Australian Plague Locust Commission

Abstract Locusts can form dense bands and swarms that can cause substantial damage to pastures and crops. For many years, State Departments of Agriculture aimed to protect crops by conducting locust control programs in their agricultural areas but in recent years the Australian Plague Locust Commission (APLC) has conducted preventive control programs that begin in locust source areas in the interior. The current preventive control programs are the culmination of more than 70 years of continuous research, conducted for many years by CSIRO and State Departments of Agriculture and more recently, by the APLC. Early research followed the sequence of outbreaks in agricultural areas but by the 1960s, there was increasing evidence that locusts commonly bred in the interior and then migrated to agricultural zones. These migrations covered long distances, often from one state to another and in 1974 the APLC was established with the specific mandate to control locusts that posed an interstate threat. The rationale was for the APLC to control locusts both at source in the interior as well as in the agricultural zone. Controlling locusts in the interior had never been attempted before and an intense research program was initiated as part of APLC operations that has culminated in the current preventive locust control programs. Preventive control involves early intervention, where treatment begins with localised populations present early in breeding sequences and continues every generation thereafter. To rapidly locate and control localised locust infestations over a large part of eastern Australia, a Decision Support System for locust management was developed that integrates data from a wide variety of sources to help operations staff determine when and where to concentrate survey and control efforts. When threatening locust populations are detected, control teams can be rapidly deployed to wherever treatment is required. An integral part of locust control programs is limiting environmental and monetary costs so that an important component of APLC research has been to focus on reducing chemical use by using the lowest effective dose and by using products that can be applied in barriers 300–500 m apart so that only a small proportion of the area is sprayed. Increasing constraints on insecticide use, including the production of organic beef in locust source areas, has led to the development of a biological alternative. The latter program led to nearly 25 000 ha of locusts being treated with the biological agent Metarhizium during the 2000–01 locust season, the first large‐scale operational use of this biopesticide anywhere in the world.

Between October 1999 and April 2000, nearly 4000 ha of nymphal bands and adult swarms of Chortoicetes terminifera (Walker) were aerially treated using a ULV oil formulation of strain FI-985 of Metarhizium anisopliae var. acridum. During the mild weather (maxima 22-30 degrees C) of spring (October), there was little change in nymphal bands during the first week but at all doses between 25-100 g (1-4 x 10(12) conidia) ha(-1), the bands rapidly declined 9-12 days after treatment reaching > 90% mortality by 14 days. Metarhizium persisted for some time as there was 50% mortality of locusts fed vegetation collected from the treated blocks seven days after treatment. Persistence was confirmed by the high mortality of bands that invaded from untreated areas and of nymphs that hatched on the plot five to seven days after treatment, though mortality was then delayed until early in the third week. During summer (January), temperatures were high (maxima 36-42 degrees C), and at all doses between 25 and 125 g (1-5 x 10(12) conidia) ha(-1), there was a rapid decline seven to ten days after treatment. By 12-14 days, there was a > 90% decline in numbers in most blocks which was confirmed by helicopter surveys two weeks after treatment that found very few adults within or near treated areas. Mortality was delayed in the high dose where there were blockages of spray equipment during treatment. The clear demonstration that Metarhizium can suppress small local populations of C. terminifera led to the limited operational use of Metarhizium on an organic farm and in a National Park where nearly 2500 ha of bands and swarms were treated. Continued research is needed to develop a commercially viable product so that Metarhizium can form a significant part of a programme of integrated pest management of locusts in Australia.

Between October 1999 and April 2000, nearly 4000 ha of nymphal bands and adult swarms of Chortoicetes terminifera (Walker) were aerially treated using a ULV oil formulation of strain FI-985 of Metarhizium anisopliae var. acridum . During the mild weather (maxima 22–30°C) of spring (October), there was little change in nymphal bands during the first week but at all doses between 25–100 g (1–4 × 10 12 conidia) ha −1 , the bands rapidly declined 9–12 days after treatment reaching > 90%mortality by 14 days. Metarhizium persisted for some time as there was 50% mortality of locusts fed vegetation collected from the treated blocks seven days after treatment. Persistence was confirmed by the high mortality of bands that invaded from untreated areas and of nymphs that hatched on the plot five to seven days after treatment, though mortality was then delayed until early in the third week. During summer (January), temperatures were high (maxima 36–42°C), and at all doses between 25 and 125 g (1–5 × 10 12 conidia) ha −1 , there was a rapid decline seven to ten days after treatment. By 12–14 days, there was a > 90% decline in numbers in most blocks which was confirmed by helicopter surveys two weeks after treatment that found very few adults within or near treated areas. Mortality was delayed in the high dose where there were blockages of spray equipment during treatment. The clear demonstration that Metarhizium can suppress small local populations of C. terminifera led to the limited operational use of Metarhizium on an organic farm and in a National Park where nearly 2500 ha of bands and swarms were treated. Continued research is needed to develop a commercially viable product so that Metarhizium can form a significant part of a programme of integrated pest management of locusts in Australia.

