Australian Plague Locust - Plagues

Plagues

When food and climatic conditions are favourable huge swarms of locusts may develop. The first recorded swarm was in 1844, with further outbreaks from the 1870s onward. After 1900, the intensity and frequency of locust swarms increased and since the 1920s, a pattern has developed of localised high density populations in some locations most years and less frequent major plagues over large areas persisting for one to two years.

Infestations in Western Australia are less frequent. Widespread heavy inland rains, especially in summer, will allow plague locusts to reach plague proportions with less regular rain maintaining these high density populations. During these condition the life-cycle pattern may change to one in which the period from hatching to maturity is reduced to two and a half months. Dry conditions will reduce populations back to background levels.

Due to its large range and frequent plagues, the Australian plague locust is the most damaging locust species in Australia. Damage is mainly confined to pasture although crop damage can occur. Advanced winter crops have generally hardened off by early summer, when plague locusts become active and therefore are not favoured but dry conditions and less advanced crops can be highly susceptible to locust infestation as can young autumn crops.

Losses in a plague can amount to $3-4 million if protection barriers are ineffective. The Australian Plague Locust Commission is responsible for the monitoring and control of locust outbreaks using the control agent fipronil and growth regulators such as diflubenzuron in the juvenile nymphal stage. Two older-generation organophosphates, fenitrothion and chlorpyrifos, are also used occasionally for auxiliary, blanket spray runs, and the bioinsecticide 'Green Guard', made from a native fungal isolate of Metarhizium acridum. The latter is based on technology developed by CSIRO and the LUBILOSA Programme and now accounts for >12% of spray applications: for protected, organic farming, or environmentally susceptible areas such as water courses.