Stripe rust of wheat may show up in Illinois this year unless the weather becomes and stays hot or dry. You may have heard about stripe rust (also called yellow rust) in other states this spring. The Arkansas Wheat Pest Management Newsletter (April 24, 2002) reports that Arkansas has experienced widespread stripe rust this spring, and stripe rust has been noted in the southeast corner of Missouri. The newsletter reports that fungicides have been applied to an estimated 200,000 to 250,000 acres of wheat in Arkansas, primarily to control stripe rust. We don't expect stripe to be a major problem in Illinois, but it is something to watch for in wheat fields. Minor levels of this disease were reported in central Illinois in 2000 and 2001, and in southern Wisconsin in 2001. Last year (2001) stripe rust was reported in central Illinois in the first week of June, but may have occurred earlier in scattered areas in the southern counties.|
Stripe rust is severely limited by climate, and this is one reason why this disease has been uncommon in Illinois. Stripe rust develops in wet and cool conditions. The disease develops most rapidly when temperatures are between 50 and 60 deg F, and stops when night temperatures are above 70 deg F. Spores may be blown up from the south to initiate infection in Illinois, and stripe rust can develop and spread quickly when weather is cool with frequent dew or rainfall. Another factor that has contributed to increased incidence of stripe rust in parts of the United States is new races of the stripe rust fungus (Puccinia striiformis). At this point we don't know which races may be most common in Illinois, although it is reasonable to consider that the common race(s) in Arkansas may become the common race(s) in Illinois too.
Stripe rust often appears earlier in the season than stem rust and leaf rust. These different rusts on wheat are distinguished by the color and pattern of the infected areas. The stripe rust pustules usually appear closely arranged in yellow stripes parallel to veins on leaves. Heads may also be infected with yellow pustules. The pustules of the other rusts are dark to light red or brown in color and are arranged singularly in an arbitrary pattern over the leaves or stems.
Stripe rust. (Photo courtesy of Bob Bowden, KSU.)
Leaf rust. (Photo courtesy of Bob Bowden, KSU.)
Stem rust. (Photo courtesy of Bob Bowden, KSU.)
Stripe rust can be managed with fungicides and to some degree with resistant wheat varieties. Some effective fungicides for control of rust include Tilt, PropiMax, Quadris, and Stratego. All of these compounds are systemic. Product labels should be consulted for proper application. If stripe rust is observed in fields with high yield potential, a decision whether or not to apply a fungicide should be made quickly, because the disease has the potential to develop rapidly if weather conditions are favorable.
The other option for management in future years may be resistant varieties, although the predominant races of the stripe rust fungus in Illinois will dictate the efficacy of different sources of resistance. Preliminary observations from Arkansas (Arkansas Wheat Pest Management Newsletter, April 17, 2002) suggest that there are differences in resistance among wheat varieties. Agripro varieties Shelby and Mallard, as well as Pioneer varieties 26R38 and 2684, were susceptible to the race(s) in Arkansas. AGS 2000, DK 1551W, and NK Coker 9663 appeared to be less susceptible in Arkansas, and they reported that field observations suggested that the following varieties had relatively fewer problems with rust this spring: AgriPro Patton, AgriPro Shiloh, Armor 3135, Armor 4045, Pioneer Variety 26R24, Pioneer Variety 2580, Delta King 9121, Delta King 9027, Delta King 9416, Sabbe, and Terral TV 8555. Again, we don't expect a major problem with stripe rust in Illinois. But this disease has the potential to be a problem, and scouting should be done to check for its appearance in Illinois.--Dean Malvick