Rice planthoppers and associated virus diseases have become the most important pests threatening food security in China and other Asian countries, incurring costs of hundreds of millions of US dollars annually in rice losses, and in expensive, environmentally harmful, and often futile control efforts. The most economically damaging species, the brown planthopper, Nilaparvata lugens (Hemiptera: Delphacidae), cannot overwinter in temperate East Asia, and infestations there are initiated by several waves of windborne spring or summer migrants originating from tropical areas in Indochina. The interaction of these waves of migrants and synoptic weather patterns, driven by the semi-permanent western Pacific subtropical high-pressure (WPSH) system, is of critical importance in forecasting the timing and intensity of immigration events and determining the seriousness of subsequent planthopper build-up in the rice crop. We analysed a 26-year data set from a standardised light trap network in Southern China, showing that planthopper aerial transport and concentration processes are associated with the characteristics (strength and position) of the WPSH in the year concerned. Then, using N. lugens abundance in source areas and indices of WPSH intensity or related sea surface temperature anomalies, we developed a model to predict planthopper numbers immigrating into the key rice-growing area of the Lower Yangtze Valley. We also demonstrate that these WPSH-related climatic indices combined with early-season planthopper catches can be used to forecast, several months in advance, the severity of that season’s N. lugens infestations (the correlation between model predictions and outcomes was 0.59), thus allowing time for effective control measures to be implemented.

Abstract Conserving large carnivores is controversial because they can threaten wildlife, human safety, and livestock production. Since large carnivores often have large ranges, effective management requires knowledge of how their ecology and functional roles vary biogeographically. We examine continental‐scale patterns in the diet of the dingo – Australia's largest terrestrial mammalian predator. We describe and quantify how dingo dietary composition and diversity vary with environmental productivity and across five bioclimatic zones: arid, semi‐arid, tropical, sub‐tropical, and temperate. Based on 73 published and unpublished data sets from throughout the continent, we used multivariate linear modelling to assess regional trends in the occurrence of nine food groups (arthropods, birds, reptiles, European rabbits Oryctolagus cuniculus , medium‐sized [25–125 kg] and large [169–825 kg] exotic ungulates [including livestock], and other small [<0.5 kg], medium‐sized [0.5–6.9 kg] and large [≥7 kg] mammals) in dingo diets. We also assessed regional patterns in the dietary occurrence of livestock and the relationship between dietary occurrence of rabbits and small, medium‐sized and large mammals. Dingoes eat at least 229 vertebrate species (66% mammals, 22% birds, 11% reptiles, and 1% other taxa). Dietary composition varied across bioclimatic zones, with dingo diets in the arid and semi‐arid zones (low‐productivity sites) having the highest occurrence of arthropods, reptiles, birds, and rabbits. Medium‐sized mammals occurred most frequently in temperate and sub‐tropical zone diets (high‐productivity sites), large mammals least in the arid and sub‐tropical zones, and livestock most in the arid and tropical zones. The frequency of rabbits in diets was negatively correlated with that of medium‐sized, but not small or large mammals. Dingoes have a flexible and generalist diet that differs among bioclimatic zones and with environmental productivity in Australia. Future research should focus on examining how dingo diets are affected by local prey availability and human‐induced changes to prey communities.

Small mammal assemblages in the aridlands of the Southern Hemisphere often have wildly fluctuating dynamics. Previous studies have attributed these fluctuations to climate-driven pulses in food resources resulting in the switching of trophic control from bottom-up (food-limited) to top-down (predation-limited) population regulation, and vice versa. In this study we use a meta-analytic approach to evaluate the evidence for the phenomenon of switching trophic control. If shifting trophic control is a unifying phenomenon that shapes small mammal assemblages in arid Australia, we would expect the abundance and species richness of small mammals to increase with increasing primary productivity and the abundance of small mammals to decrease with increasing predator abundances, which lag behind those of small mammals. We tested these predictions using data compiled from 6 unpublished and 2 published data sets containing time series (3-11 years) of small mammal and predator community dynamics. Our analyses provide moderate support for the notion that switching trophic control is a unifying phenomenon shaping small mammal assemblages. Also, our results provide evidence that top-down and bottom-up control are not mutually exclusive phenomena driving desert small mammal assemblages but rather alternative ecosystem states that exist along a rainfall-driven continuum of ecosystem energy flux through time.

