This year has been quite warm and fairly dry. We have been lucky to have received the rain that we did see come through in July after such a dry June. However, that warm, dry weather has lead to an increase in grasshopper populations this year. These grasshoppers have been a large problem in our lawns and gardens.
Grasshoppers can be a problem in grassy areas and in our gardens. They will feed on flowers and some vegetables such as lettuce, beans, and sweet corn under normal situations. However, in situations where the population is high, like this year, they can be found feeding on nearly all vegetables and in some cases even trees and shrubs. They can even be found eating paper, paint, and window screens. On our plants, you will notice a high number of grasshoppers as well as the chewed appearance of the leaves, fruits, and flowers of many of our plants.
Grasshoppers are often reduced in population due to the environment during their developmental period of life. If we have cool, wet weather right after they hatch from their eggs, typically in early to mid-May, this will help reduce the populations. The nymphs are vulnerable to death due to starvation in the early development of their lives. In most years, we face a fairly wet, cool May that helps reduce the population of grasshoppers, but this year that did not happen, so our populations are high.
Grasshoppers can be managed fairly well. There are some good cultural and mechanical practices that can help as well as some use of chemicals in other locations.
Keeping overgrown grassy areas mowed and/or tilled will help reduce the sites where grasshoppers prefer to lay their eggs, therefore helping to reduce the population. It may also help to leave some of the border areas of a large yard, especially in an acreage setting, unmowed so that the grasshoppers will stay in the unmowed areas of the lawn and not move as quickly into the lawn and garden areas. You may also plant some trap crops, such as zinnias or other flowers in these border areas to attract grasshoppers to these plants instead of your lawn or garden.
For chemical control, it is best to treat grasshoppers when they are young. Once grasshoppers become full grown adults, they have a decreased susceptibility to insecticides and they are larger which also makes them harder to control with insecticides. With all insects, management is much more effective if insecticides are applied at a younger age for the insects to be controlled.
When applying insecticides for grasshoppers, first concentrate the sprays on the roadsides and ditches where grasshoppers lay their eggs to get them when they first emerge from the eggs. Then you can focus on the lawn and garden areas. In the vegetable garden, be sure to use insecticides that are labeled for use in the vegetable garden such as sevin or eight and follow the PHI. The PHI is the amount of days to wait to harvest after spraying has been done. Most any general insecticide can be used in locations not in the vegetable garden including sevin, eight, or malathion, just make sure the label has grasshoppers and the area to be treated on it and it will work.
The information for this article came from the NebGuide: A Guide to Grasshopper Control in Yards and Gardens by Gary Hein Extension Entomologist, John Campbell Extension Entomologist, & Ron Seymour Extension Educator.