Q: Why do some herbicide labels instruct you to spray only when temperatures are between 65 and 85 degrees? Does it really matter?

A: What a terrific question, I know other people have wondered but maybe never got up the nerve to ask. Applying chemicals according to the label absolutely matters. Remember “the label is the law”. This label instruction is a good example of why it is important to follow the directions to the letter of the law. Most plants, regardless of where they are located, begin to slow down their normal growing mechanisms when the outside temperatures begin to drop. The energy of the plant during cold seasons will go to protecting the plant and placing it in a dormant stage. Since the ability of the plant to transfer chemicals throughout the vascular system via the roots is greatly diminished it is of little consequence to apply these herbicides during dormancy. As far as the high temperatures, many plants can be severely damaged or even killed if herbicides are applied when the summer temperatures reach the high eighties. So, the take home lesson is to read and follow the pesticide label. http://edis.ifas.ufl.edu/pi051

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