Weighing the benefit of recent rains has produced both a sigh of relief and an added sigh of concern from farmers in Kansas and Nebraska. Welcome rainfall and the subsequent trigger of the stripe rust disease are the key topics of conversation among farmers and agronomists now.
“I typically spray for stripe rust. Although I’ve aerial sprayed before, I think I’ll have it sprayed with a self-propelled ground rig to save a few dollars an acre,” said Jim Burton, of Haddam, Kan., a fifth-generation farmer. Burton grows
wheat, corn and soybeans.
The recommended time to spray fungicide is through mid-May.
“Once the flag leaf is out, but before the wheat head starts to flower, is the ideal time to spray to protect wheat yield,” explained Bruce Ball, owner of Rural Gas in Belleville, Kan., a commercial spraying and fertilizer operation.
Stripe rust is showing up in low levels in central Kansas. However, a Kansas State University agronomist told Midwest Producer that there’s been “an explosion of stripe rust in far southeast Kansas.”
“Many fields in southeast Kansas have been sprayed but there’s some significant damage already. Because of drier conditions further west and north, stripe rust has been slow to develop, but is out there and will increase in severity by mid-May,” said Douglas Shoup, K-State Southeast Area Extension agronomist in Chanute.
The rain increased the risk of stripe rust inching up into the critical upper leaves.
“This movement to the upper leaves is important because they contribute most of the energy used by the plant to make grain, said Erick DeWolf, Kansas State University Extension plant pathologist, referring to his latest e-update.
DeWolf advised, if stripe rust was not a concern before the rains, then producers still have some time to scout their fields and evaluate the plants before deciding whether to apply a fungicide.
“However, if stripe rust was already present on the lower leaves, it may quickly
spread, so applying fungicide may be beneficial,” he said. “However, if stripe rust has spread to 25 percent or more of the upper leaves, the crop would be less likely to benefit from a fungicide.”
Another agronomist notes, in any area where rainfall occurs when the wheat is actively flowering, the chances of fusarium head blight increases dramatically.
“Growers with varieties susceptible to fusarium and stripe rust may want to time their spray with an appropriate fungicide for fusarium control,” said Stu Duncan, Extension crops and soils specialist, KState’s Northeast Area Extension office in Manhattan. “Also, there’s freeze damage in southern Saline County in central Kansas, resulting from freezing temperatures March 25 and April 11-12, and there’s bad hail damage in Washington, Marshall and Nemaha Counties from April 24 and 25 storms,” added Duncan.
In northwest Kansas, the wheat crop is drinking in the rainfall and not negatively affected at this point. Nitrogen, top dressed earlier in the spring, has made its way to the root zone of the wheat, from rainfall.
“While nitrogen in the root zone after jointing will not affect head size, it can impact yield, especially in fields that were showing nitrogen deficiency symptoms prior to the rain,” said Jeanne Falk Jones, K-State multi-county agronomist at the K-State Northwest Area office.
Falk Jones said stripe rust had not been found in northwest Kansas this spring.
“To get an infection of stripe rust, there must be three things: wheat, stripe rust inoculum and moisture. We are in the wait-and-see stage to see if stripe rust makes its way to northwest Kansas.”
In Nebraska, agriculture industry experts are cautiously optimistic.
“The winter wheat has progressed nicely after much-needed moisture. Much of the wheat is jointing and can become more susceptible to freeze injury from a possible late frost, as the crop matures,” observed Tyler Williams, Nebraska Extension educator in Lancaster County, adding, “In eastern Nebraska, powdery mildew may be the predominant disease.” Stripe rust has been more prevalent in the southern portions.
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