Grasshoppers and locusts

Although they look similar, grasshoppers and locusts behave differently. Australian locusts often form into groups when nymph populations are dense, resulting in large-scale migrations from breeding areas. Grasshoppers generally remain solitary and localised.

Locust pests in Queensland include:

Grasshoppers in Queensland include the wingless grasshopper.

Scientific name

Phaulacridium vittatum (Wingless grasshopper)

Description

Wingless grasshoppers

  • Females are about 18–20mm long; males are smaller.
  • Body colour and patterns are highly variable.
  • In low density populations, they may have 2 white stripes along their back.
  • The hind leg is usually orange with a black mark in the middle of the 'thigh'.
  • Nearly two-thirds of adults have short ineffective wings; the rest develop longer wings and can fly.

May be confused with

Wingless grasshoppers may be confused with nymphs of other grasshopper and locust species.

Distribution and habitat

Native to Australia. Widely distributed in temperate areas with annual rainfall more than 500mm from Southern Queensland to southern Western Australia.

Hosts

A wide range of native and introduced herbaceous broadleaf plants, and some native tree species.

Damage

Locusts and grasshoppers damage crops and pastures by chewing leaves and stems.

Most damage to pastures occurs in mid-summer and autumn, following moderately dry years. Preferential feeding on the legume component of improved pastures can damage newly established areas so severely that re-sowing is necessary.

Life cycle

  • Tear-shaped egg pods containing about 12 eggs are laid into the soil.
  • Eggs diapause during winter and hatch in mid to late spring.
  • Nymphs develop through 5 instars and become adults in mid-December to early January.

Monitoring and thresholds

  • Monitor for groups of nymphs in pastures, and take action at first evidence of aggregating.
  • Treatment of low-value pastures is not usually cost-effective.

Natural enemies

  • Up to 30% of eggs may be parasitised by Scelio spp., and there are several dipteran (fly) parasitoids of nymphs and adults.
  • Nematodes are important regulators of wingless grasshopper populations in New South Wales, but are highly dependent on rainfall for successful parasitism.
  • Birds (e.g. crows, magpies and ibis) prey on wingless grasshoppers, and guinea fowl may be a useful predator in gardens.
  • Cannibalistic feeding in wingless grasshopper adults may transmit a natural amoebic disease (caused by Malmeba locustae).

Control

Chemical control

  • Use ground-sprays (not aerial) to protect valuable pastures and irrigated fodder crops, particularly when stock feed is limited.
  • Control infestations near crops with barrier treatments (spraying or baiting).
  • Baits of wheat bran mixed with insecticide are the most effective when applied to bare ground.
  • Several applications of baits or sprays may be necessary in a single season.

Cultural control

  • Maintaining a dense, grassy pasture without bare areas (where grasshoppers can lay eggs) can help keep numbers in check.
  • Effective weed control may help reduce the intensity of outbreaks.
  • Ensure pastures in areas that have had wingless grasshopper outbreaks have a high component of grass species.

Biological control

  • A biopesticide containing spores of the fungus Metarhizium anisopliae is available commercially in Australia.

Notes on managing locusts

  • Ground control for small hoppers (nymph stage) can be done with boom sprays, misting machines or knapsack sprayers.
  • Aerial application is the only efficient method of control for locust swarms.
  • The Australian Plague Locust Commission (APLC) implements control measures only where it considers the locusts to present an interstate threat. Report locust activity to the APLC on 1800 635 964 (24 hours).

Further information