Students investigated the biocontrol of sawflies and the application of remote sensing for mapping infestations in crops.
Recently, two graduate students from the College of Agriculture at Montana State University have released innovative research concerning the management of one of the region’s most destructive agricultural pests.
According to the Montana Wheat and Barley Committee, wheat stem sawflies lead to significant monetary losses for agricultural producers, costing them millions annually. Surveys by the National Agricultural Statistics Service revealed that nearly 25% of Montana farmers reported yield losses of up to 10% due to these pests, with total statewide losses projected to reach $66 million for 2024.
Doctoral student Jackson Strand and master’s student Lochlin Ermatinger, both from the Department of Land Resources and Environmental Sciences, collaborated with MSU professor David Weaver to investigate two approaches to managing sawfly infestations. Their groundbreaking methods aim to provide insights into the pest’s effects and weaknesses.
Strand’s work focused on the influence of smooth brome, a common grass species in Montana, on sawfly populations in wheat. Meanwhile, Ermatinger utilized remote sensing technologies to create a model for predicting sawfly infestations. Both students published their research this fall, with Strand’s findings appearing in the Journal of Economic Entomology and Ermatinger’s in the journal Remote Sensing.
Strand highlighted the need for alternatives to pesticides, which are ineffective against wheat stem sawfly, emphasizing the pursuit of sustainable solutions for growers who have limited time and resources to implement crop rotation. “We’re exploring whether smooth brome could be beneficial and how we can support populations of parasitoids that can fluctuate between different seasons and regions,” he explained.
Parasitoids are insects that serve as natural enemies of wheat stem sawflies. The particular parasitoids highlighted by Ermatinger immobilize and feed on the sawfly larvae that inhabit wheat stems. As native insects, they represent a potential natural strategy for reducing pest damage, Strand noted. He discovered that the presence of smooth brome near wheat fields might attract both the sawflies and the parasitoids.
Through greenhouse experiments and lab analyses, Strand aimed to uncover the reasons behind this behavior by measuring the volatile organic compounds emitted by smooth brome and wheat. Volatiles are naturally produced chemicals by plants, which become more pronounced under stress conditions.
“Plants affected by sawflies generated different compounds than unaffected plants,” Strand explained. He previously obtained his undergraduate degree from the University of Minnesota before starting his graduate studies at MSU in 2021. “Smooth brome emits the same compounds as wheat but in greater amounts. The sawflies trigger a stress response in these plants, enabling the parasitoids to detect their hosts through these specific compounds.”
While smooth brome is not a native species, it is prevalent in Montana, especially along roadsides where it was planted to prevent erosion. Strand cautioned against deliberately planting brome but suggested that maintaining existing populations could serve as a strategic alternative to protect wheat crops from sawflies.
“By refraining from mowing or applying occasional fertilizer, smooth brome could become more appealing to sawflies, which in turn would also attract parasitoids that help keep the sawflies in check,” noted Strand, who completed his master’s in entomology this fall and is set to begin his doctoral studies at MSU later this month.
While Strand focused on managing existing sawfly infestations, Ermatinger aimed to find new methods for identifying and forecasting infestations before they occur.
Hailing from Missoula, Ermatinger began his studies at MSU in 2016, earning a bachelor’s degree in environmental science with an emphasis on geospatial and environmental analysis. He became interested in remote sensing and GIS (geographic information systems), which harness data from satellites, drones, and other technologies to create sophisticated mapping solutions.
Wheat stem sawflies complicate management efforts because they live primarily inside the stems of wheat plants, making damage assessment much harder compared to other pests, Ermatinger pointed out.
“To truly gauge what an infestation looks like, one often needs to dissect the wheat stems,” he said. “We began investigating remote sensing through satellite imagery in combination with stem dissection to create a comprehensive map.”
Ermatinger gathered data on three different scales: spatial, spectral, and temporal. By analyzing the spectrum of light reflected from wheat fields over broad areas and periods, and then comparing this data to confirmed sawfly infestations through physical examinations of wheat stems, he created a model that estimates infestations based on subtle variations in reflected light throughout an entire field.
“You can’t manage what you can’t measure. We aim to use this to make more accurate estimates,” Ermatinger stated. “Currently, we can estimate the infestation rate with statistical significance. This experience emphasized the importance of capturing images throughout the plants’ life cycles.”
Both Ermatinger and Strand collaborated directly with Montana agricultural producers during their research, gaining valuable insights into the practical significance of their work.
They have both progressed further in their academic journeys than initially expected at MSU: Strand has moved from a master’s program to pursue a doctorate, while Ermatinger transitioned from undergraduate to master’s studies. They credit the supportive and collaborative environment in the Department of Land Resources and Environmental Sciences for nurturing their continued academic growth.
“I never envisioned myself pursuing a graduate degree; it seemed out of reach. But MSU has provided a wonderful community,” said Ermatinger. “It has shown me that you can explore anything that interests you, depending on the people around you. It’s given me a renewed understanding of my home state.”
