by Dr. Clark Neely, Statewide Small Grains and Oilseed Extension Specialist

Weather conditions have been drier this fall and winter than the previous two years, which is having a positive impact on wheat rust presence across the state. This time last year, producers were dealing with widespread reports of stripe rust in their wheat fields due to wet conditions (Fig. 1). This year, stripe rust has been reported in a few locations throughout Central and South Texas, however, pressure appears lighter overall and observed mainly in highly susceptible border plots (‘TAM 111’) in research trials. A few reports of very light stripe rust in producer fields in the central Blacklands was reported also. Light pressure was reported in an Ellis County trial and trace amounts were found in trials near Thrall and College Station. No stripe rust has yet been found in South Texas (Uvalde, Castroville, Corpus Christi), Northeast Texas (Greenville), or the Rolling Plains. Though inoculum is currently low, forecasted weather conditions appear to be favorable for further development beginning this weekend through mid-week as a large percentage of the state is expected to receive an inch or more of precipitation and coincide with cooler temperatures. Therefore, producers in the Blacklands should keep an eye on wheat fields over the next couple of weeks to watch for further stripe rust development.

Meanwhile, leaf rust is present in much of Southeast Texas (Fig. 2). Research plots in Thrall, College Station and Wharton all show moderate leaf rust pressure so far. Light levels of leaf rust are also reported in producer fields in Hill and McLennan Counties with a single severe case reported in ‘TAM 304’ that was sprayed with a fungicide. With plenty of inoculum present, this disease is likely to spread once temperatures increase in the coming weeks, though moisture conditions throughout the spring will influence the degree and speed to which it will increase. As of two weeks ago, leaf rust was not observed at Uvalde or the Castroville nursery and recent reports indicate little to no leaf rust further north in Northeast Texas and the Rolling Plains.

Overall wheat acreage in Texas is down to 4.5 million planted acres, the lowest since 1972. With a significant reduction in acreage, particularly in South Texas and the Coastal Bend regions, there will be less inoculum to blow northward than in a typical year. This, combined with drier conditions this winter, is likely to lead to much less stripe rust in Texas wheat for the 2017 season compared to the past two years, however, the impact of leaf rust is uncertain at this time. For rust control, flag leaf emergence remains a critical stage for fungicide applications in order to protect yield. Unlike stripe rust, applying an early fungicide application to control leaf rust alone is still uncertain whether it is an economically sound practice. However, applying cheap generic fungicides such as Tebuconazole does limit risk since it involves little investment and can often be applied while topdressing or spraying herbicides in the spring. More information on rust identification and fungicide trial results in wheat can be found at http://sickcrops.tamu.edu and http://varietytesting.tamu.edu/wheat.

Figure 1. Stripe rust observed on winter wheat (Texas A&M AgriLife Extension photo by Dr. Clark Neely)

Figure 2. Leaf rust observed on winter wheat (Texas A&M AgriLife Extension photo by Dr. Clark Neely)

Clark Neely
State Small Grains Agronomist
College Station, TX
cneely@ag.tamu.edu