Sweet Corn Herbicide Weed Control Study
Kai Umeda, G. Gal, and B. Strickland
Season-long near complete weed control in sweet corn was achieved with preemergence (PREE) herbicide applications of pendimethalin (Prowl®), metolachlor (Dual®), or thiafluamide/metribuzin (Axiom®) followed by postemergence applications of bentazon (Basagran®) or dicamba (Banvel®). Basagran applied alone POST gave very good control (>93%) of lambsquarters (Chenopodium album) and purslane (Portulaca oleracea) but did not adequately control tumble pigweed (Amaranthus albus). Prowl applied alone PREE gave acceptable control of most weeds. POST applications of prosulfuron/primisulfuron (Exceed®) caused moderate corn injury by shortening internodes and overall plant height and slight foliar chlorosis.
Herbicides may occasionally be necessary for managing weed populations in sweet corn grown in Arizona. PREE applied herbicides should be used in fields where known weed infestations will occur in a crop and POST applied herbicides might be useful if unexpected weed infestations escape tillage operations or other soil applied herbicide treatments. A sequence of PREE and POST herbicides may also be necessary in situations where weeds are a severe problem. Axiom and Exceed are relatively new herbicides recently introduced in the major corn growing regions of the U.S. The objective of this study was to evaluate potential herbicide weed control programs for sweet corn using newer chemistry herbicides applied alone or in sequential combinations.
Materials and Methods
A small plot field study was conducted at the University of Arizona Maricopa Agricultural Center, Maricopa, AZ. The test was set up as a randomized complete block design with three replicates and each plot consisted of two 40-inch beds measuring 40 feet in length. The field was listed and then beds were shaped using a "sidewinder" power incorporator-bed shaper. Sweet corn cv. Sugar Ace was planted in a single row on each bed on 04 Mar 1997. Treatments were applied using a hand-held boom with four flat fan 8002 nozzle tips spaced 20 inches apart. The treatments were sprayed with a backpack CO2 sprayer pressurized to 40 psi and delivering 25 gpa water. PREE herbicide treatments were applied on the following day on 05 Mar when the weather was clear with a slight breeze and air temperature was 75 E F. Water was applied immediately after herbicide applications using furrow irrigation and the beds were wetted completely across the surface to activate the PREE herbicides. The sweet corn was furrow irrigated as necessary during the growing season. POST herbicide applications were made on 07 Apr when the corn was at the 6-leaf stage of growth. The weeds present at the time of application were Amaranthus spp. (pigweeds) at the 4- to 8-leaf stage, Chenopodium album (lambsquarters) at the 4- to 6-leaf stage, and Portulaca oleracea (purslane) at the 10-leaf stage. The weather conditions for the POST applications were clear with slight breezes and air temperature at 74 E F. Weed control and sweet corn injury visual observations were taken on 31 Mar at 26 days after treatment (DAT) of the PREE applications and on 16 and 29 Apr at 9 and 22 DAT after the POST applications. The sweet corn was harvested on 04 Jun to determine the influence of the weed control practices on marketable yield.
Results and Conclusions
The PREE herbicide applications did not cause any visible sweet corn injury at any of the rating dates. Sweet corn injury was observed only for POST treatments of Exceed alone or when following PREE treatments. At 9 DAT, Exceed caused a streaking chlorosis on the corn foliage and slight height reduction. Exceed treated corn generally yielded less sweet corn when compared to the other POST treated corn.
Prowl gave acceptable season-long control (>85%) of pigweeds, lambsquarters, and purslane. Axiom provided near acceptable weed control of all weeds. Dual adequately controlled pigweeds and purslane but lambsquarters control was not acceptable. Basagran applied POST alone gave good control (>90%) of most weeds except tumble pigweed control was marginal at 83%. Banvel and Exceed gave marginally acceptable weed control (85%) of most weeds except Exceed alone did not control lambsquarters. Near complete weed control (>98%) was observed for Prowl plus Basagran, Prowl plus Banvel, Dual plus Basagran, and Axiom plus Basagran treated plots. Combinations of PREE followed by POST treatments improved weed control from acceptable levels to near complete control compared to when either was used alone.
The yields of harvested marketable ears showed that the herbicide treated sweet corn produced more number of ears than the untreated check except the treatment of Axiom alone applied PREE. Other Axiom treated sweet corn yielded slightly less than other treatments but did not differ significantly. Prowl, Basagran, and Banvel treated sweet corn tended to give yields with higher total weight per plot. Treatments that did not adequately control lambsquarters generally had less total sweet corn weight per plot than when better weed control was achieved.
This is a part of publication az1101:
"1998 Vegetable Report," College of Agriculture, The University of Arizona,
Tucson, Arizona, 85721.