Manufacturers spend many years and hundreds of millions of dollars to discover, research, develop and test pesticides, and create the label. However, pesticide labels often go unread or ignored. The label that accompanies the product you are using supersedes any other documentation or information about the product you may have been given by anyone else. Always read and follow label directions. The following is a discussion of the "who," "what," "when," "where," "why," and "how," of pesticide labels. This, and other important information, is listed on every pesticide label.
"Who" can use a pesticide? Pesticides are either restricted-use or general-use. If a pesticide is restricted-use, it will be very clearly indicated as such, often at the top of the first page of the label, and it can only be used by licensed applicators. Other pesticides, not labeled restricted, can usually be used by the general public. Some general-use pesticides also have additional restrictions imposed on them in certain geographic areas. For instance, a state department of agriculture may restrict when and by whom 2,4-D and other auxins may be used in certain counties. Pesticides that are particularly likely to have off-target movement or to cause harm to humans, water or pollinators may be restricted.
"What" ingredients the pesticide contains is listed under "Active Ingredients," usually on the first page of the label. Many active ingredients are sold under multiple trade names. Active ingredients can come in more than one concentration or strength. For instance, glyphosate, the active ingredient in Roundup™ and its generics, comes in many strengths, from ready to use to a 5-pounds-per-gallon concentrate. Knowing what active ingredient is in the pesticide, and in what amount, is pertinent to any discussion you may have about that product.
"Where" the pesticide can be used refers to specific crops or other areas where it can legally be applied. Applying a pesticide to any area other than those listed on the label is a violation of federal label law and may result in injury to that crop or illegal chemical residues in the end product being grown.
You need to know "when" the pesticide can be used if you are going to be successful at killing your target pest. Most pesticides today are intended to be used at a specific time in the life cycle of the target pest. Applications outside of this time of pest size or growth stage often result in poor control. Even worse, those sublethal doses can contribute to the development of pesticide resistance.
The "why" you might want to use a particular pesticide is covered by the list of pests on the label. The label also states if it will provide control or only suppression. Many pests often have regional or colloquial names that may or may not be listed on the label. Labels typically use the pest name that is commonly accepted by the professional society dealing with that pest, be it a weed, insect, disease, etc. For instance, weed names on a product labeled for use in the United States will be the ones used by the Weed Science Society of America. Proper identification of the pest is crucial to success. Various dichotomous keys and other resources are available in print and online to help with pest identification. Local experts can also be helpful if a good specimen can be collected or captured in high quality photographs.
"How" the pesticide can be used includes many things including the rate, application method and what other chemicals it can be mixed with. It also tells whether the pesticide should be applied to the crop or soil, what application equipment can be used, etc. The label also includes restrictions about how NOT to apply the pesticide. Some restrictions are for environmental factors, like wind speed and air temperature. Other restrictions include items such as if and how soon the crop can be grazed, how long before the crop can be harvested, and how soon a subsequent crop can be planted.