Mechanical cultivation of sweet corn is an effective weed management strategy when applied alone or in combination with herbicides. Selective herbicides have been used in corn for some 40 years and can decrease the number of cultivations needed per season and substantially lower the fossil fuel energy used in sweet corn production. Many sweet corn fields now receive one cultivation or no cultivations at all. Much of the cultivation used is to reduce surface crusting or to control weeds that are resistant or not controlled by the herbicide combinations selected. There is at the present time a wide selection of herbicides to control most weeds in sweet corn. However, that selection is being reduced over time because of non-reregistration of older compounds and suspensions due to leaching into the groundwater. Alachlor (Lasso) has been restricted from use in Florida because of confirmed groundwater contamination. Atrazine also is under suspicion.
Herbicide treatments are primarily categorized on the basis of the time of application and include preplant, preemergence, and post-emergence. Preplant treatments are applied before the sweet corn is planted as a surface treatment or incorporated into the soil. Preemergence application occurs after the sweet corn is planted but before sweet corn or weeds emerge. Preplant and preemergence herbicides when properly selected and applied can prevent weed competition during emergence and early seedling growth. Post-emergence applications take place after the emergence of both the sweet corn and weeds and are most effective when weeds are small.
Many postemergence labels state specific ages or growth stages of the sweet corn and weeds to be sprayed. These stages may be the spike stage, five-leaf stage, or when plants are 30 in. tall. If the label specifies directing a spray to the bottom or side of a plant, care must be taken to follow these directions or severe damage may occur. Recent research has shown that there is a difference in tolerance to herbicides, especially among sh2 (super sweet) cultivars. Because tolerances may differ growers should test herbicides on a trial basis when changing cultivars.
Herbicide performance depends on weather, irrigation method, soil type, and application timing, as well as proper selection based on the weed species to be controlled. Obtain consistent results by reading the herbicide label and other information about proper application and timing.
Several sulfonylurea herbicides labeled on field corn (i.e., Accent® and Beacon®) cause damage on a large number of sweet corn cultivars and are not recommended for use. Use only labeled herbicides and those herbicides in the proper formulations. Check the labels of each herbicide for tank mix recommendations. To avoid confusion between formulations, suggested rates listed in Tables 1 and 2 are stated in pounds of active ingredient per acre (lb. a.i. /A).
Several listed herbicides are also labeled for tank-mix combinations. Read the label of each formulation for tank-mix specifications and compatibilities. There are also several premixed herbicides labeled for sweet corn.
Read the labels for specific rates recommended.
Herbicides for preemergence weed control in sweet corn.
Herbicides for postemergence weed control in sweet corn.