Many pest species exhibit huge fluctuations in population abundance. Understanding their large-scale and long-term dynamics is necessary to develop effective control and management strategies. Occupancy models represent a promising approach to unravel interactions between environmental factors and spatiotemporal dynamics of outbreaking populations. Here, we investigated population dynamics of the Australian plague locust, Chortoicetes terminifera, using density data collected between 1988 and 2010 by the Australian Plague Locust Commission over more than 3 million km2 in eastern Australia. We applied multistate and autologistic multi-season occupancy models to test competing hypotheses about environmental and demographic processes affecting the large-scale dynamics of the Australian plague locust. We found that rainfall and land cover predictors best explained the spatial variability in outbreak probability across eastern Australia. Outbreaks are more likely to occur in temperate than tropical regions, with a faster and more continuous response to rainfall in desert than in agricultural areas. Our results also support the hypothesis that migration tends to propagate outbreaks only locally (over distances lower than 400 km) rather than across climatic regions. Our study suggests that locust outbreak forecasting and management systems could be improved by implementing key environmental factors and migration in hierarchical spatial models. Finally, our modeling framework can be seen as a step towards bridging the gap between mechanistic and more phenomenological models in the spatial analysis of fluctuating populations.

The Australian Plague Locust Commission uses the organophosphorus insecticide fenitrothion to control locust population increases across 2000000 km2 of eastern Australia. Although the impact of fenitrothion on non-target invertebrates has been studied, effects on vertebrates are largely unquantified. Lethal and sublethal impacts on vertebrates are a consequence of the use of organophosphorus and carbamate insecticides. Information detailing the effects of exposure on free-living animals, particularly for herpetofauna, is lacking. This paper reviews literature concerned with the impacts of organophosphorus and carbamate insecticides on terrestrial vertebrates and highlights the need for continued research into the effects of these chemicals, especially in Australia.

Abstract The development of recent infestations of the Australian plague locust ( Chortoicetes terminifera ) (Walker) (Orthoptera: Acrididae) has been traced using traditional survey data combined with information from several modern technologies including simulation of windborne transport trajectories, direct observation with entomological radar and satellite imagery. The results indicate that migration from spring generations in the southern and eastern parts of the species range, including agricultural areas, to the summer rainfall areas in arid western Queensland (Qld) has contributed to the development of infestations on several occasions. Migration from swarm populations in New South Wales to western Qld in November and December 1999 contributed to a rapid population increase that, over a sequence of generations, led to the major infestation of agricultural areas in March and April 2000. There is evidence that northward migrations also occurred in 1995, 1997 and 2000. These contributed to the early summer populations in Qld, but did not result in large migrations to the south in autumn. These observations suggest that a pattern of exchange migration across much of the geographical range of the species between regions of winter and summer rainfall characterizes the spatial dynamics of this species. This pattern appears to be adaptive and suggests migration in C. terminifera is sustained by contemporary natural selection.

Abstract Quality control charting was applied to a number of criteria implemented to monitor the large scale ( ca 10 million pupae per week) production of Ceratitis capitata (Wiedemann), and to assess the quality of the flies so produced. The control chart procedure was useful and indicated the development of a problem involving adult flight ability. It also illustrated the variability inherent in some parameters e.g. percent recovery of pupae from eggs, but in the absence of similar data from other rearing facilities it is not possible to state whether or not that level of variability is inherent in the process. Résumé Mise au point d'un procédé de contrôle de la qualité dans les élevages de masse de Ceratitis capitata Une procédure de contrôle de la qualité a été appliquée à une série de critères de l'élevage de masse (c'est‐à‐dire 10 millions de pupes var semaine) de C. capitata pour garantir la qualité des mouches produites. La charte de contrôle a été utile et a permis de mettre en évidence un problème concernant l'aptitude au vol des adultes. Elle a illustré la variabilité de certains paramètres, par exemple le taux de pupes obtenues à partir des oeufs, mais en l'absence de données semblables provenant d'autres élevages, il n'est pas possible de savoir quelle part du taux de variabilité est inhérente ou non à la méthode.

