Second herbicide application: A scenario

A Canola Watch reader sent us this question: I have wild buckwheat at the 3- to 4-leaf stage that somehow got missed with the first application of Liberty 10 days ago . It’s moderate in severity. Will it cause me grief at swath timing? And will it have any effect on yield? Crop stage is 6-leaf or so.

Wild buckwheat (not the farmer’s field)

Answer: If the farmer is going to spray, it has to happen now. Liberty is only registered on wild buckwheat up to the 3-leaf stage and the window for Liberty closes at the pre-bolting stage of the crop. If he can look in the centre of the plant at the main growing point and see buds forming it is too late. With crop at or past the 6-leaf stage, the yield effect of the buckwheat will be minimal. But if he doesn’t spray, he will likely return a lot of seeds to the seed bank and could run into harvest difficulty. Wild buckwheat will definitely wrap on header reels. Buckwheat control should be a priority in next year’s crop. 

Is a second herbicide application necessary?