Mark VanGessel, Extension Weed Specialist; mjv@udel.edu
If planting small grains as no-till or minimum tillage, be sure to “start clean” with a burndown herbicide. A turbo-till is not a tillage implement for weed control, so often these fields need a burndown herbicide. Poor weed control is often due to the weeds being too large and that can be traced back to not starting clean.
There has been an interest in using herbicides at planting (or shortly after planting) for weed control. There are few effective herbicides labeled for preemergence applications. Sharpen is labeled for wheat and barley but provides limited control. Valor or Afforia can be used with the burndown application, but there must be a minimum of 7 days between application and planting wheat. We have seen injury with Afforia or Valor used on coarse-textured soils, particularly if rain occurs shortly after planting or if seed is planted less than 1 inch deep.
Axiom, Anthem Flex and Zidua can be used after wheat emergence, typically at the spike stage. These products are only labeled for winter wheat, not barley. They do not provide control of emerged weeds but can have utility in situations where application can be made after wheat emergence but before weed emergence. These three herbicides require rainfall or irrigation to activate, so if we experience a dry spell after application, control can be compromised.
Axiom, Anthem Flex, Zidua, Valor and Afforia all specify that the seed must be planted at least 1 inch deep. None of these products are compatible with wheat planted by “spinning the seeds” on the soil surface and shallow incorporation with a disk or turbo-till.
As far as postemergence treatments, fall herbicide applications have been more consistent and had overall better weed control than many spring application treatments in our trials. The soil temperature remains warm for weeks after the first frost and this keeps the weeds in an active state. I find annual bluegrass, henbit, or speedwell species are often more susceptible if treated in the fall compared to early spring. Once we have consistently cold weather and soil temperatures drop, then fall treatments will be questionable. Fields may need a spring herbicide application for wild garlic control, but often broadleaf weed control is excellent with that fall treatment.