Grasshoppers Have Started Hatching

The cool and wet spring delayed grasshopper hatching. However, you may now be seeing small grasshoppers out on your rangelands or in your crops. These small grasshoppers are in the nymphal stages where they progress through 5 instars before becoming an adult (Figures 1 & 2). The nymphal stages are the best time in which to manage grasshoppers. Treatment thresholds that indicated when control measures should be taken are based on the number of grasshoppers per square yard (Table 1). Therefore, the first step in management is scouting and determining the number of grasshoppers per square yard. This can be done by estimating the number of grasshoppers visually in a one square foot area. Randomly repeat this 18 times and divided by 2 to get the number per square yard. Using four 180-degree sweeps with a 15-inch sweep net (available for use at the Extension office) would also be equivalent to the number per square yard.

If treatment thresholds are met, insecticides should be applied. Options include carbaryl such as Sevin, pyrethroids such as Warrior and Mustang Maxx, lambda-cyhalothrin such as Warrior II, and diflubenzuron such Dimilin, among others. The majority of insecticides for grasshopper control are Restricted Use Pesticides, meaning you must be licensed in order to purchase and apply them. To obtain a Private Applicator license and for a full list of insecticide options, contact the MSU Richland County Extension Office at 406-433-1206.