Although sugarcane is a relatively competitive crop, weed pressure can have a negative impact on yields. Consequently, most fields are treated with herbicides one or more times during the growing season. Regardless of whether an herbicide is primarily a pre- or postemergence product, some have the potential to persist in the soil for long periods of time. Ideally, herbicide applications would provide long-term weed control during the growing season but would dissipate to a safe level before the next crop is planted. In some situations, herbicides that persist in the soil for long periods of time can injure subsequently planted crops, or these crops can accumulate injurious herbicide residues. The potential for rotational crop injury depends on complex interactions among herbicide characteristics, soil type, soil moisture and temperature, and the sensitivity of the rotational crops. Herbicides that persist in the soil usually have a section on the product label detailing specific rotational crop (plantback) restrictions. These restrictions indicate how much time must pass between herbicide application and the planting of a sensitive crop. The rotational crop restrictions on herbicide labels take into account basic chemical properties of the herbicide, the persistence of the herbicide, typical environmental characteristics of the state or region, and the sensitivity of rotational crops.

This publication condenses rotational crop restrictions for herbicides registered for use in Florida sugarcane (Table 1). When considering the application of herbicides, it is very important to understand the effects that a persistent herbicide may have on subsequent crops. Information on herbicide labels should be used to make better decisions about the crop sequence in a rotation, about which herbicides to use or avoid in a system, and about the rate and timing of herbicide applications. When planning weed control programs, the labels for all herbicides that will potentially be used in crop rotation should be studied along with this bulletin to prevent label violations, reduce economic losses due to herbicide carryover, and avoid injurious herbicide residues.