It is well understood that weather patterns can have a significant impact on grasshopper populations year to year.
Warm, dry weather increases the survival of nymphs and adult grasshoppers, leading to increased egg production during the growing season, while cool, wet weather promotes fungal pathogens that can reduce egg and nymph survival.
Another factor influencing grasshopper populations is an abundance of food, especially broadleaf weeds. A diet high in these forbs leads to greater nymph survival, faster growth, larger adult grasshoppers, and increased egg production.
The abundance of weeds therefore can likely contribute to the noticeable number and diversity of grasshoppers currently being observed. As these weedy sources of food are exhausted or controlled, grasshoppers may shift their grazing over to anything still growing in the landscape. In areas with greater grasshopper pressure, seedling alfalfa and wheat could be at risk.
Before planting alfalfa, treatment should be considered if there are 15 or more grasshoppers per square yard around the planting area. Once planted and growing, consider treatment if 3-5 grasshoppers per square yard are found in the seedling alfalfa stand.
Vegetated borders around areas where wheat will be planted should be scouted ten days before planting. Consider treating those borders if there are 7 to 12 grasshoppers per square yard.
Once growing, three or more grasshoppers per square yard within the field can destroy seedling wheat stands. If grasshopper populations are low to moderate, seed treatments can protect emerging wheat plants for several weeks if products are applied at the highest registered rate. Seed treatments will be less effective under severe grasshopper pressure. Avoid planting too early, as this will help reduce the time that wheat must be protected.
Please refer to the most recent Alfalfa and Wheat Insect Management Guides for specific control information. Simply type into your internet browser Alfalfa Insect Management Guide KSU or Wheat Insect Management Guide KSU.
Stacy Campbell is an agriculture and natural resources agent for Cottonwood Extension District. Email him at scampbel@ksu.edu or call the Hays office, 785-628-9430.
