Predicting factors that influence wheat stem sawfly presence in Colorado

Wednesday, November 16, 2022

3:06 PM – 3:18 PM PT

Location: Vancouver Convention Centre, Meeting Room 110

Presenting Author(s)

Erika Peirce

Postdoctoral Fellow
Colorado State University
Fort Collins, Colorado

Co-Author(s)

TR

Tatyana A. Rand

Research Ecologist
USDA-ARS
Sidney, Montana
FP

Frank Peairs

Colorado State University
Fort Collins, Colorado
Punya Nachappa

Associate Professor
Colorado State University
Fort Collins, Colorado

The wheat stem sawfly (WSS, Cephus cinctus Norton) is a major pest of cultivated wheat. It is difficult to estimate the damage of this insect, but conservative calculations estimate the grain-yield loss to exceed 30% and the economic losses to exceed $350 million annually. This estimate does not include Colorado, so we expect the current figure to be much higher. Most economic loss is caused when the larva reaches the final instar when it creates a hibernaculum (stub) by cutting the stem above ground level just before harvest, which causes the wheat head to fall. Fallen stems are difficult to harvest and are easily blown away. A survey of production wheat fields in Eastern Colorado was performed from 2012 to 2022. Sites were selected based on the number of acres each county had in wheat production in 2010, proportional to 100 total samples. Then 100 stems were collected from each location and dissected to determine the presence, absence, and abundance of WSS. Using satellite data from CropsScape a USDA data layer and PRISM satellite weather data, we used several machine learning models to determine if weather or landcover could predict the presence and abundance of WSS across Colorado. Using the results from this data we hope to provide information to farmers on whether WS populations are influenced by landcover of wheat or grass, the connectedness of fields, and climactic variables. If landscape variables influence the abundance, we may be able to formulate management plans for farmers based on crop rotation.