F@stSheet Ent-1043

Grasshoppers in Agriculture: Frequently Asked Questions IN THIS F@STSHEET QUESTIONS AND ANSWERS FOR MORE INFORMATION

 Why are grasshoppers so bad this year, again?

Hot, dry summers and warm, dry autumns favor grasshopper survival and increase. Warm, dry fall weather allows grasshoppers more time to feed and lay eggs. The large numbers of grasshoppers from last years high populations left many eggs in the soil which hatched this spring. Early indications are that 2001 will be another bad year for grasshoppers in Texas.

Where do grasshoppers come from?

Grasshopper eggs are deposited in the soil ½ to 2 inches deep in weedy areas, fence rows, ditches and hay fields (see Lifecycle Diagram). 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 there is generally one generation a year, eggs hatch over a long period of time and development from egg to adult requires about 40-60 days. Thus, grasshopper problems will likely persist until late fall when old adults begin to die or when a killing frost occurs.

What can be done to reduce their numbers?

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.

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 protected area.

When should insecticides be applied?

Monitor grasshopper infestations and treat threatening infestations while grasshopper 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 Advantage Home and Garden Spray and Tempo
• Bifenthrin. Active ingredient in Ortho Ready-to-Use Houseplant and Garden Insect Killer
• Permethrin. Active ingredient in Spectracide Product and other brands
• Acephate. Active ingredient in Orthene
  

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, distchbanks 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 Atttack, 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.

What insecticides can be used on pastures and hayfields?
Malathion 57 EC and malathion ULV are labeled and have no grazing or harvest restrictions. Carbaryl, formulated as Sevin 4F, Sevin XLR, Sevin WSP, Carbaryl 4L, and others, is also labeled for pastures. Refer to the carbaryl label for waiting period after treatment before grazing or harvesting. Methyl parathion, marketed by Helena and Griffen, is also labeled for grasshopper control in pastures and has a 15 day restriction on grazing and harvest.

What is Dimilin 2L?

Dimilin 2L is a new product for grasshopper control but as of May, 2001, it is labeled only for use in rangeland and non-crop areas (roadsides, wasteland, fence rows, CRP). Rangeland is defined as land with predominantly native grasses. Dimilin disrupts the normal molting process during which young grasshoppers shed their skins. Thus, Dimilin is only effective on immature grasshoppers and does not kill adults. Control may be slow because grasshoppers must first eat Dimilin and then molt (shed their skin) before dying. However, Dimilin is rain-fast and can provide residual control of hatching grasshoppers for several weeks.   

FOR MORE INFORMATION
For more information about grasshoppers, see Extension publication L-5201, Grasshoppers and their Control.

Author:
Allen Knutson, Ph.D., Extension Entomologist, Texas AgriLife Extension Service
Reviewed by Mike Merchant

Publication information:
This publication is part of the House & Landscape Pest Series produced by the Department of Entomology, Texas A&M University, College Station, TX 77843-2475. The most recent update can be found at: http://165.95.73.17/FastSheets/Ent-1043.html . Series Editor: M. Merchant. For more information about arthropods, check out the Texas A&M Entomology Website at http://insects.tamu.edu
Last revision: July, 2005