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Title: HERBICIDE COMBINATIONS FOR WEED MANAGEMENT IN GLYPHOSATE-RESISTANT SOYBEAN (GLYCINE MAX)

Author
item GONZINI, LISA - UNIV OF ILLINOIS
item HART, STEPHEN - UNIV OF ILLINOIS
item Wax, Loyd

Submitted to: Weed Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/10/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: We conducted field experiments over two locations and two years in Illinois to compare weed management using preemergence (PRE) herbicides followed by glyphosate, or postemergence (POST) tank-mix combinations of glyphosate and other herbicides, with glyphosate applied alone in single or sequential applications. In most situations, use of a tank-mix partner or a PRE herbicide followed by glyphosate improved weed control, compared with a single application of glyphosate, and was as good as sequential applications of glyphosate. Control of giant foxtail exceeded 90% for single applications of glyphosate except at one location in 1995, when late emergence occurred. A PRE grass herbicide or a late postemergence (LPOST) application of glyphosate was necessary for season-long control of late-emerging giant foxtail. Tank-mixing glyphosate with selected other herbicides or applying glyphosate LPOST following these herbicides improved giant foxtail control. A single application of glyphosate was not as effective on common lambsquarters as were PRE herbicides followed by glyphosate or sequential applications of glyphosate. Velvetleaf control with a single application of glyphosate was only fair. PRE herbicides, followed by glyphosate, or sequential applications of glyphosate, improved velvetleaf control compared with a single application of glyphosate. These studies demonstrated various effective methods of managing common annual weeds in soybean production using glyphosate-resistant soybeans, and will be useful to public and private sector personnel who are conducting research and developing weed management guidelines for soybean production.

Technical Abstract: Field experiments over two locations and two years in Illinois compared weed control using preemergence (PRE) herbicides followed by glyphosate, or postemergence (POST) tank-mix combinations of glyphosate and acetolactate synthase (ALS)-inhibiting herbicides, with glyphosate applied in single or sequential applications. Overall, the use of a tank-mix partner or a PRE herbicide followed by glyphosate improved weed control compared to a single application of glyphosate, and was as good as with sequential applications of glyphosate. Control of giant foxtail exceeded 90% for single applications of glyphosate except at DeKalb in 1995, when late emergence occurred after POST applications. A PRE grass herbicide or a late postemergence (LPOST) application of glyphosate was necessary for season-long control of late-emerging giant foxtail. Tank-mixing glyphosate with imazethapyr, cloransulam-methyl, and CGA-277276 or applying glyphosate LPOST following these herbicides improved giant foxtail control compared with these herbicides applied alone. A single application of glyphosate was not as effective on common lambsquarters as were PRE herbicides followed by glyphosate or sequential applications of glyphosate. Velvetleaf control with a single application of glyphosate ranged from 55 to 78%. PRE herbicides, followed by glyphosate, or sequential applications of glyphosate, improved velvetleaf control compared to a single application of glyphosate. In some cases, adding glyphosate to a POST application of imazethapyr or CGA-277476 improved control of velvetleaf, but decreased velvetleaf control when added to cloransulam-methyl.