How to Manage Pests

UC Pest Management Guidelines

DESCRIPTION OF THE PEST

Mormon crickets are not true crickets but more closely related to katydids and longhorned grasshoppers. They pass the winter as eggs in the soil, preferring barren, sandy soil in sunny locations. Eggs hatch in the first warm days of spring and the crickets pass through seven nymphal stages in about 75 to 100 days. Mature adult female crickets lay eggs throughout the summer, but the eggs don't hatch until the following spring.

Adults are about 1 inch long, heavy-bodied, and tan colored. The wings are small and useless; these insects do not fly. The antennae are as long as the body, and the female has a sword-shaped ovipositor also as long as the body. Mormon crickets are active only during the warm, sunny part of the day and seek shelter at night or in cloudy or rainy weather. When they are half grown, they begin migrating from their rangeland breeding grounds. The migrations occur at air temperatures of 65° to 95°F and when winds are less than 25 mile/hour.

DAMAGE

Mormon crickets become pests very sporadically (about once or twice in a decade) when populations build to high levels and they migrate over large areas. If an alfalfa field is in the path of a migration, Mormon crickets can cause severe damage by devouring the plants.

MANAGEMENT
Management of Mormon crickets centers on preventing invasions of fields with barriers or insecticide baits.

Cultural Control
Because these insects cannot fly, linear barriers of 10-inch strips of 28- to 30-gauge galvanized iron, held on edge with stakes driven into the ground may stop swarms. Soil pits or water traps may be made at intervals to catch crickets halted by the barrier.

Organically Acceptable Methods
Cultural controls are acceptable for use on an organically certified crop.

Monitoring and Treatment Decisions
Treatments on the border of the field may be effective at limiting invasion of migrating populations of this pest; baits work well for this purpose. Check with your County Agricultural Commissioner regarding the current registration of baits to control Mormon crickets in alfalfa fields.

PUBLICATION

UC IPM Pest Management Guidelines: Alfalfa
UC ANR Publication 3430
Insects and Mites
C. G. Summers, Entomology, Kearney Agricultural Center, Parlier
L. D. Godfrey, Entomology, UC Davis
M. Rethwisch, UC Cooperative Extension, Riverside County (Blythe)
D. R. Haviland, UC Cooperative Extension, Kern County
P. B. Goodell, Entomology, Kearney Agricultural Center, Parlier
R. F. Long, UC Cooperative Extension, Yolo County

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