Watch for outbreaks when temperatures rise.
Agronomy Bulletin 105 ─ Grasshopper Damage
Grasshopper population levels are highest during hot, dry summers. Active scouting and applying appropriate crop management practices can help guard your crop from damage.
Factors to Consider
- Identifying damage
- Crop rotation
- Insect biology
- Understand the life cycle of a grasshopper. The economically significant species of grasshoppers overwinter in egg pods below the soil surface. Eggs are deposited in pods from August through October. Depending on the species, a female may produce up to 25 pods, each containing up to 100 eggs. Most grasshopper eggs hatch from late May through early July, with only one generation produced each year. Young grasshoppers (nymphs) resemble small adults without wings.
- Proactively scout for grasshoppers. Scouting should begin in May. Grasshopper infestations have the greatest impact in field crops when the weather is hot and dry. They often first appear in weedy areas of roadsides, fencerows and irrigation ditches. After those plants are eaten or dried down, grasshoppers migrate in search of new food sources, such as irrigated crops or newly emerged winter wheat. Grasshoppers begin feeding on food sources in field margins and then multiply throughout the field.
- Identify damage. Grasshopper injury is most often associated with rangeland, corn, small grains and vegetable crops. However, during heavy infestations, they will attack trees, shrubs, flowers, lawn grasses and other types of vegetation. Grasshoppers have chewing mouthparts, and their feeding destroys the plants.
- Consider control options. Begin by estimating the number of grasshoppers per square yard, surveying several sites within a field to ensure a representative estimate of the infestation level. Refer to Table 1 from Colorado State University to determine the need for treatment. Depending on individual situations, including the value of the crop, treatment may be necessary when populations reach or exceed 40 nymphs per square yard.
- Take action with insecticides. Depending upon the infestation level of the grasshoppers, their size and other considerations, field margins can be treated effectively with low rates of an appropriate insecticide. Larger-sized grasshoppers can require higher rates. For control of grasshoppers, consider Cobalt® Advanced insecticide. As always, growers, consultants and applicators should understand and follow all label directions.
Uncontrolled grasshoppers can reduce yield in row crops during hot, dry summers. Work with your Mycogen Seeds customer agronomist or trusted agronomic adviser to assess infestations and determine the appropriate course of action to prevent damage.