K-State Extension plant pathologists and agronomists report that stripe rust and leaf rust continue to be found on wheat in Kansas.
Stripe rust was reported in southwest and southeast Kansas this week. The disease could not be found a week ago, despite multiple reports of stripe rust in central and north central Kansas. This suggests that multiple incursions of stripe rust have occurred during the past month. Most reports are indicating that stripe rust is most active in the mid canopy, but there are a few reports of stripe rust occurring on the F-1 and flag leaves in a few locations. I've found local fields in Finney County with varying degrees of the rust present. Leaf rust also has been observed at multiple locations this past week and appears to have moved to the flag leaf in some susceptible varieties in south-central Kansas, near Hutchinson.
The wheat in Kansas ranges from flowering in southern Kansas to flag leaf emergence in northern Kansas. All information to date suggests that the risk of disease-related yield loss is high in most parts of Kansas. Oklahoma now is reporting severe stripe rust and leaf rust in many areas. Remember, Oklahoma was reporting low levels of disease just a few weeks ago — much like we are seeing in Kansas now. This suggests that (1) additional stripe rust and leaf rust are likely to move north into Kansas; and (2) the low levels of rust we are seeing in Kansas could reach damaging levels very quickly.
Growers in Kansas should be checking their fields for signs of stripe rust or leaf rust. Fields with 40-bushel yield potential and seed production fields may warrant a fungicide application. Varieties with susceptibility to multiple diseases are most likely to give a strong yield response. K-State plant pathologists suggest they might be more conservative to spraying fields with lower yield potential resulting from late planting or areas where moisture may ultimately limit yield potential.
Here is a listing of the varieties and how they tolerate the rusts that are now being found across the area: varieties with leaf rust and stripe rust susceptibility — Jagger, Jagalene, Overley, TAM 112, 2137; varieties with stripe rust susceptibility but moderately resistant to leaf rust — Fuller, PostRock, Santa Fe, Smoky Hill, Hitch, Art and varieties with resistance to stripe rust but susceptible to leaf rust — TAM 111, and T81. Compare your seeded acres with this list and make field visits on a daily basis. Timing is very important to get the greatest benefit if spraying is needed. Identifying the different kings of rust is not that difficult with a little practice and a good pictorial guide. K-State has two bulletins that are available at the Extension Office or on the website at www.ksre.ksu.edu or search for publication MF-2919 "Identifying Rust Diseases of Wheat and Barley" and EP-130, which is the "Foliar Fungicide Efficacy Rating for Wheat Disease Management 2010." The later is the guide to the different fungicides and their effectiveness if applied at the appropriate application timing.
For more information or assistance on this or other topics, please call the Extension Office at 272-3670, located at 501 S. Ninth St. in Garden City.