelLarry SteckelFollow this and additional works at: http://trace.tennessee.edu/utk_agexcropPart of the Agriculture CommonsThe publications in this collection represent the historical publishing record of the UT Agricultural Experiment Station and do not necessarily reflectcurrent scientific knowledge or recommendations. Current information about UT Ag Research can be found at the UT Ag Research website.This Cotton - Production, Insects and Diseases is brought to you for free and open access by the UT Extension Publications at Trace: TennesseeResearch and Creative Exchange. It has been accepted for inclusion in Field & Commercial Crops by an authorized administrator of Trace: TennesseeResearch and Creative Exchange. For more information, please contact trace@utk.edu.Recommended Citation"W291-A Preventing Off-target Herbicide Problems in Cotton Fields," G. Neil Rhodes Jr., Trevor D. Israel, and Larry Steckel,W291-A, http://trace.tennessee.edu/utk_agexcrop/136   Preventing Off-target  Herbicide Problems in Cotton Fields G. Neil Rhodes Jr., Professor and Extension Weed Management Specialist Trevor D. Israel, Extension Assistant Larry Steckel, Associate Professor and Extension Weed Management Specialist  Introduction Off-target movement of agricultural chemicals, including pasture and right-of-way herbicides, can be detrimental to cot-ton production. While these herbicides are valuable tools for weed management, off-target damage to cotton often results in expensive fines and/or lawsuits, delayed harvests, reduced yields, and bad publicity for the industry. Fortunately, pre-ventive steps can be taken to avoid these problems.   Herbicide Selection Although highly effective on several broadleaf weeds in pas-tures and rights-of-way, the auxin, or growth regulator herbi-cides, can damage sensitive crops if not used properly. The characteristics of these herbicides determine which product to use in different situations. Under the right conditions, volatile herbicides change from a liquid to gas or vapor and move away from the target. Typically, dicamba and 2,4-D are more volatile than aminopyralid or picloram. Keep in mind that while ester formulations are more likely to volatilize than amine (salt) formulations, some salts of 2,4-D and dicamba are more volatile than others.   The persistence of herbicides is also important to consider when choosing a product. While dicamba and 2,4-D are highly active on cotton even in minute doses, these materials are relatively nonpersistent in soil and in treated pasture grasses and hay. However, aminopyralid and picloram can stay ac-tive in soil, pasture grass and hay for a year or longer. When these forages are consumed by animals, the chemical passes through their digestive and urinary systems without change and into the manure and urine. It takes several days for aminopyralid and picloram to pass through the digestive and urinary systems of an animal. Producers should handle treated hay and manure so that placement will not affect future production. Herbicides that contain aminopyralid or picloram are for use in permanent grass pastures and grass hay fields only. They should not be used in fields that will be rotated to cotton or other broadleaf crops.  Another characteristic to consider is water solubility. Picloram is more soluble than aminopyralid and therefore more likely to be moved off-site by runoff. Newer pasture and right-of-way herbicides such as aminopyralid have strong attributes in that they control some of our worst pasture and hay field weeds such as horsenettle, tall ironweed and beggarweed. Also, volatility, unlike in the case of 2,4-D, is not an issue.  Fig. 1. Off-target herbicide damage to cotton. W 291-A  2  Drift Prevention Because cotton is sometimes planted near pastures, hay fields and other row crops, the probability of herbicide drift is high unless preventive measures are taken. Several factors can contribute to herbicide drift to sensitive areas. Two types of drift, physical and vapor, can occur. Physical drift is the movement of liquid spray droplets away from the target, and it is influenced by spray equipment and wind. Calibrating your sprayer for low pressure (30 psi or less) and high volume (20 to 30 gallons per acre) applications will reduce the number of fine spray droplets. Lowering the boom height also reduces drift, but make sure that the correct spray pattern overlap is achieved. New advances in spray tip design, such as air induction technology and Turbo TeeJet Induction nozzles have allowed for adequate spray patterns while producing large droplets. In many cases, induction nozzles require higher operating pressures than flat fan nozzles, so be sure to check the nozzle specifications. Another rule of thumb is to spray on calm days and when wind direction is away from sensitive areas. Calm conditions are more likely to occur early or late in the day. Another common sense approach is to allow some buffer area that is not sprayed adjacent to sensitive crops. Drift reduction agents can also be used to reduce physical drift, but check the labels for compatibility. Vapor drift is the movement of spray vapor away from the target after the herbicide has been deposited on the target. It is mainly influenced by air temperature but also by relative humidity (RH) and herbicide formulation. Some chemicals volatilize readily at warm (higher than 85 F) temperatures, and dry air (RH less than 40 percent) increases the likelihood of vapor drift. Cotton is especially sensitive to 2,4-D. If sensitive crops are nearby, use the amine formulation of 2,4-D rather than the low volatile ester formulation. Amine formulations are much less volatile than the low volatile ester for-mulation. During late spring to summer applications, warm temperatures are likely to be encountered at or shortly after spraying. Keep in mind that vapor drift will be worse under warm conditions, and that it can occur even a few days after application. Dicamba herbicides are also temperature sensitive (see table). Drift reduction measures such as low pres-sure, special nozzles, drift retardants, etc. do not reduce vapor drift. Other considerations to bear in mind are proximity to sensitive fields and timing of herbicide application. Be familiar with adjoining properties and owners, so you know when they will be planting