Australian Plague Locust

Chortoicetes terminifera

Family: Acrididae

Order: Orthoptera

Description:

Colour - Swarming locusts are light brown. Solitary locusts are yellow or green.

Body - 24-50 mm long 15 mm wide.

End section of leg (Tarsi) has 3 segments.

Antennae less than half the length of the body.

Sings or make clicking sounds and stops when approached.

Have wings and flies. Hind wings have a characteristic black tip.

Chewing mouthparts.

Strong rear legs for jumping that have a red patch on the inside.

Front segment of thorax has a strong shield (pronotum).

Abdomen has 11 segments. Spiracles on segments 1 to 8.

Antennae have 7 or more segments.

Biology:

Locusts can eat their own weight of green food each day.

They tend to gather to mate and lay eggs which are often in "egg beds" on hard, bare ground, along fence lines or other uncultivated areas.

Life Cycle:

Eggs are laid in pods 10-80 mm below the soil surface. Bare compacted soils are preferred for egg laying. Over-wintering eggs hatch in late August or September (in WA) as soil temperatures rise above 150C to become a nymph (or miniature adult) about the size of a house fly (3 mm long). Initially they are white but darken within a few hours of hatching. They have 5 growth stages before reaching their final size in 4-8 weeks. If conditions are good and green food is available, they mate and lay eggs over the next three weeks. In dry conditions, egg laying may be delayed up to a month until rain falls. Three pods of 70 eggs may be laid by each female if green feed and rain is available during development. Under dry conditions there may be no egg laying. If the soil is dry eggs may not hatch until summer rain occurs. If conditions remain dry most of these eggs will die. If the soil is moist, the eggs will hatch in 2-3 weeks. Dry summers often kill most of this generation including eggs. The survivors mature and lay eggs which remain in the soil over winter to emerge in the following spring. There may be two or more generations per year which results in the quick production of plague numbers.

Each growth stage can be identified by the size and wing development.

1st stage- Nymph - 3-6 mm long

2nd stage - Hopper - 6-10 mm long

3rd stage - Hopper -10-13 mm long, wing buds apparent.

4th stage - Hopper - 13-20 mm long, wings as long as collar.

5th stage - Hopper - 20-25 mm long, wing twice as long as collar or half its body length.

6th stage - Adult - 25-40 mm long, wing extends beyond the tail and the locust can fly.

Habitats:

The preferred food is green grass but any green material will be consumed including Pine tree seedlings.

Nymphs stay close to the egg bed for a day or two after hatching then moves randomly away from it. The distances moved increase as the temperature rises and the Locusts become larger. At the 3rd stage the Locust may start moving in an orderly fashion to form bands in hot weather during the day and when feed is limited. These bands may move 100 m per day and often disperse overnight. Adult locusts tend to fly short distances then stop to feed and rest. On hot days they may form swarms and fly several kilometres at altitudes of up to 10 m. Occasionally, they will congregate and take off in massive swarms overnight and travel up to several hundred kilometres downwind at altitudes of up to 1000 m.

Origin and History:

Native to Australia.

In WA plagues have occurred in 1981/82, 1990/91 and 1995. Prior to this, various plagues have occurred but the particular species involved was not certain.

Distribution:

All states.

Significance:

Locusts may build up to large numbers after drought breaking rains in the semi arid grasslands. Plagues are more common in NSW, Victoria and SA than they are in WA. They usually build up when desert areas receive rain and then migrate to the coastal agricultural areas. If summer rain and green feed is available they survive and build up and may cause severe economic losses in the second and subsequent years. Individuals may migrate large distances (hundreds of kilometres) in dense swarms at night. During the day, swarms of flying adults or bands of hoppers move and devour crops and pastures in their path. The bands of hoppers develop from nymphs from dense egg beds. Swarms of Australian Plague Locusts occur more frequently than the Migratory Locust. They can cause severe economic losses and campaigns are often undertaken to reduce the effects. They will eat almost anything green and ripening cereals and perennial pastures may be devastated by swarms. In WA, cereals, broadacre crops and annual pastures are often dry by the time Locusts reach damaging sizes and densities so their impact is reduced. Perennial crops and pastures, trees, gardens and horticultural crops usually suffer the greatest damage. Green pastures, sparse, late maturing crops and the edges of crops near pasture are often damaged by young locusts. Older locusts may cause damage to partly green crops and may lop cereal heads. Mature tree plantations are not usually damaged by young locusts, but can be damaged by adults.

Night flying swarms usually move further than day flying swarms.

Body parts of locust may contaminate harvested grain causing downgrading.

Losses of $20-200M are expected from plagues that are not controlled.

Management and Control:

In most years control is not economical. When plagues occur concerted campaigns are mounted involving spraying of egg beds, hoppers, bands and swarms.

Hoppers may be controlled by a number of insecticides very effectively, however flying or swarming locusts can devastate pastures and crops very quickly and randomly which makes control very difficult.

Egg beds should be treated each week with insecticide when young locusts are hatching before they spread.

If locusts form bands at the 3rd growth stage (10-12 mm long locusts) these should also be sprayed with insecticide.

Swarms can be difficult to target and spray.

Adult Locusts surviving for more than 3 weeks in hot dry weather will probably not lay eggs and will often die without spraying.

Most Locusts sprays are usually more effective on fine hot days when the Locusts are active and when applied during the warmest part of the day. Use small droplet sizes.

Research into biological control is being conducted by the CSIRO. There are several fly parasites that heavily parasitise the second generation. In the South West of WA a wasp, Scelio fulgidus can heavily parasitise egg beds.

Thresholds:

5 adults per square metre are usually worth spraying in pastures.

In cereal crops, spray as soon as damage or head lopping is seen.

Related Species:

Wingless Grasshoppers usually have a light coloured stripe down each side of the body. The wings are usually poorly developed and only occasional individuals can fly. The hind wings never have a black tip or blotch.

Grass hoppers, Crickets, Sandgropers.

Similar Species:


References:

CSIRO. The Insects of Australia. Melbourne University Press. (1991) p70, 71(development diagram), 105, 107, 108, 371(diagram), 377, 391, 392(diagram).

WADA. Insects and Allied Pests of Extensive Farming. Department of Agriculture - Western Australia Bulletin No. 4185. p59.

Farmnote 82/2000: Australian Plague Locusts: broad-scale control

Acknowledgments:

Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information.