Monday, November 13, 2006
24-3

Soil Applied Residual Herbicide Affect on Conventional and Imidazolinone Resistant Canola in the Southeastern US.

Timothy Grey, Paul Raymer, and G. David Buntin. Univ of Georgia, Crop and Soil Science Dept, 115 Coastal Way, P.O. Box 748, Tifton, GA 31794

Weed control in southeastern US crop and vegetable production utilizes residual herbicides that have rotational restrictions for canola.  Traditional (c.v. ‘Flint’) and imi-resistant (Clearfield) canola have potential as a winter crop in this region.  However, rotational issues must be considered.  Imi-resistant canola may be more suited for rotation in southeastern production due to the prevalence of acetolactate synthase (ALS) inhibiting chemistries.  The ALS herbicides imazapic, diclosulam, chlorimuron, pyrithiobac, and trifloxysulfuron are used for weed control in this area.  Protoporphyrinogen oxidase (PPO) herbicides flumioxazin, fomesafen, and sulfentrazone are also used.  Rotational restrictions for herbicide registrations are based on traditional canola, but not for imi-resistant cultivars.  Hence, rotationally planted canola following cotton, peanut, soybean, vegetables, or corn could experience stand failure due to injury from previously applied herbicides.  Research was conducted to determine herbicide tolerance levels for traditional and imi-resistant canola to the previously stated ALS and PPO herbicides at ¼, ½, and 1x active ingredient rates.  Imi-resistant and Flint canola exhibited extensive injury, nearly complete stand failure and crop loss with PPO herbicides flumioxazin, fomesafen, and sulfentrazone at all rates.  For the ALS herbicides imazapic, chlorimuron, pyrithiobac, and trifloxysulfuron, imi-resistant canola injury was 17% or less for all rates and yields were not different from the control.  Imi-resistant canola exhibited excellent tolerance to imazapic at any rate.  In contrast, Flint canola exhibited 57% injury or greater and yield reductions for imazapic, chlorimuron, pyrithiobac, diclosulam, and trifloxysulfuron at all rates.  Imi-resistant canola exhibited dose response injury of 21, 43, and 63% for ¼, ½, and 1x rates of diclosulam, respectively.  Additionally, stand was reduced from 26 to 14 plants/m row when comparing the control to diclosulam at 26 g/ha, respectively.  This indicates imi-resistant canola is not resistant to all ALS herbicides and this should be considered when planning rotational options for canola.  

Handout (.ppt format, 1580.0 kb)

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