Applying herbicides at layby can prevent the establishment of yield limiting weeds such as itchgrass, seedling johnsongrass, annual grasses, and morningglories (tie-vines).

Itchgrass continues to be a major weed issue in many areas of the state and preemergence herbicide options are limited at this stage of the crop. Trifluralin (Treflan/Trifluralin/others) is still a viable preemergence option for itchgrass, seedling johnsongrass, browntop millet, and other annual grasses. To maximize weed control with trifluralin, it needs to be incorporated into the soil within 24 hours of application to lessen loss due to volatilization. Incorporation should be limited to the top one to two inches of soil. Other herbicides should be applied to the soil surface for broadleaf weed control.

Pendimethalin (Prowl/Prowl H2O /others) is another preemergence option that can provide a similar level of preemergence grass control as trifluralin. Keep in mind that pendimethalin is marketed under several trade names with differing amounts of active ingredient per gallon. In sensitive areas, consider applying the 3.8-pound encapsulated formulation (Prowl H2O/others), which has a less offensive odor. Pendimethalin can be tank-mixed with other products that provide preemergence broadleaf weed control.

Johnsongrass is also a problematic weed in many areas of the state. Metribuzin applied alone can provide preemergence control of seedling johnsongrass, annual grasses, morningglories and other broadleaf weeds. S-metolachlor (Dual II Magnum/Dual Magnum/others) applied at 0.98 qt/a will provide around 70-75% control of seedling johnsongrass. It also provides control of other grasses like vaseygrass, crabgrass, and goosegrass at rates as low as 1 pt/a. Keep in mind that S-metolachlor only has preemergence activity and provides poor control of itchgrass and Texas panicum. It can be tank-mixed with other commonly used sugarcane layby herbicides to broaden the weed control spectrum.

Several species of morningglories can be problematic weeds in Louisiana sugarcane fields. Some preemergence control options include atrazine, metribuzin, diuron, mesotrione (Callisto 4L/others), sulfentrazone (Spartan 4F/others), and flumioxazin (Valor SX 51 WDG/others). Please note that when using diuron, sulfentrazone, or flumioxazin, care must be taken not to get these products into the whirl of the cane. For additional information, please refer to the Louisiana Suggested Chemical Weed Control Guide or the herbicide label.