In most states, the commercial application of herbicides requires state-approved certification and licensing before an individual commences work with these often-dangerous chemicals.
Most states require individuals working with herbicides to take a training course and pass an exam. Each course is different but the general topics covered include how to use and repair herbicide spray vehicles and which herbicides destroy what types of vegetation.
Once you have completed the training course you can then apply for an applicator's license. You will have to register for the type of license you need. For example, Wisconsin has several types of licenses including commercial applicator, commercial applicator for hire and commercial applicator not-for-hire. Depending on your state, you may have to take additional training courses or undergo annual reviews to keep your license current.
Some states, such as Florida, have further specializations for which you must register. Florida differentiates those people who work with aquatic herbicides for areas that are on or near running waterways, such as shorelines and riverbanks.