Reports of stripe rust have been steadily coming in over the last week, and now it is being reported in 17 counties in Arkansas. Realistically, stripe rust is throughout the delta region and has been reported as far north as the Missouri Boot Heel. To date, there have been no reports of stripe rust on the western side of the state. With the strong southerly winds we have had the past few days, spores have most likely been spread throughout the region and points much further north.
I have compiled a list of wheat varieties that stripe rust is showing up on. The varieties listed are from fields or plots where stripe rust has been verified. This is a not an all-inclusive list, but it indicates varieties which have been reported as having stripe rust so far this year. All wheat fields need to be carefully scouted even if your variety is not listed below.
|AGS 2035||Delta Grow 4500||Dyna-Gro 9053||Progeny 117||Terral TV8525|
|AGS 2060||Delta Grow 7500||Dyna-Gro Baldwin||Progeny 185||Terral TV8848|
|Armor Renegade||Delta Grow 8600||HBK 3266||Roane||USG 3562|
|Armor Ricochet||Delta King 9577||Jamestown||Syngenta Arcadia|
|Croplan Gen. 8925||Dixie 454||Pioneer 26R20||Syngenta Beretta|
|Croplan Gen. 9004||Dixie Bell 620||Pioneer 26R22||Syngenta Oakes|
The following are recommendations from Dr. Gene Milus, Professor of Plant Pathology at the University of Arkansas:
The early and widespread findings of stripe rust across most of the wheat-growing regions of Arkansas could have significant impacts on yield, test weight, and profitability. Conditions for stripe rust usually are also favorable for high yields, so yield potentials could be above average this season. However, managing stripe rust will be a key component for realizing these above-average yield potentials. The most cost-effective means of managing stripe rust at this time of the season is to scout your wheat fields and apply a fungicide sooner rather than later if conditions warrant a fungicide application.
Because of the unusual nature of this year’s epidemic, it would be wise to scout all fields regardless of variety. However, known susceptible varieties such as Armor Renegade, Croplan Genetics 544W, Hornbeck 3266, Progeny 185 and previously resistant varieties with multiple reports of significant stripe rust such as Syngenta Beretta and Progeny 117, should receive higher priority for scouting. At this time, it is important to identify fields with “hot spots” of stripe rust. Each hot spot likely is the result of a single spore infecting a single leaf last fall. Because of the mild winter, these fall infections have multiplied and spread to surrounding plants much earlier than normal. Based on observations from east-central Arkansas, hot spots are huge for this time of season and growth stage of wheat plants, and spores from hot spots have already spread across the field and likely to other fields on prevailing winds that have been blowing hard out of the south for the past several days. The current rains passing through the state will provide moisture for dew formation over the next couple weeks that is necessary for spores to infect plants. It takes about 2 weeks from the time of infection until stripe rust lesions are visible on the leaves. Therefore, if there are hot spots in a field, there likely will be an explosion of stripe rust across that field 2 to 3 weeks from now when new infections become evident.
If one or more hot spots are found in a field, the field should be sprayed with a fungicide. If fields with hot spots have not been sprayed yet, they should be sprayed as soon as weather permits. Fungicides only need about 1 hour of drying to be rain-fast. It is okay to apply fungicides to plants with dew as long as the dew dries for 1 hour before a rain. Any of the registered wheat fungicides will work, but propiconazole (Tilt and generics) and tebuconazole (Folicur and generics) are the least expensive and best for stopping infections that have already occurred and ok for stopping new infections. Strobilurin fungicides such as azoxystrobin (Quadris) and pyraclostrobin (Headline) are best for preventing new infections but weak for stopping existing infections. Combination products such as Quilt, Stratego, Absolute, and Twinline are good for stopping both new and existing infections. Prosaro (prothioconazole + tebuconazole) and Caramba (metconazole) are primarily used at flowering time to suppress fusarium head blight (scab). Timing (last week, yesterday, today, or tomorrow) is more important than the particular fungicide used. A second fungicide application may be needed, so don’t spend a lot on this early application.
If you have questions or concerns about wheat stripe rust, please contact Extension Wheat Specialist, Dr. Jason Kelley at firstname.lastname@example.org, or Dr. Gene Milus, Professor of Plant Pathology, at email@example.com, or refer to your local County Extension Agent.