Australian Plague Locust
Introduction
The Australian Plague Locust (Chortoicetes terminifera) is a species of short-horned grasshopper in the family Acrididae, native to Australia. It is regarded as the most significant pest species in the country due to its potential to form dense migratory swarms, which can cause extensive damage to agricultural crops and pastures.
Biology and Life Cycle
The Australian Plague Locust exhibits a typical grasshopper life cycle, consisting of three stages: egg, nymph, and adult. The duration of these stages is highly dependent on environmental conditions, particularly temperature and humidity.
Egg Stage
The female locust lays her eggs in the soil, usually in areas of bare ground or sparse vegetation. The eggs are laid in pods, each containing around 50-100 eggs. The egg stage lasts for about 10-14 days in optimal conditions, but can be extended in cooler weather.
Nymph Stage
Upon hatching, the locusts enter the nymph stage. This stage is characterized by several molts, during which the locust grows in size. The nymph stage lasts for about 20-25 days, after which the locust reaches adulthood.
Adult Stage
Adult locusts are capable of reproduction and can form swarms. The adult stage lasts for about 20-30 days, although this can be extended in favourable conditions.
Behaviour
The Australian Plague Locust is known for its swarming behaviour, which is triggered by high population densities. Swarms can contain millions of locusts and can travel large distances, driven by wind conditions.
Swarming Behaviour
Swarming behaviour is a survival strategy that allows locusts to exploit resources in a variable environment. Swarms form when locusts reach a critical population density, which triggers changes in behaviour and physiology. These changes include increased mobility and the development of a gregarious phase, characterized by dark colouration and a strong tendency to aggregate.
Migration
Swarms of Australian Plague Locusts can travel large distances, driven by wind conditions. Migration allows the locusts to exploit new areas of vegetation, and is a key factor in the species' ability to cause widespread damage to agriculture.
Impact on Agriculture
The Australian Plague Locust is considered a significant pest species due to its potential to form large swarms, which can cause extensive damage to crops and pastures. The locusts feed on a wide range of plant species, but show a preference for grasses and cereals.
Control Measures
Control of the Australian Plague Locust typically involves a combination of monitoring, forecasting, and direct control measures. The Australian Plague Locust Commission (APLC) is responsible for managing locust outbreaks in eastern Australia.
Monitoring and Forecasting
Monitoring and forecasting are crucial for effective locust control. The APLC maintains a network of monitoring sites across eastern Australia, which provide data on locust numbers and breeding activity. This information is used to predict locust outbreaks and to plan control measures.
Direct Control
Direct control measures include the use of insecticides and biological control agents. Insecticides are typically applied by aircraft, while biological control agents, such as the fungus Metarhizium anisopliae, are used in more targeted applications.