Steamboat Springs Moisture and cooler temperatures in the Yampa Valley will aid grasshoppers, entomologist Frank Peairs said.
With most of the insects in the adult phase of their yearlong lives, added moisture and mild conditions will increase food supply. That could enable the pests to lay more eggs in the fall, Peairs said.
Peairs is a Colorado State University professor who aids cooperative extension agents in Routt County.
"It's true that cool, wet weather is detrimental to grasshoppers in their younger stages," he said.
During the first four to eight weeks of their lives, the insects are vulnerable to diseases caused by cool temperatures and moist conditions. The frost and snow in June last summer in the Yampa Valley, for example, killed a large percentage of grasshopper eggs.
That didn't happen this year. High temperatures this spring, coupled with dry conditions, produced one of the largest grasshopper infestations Northwest Colorado has had in living memory.
Typically, three to four grasshoppers feed in a square yard of a meadow. This year, experts said some fields could have 200 in a square yard.
Peairs said the drought increased the number of grasshoppers as well as funneled the population into small areas. The combination of the two created the high density in some fields.
As the monsoon season in the Yampa Valley swells into August, the grasshoppers become weather-resilient adults. The moisture and mild conditions increase food supply for the insects. More food could increase egg productivity.
In addition to that, the moisture spreads out the population to larger areas. This gives some density relief in the fields. But it also allows the grasshoppers to lay more eggs.
National Weather Service science and operations manager Mike Meyers said precipitation should be above average between August and October, thanks to a stronger than normal monsoon season.
If that holds true, Peairs said more moisture could equate to more grasshopper eggs this fall. That could set Northwest Colorado up for a larger infestation of the insects next summer weather pending.
However, Peairs said nothing is certain at this point.
Rain in the Yampa Valley is forecast to stick around through today, Meyers said. The valley is forecast to be dry over the weekend, but moisture should return next week. Showers are expected to be a common occurrence in August, breaking the summer's drought.