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Locusts and grasshoppers cause considerable economic damage to agriculture worldwide. The Australian Plague Locust Commission uses multiple pesticides to control locusts in eastern Australia. Avian exposure to agricultural pesticides is of conservation concern, especially in the case of rare and threatened species. The aim of this study was to evaluate the probability of pesticide exposure of native avian species during operational locust control based on knowledge of species occurrence in areas and times of application. Using presence-absence data provided by the Birds Australia Atlas for 1998 to 2002, we developed a series of generalized linear models to predict avian occurrences on a monthly basis in 0.5 degrees grid cells for 280 species over 2 million km2 in eastern Australia. We constructed species-specific models relating occupancy patterns to survey date and location, rainfall, and derived habitat preference. Model complexity depended on the number of observations available. Model output was the probability of occurrence for each species at times and locations of past locust control operations within the 5-year study period. Given the high spatiotemporal variability of locust control events, the variability in predicted bird species presence was high, with 108 of the total 280 species being included at least once in the top 20 predicted species for individual space-time events. The models were evaluated using field surveys collected between 2000 and 2005, at sites with and without locust outbreaks. Model strength varied among species. Some species were under- or over-predicted as times and locations of interest typically did not correspond to those in the prediction data set and certain species were likely attracted to locusts as a food source. Field surveys demonstrated the utility of the spatially explicit species lists derived from the models but also identified the presence of a number of previously unanticipated species. These results also emphasize the need for special consideration of rare and threatened species that are poorly predicted by presence-absence models. This modeling exercise was a useful a priori approach in species risk assessments to identify species present at times and locations of locust control applications, and to discover gaps in our knowledge and need for further focused data collection.

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.

Processed Landsat multispectral data were used to determine areas in the Riverina region of New South Wales, Australia, in which eggs were likely to have been laid by swarms of the Australian plague locust ( Chortoicetes terminifera (Walker)), which invaded the region at the end of March 1987. A map was produced from the processed data with potential eggbed areas highlighted, which could be used for field survey purposes in the spring and summer when hatching started. The results showed that > 95 per cent of all nymphal band targets were in the areas defined by a normalized difference vegetation index as being those where vegetation growth had resulted from rain during March. Furthermore, a maximum-likelihood classification using a known eggbed location as a training area, produced an excellent correlation with locusts hatching in September/October 1987. The results are discussed in relation to the future operational use of such techniques by the Australian Plague Locust Commission.

Context Risk assessments currently undertaken to approve pesticides for use against locusts in Australia are predominated by laboratory-generated data, often collected from non-endemic species. Very little information exists concerning the potential ecological effects of insecticides used for locust control. Aim To determine the effect of aerial ultra-low volume (ULV) applications of the organophosphorous insecticide, fenitrothion (used for locust control), on avian assemblages in arid and semiarid agro-ecosystems. Methods Avian abundance was surveyed in pesticide-exposed and unexposed locations during standard locust control operations, using fenitrothion, in western New South Wales and Queensland in the spring and summer of 1996, 1997 and 2000, using a transect-point method. Temporal changes in assemblages were analysed using multi-dimensional ordination (MDS) and permutational analysis of variance (PERMANOVA) with PRIMER (V7). Key results Avian assemblages varied over time, independent of pesticide application, reflecting significant redistribution and mobility of birds across a highly disturbed agricultural landscape, irrespective of pesticide exposure. Additionally, pesticide exposure did not affect species abundance or diversity. Conclusions There was no evidence that ultra-low volume (ULV) applications of fenitrothion, currently used in locust control, are impacting avian assemblages, despite previous research indicating that individual birds co-occurring with spray operations suffer suppressions in the enzymatic biomarker for OP exposure, plasma acetylcholinesterase (AChE). Implications Although the risk to avian assemblages associated with the aerial application of locusticides is reduced by the small proportion of the landscape where locust control activities are focused, any change in spray application parameters would necessitate a re-evaluation of the risks associated with insecticide exposure.

