Grasshoppers have a misleading name as many of them don’t just feed on grass - they also consume the leaves of many broadleaf plants. Grasshoppers and locusts are closely related members of the family Acrididae within the order Orthoptera. They both have chewing mouthparts that leave distinctive ragged holes and chewed edges on leaves.
There are more than 700 species of grasshoppers and locusts in the family Acrididae found in Australia, but only a few species are considered to be pests.
Grasshopper and locust species are most likely to cause problems in gardens include the Wingless Grasshopper of south-eastern Australia and south-west Western Australia; the Plague Locust and Spur-Throated Locust of inland Australia; and the Giant Grasshopper of northern Australia.
We have all seen alarming television footage of armies of advancing grasshoppers and clouds of swarming locusts, but luckily such occurrences are not as common in Australia as they used to be. Millions of dollars are spent every year monitoring and controlling locusts to reduce the likelihood of such severe outbreaks.
A few grasshoppers here or there won’t cause much harm in the garden, but if the numbers increase, the situation may change. Grasshoppers and locusts are most common during the warmer months, and during drought periods our gardens are a magnet for grasshoppers and locusts. It pays to be vigilant.
If you have vulnerable plants such as those in vegetable beds, prevention is the key. The simplest thing to do is net vulnerable plants where practical. If numbers of grasshoppers are increasing, there are several things you can do to prevent the situation from getting out of hand (see Prevention).
Grasshoppers and locusts have many natural enemies and it is a good idea to encourage them into your garden (see Natural enemies). If you do experience a rare locust swarm, it’s important to know that locusts usually feed and move on. Locusts may leave a trail of destruction, but at least they usually don’t stay for long in the same spot.
If treatment is needed for grasshoppers on ornamental plants (all non-edible plants), use Yates Baythroid Advanced Insect Killer for Gardens. Spray plants directly and thoroughly when grasshoppers are seen. Repeat treatments may be necessary, especially if the infestation is severe.
Grasshoppers and locusts are members of the insect order Orthoptera, a group of insects best known for their powerful jumping abilities and their ‘singing’ (technically known as stridulating). Grasshoppers and locusts communicate by either rubbing their hind legs together or snapping their wings together in flight causing a buzzing or crackling sound.
The Wingless Grasshopper (Phaulacridium vittatum) is found in southern Australia and has become more common as native grasslands and scrublands have been replaced with improved pastures. As pasture vegetation dries off in summer, the grasshoppers disperse and invade horticultural crops and orchards, as well as parks and home gardens.
The Giant Grasshopper (Valanga irregularis) is endemic to tropical northern Australia and is our biggest grasshopper. This grasshopper feeds on the leaves of trees and shrubs, including roses. Damage can be serious if many grasshopper’s attack trees and shrubs. Outbreaks are relatively common in Queensland, especially around Brisbane.
Locusts are a type of grasshopper that form swarms – the best known being the Australian Plague Locust (Chortoicetes terminifera). Locust swarms eat everything in their path, but fortunately major locust attacks in gardens and parks are not common. Another significant pest is the Spur-Throated Locust (Austracris guttulosa) that is mostly a tropical species.
The Yellow-Winged Locust and several other grasshopper species also visit gardens but are usually less troublesome.
Adult Wingless Grasshoppers are greyish brown, with orange hind legs and two light coloured stripes on top of the thorax. Females are about 18 mm long and males are about 12 mm long. Most adult Wingless Grasshoppers have short, non-functional wings – hence, their common name of ‘wingless’ grasshopper. Only a small percentage of any Wingless Grasshopper population has functional wings.
Giant Grasshopper females are 60–75 mm in length and males 45–55 mm, and often grey in colour.
Adult Australian Plague Locusts are 25–35 mm long and vary in colour from light to dark shades of green or brown. Distinguishing features are a dark blotch at the edge of the hindwings, and red hind legs.
The Spur-throated Locust is a large locust, with adults measuring between 50 and 80 mm long. All growth stages of this locust have a conspicuous spur between the front legs. Spur-throated Locusts are usually greenish to light brown in colour, and adults often have a white longitudinal stripe on their back.
Yellow-winged Locust adults are 35 to 50 mm long, with distinctive bright yellow hindwings that are evident when the locust takes flight. The Yellow-winged Locust also stridulates in flight.
All grasshoppers and locusts develop through a life cycle of gradual metamorphosis. Females lay eggs in groups (pods) in soil. Nymphs (often called ‘hoppers’) hatch from eggs and resemble miniature versions of the adults, but without wings. The nymphs progress through a series of moults to the adult form. Grasshoppers usually only have one generation per year, but some locust species can have three or four. Grasshoppers and locusts usually overwinter as eggs.
Image above: Giant Grasshopper (Valanga irregularis) nymph