 |
Crop Weeds |
|
|
|
Barley Injury Potential from Wild Oat Herbicides
Alvin J. Bussan, Crop Weed Extension Specialist, MSU-Bozeman
Dry conditions are stressing barley seedlings prior to irrigation. As a result research plots at Huntley and Amsterdam, MT, have shown severe injury to barley following both Puma and Achieve herbicide applications.
Drought stress decreases the ability of plants to metabolize and deactivate herbicide after it enters wheat. As a result, it persists in its herbicidal form inside the plant and is able to inhibit the enzyme at the site of action resulting in crop injury.
Barley injury due to Achieve or Puma will occur at the growing points. Whorl leaves will appear chlorotic or have chlorotic stripes or zones. Under worst case scenarios, whorl leaves will turn necrotic and regrowth is unlikely if the whorl leaf can be easily pulled from the plant and the bottom appears pinched off. If this occurs the primary tiller is dead and the plants will likely die over time.
What to do to prevent the injury?
1) Wait until the growing conditions change. Either wait for significant precipitation to occur so that the barley plants start growing or irrigate prior to application of Achieve or Puma. This should allow plants to metabolize the herbicide and prevent injury.
2) Apply prior to jointing. At the jointing stage, seed head formation occurs and increases barley susceptibility to injury.
3) Do not apply herbicides when night time temperatures approach freezing. Freezing and or frost can shut down plant metabolism as well. Combinations of drought stress and cool/freezing night time temperatures can have dramatic effects on injury potential. Puma should not be applied when night temperatures approach 40 F. Achieve should not be applied when night temperatures approach freezing.
4) Tank mix herbicides with growth regulating herbicides. Puma in particular is safened when applied in combination with MCPA ester.
5) Jim Mickelson at the Southern Agricultural Research Center in Huntley has noted decreased injury in barley following Puma application if he delayed irrigation for several days after application. Not sure how or why this happened or if it is repeatable, but may be of value to growers who flood irrigate and cannot water prior to herbicide application.
Barley is more sensitive than wheat to injury from Achieve, Puma, and other herbicides in this chemical family (Hoelon and Discover). However, wheat may show injury under stress conditions as well. If crop injury to barley or wheat does occur, contact the dealer who provided the herbicide or made the application immediately. That way an assessment of the injury can be made as soon as possible and remedies can be identified and implemented to minimize potential yield impacts.