September 27, 2010
What is the situation with the numerous grasshoppers in my yard? Is there anything I can do about them?
The numerous grasshoppers in yards may persist until there is a hard frost. Grasshoppers are some of the most difficult insect pests to control, since they are so mobile. There are over 100 species in Colorado and their food habits vary. Many feed on grasses or sedges, others prefer broadleaved plants. The problem ones are those that feed on garden and landscape plants. In the vegetable garden, they will eat lettuce, carrots, beans, sweet corn and onions. Grasshoppers rarely feed on trees or shrubs, however in a year like this, they may. There have even been reports of them chewing holes in window screens.
Natural predators include adult robber flies and many birds, such as horned larks and kestrels. They are also frequently eaten by coyotes.
But what can we humans do? The good news is that experts can predict grasshopper populations. Homeowners should watch for the nymphs and spray insecticide. The bad news: the timing for this year has passed and now we must deal with the adults. Some insecticides may be applied directly to the plants being eaten, however plants may be harmed. The choice of insecticides is limited since few allow direct application to garden fruit and vegetables.
Insecticides that can be used carefully on vegetables now are carbaryl and permethrin. These have many trade names. Other chemical grasshopper controls must be used before they become adults. Whenever dealing with edible crops always follow the manufacturer’s recommendations for applying insecticides in relation to harvest intervals.
More information is available at the Colorado State University Extension web site at http://www.Ext.ColoState.edu.