The Central American locust, Schistocerca pi ceifrons ssp. piceifrons (Walker), often becomes a major pest of staple and cash crops in Mexico and Central America (Barrientos-Lozano et al. 2002). In 1993, laboratory and field studies were initi ated to develop a biological control strategy for S. piceifrons. The National Centre for Biological Control (Centro Nacional de Referencia de Con trol Biol?gico-CNRCB) has in its entomopathogen collection 35 isolates of Metarhizium anisopliae var. acridum (M. a. acridum) from S. piceifrons in Mexico. Our laboratory studies have shown that the isolates MaPL32 and MaPL40 are 2 of the most virulent against S. piceifrons (Barrientos Lozano et al. 2002). Field trials with M. a. acridum oil-formulated spores have demonstrated effective control of S. gregaria Forskal in Africa (Langewald et al. 1997), Locusta migratoria (L.) and Chortoicetes ter minifera (Walker) in Australia (Hunter et al. 1999, 2001), Rammatocerus schistocercoides (Rehn) in Brazil (Magalhaes et al. 2001) and S. piceifrons in Mexico (Hern?ndez-Vel?zquez et al. 2003). One of the perceived disadvantages, evident in these tri als, is the length of time (13 to 14 d) that the target insect takes to die after the application. However, in practical terms, successful control of locust is re flected by a reduction in food consumption; a locust that has ceased to feed due to infection is no longer a significant pest (Moore et al. 1992). Studies by Moore et al. (1992) and Seyoum et al. (1994) both reported significant reductions in feeding by S. gregaria following infection with M. a. acridum; similar results were also observed with the grass hopper Zonocerus variegatus (L.) (Thomas et al. 1997). All of these reported studies were carried out using a high dose of the pathogen, in some cases with few insects per treatment, without con trols, and a mixture of instars. The aim of the present work was to examine the effect of a conidia low dose (6 x 104) per S. piceifrons adult on both feeding rate and feces production. First instars of S. piceifrons locusts were col lected in Tizim?n, Yucat?n, Mexico. Locusts were kept in 1 x 1 x 1 m cages inside a controlled envi ronment (CE) room and fed on a diet of leaves of the grass Cynodon dactylon (L.) and rolled oats. The mean daily temperature and relative humid ity (RH) in the CE room was 27?C and 70 ? 5% re spectively, with a photoperiod of 12:12 h (L:D). The fungal isolate was a monospore isolate (EH-502/8) of M. a. acridum MaPL40 from S. pi ceifrons (Hern?ndez-Vel?zquez et al. 1997). Fun gal conidia were produced by a diphasic method. In the first phase, the fungus was cultured in a liquid medium of 2% sucrose and 2% yeast extract (Jenkins & Prior 1993). Fungal biomass was transferred to rice in a plastic bag (250 g/bag) with a cotton filter for further growth and sporu lation. After 14 d the bags were opened in the CE room which allowed the fungus to dry to a mois ture content of approximately 9%. Conidia were separated from the rice by sieving through a 300 um mesh. The resulting conidia powder was then re-sieved through a 90-um mesh to remove any remaining rice-dust particles. Conidial suspensions were formulated in citro line (a mineral oil derived from petroleum for ag ricultural use in Mexico) by mixing 1 g of conidial powder in 100 mL with a magnetic stirrer. It was then adjusted to 3 x 107 conidia/mL with use of a Neubauer haemocytometer. Germination rates were determined by randomly examining 100 conidia per plate with a compound microscope (400x). A conidium was considered to have germi nated if the germ tube was at least as long as the width of the conidium. Germination of conidia was 95-100% immediately after formulation and just before locust infection. Each treatment consisted of 20 adult locusts, 7 d post-fledging, each receiving 2 uL of the formu lation applied on the pronotum via a Hamilton SGE syringe. Control groups received 2 uL of ei ther citroline or sterile distilled water with Tween 80 (0.1%, v/v, Difco ) without conidia. Following treatment, locusts were placed in subgroups of 4 insects in 13 x 10.5 cm plastic containers, covered with muslin. Containers were maintained at 28?C and 70 ? 5% RH. The experiment was replicated 4 times. Mortality was recorded daily for 12 d; dead insects were placed individually in Petri dishes on moist filter paper at 27?C for 4 d to allow growth

Temporal water and nitrogen relations of curly Mitchell grass, Astrebla lappacea (Lindl.) Domin, in response to single waterings of 0, 20, 60 and 180 mm were studied. Effects on the survival and development of the common armyworm, Mythimna convecta (Walker), and the Australian plague locust, Chortoicetes terminifera (Walker), were recorded. Glasshouse trials were conducted to ascertain the level of rainfall required for insect survival. More than 20 mm of rainfall was needed for insect survival. Even at 60 mm, development was retarded in some instances. Plant nitrogen was positively correlated (R2 = 0.51) with plant moisture. Insect survival was better correlated with plant moisture (R2 = 0.61) than with plant nitrogen (R2 = 0.41).

