The broad impact of Jeff Bradshaw’s research is to improve the lives of agricultural producers in western Nebraska, improving the human condition along the way.

Bradshaw is an associate professor of entomology and Extension entomologist at the University of Nebraska–Lincoln Panhandle Research and Extension Center in Scottsbluff, where he conducts research on the wheat stem sawfly. 

Nebraska is in the top 12 wheat-producing states in the United States, harvesting nearly 70 million bushels annually.

THE WHEAT STEM SAWFLY 

The wheat stem sawfly is a small black and yellow wasp that attacks wheat. As an adult, it lays eggs in the wheat stem. Once the eggs hatch, the larvae feed on the inside of the wheat stem, causing physiological problems with the plant and loss of yield. 

Bradshaw said as the season progresses, the insect migrates down the stem, girdles the stem and pupates inside the crown. The girdling causes the wheat tiller to break if there is a windstorm, which results in lodging that impacts the wheat yield. The lodging of the wheat stem sawfly also can cause residue loss in dryland wheat systems. 

Bradshaw said the wheat stem sawfly primarily is a pest of the western United States, including Nebraska. Winter and spring wheat growing regions overlap with the range of the wheat stem sawfly. The pest typically affected the northern Great Plains prior to 2010, but since that time, the wheat stem sawfly has moved farther down into the central and southern plains, including Nebraska. The wheat stem sawfly currently impacts Colorado, Kansas and Nebraska – states that now are on the most eastern and southern edge of the sawfly’s range.

Wheat is the primary crop impacted by the wheat stem sawfly, but the pest can wreak havoc on the entire dryland system, Bradshaw said. The dryland system’s nonirrigated agriculture is used to grow field crops in regions with a cool, wet season and a hot, dry season that typically receives less than 15 inches of annual precipitation, he said. The wheat stem sawfly can infest fields to the point that there is little residue left in wheat fields; without residue, the fields can’t catch snow over the winter, eliminating a source of needed moisture. The reduction in soil moisture impacts any crop that is in rotation with wheat, thus impacting the overall dryland ecosystem. 

The Nebraska Panhandle is in the eco-region classified as semiarid high plains; primarily grassland. Much of the area is above 3,000 feet in elevation, Bradshaw said. Historically, pioneering Nebraskans built houses made of sod instead of wood because there was an abundance of grassland, but few trees – due to the semiarid environment.

“Once you understand the dryland system, you can understand the potential impact of the wheat stem sawfly,” Bradshaw said.

“Elevation and annual precipitation both have a profound impact on the crops that can be grown. Generally, high elevation and low precipitation lower yield potential. Our average annual precipitation is very near the minimum soil-moisture requirements to grow common commodities, like corn or wheat, profitably,” Bradshaw said. 

Bradshaw conducts research on the wheat stem sawfly in a partnership with producers, agronomists and co-op agriculturalists, he said. He sends out a survey on the wheat stem sawfly that includes sampling protocols and procedures on how to sample fields for the wheat stem sawfly. In some cases, producers collect samples for the researchers to help identify fields and gather more diverse data. Bradshaw sought out collaborators and cooperators in the wheat stem sawfly project; they formed a network of agriculturalists, growers and co-op partnerships that collect data that report findings to growers. 

“We can improve the viability of wheat by finding some sort of resistance trait that is made to be targeted regionally, because we have this survey data set and we can help improve the life out here of some of these growers,” Bradshaw said.

DATA AIDS SAWFLY RESEARCHERS

“Big data” is a common term in the scientific community for large, complex data sets in which a researcher can look at trends or certain attributes of the data that could be described in a way that couldn’t happen with a smaller data set, Bradshaw said. 

The role of data in wheat stem sawfly research involves understanding and describing the sawfly population and its progression, Bradshaw said. The information can be shared with collaborating producers, the Nebraska Wheat Board and with the United States Department of Agriculture, among others. Sharing the research data with organizations confirms there is a problem and establishes the extent of the infestation. Nebraska Extension works to share the collected information with the state’s wheat producers. 

The wheat stem sawfly survey results are available to the public and other research is published in peer review journals. Field data also is collected, which provides data associated with the samples. Samples could include when, where and how the data was collected, from what crop and from what landscape. Bradshaw hopes to conduct more research and analysis in the future in regards to what factors are impacting the wheat stem sawfly population or the parasitoid population. For more information on the data collected, visit cropwatch.unl.edu/2016/wheat-insects-2016. 

The survey helped make producers aware of the sawfly problem and improved the ability of producers to identify the pest. The producers also report their own ideas to Bradshaw. 

“A big part of the project is just providing the information back to cooperators, giving them a platform to think creatively about how to solve some of these problems,” Bradshaw said. 

RESEARCH AND EXTENSION CENTERS

The Panhandle Research and Extension Center in Scottsbluff is one of the university research and extension centers located in key sites throughout Nebraska, in both rural and urban areas. They are operated through the Institute of Agriculture and Natural Resources, in cooperation with the Agricultural Research Division and Nebraska Extension. The purpose of each center is to conduct research and extension programming that is relevant to the region, serving the economic, environmental and social needs and interests of that center’s region, as well as all of Nebraska.