Early spring control of weeds in thin stands of wheat
Some areas of Kansas have unusually thin wheat stands because of dry conditions last fall and early winter. Thin, late-developing wheat is likely to have excessive weed problems because of the open space and canopy, but treatment decisions can be difficult. Residual herbicide products such as Finesse, Ally, Rave, or Amber probably will provide the best weed control because they have both foliar and soil residual activity. These types of products may be the best option is you are committed to keeping the wheat crop for grain harvest.
However, these herbicides all have crop rotation restrictions, so if there is a crop failure, you may not have a lot of recrop options. Make sure to check the recrop guidelines on all herbicides before planting a subsequent crop. If you want to keep your options open for planting a summer crop, you probably need to consider using a short-residual herbicide such as MCPA, 2,4-D, dicamba, or Affinity, but realize that these products will not provide much residual control of later-germinating weeds.
Winter annual weed control
Some wheat fields may have heavy winter annual weed infestations if moisture was received after planting last fall. There are several options available to control these weeds now. In general, the sooner this is done, and the smaller the weeds, the better the results will be. Spring applications generally are most effective on winter annual broadleaf weeds soon after green-up when weeds are still in the rosette stage of growth, and during periods of mild weather. Once weeds begin to bolt and wheat starts to develop more canopy, herbicide performance often decreases dramatically.
When applying herbicides at this time of year, near jointing, there are some timing issues related to the growth stage of wheat that producers will have to take into account.
Dicamba can be applied to wheat between the 2-leaf and jointing stages of wheat. Application of dicamba after wheat reaches the jointing stage of growth causes severe prostrate growth of wheat and significant risk of yield loss. Dicamba is effective for control of kochia, Russian thistle, and wild buckwheat, but is not good for control of mustard species. Kochia, Russian thistle, and wild buckwheat are summer annual weeds that may emerge before or after wheat starts to joint, so timing of dicamba for control of these weeds can sometimes be difficult. Fortunately, dicamba provides some residual control of these weeds following application. Herbicides containing dicamba include Banvel, Clarity, Rave, Pulsar, Agility SG, and several generic dicamba products.