Wheat stem sawflies heavily damage more wheat than any other insect in Montana, and now Colorado and Nebraska are experiencing unprecedented outbreaks, says Montana State University entomologist David Weaver.

Continuing to search for solutions, experts from three countries and four states will share their findings at the Sixth International Wheat Stem Sawfly Conference to be held April 3 and 4 at the Procrastinator Theatre in MSU's Strand Union building. The conference is free and open to the public, but seating is limited so people who want to attend are asked to notify the organizers at wheatstemsawfly@gmail.com

"We all recognize that problems associated with wheat stem sawfly are dynamic and evolving," Weaver said. "It is a devastating pest with features in its life cycle that make it very difficult to manage. This results in an ability to cause very large economic losses at the level of individual growers through to the large-scale regional impacts in much of the northern and central parts of the wheat belt."

MSU economist Anton Bekkerman, who will give two presentations at the conference, conducted the first formal economic study on the impacts of wheat stem sawfly in Montana. During his talk from 10 to 10:30 a.m. April 3, he will give a 15-year perspective on the damage it caused.

"The high wheat prices observed in 2012 resulted in estimated direct damages of approximately $80.1 million to Montana farmers," Bekkerman said. "What is perhaps equally as important is that these damages implied that nearly 9.7 million bushels of Montana wheat did not reach consumers. This has important indirect economic implications all along the wheat marketing chain."

The estimated expected losses to individual farmers with 2,000-acre operations were between $15,000 and $20,000 for spring wheat producers and $25,000 and $47,000 for winter wheat producers in 2012, Bekkerman said. Winter wheat producers in high impact areas were expected to lose $110,000 and $120,000 per farm.

"In evaluating two widely used management strategies – solid stemmed varieties and swathing – the results indicate that highest long-run economic returns are likely when using a slightly less yielding solid stem variety that minimizes the chances of the sawfly population growing rather than planting higher yielding varieties and swathing, which can increase long-run sawfly populations and exacerbate damage," Bekkerman added.

Other conference speakers will give updates on the southward expansion of wheat stem sawflies and share their findings about biological control, integrated pest management, host plant resistance, the genetics of both wheat stem sawfly and wheat, population monitoring, and chemical ecology.

A keynote speaker will be Marie-Claude Bon from the European Biological Control Laboratory in France. She will speak from 1:30 to 2 p.m. April 3 on genetic variation among wheat stem sawfly populations.

Genetic variation is probably one reason that wheat stem sawflies are so persistent and intractable in Montana, Weaver said. Compared to other areas of the northern Great Plains, the genetic diversity of wheat stem sawflies in Montana is much greater. Bon will discuss this variation and its implications.

Another reason that wheat stem sawflies are a problem is because they have not yet been managed using any known insecticides, Weaver said. As a result, researchers are continually testing new insecticides and investigating other options, including the exploration of newly discovered genetic traits in existing wheat germ plasm that provide additional resistance.

The Wheat Stem Sawfly Conference is held every two years, with the 2012 conference also held at MSU. Since beginning in 2003, the conference has been held in Bozeman three times and has been part of past Pacific Branch-Entomological Society of America and Entomological Society of Canada meetings. The conferences draw scientists, members of the agribusiness community, agricultural leaders and wheat growers.

"Agricultural research has had these wonderful and highly supportive relationships with wheat growers in the state," Weaver said. "They are very interested in attending these presentations to find out more about the wheat stem sawfly research that is being conducted."