Amanda de Oliveira Silva, Small Grains Extension Specialist and Misha Manuchehri, Weed Extension Specialist

November has been cooler than normal and that has limited wheat growth across the state. Most of fields where wheat was planted earlier have the crown roots slowly developing and top growth is lower than expected. Many of these fields have very thin stands and will probably not have enough forage to feed the cattle. In many areas, planting was delayed due to either lack or excess of moisture. Most of fields that were planted late are at 1-2 leaf stage with seminal roots developing. Plants are showing signs of cold injury but should grow out of it well.

Fall or Spring Herbicide Application for a slow-developing wheat?

Moisture has been plentiful in many areas in Oklahoma this fall. As a result, several winter annual weeds have emerged. These weeds are competing well with our wheat crop, which is behind in many areas due to cold temperatures. If you are investing in a herbicide application this year, you may be thinking “when should I apply”? The answer is not always simple but there are several things to consider before making this decision.

1. Is your wheat at an approved growth stage per the herbicide label?

Many postemergence herbicides labelled for use in wheat recommend the crop be at 2 or 3 leaves. Be sure to check these requirements to ensure crop safety.

2. What are your target weeds?

Many producers chose to apply a postemergence herbicide in the spring when top-dressing N to limit the number of passes made across their fields. This often makes sense for weeds that have multiple flushes, as two applications often are not financially feasible. For example, Italian ryegrass that is not managed with a delayed preemergence herbicide (Anthem Flex, Axiom, or Zidua) may be sprayed in the late winter vs. fall to target multiple flushes. On the other hand, early emerging, difficult-to-control grasses like rescuegrass, are best managed in the fall before entering “dormancy”.

3. What are daytime temperatures like? Are your wheat and weeds actively growing?

All postemergence herbicides labelled in wheat move in living tissue. Herbicide application will be most successful when your wheat AND your weeds are actively growing.

4. Have you applied this product before? Was it successful at that timing?

We can learn a lot from field history. If a product wasn’t successful in the past, we need to learn why so that we can make the necessary changes to increase its success or perhaps it is time to use a new weed management method. Finally, selection for herbicide resistant weed biotypes can occur quickly. If you are unsure if you have resistance, please send in a seed sample to the weed science lab.