Analysis of the development of major plagues of the Australian plague locust Chortoicetes terminifera (Walker) using a simulation model

Abstract

The development and decline of all the past major plagues of Chortoicetes terminifera in Australia has been analysed using all available locust data and a simulation model to estimate the course of events for periods when few locusts were reported. The model is based on the developmental biology of the locust and tnchides methods of estimating the duration of egg. nymphal and adult development and uses a pasture growth index and potential night displacement index to assess likely survival and migration.The analysis shows that five ofthe six plagues originated in the arid interior, where good spring and summer rain allowed two or three consecutive generations of successful breeding, before emigration to the agricuhural country occurred in the late summer or early autumn. This is contrary to the idea held previously that most plagues developed from local bi'eeding in established outbreak areas in the agricultural belt. The applications of these results, to improve population monitoring and control strategy' by suggesting the best timing for surveys and when control would have most effect, are discussed.

Spatial scales of desert locust gregarization

“…Existing attempts to predict the emergence of swarms based on time-series analyses of outbreaks have been largely unsuccessful (16)(17)(18). Ecologically based forecasting models for S. gregaria and other locust species show more promise (19)(20)(21)(22)(23)(24)(25)(26). These models have been based on the properties of populations not individuals.…”

Parasitism of Eggs of the Australian Plague Locust Chortoicetes terminifera (Walker) (Orthoptera: Acrididae) by Scelio fulgidus Crawford (Hymenoptera: Scelionidae)

“…When C. terminifera are at plague levels, even low parasitism means a very high absolute abundance of S. fdulgidus. After plague collapse, usually from dry conditions in late spring or early summer (Wright 1987, Wright et al 1988, the large numbers of S.fuldgidus present attack the remnant host population, resulting in very high parasitism. The high post outbreak parasitism levels were not reached during 1990-94, when a preventative control program kept locust populations from reaching plague proportions: lower host numbers mean a lower absolute abundance of S. fidgidus, so when host populations collapsed, the parasitism in residual locust populations increased less.…”

“…Most plagues of C. terminifera begin when rains originate in the arid interior (Wright 1987, Hunter 1996. During these rainfall sequences, moderate numbers of C. terminifera eggpods are parasitized by S. fulgidus.…”

“…Most plagues of the Australian plague locust, Chortoicetesterminifera (Walker) originate in the arid interior after favourable sequences of rain that allow several generations in succession (Wright 1987). Subsequent migrations of 500-1000 km over several nights may result in invasion of agricultural areas to the south and east (Farrow 1975, Hunter 1982, Drake and Farrow 1983, Casimir 1987.…”

The rapid and long‐lasting growth of grasses following small falls of rain on stony downs in the arid interior of Australia

“…Most plagues of the Australian plague locust, Chortoicetes terminifera (Walker), originate in the channel country of western Queensland (Wright 1987). In this area, locusts are most common in open clay plains and stony downs (McCulloch & Hunter 1983).…”