Grasshopper Control - June 2, 2004
Jeff Schalau, County Director, Agent, Agriculture & Natural Resources
Arizona Cooperative Extension, Yavapai County
There are about 400 species of grasshoppers found in the 17 Western States. Only a few of these species (17.4%) are considered serious pests. These pest species normally feed on native vegetation (primarily grasses). However, when grasshoppers can access other plant species, they can eat them preferentially. This is the case with many annual flowers, vegetables, and forage crops. New leaves and fruits of woody plants may also be impacted, but these plants better tolerate grasshopper damage and will recover. Gardens and landscapes that receive the highest impact are often adjacent to grass and/or shrub lands.
Grasshoppers lay clusters of eggs in the soil during fall. Each cluster has 8 to 30 eggs and each female lays 7 to 30 clusters varying by species. The eggs overwinter in the soil and are extremely resistant to cold temperatures. Hatching date is determined by the weather and can be predicted by the maturation of the egg and soil temperature.
Juvenile grasshoppers look like smaller versions of the adult and immatures are called nymphs. Most nymphs start feeding right away and continue to feed on the same plants as they mature into adults. To distinguish nymphs from adults, look for wings. Nymphs have wing buds and cannot fly. Adults have fully developed wings and fly quite well. Grasshoppers begin laying eggs one to three weeks after reaching adulthood.
Grasshoppers have some natural enemies which include parasites, predators, and diseases. Small wasps of the family Mymaridae parasitize grasshopper eggs to offer some natural control. Parasitic nematodes, also called threadworms or hairworms, feed coiled up inside grasshoppers and can cause death, sterility, or reduced vigor of the insect. Blister beetles and crickets are predators of grasshopper eggs. Spiders, wasps, robber flies, rodents, and birds eat nymphs and adult grasshoppers. I have a flock of chickens in my yard and they seem to be somewhat effective at controlling grasshoppers.
Grasshoppers are susceptible to a large array of natural diseases caused by bacteria, viruses, protozoa, and fungi. Nosema locustae is a pathogenic protozoan (single-celled animal) which is mixed with oat bran to create a bait. Grasshoppers eat the bait and become infected with the pathogen. The effects are not immediate, but the pathogen causes the hoppers to stop feeding and become lethargic. It is most effective on nymphs and offers little or no control of adults. The best time for application is the spring just after they hatch out. It is most effective when applied over large areas (one acre or more) because of distances traveled by grasshoppers.
Chemical controls offer the advantage of quick results but require the proper equipment and knowledge of safe application practices. Some of the active ingredients labeled for grasshopper control are: bifenthrin, cyfluthrin, lambda-cyhalothrin, permethrin, esfenvalerate, and carbaryl. As with all pesticides, the label should be consulted to see if the pest (grasshopper) and the crop or ornamental plant are listed for use with that pesticide formulation. Always follow the directions found on the label.
Home gardeners may also want to consider using a physical barrier made of lightweight, spun fabrics (Remay and others). These fabrics are often used for row covers and allow light penetration and some air circulation. These products may be found at garden centers and through mail order catalogs. Under severe circumstances, grasshoppers may start to feed on the fabric. In these situations, you may consider application of a residual insecticide to the fabric using the same precautions you would if applying it to a plant.
The University of Arizona Cooperative Extension has publications and information on gardening and pest control. If you have other gardening questions, call the Master Gardener line in the Cottonwood office at 646-9113 ext. 14 or E-mail us at firstname.lastname@example.org and be sure to include your address and phone number. Find past Backyard Gardener columns or submit column ideas at the Backyard Gardener web site: http://cals.arizona.edu/yavapai/anr/hort/byg/.
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Last Updated: May 27, 2004
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