It turned out to be the year of the grasshopper in many areas of eastern Montana. Many regions did not notice these voracious pests early in the spring, but by summer’s end, hoppers had appeared in droves throughout eastern Montana. Dave Branson, USDA/ARS Northern Plains Agricultural Research Lab ecologist, Sidney, notes that grasshopper populations were particularly high in certain regions, with highest populations largely south and west of Richland County.
“We saw areas in eastern Montana with extremely high grasshopper populations, particularly in Garfield County, which had 80 grasshoppers per square yard in some areas,” Branson comments. “Other areas had 20-30 grasshoppers per square yard, which is a high number.”
Branson points out that grasshoppers seemingly appeared out of nowhere because of a very late hatch this spring. “People thought there were no grasshoppers, but there were,” Branson comments. “The hatch was very late this year because of the cold spring and late arrival of summer. The hatch depends on degree days, and this year was way behind the long term average.”
He adds, “In the late ‘80s when we had 100º days in May, some species were already adults by early June, but this year, those same species didn’t even hatch until late June.”
Branson cannot recall such a late hatch in all the time he’s spent working on grasshopper research in eastern Montana. “This year was definitely close to the extreme as far as late hatch goes,” he remarks. “This year was the latest hatch I’ve seen.”
A few early hatching species did arrive on the scene in time to devour garden plots in certain areas, but most rangeland hopper species made a late arrival, fooling some people into believing the grasshopper populations would be small.
“Early on, there were no grasshoppers on rangeland,” Branson says. “Ranchers looked for hoppers when they normally do and nothing was out there. They often didn’t pay much more attention to grasshoppers until all of a sudden they had a problem.”
He continues, “We were lucky this was a green, wet year because although grasshoppers did decimate some areas, in most cases there was enough vegetation out there to go around. In a drought year, in many places the grasshoppers would have wiped out what’s there. Although a major grasshopper year, it would have been much more severe in a drought year.”
Branson cannot yet accurately predict what to expect for grasshopper populations next year. Weather factors and available food, as well as disease and reproduction will all impact the grasshopper population next year. “We’ll take a close look this winter and dissect some female grasshoppers to determine the number of eggs laid,” Branson says. “Because of the late hatch, there is a narrower window for grasshoppers to lay eggs. We’ve also seen a lot of parasitoids on grasshoppers at one location, which helps to knock the grasshopper population down, but we don’t know if the parasitoids are widespread.”
“However,” he continues, “Late August and early September were warm, and grasshoppers like heat. The vegetation also stayed green in many areas so the protein content was higher than normal for August and September, so the food was there for grasshoppers to develop and lay eggs.”
Branson points out that these varied conditions leave a lot of unknowns for next year. “We’ll look at all the factors,” he comments. “Given the warm fall and good food supply, the risk looks high for large grasshopper populations next year, but we’ll get a better idea this winter when we finish our lab work.”
He concludes, “The day length is short now, so even if temperatures reach 80º during the mid afternoons, grasshoppers can’t do a lot. It’s cold at night, so the window for reproduction and significant vegetation damage is largely over for this year.”
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