|Description of adult|
The giant grasshopper is the largest of the short horned (antennae) grasshoppers in Australia, with adults growing up to 90 mm long. Adults are creamy brown to grey. Their colouration and markings are extremely variable, hence the species name (irregularis). Giant grasshoppers have enlarged hind legs used for jumping and short antennae. They have a spur or peg on the throat between the forelegs. Adults can be distinguished from the spur-throated locust (Austracris guttulosa) by their larger size, the absence of a white stripe along the top of the body, the blacked-tipped orange to red spines on the hind leg tibia (instead of black tipped white spines) and two dark marks on the top of the hind femura in both adults and nymphs.
Eggs are 5-6 mm in length and are laid in pods up to 90 mm deep in moist soil. The pods consist of up to 150 eggs at the bottom of the tubular hole with a frothy plug from the top of the eggs up to the soil surface. The frothy plug has a less dense area up the centre and, at hatching, hoppers escape by moving up this centre. Nymphs (hoppers) are pale green and wingless on hatching. They later develop a black stripe down the middle of their back and the green colour may change to light brown as they approach the adult (winged) stage.
Eggs are deposited in October-November. There are seven nymphal stages before adulthood is reached.
Nymphs are present from September to March and adults from April to November. No breeding takes place during winter. There is one generation per year.
This grasshopper is native to tropical and subtropical Australia and is found throughout Australia from about Sydney north.
The giant grasshopper feeds on a wide range of shrubs, trees and herbaceous plants including hibiscus, coffee and citrus.
Giant grasshoppers feed mainly on foliage and sometimes on very young coffee berries. They are often very patchy with concentrations of nymphs close to where they emerged from the soil.
Deep feeding gouges on very young berries heal to disfiguring chalky-white scars.
Edges of leaves and tips of shoots are chewed.
When monitoring for other pests, check for damaged leaves, or for the presence of grasshopper adults and nymphs. Examine five plants at six locations widely spread throughout the crop.
In coffee, action is required when giant grasshoppers damage 25% or more of young shoots.
In home gardens, grasshoppers can be removed from plants by hand and destroyed. They are most readily detected in the early morning when they tend to bask in the sun on the tops of foliage.
The small wasp Scelio flavicornis parasitises eggs. Flies from the genus Blaesoxipha parasitise the adults and large nymphs. The adult flies are about the size of a house fly. Their larvae (maggots) eat out the insides of their host and kill it as they leave to pupate through a hole in one of the inter-segmental membranes, often between the head and thorax.
It might be possible to spot spray heavily infested areas. This will require fairly intensive monitoring throughout the crop.
Chemical registrations and permits
Check the Australian Pesticides and Veterinary Medicines Authority chemical database and permit database for chemicals registered or approved under permit to treat this pest on the target crop in your state or location. Always read the label. Always observe withholding periods.