Over the past couple of weeks I have heard several people discuss their fungicide intentions for the remainder of the wheat season. During the past two weeks quite a few fields have been observed to have severe stripe rust “hot spots” in localized areas that in some cases have developed into much larger areas in short periods of time. But, with that said, all fields do not contain hot spots and this requires a good deal of scouting to verify the presence of the disease. A popular fungicide chemistry for use in wheat, especially to manage such diseases as stripe rust (based on efficacy as well as cost), have been products that contain the active ingredient tebuconazole as a stand-alone product. The specific products with a label for wheat include:
NOTE: some of the above products may have a Federal label but NOT be labeled for application to wheat in Mississippi. Based on my search it appears that Embrace may not labeled for use in MS.
The labeled rate for application in wheat is 4 fl oz/A. However, keep in mind, that ALL of the fungicides listed above make one specific restriction that is clearly defined on the label:
“A maximum of 4 fI. oz. of a product may be applied per acre per crop season.“
Therefore, if you have applied a stand-alone tebuconazole fungicide this season you cannot come back at a later application timing (such as 10.5; heading complete and immediately prior to beginning flowering) and make an application with Prosaro. Even though information is lacking on the Prosaro label as to this specific restriction the terminology on the Prosaro (prothioconazole + tebuconazole) label also indicates that a maximum of 8.2 fl oz/A of Prosaro can be applied per acre per crop season. A full label rate, or 8.2 fl oz/A of Prosaro, contains 4 fl oz of tebuconazole.
Please keep this in mind prior to deciding on a fungicide application product. I suspect that much of the decision regarding the use of Prosaro as a fungicide late in the season is simply due to one of the latest application timings available on the label in addition to being a good product for preventing Fusarium head blight (Feekes 10.5.1; beginning flowering). Several other fungicides have a label for Fusarium head blight, as well as a late, Feekes 10.5, application timing pre-harvest interval should you need to make an application of a fungicide targeted at Fusarium head blight.