The 2018 cool wet spring may lead to reduced grasshopper populations, compared to 2017 says SDSU Extension entomology team.
“During 2017, many of the grasshoppers that we observed were several weeks behind schedule in growth,” said Adam J. Varenhorst, Assistant Professor & SDSU Extension Field Crop Entomologist.
However, Varenhorst explained that trying to predict insect populations is difficult as many additional factors can contribute to their winter survival and overall spring populations.
“Our recommendation is to scout for spring grasshopper populations, as they will be the first indicator of potential problem areas,” he said. “Depending on the 2018 growing season, areas with limited rainfall or drought conditions may experience increased grasshopper populations.”
A look back on 2017:
In 2017, researchers at South Dakota State University completed a grasshopper survey of Eastern South Dakota (Figure 1).
The last grasshopper survey conducted in Eastern South Dakota was published in 1925. Those involved in this survey included: Erica Anderson, SDSU Graduate Student; Patrick Wagner, SDSU Extension Entomology Field Specialist; Philip Rozeboom, Research Associate; Laura Edwards, SDSU Extension State Climatologist and Amanda Bachmann, SDSU Extension Pesticide Education & Urban Entomology Field Specialist.
2017 was an interesting growing season with areas of South Dakota experiencing severe drought conditions.
“In some of these areas, we found that grasshopper populations were causing defoliation injury to already drought-stressed crops,” Varenhorst said.
He explained that factors that can lead to increased grasshopper populations include long, warm falls, decreased ground cover, and limited spring rainfall.
Leading up to 2017, we experienced several warm falls where the first frost date occurred much later than normal.
“These conditions allowed grasshoppers to successfully lay eggs for a much longer period of time and were likely part of the reason why we saw increased grasshopper populations in the eastern half of the state,” he said.
Areas of South Dakota with grasshopper populations that reached or exceeded the threshold of eight or more grasshoppers per square yard included: Hyde, Hand, Beadle, Kingsbury, Spink, Buffalo, Jerauld, Brule, Aurora, Douglas and Hutchinson counties. In addition, there were several other counties that had multiple samples near threshold levels.
