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Do you have tips on managing grasshoppers in my yard?
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During the current drought cycle, grasshoppers have become a common occurrence in the home yard. There are hundreds of species of grasshoppers in North America, but only a few of them cause economic damage to plants. The short-horned or Acridid grasshoppers are the primary culprits. The slant-faced grasshoppers (angled faces, long, thin bodies) feed primarily on grasses; spur-throated grasshoppers (projection under their throat) feed primarily on herbaceous plants; and banded-winged grasshoppers (brightly colored hind wings that rattle when they fly) feed on both grasses and herbaceous plants.
Most problems occur in home yards when large populations of grasshoppers migrate from surrounding open fields, range and other less disturbed grasshopper egg-laying sites. Eggs are laid in undisturbed ground in the summer and fall, then over-winter. Eggs hatch the following spring, and emerging young (nymphs) feed on green vegetation. When field vegetation begins to dry, large flushes of grasshoppers migrate and overrun nearby succulent landscapes and gardens. The best way to combat grasshoppers in these circumstances is to work with neighbors to coordinate treatment. Consider these tips.
A number of insecticide choices are available to kill grasshoppers. They include acephate (Orthene), azadirachtin (Neem), bifenthrin (Talstar), carbaryl (Sevin), cyfluthrin (Tempo), diazinon, malathion, permethrin (Astro) and pyrethrin. Most of these are not labeled for food crops, so be sure to read and follow label directions carefully.
Two biological insecticides are effective on grasshoppers. Beauveria bassiana is an insect-attacking fungus. Nosema locustae is a protozoan that, upon ingestion and sporulation in the gut, infects fat tissues of the grasshopper. Nosema is slower acting than conventional insecticides and can take 4-6 weeks to kill grasshoppers.
Insecticide baits offer a longer-lasting option for grasshopper control. Baits formulated with grain to attract feeding grasshoppers include Nosema locustae (Nolo Bait, Semaspore) and carbaryl.
Grasshoppers are easier to kill in their early nymphal stages. Older nymphs and adults are the most voracious feeders and cause the main injury to plants. If grasshoppers move to your property from surrounding land, place a 6-8 foot band of bait around the property border and into the adjacent field. Do this in late spring to early summer when populations of small nymphs begin to increase. To maintain active insecticide, re-treat every two to three weeks while grasshopper populations are increasing (during egg hatch), and especially following heavy irrigation or rain.
Other management strategies include spot or target spraying nymphs when they are seen feeding in the yard, or treating adjacent vacant lots or fields that have nymph infestations.
Remember that not all grasshoppers will cause harm and low numbers can be tolerated. Most insecticides are not selective (Nosema locustae is an exception), and beneficial insects and spiders will be killed as well as pests. For effective grasshopper suppression, it is important to start early when grasshoppers are small and to maintain control until eggs have hatched and new waves of nymphs are no longer detected. Once flying adults are on the scene, it is too late for effective control that year.
For more information, visit http://extension.usu.edu/insect/fs/grassho3.htm to view “Grasshoppers in Utah: General Biology” by Edward W. Evans or visithttp://extension.usu.edu/insect/fs/grasshop.htm to see “Grasshoppers and their Control,” by Alan H. Roe.
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