Glyphosate application for weed control in brassica

Abstract

The disclosure provides methods of applying glyphosate to improve weed control in a field containing herbicide tolerant brassica species. More specifically, glyphosate treatments are applied to a substantial portion of herbicide tolerant brassica plants which are beyond the 2-6 leaf stage such as for example to a substantial portion of herbicide tolerant brassica plants which are at the 10% open flowers to about 10% pod stage. The disclosure provides methods that apply glyphosate at late stage brassica development.

That which is claimed: 
     
         1 . A method of applying glyphosate to improve weed control in a field containing herbicide tolerant  brassica  species, the method comprising:
 applying a glyphosate treatment comprising an effective amount of glyphosate over a population of glyphosate tolerant  brassica  plants,   wherein a substantial portion of the  brassica  plants are at about the flowering stage exhibiting at least about 10% open flowers to about 10% pod stage or beyond the flowering stage and wherein a substantial portion of open flowers or pods do not show significant discoloration post-glyphosate treatment.   
     
     
         2 . The method of  claim 1 , wherein the glyphosate tolerant  brassica  plants express a glyphosate acetyl transferase (GAT) enzyme. 
     
     
         3 . The method of  claim 1 , wherein the glyphosate tolerant  brassica  plants express a glyphosate acetyl transferase (GAT) enzyme in combination with an enzyme that provides tolerance to glufosinate herbicide. 
     
     
         4 . The method of  claim 1 , wherein the open flowers do not show significant discoloration within 5 days post-glyphosate treatment. 
     
     
         5 . The method of  claim 1 , wherein the glyphosate treatment comprises in g acid equivalent/hectare of glyphosate as the active ingredient of about 675, 1350, 2025 or 2700 in a single application. 
     
     
         6 . The method of  claim 1 , wherein the glyphosate treatment comprises up to about 5400 g acid equivalent/hectare of glyphosate as the active ingredient in one or more cumulative applications. 
     
     
         7 . A method of applying glyphosate to improve weed control in a field containing glyphosate-tolerant  brassica  species, the method comprising:
 (a) applying one or more glyphosate treatments comprising an effective amount of glyphosate over a population of glyphosate tolerant  brassica  plants, wherein a substantial portion of the  brassica  plants are at a stage that is beyond the 6-leaf stage and wherein the glyphosate tolerance is due to the expression of a glyphosate metabolizing enzyme in the  brassica  plants; and   (b) obtaining  brassica  seeds from the  brassica  plants, wherein a substantial portion of pods are not aborted post-glyphosate treatment.   
     
     
         8 . A method of preventing yield loss or yield penalty at harvest of  brassica  plants, the method comprising:
 (a) applying a first glyphosate treatment comprising an effective amount of glyphosate over a population of glyphosate tolerant  brassica  plants, wherein a substantial portion of the  brassica  plants are at the cotyledon stage and the  brassica  plants express a glyphosate metabolizing enzyme;   (b) applying one or more additional glyphosate treatments comprising an effective amount of glyphosate over a population of glyphosate tolerant  brassica  plants, wherein a substantial portion of the  brassica  plants are at a stage that is beyond the 6-leaf stage; and   (c) obtaining  brassica  seeds from the  brassica  plants, wherein the yield loss is minimized due to a substantial reduction in discoloration or pod abortion after one or more late-stage applications of glyphosate.   
     
     
         9 . The method of  claim 8 , wherein the  brassica  plants express glyphosate acetyl transferase. 
     
     
         10 . The method of  claim 8 , wherein the average  brassica  yield is reduced by no more than 5% compared to a control treatment. 
     
     
         11 . A method of weed control in a field, the method comprising:
 (a) planting a population of glyphosate tolerant  brassica  plants in the field, wherein the  brassica  plants express a glyphosate acetyl transferase enzyme; and   (b) applying a glyphosate treatment to a  brassica  field containing one or more weeds, wherein a substantial portion of the  brassica  plants are at a late developmental stage selected from the group consisting of inflorescence emergence, flowering, seed development and ripening and thereby substantially reducing the growth of weeds in the  brassica  field.   
     
     
         12 . A method of late season weed control in a field having  brassica  crop without adversely affecting the yield, the method comprising:
 (a) planting a population of  brassica  plants that are tolerant to glyphosate wherein the plants express a glyphosate metabolizing enzyme such that the expression of the enzyme results in effective glyphosate tolerance;   (b) applying an effective amount of glyphosate to the  brassica  plants wherein a substantial portion of the  brassica  plants are beyond the 6-leaf stage and wherein the glyphosate application does not result in significant chlorosis; and   (c) controlling the growth of weeds in the field and wherein the  brassica  crop yield is not reduced by more than 5% compared to control  brassica  plants not expressing the glyphosate metabolizing enzyme.   
     
     
         13 . The method of  claim 12 , wherein the glyphosate treatment comprises 1350-2700 g ae/hectare of glyphosate and a substantial portion of the  brassica  plants are at about 10% flower stage. 
     
     
         14 . The method of  claim 12 , wherein the glyphosate application further comprises a disease control agent selected from the group consisting of insecticides, fungicides, and pesticides. 
     
     
         15 . The method of  claim 12 , wherein the glyphosate application further comprises a late season nutrient application. 
     
     
         16 . The method of  claim 12 , wherein the glyphosate is premixed with a disease control agent selected from the group consisting of insecticides, fungicides, and pesticides. 
     
     
         17 . A method of controlling weeds in a  brassica  field, the method comprising applying a second glyphosate treatment to a population of glyphosate-tolerant  brassica  plants, wherein a substantial portion of the  brassica  plants are at the reproductive growth stage and wherein the  brassica  plants express a glyphosate metabolizing enzyme. 
     
     
         18 . The method of  claim 17 , wherein the glyphosate metabolizing enzyme is a GAT polypeptide. 
     
     
         19 . The method of  claim 17 , wherein the glyphosate-tolerant  brassica  plants do not express an insensitive EPSPS.