   Grasshoppers - October 13, 1999 Jeff Schalau, County Director, Agent, Agriculture & Natural Resources Arizona Cooperative Extension, Yavapai County Grasshoppers are a common garden pest in Arizona and can wipe out a garden or damage a landscape overnight. Earlier this year, grasshoppers covered houses and completely defoliated landscapes near Prescott. In most of these cases, the most severely damaged gardens were adjacent to open rangelands where grasshopper eggs are hatching out and nymphs can feed. They are attracted to the lushness of irrigated landscapes and nonnative plants found in gardens. They find vegetables, especially leafy types, exceptionally appealing. Understanding the life history and biology of grasshoppers will make it easier to control them in your garden. 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. 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 are closely related to crickets, katydids, and locusts. In fact, often people mistake cricket damage for grasshopper damage. Crickets feed mostly at night, so you will rarely notice them. Grasshoppers are much more noticeable feeding mostly daytime. Grasshopper mouthparts function like an eating machine. They can easily eat leaves of many plants as well as seeds and small fruit. Their long, muscular back legs allow them to jump 20 times their body length or propel adults into flight. This also allows them to easily migrate to new food sources like your garden. Grasshopper control strategies can take many forms with varying efficacy. Cultural controls include tillage, eliminating weeds, planting attractant areas, and planting resistant crops. Spring tillage can destroy egg cases through mechanical damage, exposure to predators, parasites, weather, and the elements. One natural predator of grasshopper eggs is the blister beetle: a voracious pest on its own. Tillage is not practical in most home settings, but may offer some control on large acreages of cropped land. Small wasps of the family Mymaridae parasitize grasshopper eggs to offer some natural control. If your garden is adjacent to an open wildland area, a well-watered, lush attractant area can preoccupy grasshoppers. If your garden is also lush, then the attractant area may only serve as a stepping stone to your garden. Biological controls offer some promise and are now commercially available. 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 passed from one grasshopper to another as they cannibalize the diseased individuals. It is most effective on nymphs. Nosema offers little or no control on 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. Many nurseries are carrying this product under the name Nolo Bait. It does not affect organisms other than grasshoppers. Chemical controls offer the advantage of quick results but require the proper equipment and knowledge of safe application practices. Organophosphates (acephate, diazinon, malathion, parathion, etc.) and carbamates (carbaryl and carbofuran) offer effective grasshopper control. 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. Always follow the directions found on the label. Experienced gardeners always weigh the alternatives before using any pest control measure. Once the decision is made to take action, an integrated approach is usually most effective. Often cultural and biological controls alone will give acceptable results. Chemical control measures can be used to add a higher level of control if needed. I hope you can use this information to "get a jump" on the grasshoppers next spring. The University of Arizona Cooperative Extension has publications and information on insect identification and control. If you have other gardening questions, call the Master Gardener line in the Cottonwood office at 646-9113 or E-mail us at mgardener@kachina.net and be sure to include your address and phone number. |