Grasshoppers (Melanoplus spp.) feed on a wide variety of plants and can be pests of corn. Grasshoppers pass the winter as egg masses that were deposited about one inch below the ground surface the previous fall. Eggs hatch in May and into June. Because the soil-born eggs are destroyed by fall and spring tillage grasshopper survival is greatest in no-tillage situations, along field margins, and in other undisturbed land away from fields (e.g. in pastures). As the grasshoppers hatch, nymphs first remain near the site of hatching but slowly spread as they get larger. Winged adults develop by mid-summer and spread across the landscape. In most cases grasshoppers move into corn fields from edges bordering undisturbed areas and also show some movement in and out of fields on a daily basis. See scouting guidelines for mid-season insects. In the field grasshoppers feed on leaves, silks, and ear tips. In years of high grasshopper populations, damage can spread far into and even completely across fields, although this is unusual. Populations in corn are often much higher following drought years and when corn is no-tillage planted into soil containing lots of eggs (e.g. killed pasture, lespedeza, or alfalfa fields).
No specific management strategy for preventing grasshoppers is recommended as they are only sporadic pests. Insecticides are sometimes employed to reduce populations and are often applied as spot treatments along field margins and headlands. To determine the need for treatment, defoliation should be estimated; a 5% yield loss potential will normally justify treatment. In addition to the defoliation estimate, a survey for the presence of grasshoppers and the extent of their movement will help estimate the potential for further damage and the possibility for spot treatment.