The University of Wyoming recently issued a warning: Be on the lookout for a high grasshopper year. Scott Schell, UW Extension entomologist, warns that mid-May through June is the best time to check for these problem bugs, which hatch in large numbers.
And with grasshoppers, early action can pay off. “If you had lots of grasshoppers last year or already have them hatching this spring, then treating [them] early in the season before they become adults is the best way to reduce their numbers,” Schell says.
The state of Wyoming has more than 120 species of grasshoppers, but only about a dozen are considered important. There are some grasshoppers not considered pests because they have low reproduction rates and never reach damaging population densities. And there are some grasshopper species that eat only undesirable weedy plants and are beneficial. A good example is Hesperotettix viridis, better known as the snakeweed grasshopper or meadow purple-striped grasshopper.
As for the grasshoppers that do cause trouble, Schell suggested looking in field areas that warm up first, like south-facing slopes or borrow ditch banks.
It's tough to stop grasshopper outbreaks when spring weather is favorable for their survival, and conditions that may have reduced grasshopper predators or pathogens are beyond the landowners' control, he says.
Why grasshoppers are a problem
In Wyoming, grasshoppers are solid competitors for forage. In fact, they can outcompete livestock and wildlife. They can clip down forage and then eat the grass as it grows from the crown. This prevents forages from getting tall enough for larger grass-eating animals to grasp with their teeth.
To get a sense of how troublesome they can be, a recent publication from the University of Wyoming notes that research has shown a population density of just 10 adult two-striped grasshoppers per square yard can defoliate a field of knee-high corn plants. That population density is about 60 pounds of grasshoppers per acre, each of them capable of eating their body weight daily in green leaves, and clipping more leaves than they can consume.
To help avoid trouble, Schell recommends good grazing management to reduce bare ground as a possible prevention method. Bare ground favors some grasshopper species. Working with neighbors who have infestations is the best way to get comprehensive control.
The University of Wyoming has a range of links to help you manage grasshoppers. Check them out:
• Grasshoppers of Wyoming and the West
• Grasshopper Identification and Management Poster
• Wyoming Weed and Pest Council Offices