Background
The migratory grasshopper (Melanoplus sanguinipes) is a very successful species. It has adapted to every ecoregion of the Canadian grasslands and exhibits remarkable variability in colour and physical proportions, such as length of the wings. Of all the species within the genus Melanoplus, M. sanguinipes is the most widely distributed, occurring as far south as Florida.
For general grasshopper information, see the Overview.
Identification
Adult grasshoppers are brownish to yellowish and approximately 23 to 28 mm (0.9 - 1.1 inches) long. Their hind legs are marked with a series of black bands. The newly hatched grasshoppers have black bands on the top of their thorax. In the adult stage, these bands are on the sides of the thorax (Figure 1).
Figure 1. A migratory grasshopper (Melanoplus sanguinipes). This pest grasshopper can be recognized by the dark bands just behind the eyes.
Habitat
The adult female lays her eggs mainly in stubble fields, but also in drift soil, weedy pastures, brome and alfalfa pastures as well as roadside ditches. Summerfallow fields kept free of weeds are generally free of eggs even though the fields may have a substantial covering of trash.
Food supply
Because the migratory grasshopper is a mixed feeder, it thrives in weedy grain fields, cultivated pastures, hay fields and rangeland. Large numbers may be found in crops adjacent to stubble fields, especially if these fields are summerfallowed in late spring and trap strips have not been used.
Grasshoppers hatching in crops seeded on stubble fields feed on growing seedlings, and damage may go unnoticed until extensive leaf chewing has taken place. Extensive head clipping in cereal crops may occur in late summer when much of the leafy vegetation has been eaten or has matured.
Host plants and damage
The migratory grasshopper (Melanoplus sanguinipes) is one of the most destructive pests in western Canada. Outbreaks can lead to costly losses for grain growers. This species attacks both field and garden crops, especially cereals, tomato, celery, onion and carrot.
Life cycle
Overwintering
Females lay pods of about 25 eggs in stubble and wheat fields, between clumps of grass or in other patches of dry soil during August and September. The eggs of this species and others in the genus Melanoplus can complete up to 85% of their embryonic development before winter.
Spring appearance
Eggs hatch between early May and mid-July, although the date depends upon temperature and moisture conditions in both spring and the preceding fall. Watch for signs of hatching in stubble fields and along roadsides and pastures where adults were seen in August and September.
Number of generations
As with all of Alberta's pest grasshopper species, migratory grasshoppers have one generation per year.
Monitoring
Late summer and fall surveys of grasshopper adults have been carried out by Agriculture Fieldmen in Alberta since 1932. Grasshopper population maps are produced yearly from data collected in about 1,700 townships.
Spring surveys of grasshoppers and grasshopper eggs are also conducted in years when high grasshopper numbers are expected. In this way, improved estimates are obtained for time of hatch, population density, and the effects of predators and parasites.
Natural enemies
Next to weather, natural enemies are the grasshopper's most important population control factor. In some localized areas, natural enemies may cause even more mortality than the weather. Find out about predators, parasites, pathogens and other grasshopper natural enemies.
Economic thresholds
The migratory grasshopper is normally the most abundant pest grasshopper species in Western Canada. It is often injurious to cereals. Find out about determining factors and types of crop loss: Grasshopper – Economic thresholds.