Overall, the wheat started slow out the gate, but has started to finally get some growth as of late.
Wheat grain producers are starting to estimate the potential for this crop and are beginning to initiate spring management practices. Topdressing season already has started, and potential weed, insect and disease issues are on the horizon.
As far as how late can wheat be topdressed with nitrogen, field research conducted by Oklahoma State University the past three seasons has shown it might be later than your think. These grain-only trials have proven that topdress applications made 80-100 growing degree days after planting, typically early to mid-March, yielded the same as early and late-winter applications. Wheat quality, particularly grain protein, seemed to increase with later nitrogen applications as well.
This doesn’t mean to wait until the last minute to topdress, but supports extending the window to apply nitrogen. Applying later in the season can increase nitrogen use efficiency. As the crop progresses, a better estimation of grain yield can be more accurately determined and topdress rates can be altered accordingly. If covering large acreage, wheat producers should initiate topdress applications sooner to allow enough time to get the job done especially if weather delays application.
In addition to topdressing nitrogen, disease management has shown to have good yield savings over the years. If applied timely, most commercially available fungicides have had good yield protection in OSU field trials. If only one application is budgeted, it is best to apply late and protect the flag leaf. Long-term data typically average about 10 to 20% yield increase compared to no fungicide.
The OSU variety trial near Lahoma has evaluated more than 50 wheat varieties with and without a fungicide applied around the boot to flagleaf growth stage. Some varieties had good rust resistance and had little to no benefit to a fungicide application, while others had yield reductions of 20 to 40%. Including all varieties at Lahoma, there has been a 22.7% average increase in grain yield over the past six years when a fungicide was applied.
The disease has to be present to save yield with a fungicide application. Knowing whether or not your wheat variety has good tolerance or resistance to leaf diseases is another factor to be considered. At current wheat prices, if the wheat has a yield potential of at least 30 bushels per acre, then more than likely it will be economical to apply a fungicide.
Timely field scouting is the only way to determine if a pest is present and if an application of an herbicide, insecticide or fungicide is warranted. The only way for one of these pesticides to protect yield and have a positive return on investment would be knowing what pests are present and knowing how much yield potential can be saved if applied correctly.