In Australia, where approximately 80% of the land area is arid or semiarid, rainfall is the major factor limiting acridid populations. Rainfall is not only limiting in terms of quantity but also in being highly variable, both temporally and spatially. In this paper, the main adaptations seen in Australian Acrididae to overcome limiting rainfall are discussed with special reference to economically important species.In the arid to semiarid subtropics (lat 23–33°S) rainfall is slightly summer-dominant but extended dry periods can occur in any season. Chortoicetes terminifera, the main pest species, avoids dry periods through embryonic diapause or survives dry periods as quiescent eggs or adults. Migration is critical for survival as it allows locusts to locate areas of localized rainfall. Outbreaks are frequent and develop when enough rain falls to allow continuous breeding over three to four generations.In temperate areas of subcoastal southern Australia, summers are dry and most rain falls in winter or early spring. Austroicetes cruciata, a univoltine pest species, avoids the dry summers by having an embryonic diapause between summer and early winter.In the tropical north (lat 13–23°S), rainfall is strongly summer-dominant and Austracris guttulosa, another univoltine species, survives the dry winter as immature adults in reproductive diapause. Adults mature after feeding on the green vegetation present following early rains of the wet season. But the early rains are often localized and adults migrate until they encounter these localized areas of rain. Adults then mature and lay, but the survival of their offspring eggs and very young nymphs is assured only if there is further rain within 6 weeks. Outbreaks develop only when there are several years of regular rains both in outbreak areas and adjacent areas of the arid zone.Locusta migratoria does not have a stage that can survive extended dry periods. Consequently, it is mainly restricted to subcoastal areas of moderate rainfall. In the main outbreak areas of subtropical Queensland, populations often decline during the commonly dry winters but outbreaks develop when good rain falls in all seasons.

The introduction of novel bluetongue serotypes and genotypes into northern Australia is considered possible via the long-distance windborne dispersal of Culicoides (Diptera: Ceratopogonidae) vectors from Southeast Asia. Initial findings from simulation modelling of potential dispersal over a 15-year period revealed that the greatest risk for incursion of windborne Culicoides from the island of Timor into northern Australia occurs during December-March. The regions at greatest risk for incursion include the top end of the Northern Territory and the Kimberley region in Western Australia, but there is potential for more widespread dispersal into northern Australia based on Timor as the putative source. The establishment of a more pathogenic strain of the virus, or of a novel Culicoides vector introduced by such inter-continental dispersal events, could dramatically alter Australia's current bluetongue disease status.

The Australian Plague Locust Commission (APLC) has a mandated role in monitoring, forecasting, and managing populations of key locust species across four Australian states. Satellite normalized difference vegetation index (NDVI) imagery is used to monitor vegetation condition in locust habitat and is integrated with mapping software to support forecasting and operations within the strategic framework of APLC activities. The usefulness of NDVI data for monitoring locust habitats is tested using historical control and survey records for the Australian plague locust, Chortoicetes terminifera (Walker). In arid habitat areas, control of high-density nymphal populations was consistently associated with high and increased relative NDVI during summer and autumn, providing important information for locating possible infestations. Regression models of NDVI data and regional biogeographic factors were fitted to summer survey records of C. terminifera presence and abundance. Models identified increased vegetation greenness, measured by a one-month positive change in NDVI, as having a significant positive relationship with nymph distributions, while NDVI was significant in adult distributions. Seasonal rainfall regions and a binary habitat stratification were significant explanatory factors in all models.

Abstract The environmental conditions that allow the growth of Barley Mitchell grass, Astrebla pectinata , and the development of the Australian plague locust, Chortoicetes terminifera , are similar. A single fall of more than 20 mm rain and a mean monthly maximum temperature above 23°C ensures sustained growth of Barley Mitchell grass and hatching of eggs of the Australian plague locust. Curly Mitchell grass, Astrebla lappacea , is found in heavier clay soils and requires about 40 mm to respond. Both Mitchell grasses normally remain green for about 2 months after rain which is slightly longer than the duration of locust development to the adult stage. As a result, locusts in Mitchell grass areas can complete their development to migration and laying on a single substantial fall of rain: an adaptation of critical importance in the arid zone where follow‐up rain is unlikely. Under similar circumstances, ephemerals like Button grass, Dactyloctenium radulans , are dry in approximately 6 weeks. The locusts are usually at the late nymphal stage by this time and even though Mitchell grass is still quite green, nymphal growth is retarded, resulting in adults which are smaller than normal. These adults are able to accumulate the fat needed for migration by feeding on the dry green Mitchell grasses. In the absence of dry green or green Mitchell grass, the locusts persist locally and die without laying unless there is further rain.

Abstract Long distance migration by adults of Chortoicetes terminifera (Wlk.) in Australia was shown to be associated with the accumulation of fat-body lipid. Lipid was accumulated if the plant growth index was 0·3 or more within a week of the final moult; when the plant growth index was less than 0·3, there was little fat accumulation. Locusts with large amounts of fat-body lipid migrated on nights with warm strong winds, while those with little persisted.

