Grasshoppers – Frequently asked questions 2011

Allen Knutson, Extension Entomologist, Texas A&M Research & Extension Center, Dallas
Why are grasshoppers so bad this year, again?
Consecutive years of hot, dry summers and warm, dry autumns favor grasshopper survival and reproduction. Warm, dry fall weather allows grasshoppers more time to feed and lay eggs. Large numbers of grasshoppers in the late summer can deposit large numbers of eggs which hatch in the spring. Also, rains in the spring when eggs are hatching drown young hoppers and encourage fungal diseases which kill hoppers. Thus, dry weather in the spring favors their survival.  During hot, dry summers, weedy hosts dry up and grasshoppers fly in search of green plants. The search for food can result in large numbers of grasshoppers concentrating in orchards, crops and irrigated landscapes.
From where do grasshoppers come?
Grasshopper eggs are deposited in the soil ½-2 inches deep in weedy areas, fence rows, ditches and hay fields. The eggs hatch in the spring and early summer. Eggs of different grasshopper species hatch out at different times, so young grasshoppers can be seen throughout the spring and early summer.  Young grasshoppers, called nymphs, feed for about six weeks. Once nymphs reach the adult stage, they can fly. As weedy plants are consumed or dry in the summer heat, adult grasshopper can fly from weedy areas and pastures to more succulent crops and landscapes.
When will grasshopper numbers decrease this season ?
Although grasshoppers complete only one generation a year, eggs hatch over a long period of time. Development from egg to adult requires about 40-60 days. Also, eggs of different species hatch at different times so small grasshoppers can be found throughout the growing season. Grasshopper can persist until late fall when old adults begin to die or when a killing frost occurs.
What can be done to reduce their number ?
Weed control. Eliminating weeds will starve young hoppers and later discourage adults from laying eggs in the area. Destroying weeds infested with large numbers of grasshoppers can force the hungry grasshoppers to move to nearby crops or landscapes. Control the grasshoppers in the weedy area first with insecticides or be ready to protect nearby crops if they become infested. Grasshoppers deposit their eggs in undisturbed soil, as in fallow fields, road banks, and fence rows.. Shallow tillage of the soil in late summer may be of some benefit in discouraging egg lay.
Are insecticides effective?
Grasshoppers are susceptible to many insecticides. However, insecticides typically do not persist more than a few days and grasshoppers may soon re-invade the treated area. The length of control will depend on the residual activity of the insecticides and the frequency of retreatment. Controlling grasshoppers over a large area will reduce
the numbers present which can re-infest a treated area. Dimilin 2L provides long residual of young hoppers but is not effective against adults.
When should insecticides be applied?
Monitor grasshopper infestations and treat threatening infestations while grasshoppers are still small and before they move into crops and landscapes. Immature grasshoppers (without wings) are more susceptible to insecticides than adults.
Some insecticides for controlling grasshoppers in the home landscape include:
Cyfluthrin. The active ingredient in Bayer Advanced Home and Garden Spray and Tempo
Bifenthrin. Active ingredient in Ortho Ready-to-Use Houseplant and Garden Insect Killer
Permethrin. Active ingredient in Spectracide and other products.
Acephate. Active ingredient in Orthene.
Note: Tempo (cyfluthrin) and Demon (cypermethrin) are labeled for use by Professional Pest Control Operators for insect control in lawns and landscapes.
What about insecticide baits for grasshopper control ?
Sevin 5 Bait is a ready-to-use bait which can be applied to many crop and non-crop sites, including around ornamentals and many fruit and vegetable crops.
For those wanting to make their own grasshopper bait, the labels for Sevin XLR and Sevin 4-Oil ULV provide directions for mixing these product with cereal grains to make a 2% to 10% carbaryl bait. The bait is labeled for use in rangeland, wasteland, ditch banks and roadsides. The label further states the bait is for use “only by government personnel or persons under their direct supervision (e.g. USDA, state and local extension personnel, etc.)”
Are biological control products such as Nolo Bait, Grasshopper Attack, and others effective?
These products contain spores of a protozoan called Nosema locustae, formulated in a bait. Grasshoppers consuming the bait become infected by the Nosema organism. Some immature grasshoppers die while adults often survive but females lay fewer eggs. Nosema baits act too slowly and kill too few grasshoppers to be much value when the need for control is immediate.
What other non-pesticide controls can be used?
Floating row covers can protect vegetables, flower gardens, small fruit trees and other small areas from grasshoppers. These lightweight fabrics let sunlight in while protecting plants from insects and cold. However, under heavy attack, grasshoppers may chew through the fabric to get to plants.
For more information, see: Extension bulletin L-5201 Grasshoppers and Their Control
What insecticides can be used on pastures and hayfield?
Some Insecticides Labeled for Grasshopper Control in Pastures and Hayfields.
Always read and follow all label instructions on pesticide use and restrictions. Information below is provided for educational purposes only. Read current label before use.

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About Dr. Michael "Shane" McLellan

County Extension Agent-Ag McLennan County
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