How to Manage Pests
UC Pest Management Guidelines
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.
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.
UC IPM Pest Management Guidelines: Alfalfa