Early reports of stripe rust and leaf rust in wheat
Stripe rust: There have been some early reports of stripe rust in Kansas this week. The K-State Extension Team has been out scouting to help document its distribution in the state. To date, most of the reports of stripe rust have come from southeast Kansas where the crop is at boot and heading stages of growth (Figure 1). There have been a few reports of stripe rust in the south central region of the state. Wheat in this part of the state is at flag leaf emergence and approaching boot stages of growth. The disease is mostly in the lower or middle canopy at the moment but there are few reports of stripe rust in the upper canopy in the southeast.
Outlook for severe stripe rust: The recent period of cool temperatures and frequent rainfall has been highly conducive for the continued spread of the disease. We will likely see more signs of disease continuing to show up over the next 14 days. What happens after this first wave of infections is critical to the development of an epidemic. The risk of severe disease and yield loss will increase if we get into another period of cool temperatures (44-55 degrees F) and frequent rains. Temperatures above 60 F at night often slow the development of stripe rust.
Leaf rust: We continue to hear reports of leaf rust in Oklahoma and Texas. The disease has caused some problems for growers in Texas and there are multiple reports of low to moderate levels of leaf rust in central Oklahoma as far north as Stillwater. We also received a report of leaf rust in wheat south of Wichita this week. We are still gathering information about this field but it appears that leaf rust is on the move in the state also.
Suggested action: It is critical that growers intensify their efforts to scout for stripe rust and leaf rust. Scouting priorities should include seed production fields, and general production fields with good yield potential that are planted to susceptible wheat varieties. Fields with stripe rust on the flag leaf or the leaf just below it (F-1) are at risk for serious yield loss and would be a candidate for fungicide application.
Information on fungicide options can be found at: http://www.bookstore.ksre.ksu.edu/pubs/EP130.pdf
Erick DeWolf, Extension Plant Pathology
Romulo Lollato, Wheat and Forages Specialist