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Grasshoppers

Order Orthoptera: Family Acrididae


Redlegged grasshopper (Melanoplus femurrubrum)

Differential grasshopper (Melanoplus differentialis)

Twostriped grasshopper (Melanoplus bivittatus)

Migratory grasshopper (Melanoplus sanguinipes)

DESCRIPTION:

Adult: About 1-2 inches long with a robust body, hind legs with enlarged femurs for long-distance jumping, and relatively short antennae (Fig. 6.2).

Figure 6.2Figure 6.2 -An adult grasshopper; note the fully developed wings.

Egg: About the size as a grain of rice, eggs are contained in pods of up to 100 eggs in the upper 2 inches of soil.

Nymph: Five nymphal stages or instars. Instars grow from around ¼ inch (1st instar) to 1 inch (5th instar) (Figs. 6.3 and 6.4). Wing pad size gradually increases with each instar until they are able to fly, indicating adulthood.

LIFE HISTORY:

Female grasshoppers lay eggs in undisturbed soils in late summer and fall. Eggs hatch in mid- to late-spring when soil temperatures warm and new nymphs feed on nearby plants. In some years, populations can increase in undisturbed areas and move into crop sites where they cause massive defoliation. Most grasshopper species in Utah have one generation per year.

DAMAGE:

Grasshoppers have chewing mouthparts that leave random, ragged holes in leaves and flowers (Fig. 6.5), and can devour entire plants. In general, they prefer young green plants of corn, lettuce, bean, carrot, onion and some annual flowers. Damage occurs in the early summer after rangeland weeds dry up and usually lasts for a few weeks.

Figure 6.5Figure 6.5 - Grasshoppers feed on leaves and flowers leaving ragged holes and can devour entire plants.

MANAGEMENT:

Because grasshoppers are able to travel long distances, especially as adults, it is important to treat large areas. The best time to treat is in mid-spring when nymphs are young.

Cultural:

  • Use floating row covers or lightweight plant fabric. Row covers will exclude the grasshoppers, and should be removed during crop flowering for pollination. This can be done in the morning hours when pollinators are most active
  • Hand removal. Grasshoppers can be handpicked and squashed, especially when populations are low

Chemical:

  • Baits. The insecticide, carbaryl, is mixed with wheat bran to create a bait. Spread it evenly throughout the habitat and re-apply weekly. The bait can also be placed inside a container, such as PVC pipe segments, to protect it from getting wet (wet bait is no longer attractive to grasshoppers).
  • Dusts. Dusts have short residuals and must be reapplied weekly and after rain or irrigation.
  • Sprays. Sometimes aerial sprays can be coordinated with the Utah Department of Agriculture and Food. The USDA threshold for rangelands is 9 nymphs per yd2; agricultural thresholds would likely be lower.

Biological:

Nosema locustae is a biological insecticide bait that must be applied to early nymph stages and is specific to grasshoppers. After feeding on the bait, grasshoppers stop feeding, become lethargic, and die. The disease is contagious and will infect other grasshoppers that cannibalize diseased grasshoppers in the area.