Two special purpose insect-detecting radar units have operated in inland eastern Australia, in the region where nocturnal migratory movements of Australian plague locusts Chortoicetes terminifera occur, for over 10 years. The fully automatic radars detect individual insects as they fly directly overhead and “interrogate” them to obtain information about their characters (size, shape, and wing beating) and trajectory (speed, direction, and orientation). The character data allow locusts to be distinguished from most other migrant species. A locust index, calculated from the total count of locust-like targets for a night, provides a simple indication of migration intensity. For nights of heavy migration, the variation of numbers, directions, and speeds with both height and time can be examined. Emigration and immigration events can be distinguished, as can “transmigration,” the passage overhead of populations originating elsewhere. Movement distances can be inferred, and broad source and (more tentatively) destination regions are identified. Movements were typically over distances of up to 400 km. Interpretation of radar observations requires judgment, and the present two units provide only partial coverage of the locust infestation area, but their capacity to detect major population movements promptly, and to provide information between necessarily infrequent surveys, has proved valuable.

Linking demographic and genetic dispersal measures is of fundamental importance for movement ecology and evolution. However, such integration can be difficult, particularly for highly fecund species that are often the target of management decisions guided by an understanding of population movement. Here, we present an example of how the influence of large population sizes can preclude genetic approaches from assessing demographic population structuring, even at a continental scale. The Australian plague locust, Chortoicetes terminifera, is a significant pest, with populations on the eastern and western sides of Australia having been monitored and managed independently to date. We used microsatellites to assess genetic variation in 12 C. terminifera population samples separated by up to 3000 km. Traditional summary statistics indicated high levels of genetic diversity and a surprising lack of population structure across the entire range. An approximate Bayesian computation treatment indicated that levels of genetic diversity in C. terminifera corresponded to effective population sizes conservatively composed of tens of thousands to several million individuals. We used these estimates and computer simulations to estimate the minimum rate of dispersal, m, that could account for the observed range-wide genetic homogeneity. The rate of dispersal between both sides of the Australian continent could be several orders of magnitude lower than that typically considered as required for the demographic connectivity of populations.

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 includes 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 of the 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 agricultural country occurred in the late summer or early autumn. This is contrary to the idea held previously that most plagues developed from local breeding 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.

Huge aggregations of flightless locust nymphs pose a serious threat to agriculture when they reach plague proportions but provide a very visible and nutritious resource for native birds. Locust outbreaks occur in spring and summer months in semiarid regions of Australia. Fenitrothion, an organophosphate pesticide, is sprayed aerially to control locust plagues. To evaluate fenitrothion exposure in birds attending locust outbreaks, we measured total plasma cholinesterase (ChE), butrylcholinesterase (BChE), and acetylcholinesterase (AChE) activities in four avian species captured pre- and postfenitrothion application and ChE reactivation in birds caught postspray only. Eleven of 21 plasma samples from four species had ChE activity below the diagnostic threshold (two standard deviations below the mean ChE activity of prespray samples). Granivorous zebra finches (Taeniopygia guttata) and insectivorous white-winged trillers (Lalage sueurii) had significantly lower mean plasma total ChE, BChE, and AChE activity postspray, while other insectivores, white-browed (Artamus superciliosus) and masked woodswallows (Artamus personatus), did not. Cholinesterase was reactivated in 19 of the 73 plasma samples and in one of three brain samples. We conclude that native bird species are exposed to fenitrothion during locust control operations. This exposure could have detrimental impacts, as both locust outbreaks and avian reproductive events are stimulated by heavy summer rainfall, leading to co-occurrence of locust control and avian breeding activities.

Abstract Factors involved in the origin of plagues of Schistocerca cancellata (Serville) in Argentina were examined using a simple model for locust development. Plagues were present in 48 of the 58 years between 1897–1954 with plague sequences occurring before 1900, 1903–11, 1913–28, 1931–38 and 1944–54. Plagues originated when winter rain fell in the outbreak areas in La Rioja and Catamarca resulting in three generations in a season. Plagues continued for 8–15 years. Their decline was usually gradual resulting from a combination of several seasons when it was dry in the outbreak areas, and only one generation per year was possible. Before 1954, locust swarms were common in 15 of Argentina's 22 provinces but it was not obvious where the plagues originated. Since then most swarms have been reported from two provinces in the northwest: La Rioja and Catamarca. Within these provinces, bands and swarms have been most common in the semi-arid outbreak area. Populations have been highest when the outbreak area received winter/spring/summer rain which allowed three generations in a season. However, infestations have never approached plague proportions in recent years because regular control of bands and swarms in the outbreak area has kept populations in check.