KSU-ARCH Wheat Day looks at stem sawfly
By Larry Dreiling
The coming attack of the wheat stem sawfly on the Kansas wheat crop was a part of the focus of the annual Wheat Day activities at the Kansas State University Agricultural Center-Hays.
J.P. Michaud, assistant professor of entomology, and Integrated Pest Management leader, discussed how this pest is slowing entering western Kansas wheat fields.
“Insect populations are always changing and this one is not changing for the better,” Michaud said.
The basic fact is the sawfly was identified over a century ago and has been in Kansas for some time but has left alone the crop in the nation’s traditional wheat production state.
It was first reported attacking wheat in Canada in 1896 and soon spread to become a serious pest of spring wheat throughout the Dakotas, Montana, and Wyoming. Historically, only spring wheat was attacked. It was not until the 1980s that infestations were observed in winter wheat. By 1996, scientists working in Montana determined that the pest had evolved faster and was emerging some 20 days earlier than it previously had, enabling it to survive in early maturing winter wheat. The wheat stem sawfly also has long been present in wild grass species over a much broader range, including Nebraska and Kansas, although neighboring wheat fields were unaffected.
Collectively, research suggests that attacks on winter wheat may have been occurring for some time but went unnoticed because larvae did not complete development. This may be the case in Kansas currently, with populations under strong selection to evolve faster development.
“Winter wheat matures so quickly that the insect doesn’t have time to complete development.” Michaud said. “Sometimes they may lay an egg in that wheat, but those larvae don’t develop until jointing and stem elongation. So, there’s a narrow window for those larvae to complete development.
It is not yet clear if recent winter wheat infestations in the Nebraska Panhandle and northeastern Colorado result from local populations evolving to exploit winter wheat, or the southerly range expansion of an adapted strain. Local populations express significant variation in biology, behavior, and genetics that suggest regional adaptations.
Presently, Kansas is on the southeastern boundary of the region experiencing wheat stem sawfly problems in winter wheat, which is why Michaud is out to reduce the oncoming footprint of the sawfly.
“It’s moving slow, but it is moving,” Michaud said. “Where it stops, when it ends, and its range is really unknown, since we are on the frontier of that range expansion.”
Larry Dreiling can be reached by phone at 785-628-1117 or by email at firstname.lastname@example.org.