Evaluation of CGA-136872 and DPX-V9360 for postmergence use in corn

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Virginia Tech

The potential of CGA-136872 (3-[4,6-bis(difluoromethoxy) pyrimidin-2-yl-1-(2-methoxycarbonyl-phenylsulfonyl) urea) and DPX-V9360 (3-pyridinecarboxaminde, 2-(((4,6-dimethoxy pyrimidin-2yl) aminocarbonyl)) aminosulfonyl) ))-N,N-dimethyl) were investigated for postemergence use in corn, including corn tolerance, weed control and combinations of CGA-136872 with other postemergence corn herbicides for weed control.

CGA-136872 Applied at rates of 1.2, 2.5, 5.0 and 10.0 times the suggested recommended use rate in corn (variety Southern States 565) caused more injury at the 5-leaf stage than at the 7- and 9-leaf stage of corn. Recovery from injury was rapid and complete at 5 weeks after treatment (WAT) and no yield reduction was observed. Several corn varieties treated with twice the suggested use rate of CGA-136872 and DPX-V9360 showed injury that was both herbicide and variety dependent. Most injury occurred at 1 and 2 WAT. Corn recovery was complete at 5 WAT, but yield reduction on some varieties was observed with CGA-136872 treatments.

In the weed control study, both herbicides showed high activity on johnsongrass (Sorghum halepense (L.) Pers.), giant foxtail (Setaria faberi Herr.), common lambsquarters (Chenopodium album L.) and redroot pigweed (Amaranthus retroflexus L.), particularly with early applications. However, johnsongrass rhizome regrowth prevented full season control of this species with early postemergence applications.

Combinations of CGA-136872 with several other herbicides resulted in significant benefit in control of common lambsquarters and redroot pigweed while johnsongrass and giant foxtail control was not improved. Reduced control of johnsongrass was observed when CGA-136872 was applied in combination with paraquat (1,1’-dimethy1-4,4’-bipyridilium ion). Similar results were observed for giant foxtail control when CGA-136872 was applied with 2,4-D ((2,4-dichlorophenoxy) acetic acid) and dicamba (3,6-dichloro-2-methoxybenzoic acid).

Results of this research indicate that both CGA-136872 and DPX-V9360 have good potential for postemergence use in corn, and could represent an important supplement to existing postemergence corn herbicides.