Stripe rust outlook for 2018
The days are getting longer and temperatures are giving us all hope for spring. This is also the time of year that producers start asking about the outlook for wheat diseases in Kansas.
Recent research suggests that regional weather conditions early in the growing season influence the risk of problems with stripe rust. This research identified that regional soil moisture conditions in February are strongly associated with outbreaks of stripe rust. Weather conditions in Texas appear to play a critical role in the development of regional outbreaks of stripe rust. Keep in mind that the wheat in Texas is actively growing this time of year and often approaching the jointing stages of growth by the end February. Outbreaks of stripe rust in Texas during February often set the stage for the disease to move north into Kansas and the Central Plains. The research noted that wet conditions in key wheat-producing regions of central Texas often increase the risk of regional outbreaks of stripe rust. Dry conditions in this region often suppress the risk of outbreaks. Maps of soil moisture conditions in February help illustrate this pattern (Figure 1). In these maps, dry conditions are shown as red or orange colors, wet conditions are green, and white is “mid-range” (neither unusually dry nor wet). Notice that in the low disease years, dry conditions dominate in central and south central Texas. In years with severe disease, mid-range soil conditions are prevalent in these same regions of the country. The map for this year indicates the risk of severe stripe rust is low-to-moderate at the current time. Let’s keep an eye on the disease situation and see what develops this year.
Figure 1. Maps of soil moisture levels in the central and southern Great Plains region from 2013-2018. Research indicates that soil moisture conditions in central Texas are often associated with regional outbreaks of stripe rust. Dry conditions in these regions often decrease the risk of severe disease. Mid-range or wet conditions favor disease development and regional outbreaks of disease. Soil moisture maps are based on NOAA “Palmer Z-Index”.
Observations of Disease
Scouting reports from Texas and Oklahoma are also useful sources of information. Remember, reports of problems with rust to our south this time of year often indicates that we are heading for trouble here in Kansas. So far, reports from Texas indicate that rust was not an issue at most locations. However, stripe rust was reported at one research location west of San Antonio suggesting at least some risk for problems with stripe rust this year. To date, there have been no reports of stripe rust from Oklahoma in 2018. Trace levels of leaf rust were detected near Stillwater by Bob Hunger, OSU Plant Pathologist. Reports of leaf rust are not unusual for this time of year and are not cause for major concern. We should monitor the disease situation in Texas and Oklahoma carefully over the next month. At the moment, it appears dry conditions are holding the diseases in check and the risk of severe problems with stripe rust and leaf rust is moderate to low.
Erick DeWolf, Extension Plant Pathologist