Clear-winged grasshopper

Background

The clear-winged grasshopper (Camnula pellucida) can be found throughout Alberta. However, this grasshopper exhibits extreme fluctuations in abundance from year to year.

For general grasshopper information, see the Overview.

Figure 1. A mature clear-winged grasshopper female

Identification

The adults are yellowish to brownish and approximately 21 to 32 mm (0.8 - 1.3 inches) in length. Their wings are clear but mottled with dark patches, and they have 2 stripes beginning at the thorax and converging at the tip of the forewings (Figure 2). The newly hatched young are black with a distinctive white band encircling the thorax.

Figure 2. Clear-winged grasshoppers feeding on wheat

Habitat

The clear-winged grasshopper prefers to lay its eggs in sod on road allowances, overgrazed pastures and dried out marshy areas. Congregation of the adults during egg laying may result in as many as 10,000 or more eggs per square metre.

Food supply

The clear-winged grasshopper is primarily a grass feeder that prefers cereal grains and some of the more succulent cultivated grasses. It seldom feeds on broad-leaved plants like pulses and canola. This can be the case when other preferred crops are not available. Large pastures of native grasses are usually only infested around their margins where cultivated fields are close by.

Host plants

C. pellucida is mainly a grass feeder. Economic damage is primarily to cereals, especially wheat and barley. Clear-winged and migratory grasshoppers have together destroyed areas of range grass and hay almost entirely.

The nutritional qualities of the chief food plant can affect longevity and egg production of grasshoppers. Kentucky blue grass is one of the best foods for high survival and egg production. Western wheatgrass is one of the worst foods for grasshoppers and could be a factor that limits distribution of this grasshopper on the Prairies. It may be the only green grass available to attract females at egg laying time.

Life cycle

Overwintering

Clear-winged grasshopper eggs are laid in the fall and hatch the following spring. Each female lays an average of eight egg pods (about 175 eggs) usually in unbroken sod. The short vegetation of dry, mowed roadsides and sparse, over-grazed pastures is especially favoured for egg deposition. Males are conspicuous at egg laying sites; their undersides become bright yellow during the mating and egg laying period. They stake out a territory and wait for females to come to oviposit.

Spring appearance

If the previous fall was warm, eggs of the clear-winged grasshopper will be the last of the pest grasshopper species to hatch. They hatch in late May to early June. The embryos of this species undergo a maximum of 50% of their total development before winter. The other pest species can complete more of their development in the fall and consequently need less time in the spring to complete pre-hatch development.

Number of generations

As with all of Alberta's grasshopper pests, clear-winged grasshoppers have one generation per year.

Damage assessment

Damage description

Damage to cereal crops is generally concentrated near field margins and is caused when hatchling grasshoppers move out of egg beds into field edges; damage to grasslands tends to be more evenly distributed.

Damage to cereals includes leaf notching and stripping but is most costly when stems are severed just below the heads of maturing or mature crops. When grasshopper numbers are extremely high and natural plant hosts in short supply, grasshoppers will consume or attempt to consume any plants or plant products that they come upon during their migrations in search of food.

Sampling and monitoring methods

Walk through the infested area and estimate the number of grasshoppers per square metre as they jump in front of you. A sampling 'T' will likely improve your estimate. The 'T' consists of a metre-long measuring stick, carried by a handle so that a square metre can be visualized at crop height. Walk and carry the 'T' just above the crop.

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

Clear-winged grasshopper has been, on average, the most economically important species of grasshopper in Canada, although over the years its importance relative to other species has changed gradually. The first record from the Prairie Provinces was from Saskatchewan in 1800. Clear-winged grasshoppers did not become abundant, however, until about 1900 when road-building, drainage and cultivation in southern Manitoba created favorable breeding sites and greatly increased the abundance of suitable food plants.

In recent years, there has been a marked decrease in the intensities of outbreaks in Manitoba. This may be related to changes in agricultural practices that have reduced populations of certain grasses. See also Grasshopper – Economic thresholds.

Related

• Alberta Insect Pest Monitoring Network
• Prairie Pest Monitoring Network
• Field Heroes