cotton, and in which field. If you are planting cotton, be sure that your neighbors know your plans. Try to spray at a time of year when sensitive crops are not growing. This is often difficult to accomplish, because the optimum time for weed control may occur when a sensitive crop is in the field. However, some weeds, such as musk thistle, may be treated after mid-October with 2,4-D. Winter annual weeds such as buttercup also can be sprayed with 2,4-D in early spring. These are good approaches for a field across the fence from your neighbor’s cotton field, in that you could treat at a time of year when the crop is not up or has already reached maturity. A little communication with your neighbors can go a long way to reduce the likelihood of negative consequences. Common auxin herbicides. Common name  Chemical family  Trade names aminopyralid  Pyridine‐carboxylic acid Milestone, ForeFront R&P, ForeFront HL, GrazonNext picloram  Pyridine‐carboxylic acid Tordon, Surmount, Grazon P+D 2,4‐D  Phenoxyacetic acid Various names and mixtures dicamba  Benzoic acid  Banvel, Clarity, Oracle, Rifle, Brash, Rangestar, Weedmaster  Fig. 2. Healthy cotton results from good planning when pasture herbicides are used nearby. (Photo by Bob Hayes)  3  Sprayer Contamination A common way for pasture herbicides to make it into cotton fields is through sprayer contamination. Pasture herbicides are notoriously difficult to rinse from sprayers. Rinsing with water does not remove all herbicide residues from a sprayer and hoses. Residues are bound to porous materials such as rubber, plastic and polyethylene and can be dissolved later when another application is made. Common solvents used for cleaning sprayers include ammonia and various commer-cial cleaning agents. The longer a herbicide sits in the sprayer, the more difficult it will be to clean, so always try to end the day with a clean sprayer. Stainless steel tanks can be easily cleaned, but rubber hoses and fittings should be replaced to avoid contamination. Be sure to read the herbicide label for proper cleaning instructions. Due to the difficulty with which these herbicides are removed from a sprayer, dedicating a sprayer to be used only on pastures and hay fields is the best way to avoid herbicide tank contamination issues on cotton and other sensitive crops.   Field Selection The location, characteristics and history of a field     influence future management strategies. A proper risk     assessment should be performed before spraying a pas-ture with some of these herbicides. Rains can wash  certain herbicides downhill to sensitive areas. Applica-tions of picloram should not be made on sites with steep slopes and bare soils. It is also important to avoid situations where herbicide runoff can contaminate streams or reservoirs that may be used to irrigate cotton or other sensitive crops. Vegetated buffer strips around ponds can help to reduce herbicide surface movement. Hay feeding areas should not be rotated to cotton or other sensitive broadleaf crops. Also, treated bales should not be stored on land where cotton will be planted, as herbicides can leach into the ground and injure the  next crop. Monitoring Results Producers are encouraged to assess the performance of herbicides in pastures and hay fields. It is important to keep a log of all applications with dates, products, field locations and weather conditions. (This practice is required by law for    picloram, as it is a restricted use pesticide.) Adequate records will help producers keep herbicides contained within the target area, thereby reducing negative impacts to other farm operations and ensuring the availability of these important tools for the foreseeable future.  Important considerations for spraying near cotton fields:  Proximity of sensitive crops.   Herbicide label instructions.  Potential volatility of the herbicide you choose.  Separate sprayer for pastures and hay fields.  Current and forecast weather.  Sprayer calibration and adjustment to minimize drift.  Potential runoff into sensitive areas or irrigation waters.  Inform your neighbors of your plans. Fig. 3. Off-target herbicide damage to cotton can delay har-vest and reduce yield. (Photo by Andy Rowsey)  4  References Anonymous. 2012. Aminopyralid Stewardship Sheet. Dow AgroSciences. Available online at                                       http://www.dowagro.com/range/products/milestone.htm Anonymous. 2012. Milestone herbicide label. Dow AgroSciences. Johnson, Bill, Bill Casady, Dallas Peterson, and Dennis Kuhlman. 1997. Cleaning field sprayers to avoid crop injury.  University of Missouri Extension Publication G4852. Steckel, L., C. Craig, and A. Thompson. 2005. Cleaning plant-growth-regulator (PGR) herbicides out of field sprayers.  University of Tennessee Publication W071.     Development of this fact sheet was funded in part by a grant from Philip Morris International, with additional support from Dow AgroSciences and DuPont Crop Protection.             http://ag.tennessee.edu W 291-A 12/12  13-0149 Programs in agriculture and natural resources, 4-H youth development, family and consumer sciences, and resource development.  University of Tennessee Institute of Agriculture, U.S. Department of Agriculture and county governments cooperating.  UT Extension provides equal opportunities in programs and employment. Disclaimer The recommendations in this publication are provided only as a guide. It is always the pesticide applicator's responsibility, by law, to read and follow all current label directions for the specific pesticide being used. The label always takes precedence over the recommendations found in this publication.  Use of trade or brand names in this publication is for clarity and information; it does not imply approval of the product to the exclusion of others that may be of similar, suitable composition, nor does it guarantee or warrant the standard of the product. The author(s), the University of Ten‐nessee Institute of Agriculture and University of Tennessee Extension assume no liability resulting from the use of these recommendations.  

W291-A Preventing Off-target Herbicide Problems in Cotton Fields

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W291-A Preventing Off-target Herbicide Problems in Cotton Fields

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