New corn herbicides receive federal registration

Four new herbicide products containing the new active ingredient pyroxasulfone have received federal registration and will be available for use on corn this spring in Kansas.

Pyroxasulfone, developed by Kumiai Chemical Industry Co., Ltd., inhibits long chain fatty acid development, killing the susceptible weed seedling before emergence. Like other chloroacetamide herbicides, pyroxasulfone is classified as a seedling growth inhibitor. Examples of other chloroacetamide seedling growth inhibitor products include acetachlor (Harness, Degree, TopNotch, Breakfree, Surpass, others), alachlor (Intrro, MicroTech, others), dimethenamid (Outlook, others), and S-metolachlor (Dual II Magnum, others). These products control weeds in a very similar manner as pyroxasulfone.

As a seedling growth inhibitor, pyroxasulfone must be activated by rainfall and absorbed by the root and shoot tissues before the weeds have emerged to be effective. The pyroxasulfone products provide residual, preemergence control of many small-seeded broadleaf and grassy weeds, along with some large-seeded broadleaf weeds, including velvetleaf. 

Pyroxasulfone products will provide excellent control of pigweed species including Palmer amaranth and waterhemp, Eastern black nightshade, and annual grasses including barnyardgrass, crabgrass, fall panicum, foxtails, witchgrass, and others. Additional broadleaf weeds that pyroxasulfone may control include marestail, kochia, common lambsquarters, morningglory, common ragweed, prickly sida, and others. This includes populations of the weeds listed above that are resistant to other herbicides, such as ALS-inhibitors, ACCase inhibitors, triazines, and glyphosate.

If any of these weeds has emerged at the time of application, pyroxasulfone will not control them. 

The products registered for corn include one with pyroxasulfone alone, and three premixed with other herbicides.

Zidua (BASF) -- pyroxasulfone

Zidua is the only product that contains pyroxasulfone only. It is now registered on corn, and at some future time it may be registered on soybeans, wheat, cotton and sunflower. Zidua can be applied in the fall, early preplant, preemergence, and early postemergence up to 4-leaf corn. It has no activity on emerged weeds when applied as an early postemergence, thus must be tankmixed with other effective herbicides to provide control of emerged weeds. 

• Use rate: 1.5 to 4 oz product/ acre, 85% WG pyroxasulfone
• Use preemergence at 1.5 to 2.75 oz/acre on coarse soils, 2.0 to 3.0 oz/acre on medium soils, and 2.5 to 4 oz/acre on fine-textured soils. Do not apply more than a total of 2.75 oz/acre on coarse soils and 5 oz/acre on medium- and fine-textured soils per crop season.
• Controls grass and broadleaf weeds, including pigweeds. Has more activity on velvetleaf and morningglory than other chloroacetamides
• Before applying to sweet corn, popcorn or inbred lines of seed corn, verify with seed company the response to Zidua to avoid potential crop injury.
• Preharvest interval for sweet corn for human consumption is 37 days. 

We have tested pyroxasulfone products in corn at K-State. The results of some of our 2012 tests are in the three charts below.