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The last several years have witnessed the development of several unique and novel approaches to herbicide application. Since the widespread adoption of the use of herbicides in the 1940s the most widely used method of application has been hydraulic spray techniques. This method utilizes forcing a liquid containing the herbicide through various designs of orifices that meter and direct the solution onto the area to be treated. This method of application remained largely unchanged until the late 1970s.
With the commercial introduction of glyphosate (N-[phosphonomethyl]glycine) in the mid-1970s, changes began to take place in application technology. Glyphosate is formulated as the isopropylamine salt in the commercial product Roundup® herbicide. Glyphosate has some unique properties that prompted the search for new application techniques. It is a post-emergence, nonselective herbicide (at normal use rates) with broad-spectrum activity on both grass and broadleaf plants. It is translocated in plants, so that contact with the foliar portion of a plant results in the destruction of both the aboveground and the belowground portions of the plant. These features of glyphosate have prompted a wide range of unique application techniques to be developed or improved upon.
The principal motivation in the development of these new application techniques has been to utilize the activity of glyphosate in a selective manner. Another primary goal of some application techniques is the reduction in herbicide cost. Some techniques are able to reduce the amount of herbicide applied to a given area. Substantial cost savings can often be realized compared with conventional broadcast applications.
Within a short time after the introduction of glyphosate, several methods of selective application began to be developed. All utilized the same common principle. The herbicide is applied directly to the undesirable foliage while avoiding or minimizing contact with the foliage of the crop or desirable vegetation. By applying the herbicide in such a manner the weeds can be destroyed without damage to the crop.
Among the application methods developed were recirculating sprayers, rope-wick applicators, carpet wipers, roller applicators, and sponge wipers, as well as modifications to hooded and shielded applicators. Later unique concepts regarding broadcast applications were developed in an effort to improve the economics of pesticide application.
The characteristics of glyphosate are discussed. The advantages and disadvantages of various application techniques are summarized as are the precautions that should be exercised when applying glyphosate regardless of the application technique utilized.
glyphosate, herbicide, sprayers, recirculating sprayer, rope-wick, roller applicator, wiper applicator, CDA
Technical Manager, Glyphosphate Products, Monsanto Company, St. Louis, MO