Of the fields scouted across the state, about 25 percent had symptoms of stripe rust at varying levels of prevalence within a field.
Stripe rust has increased substantially during the past week in some areas of North Dakota.
The higher severities are being reported in winter and spring wheat fields. The greatest severities are in northern counties where weather conditions have been consistently cooler and wetter than much of the state, but some other locations also are reporting fairly abundant stripe rust.
Of the fields scouted last week across the state, about 25 percent had symptoms of stripe rust at varying levels of prevalence within a field.
“In some fields, there were heavy orange stripes of spores, while in other fields, stripe rust lesions are going into the overwintering, dormant stage,” says Marcia McMullen, North Dakota State University Extension Service plant pathologist. “In the black spore stage, the long stripes turn black and don’t disperse to infect the crop during the summer.”
This week’s heat in parts of the state may push the crop and result in more stripe rust spores going into the dormant or black spore stage.
Many wheat fields may be too advanced in growth stage (past flowering) for a fungicide application (remember preharvest intervals of fungicides used) or the disease may be too advanced for successful management (flag leaf with greater than 1 to 5 percent severity or going into the black spore stage).
“A fungicide application on infected leaves will not rescue the leaf tissue,” McMullen says. “However, if the crop is still in the boot or early heading stage, with only a few pustules of stripe rust, growers may need to treat with a fungicide as soon as possible because the stripe rust can advance rapidly when moderate temperatures and dew occur.”
Fungicides to control stripe rust have not been evaluated in North Dakota. However, wheat pathologists from states such as Kansas and Nebraska have concluded that Headline, Caramba, Folicur, Prosaro, Twinline, Quilt and Quilt Excel provide excellent control. Products with very good control are Tilt, Stratego EC and Stratego Yld.
For more information on wheat rust diseases, click here.