1. The Australian plague locust, Chortoicetes terminifera, develops following rainfall in an environment dominated by two host plants, the annual Dactyloctenium radulans and the perennial Astrebla lappacea. This simple system provides an ideal opportunity to explore the relationship between plant quality, individual herbivore performance and population responses. 2. We compared the two grasses chemically and structurally, and the behavioural, physiological and developmental responses of locust nymphs to these diets. 3. The grasses appeared to be of similar nutritional quality in terms of their chemical composition, although they differed in their physical properties. Early instar nymphs performed equally well on both grasses. However, older nymphs consuming D. radulans developed faster, survived better and attained a higher body weight compared with those consuming A. lappacea. 4. The differences in performance by the older nymphs related to the rate and ratio of supply of carbohydrate and protein from the two grasses, with less carbohydrate being assimilated from A. lappacea than D. radulans per unit of protein assimilated. Experiments showed that these differences arose as a direct result of the physical barrier to nutrient extraction provided by cell walls and indirectly through the amount of water contained within each cell. Paradoxically, nitrogen did not limit performance in the traditional sense through shortage,but rather its relative excess in A. lappacea appeared to impede intake and assimilation of adequate carbohydrate. 5. As a consequence, we predict that the length of time D. radulans remains available following rainfall will influence plaguing dynamics, although not for the reasons previously thought. 6. The results highlight the need to consider nutrient balance and actual rates of supply (rather than simply measuring the chemical composition of the plant) when attempting to understand herbivore nutritional ecology.

Effects of substrate salinity on oviposition, embryonic development and survival in the Australian plague locust, Chortoicetes terminifera (Walker)

Future climate change likely to reduce the Australian plague locust (Chortoicetes terminifera) seasonal outbreaks

Some factors affecting flight in field populations of the Australian plague locust, Chortoicetes terminifera (walker), in New South Wales

On three adjacent experimental plots in central western New South Wales, from 1971 to 1974, population fluctuations of the Australian plague locust were interpreted in terms of the interactions between reproductive rates (Ro) between generations and net migration losses or gains (M plus or minus ) within generations. Changes due to variations in net migration fluctuated over a greater range than those due to variations in reproductive rates, and were the major cause of the population fluctuations during the 16 generations studied. Variations in rainfall during breeding accounted for nearly 90% of the variance in reproductive rates, provided rain followed relatively dry periods. Changes caused by migration resulted from episodic, often long-range and generally southward displacements of adults at night in the gradient wind during disturbed weather. The frequency and intensity of migration depended primarily on the availability of potential emigrants and secondarily on the incidence of weather favourable for takeoff and prolonged flight. The incidence of rainfall before periods of migration was higher than expected. Adults thus migrated into areas already favourable for successful breeding. Long-term median rainfall during breeding at Trangie gave mean reproductive rates greater than 1 per generation. Hence, population surpluses tend to be produced and generally disperse south to areas less favourable for breeding. There was close correspondence between the occurrence of heavy drought-breaking rains, leading to substantial population increases and migrations, and the observed incidence of outbreaks in this area. Changes in the relative importance of reproduction and migration in the drier breeding areas further inland are discussed in relation to historical changes in the distribution and abundance of the plague locust.

An important outbreak of the Australian plague locust, Chortoicetes terminifera (Wlk.), occurred in 1973 in central western New South Wales. The dynamics of the outbreak could be resolved into a sequence of five principal interacting events: (1) Sustained population increases in low-density populations in northern central western New South Wales during three successive breeding periods in 1972. The increases were a result of successful, local multiplication, immigration from more northerly breeding areas and restricted opportunities for dispersal. The continuing concentration of locusts in the northern central west led to local gregarisation and swarm formation in autumn and spring 1972. (2) Massive southward displacements at night during an intense tropical disturbance between 29 January and 4 February 1973, which resulted in an invasion and concentration of infestations in southern central western New South Wales. (3) Substantial multiplication increases (10- to 30-fold), as a result of the drought-breaking rainfall in the autumn and spring of 1973 in the central-west. This resulted in an intensification of the plague with the production of numerous, slow-moving swarms. (4) Massive southward displacements during several periods of disturbed weather in spring 1973, which led to the disappearance of adult infestations from the central west and a dispersal of infestations in areas invaded further south. (5) Heavy mortality in residual populations of hoppers and eggs. The combined effects of parasites, predators and a reduced viability of eggs and hoppers resulted in a complete collapse of the plague in the central west by December 1973.Although displacement by adults at night is shown to be the principal factor regulating both population fluctuations in specific localities and the spread of plagues through southward invasions, outbreaks are ultimately determined by initial multiplication increases in relatively sedentary recession populations. Both multiplication and migration were influenced more by variations in synoptic weather than by any other factor. Diurnal swarm movements, although conspicuous, did not significantly influence the overall spread of the outbreak studied.The quality and quantity of available fresh green food did not appear to limit further successful breeding during the decline of the plague. Although influxes of locusts into the central-west continued during disturbed weather in 1974, none remained to breed and densities fell to levels (<1/ha) lower than those of drought seasons. It appears unlikely, therefore, that plagues can be sustained in any one area, even when environmental conditions remain favourable for breeding, because of: (1) mass emigration during disturbed weather; (2) increased effectiveness of natural enemies; and (3) declines in viability and fecundity in moist conditons.

Locusts increase carbohydrate consumption to protect against a fungal biopesticide

Ecological phenomena operate at different spatial scales and are not uniform across landscapes or through time. One ecological theory that attempts to account for scaling and spatiotemporal variances is hierarchical patch dynamics. It introduces a hierarchical patch network with smaller spatiotemporal scales being nested within larger scales. However, few studies have modeled its presence within animal population dynamics. Locusts are an excellent model for investigating the spatiotemporal hierarchy of animal population dynamics, due to their high migratory capacity, large geographic ranges that extend across widely differing environments, and available long‐term data on distributions. Here, we investigated the influence of preceding vegetation growth on desert locust Schistocerca gregaria and Australian plague locust Chortoicetes terminifera outbreaks on three spatial levels (species range > geographic region > land unit) and between seasons. Both species are dryland herbivores with population dynamics linked to habitat productivity pulses after rain. We used NDVI data (MODIS imagery) as a measure of vegetation growth in hierarchical generalized additive models at different scales. Locust outbreaks were either preceded by vegetation growth between 78 and 32 days (Australian plague locusts) or 32 and 20 days before (desert locust) the observation. Although prior vegetation growth characterized outbreaks of both species, the temporal pattern of NDVI differed between spatiotemporal levels. All model selection criteria selected for a similar spatial hierarchy for both species: geographic region > land unit which supports the hierarchical patch dynamics paradigm. Further, it illuminates important timing differences between geographic regions and land units for preceding vegetation growth and locust outbreaks which can help locust managers identify when and where outbreaks occur. By acknowledging the spatiotemporal patterning of locust abundance, we account for heterogeneity of population dynamics throughout species ranges. Our findings demonstrate the importance of incorporating spatiotemporal variation in population models of insects and other animals.

A dozen species of locusts (Orthoptera: Acrididae) are a major threat to food security worldwide. Their outbreaks occur on every continent except Antarctica, threatening the livelihood of 10% of the world’s population. The locusts are infamous for their voracity, polyphagy, and capacity for long-distance migrations. Decades of research revealed very complex bio-ecology of locusts. They exist in two, inter-convertible and density-dependent states, or “phases.” Despite the evident progress in understanding locust behavior, our ability to predict and manage locust outbreaks remains insufficient, as evidenced by locust plagues still occurring during the 21st century. One of the main reasons is that locusts typically inhabit remote and scarcely populated areas, and their distribution ranges often spread across continents. This creates tremendous obstacles for locust population monitoring and control. Traditional ground locust surveys are inadequate to address the enormous spatial scale of the locust problem in a limited window of time dictated by the pest’s development. Remote sensing (satellite information) appears a promising tool in locust monitoring. Satellite data are increasingly used for monitoring and forecasting two locust species, the desert and the Australian plague locust. However, applications of this geospatial technology to other locust species remain rare.