Time filter

Source Type

The Australian plague locust, Chortoicetes terminifera (Walker), is an important agricultural pest that oviposits into soil across vast semi-arid and arid regions. This study aimed to determine whether gravid female locusts can discriminate among substrates of increasing salinity (0, 4, 8, 12, 16, 20, 24, and 28 ppt NaCl) when attempting oviposition, and quantify the effects of saline substrate on direct developing egg viability, and subsequent hatchling nymph body weight and survival. Gravid female locusts increasingly excavated and withdrew prior to completing oviposition in substrates of increasing salinity, but similar numbers of completed egg pods were observed across treatments. Egg weight at 50% total development time and successful egg development to nymph emergence decreased with increasing substrate salinity. Water balance equilibrium between the egg and the substrate occurred at approximately 12 ppt NaCl corresponding to a water activity of ∼0.995. Eggs oviposited into sand containing ⩽12 ppt NaCl weighed ⩾6.26 ± 0.91 mg and had ⩾76.8% successful development to nymph emergence. Eggs oviposited into sand containing >12 ppt NaCl weighed ⩽5.16 ± 1.27 mg and had ⩽45.6% successful development to nymph emergence. Hatchling nymph body weight and survival to second instar also decreased with increasing substrate salinity. Nymphs that hatched and emerged from sand containing ⩽12 ppt NaCl weighed ⩾5.55 ± 0.43 mg at emergence and had ⩾68.9% survival. Nymphs that hatched and emerged from sand containing >12 ppt NaCl weighed ⩽5.28 ± 0.67 mg at emergence and had ⩽52.0% survival. These results indicate that C. terminifera is sufficiently resilient to develop and survive in saline substrates over most of their range. © 2016


Alistair Drake V.,University of New South Wales | Alistair Drake V.,University of Canberra | Wang H.,Australian Plague Locust Commission
Journal of Applied Remote Sensing | Year: 2013

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. © 2013 The Authors.


Anderson K.L.,James Cook University | Deveson T.E.,Australian Plague Locust Commission | Sallam N.,BSES Ltd | Congdon B.C.,James Cook University
Journal of Applied Ecology | Year: 2010

1. The identification of dispersal mechanisms which facilitate particular biological invasions is paramount for the successful management of invasive species. If the dispersal mechanism promotes high propagule pressure, the probability of successful establishment and spread is enhanced. 2. Invasive species may enter mainland Australia from Papua New Guinea via the Torres Strait islands, and their dispersal through the region may be assisted by wind. The island sugarcane planthopper Eumetopina flavipes is of particular concern to Australian quarantine authorities. Long-distance, wind-assisted immigration from Papua New Guinea may be responsible for the continued presence of E. flavipes in the Torres Strait islands and on the tip of mainland Australia. Simulation was used to predict E. flavipes wind-assisted migration potential from Papua New Guinea into the Torres Strait islands and mainland Australia. Field studies were used to test the predictions. 3. Wind-assisted immigration from Papua New Guinea was predicted to occur widely throughout the Torres Strait islands and the tip of mainland Australia, especially in the presence of tropical depressions and cyclones. Simulation showed potential for a definite, seasonal immigration which reflected variation in the onset, length and cessation of the summer monsoon. 4. In general, simulation predictions did not explain E. flavipes observed infestations. The discrepancy suggests that post-colonization processes such as the temporal and spatial availability of host may be equally or more important than possible wind-assisted immigration in determining population establishment, persistence and viability. 5. Despite the potential for wide-spread, annual immigration throughout the Torres Strait islands and the tip of mainland Australia, E. flavipes control may be possible by managing the cultivation of host plants on an ongoing annual basis to avoid recolonization, especially prior to or during critical immigration periods. 6. Synthesis and applications. Wind may promote significant incursions of E. flavipes from Papua New Guinea into northern Australia. Management strategies should consider the relative importance of both pre- and post-invasion processes in determining establishment success, so that response measures can be implemented at the appropriate stage of invasion. In this way, successful control may be enhanced, serving to reduce the overall cost of invasion. © 2010 The Authors. Journal compilation © 2010 British Ecological Society.


Wang H.,Australian Plague Locust Commission
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2014

Australian Plague Locust, Chortoicetes terminifera (Walker), can rapidly increase in population size in the remote interior of eastern Australia under favorable habitat conditions and cause severe agricultural damage. To minimize losses, earlydetection of locust outbreaks is essential to the implementation of preventive control. Quantitative measurement of locust habitat suitability is critical for improving the efficiency of ground and aerial surveys, and providing vital information for locust population forecasting. Here, routine locust survey by the Australian Plague Locust Commission during 2003 and 2011 is investigated in relation to the habitat greenness derived from the fortnightly 250 m composites of Normalized Difference Vegetation Index (NDVI), and the rainfall amount from the weekly 5 km grids of modelled precipitation, using the spatial analysis and statistics of ESRI ArcGIS. The sighting dates of high-density locust nymphs (band and sub-band) were assigned into 5 groups corresponding to the nymphal development stages, and the fortnightly NDVI values and weekly rainfall totals for the locust locations were extracted for the previous 13 weeks. The averaged NDVI values for locust habitats showed a slight increase of 0.04-0.13 from initially 0.23-0.29 within 4-7 weeks before 2nd-5th instar bands and sub-bands were sighted. The median values of NDVI increase were on an equivalence scale of 0.05-0.15 from the background of 0.21-0.26; the increments were equal to 12-37% in the historical range from 13-22% and equal to 38-59% from the 11-18% of seasonal maxima, which indicated by normalized NDVI anomalies that the majority of high-density nymphs had all experienced a period of better than average conditions in both historical and seasonal perspectives. However, 5th-instar bands and sub-bands were consistently found in slightly dried habitats, while 1st-instar bands were mostly seen in much green areas but on the trend of dry-off. The time-series of habitat greenness for 1st-instar bands illustrated a very different pattern from the others, which could have resulted from the limited dataset mainly from the winter rain zone. Significant single rainfall of 25-30 mm was required to trigger the locust breeding sequence, and in excess of 40-50 mm total rainfall for locusts to survive the entire nymphal period. These findings will improve the understanding of locust plague mechanisms related to habitat condition, potentially provide practical means to monitor locust habitat conditions remotely and improve the underlying basis for locust survey and population management in Australia. © 2014 SPIE.


Woodman J.D.,Australian Plague Locust Commission
Australian Journal of Zoology | Year: 2013

The population dynamics of the Australian plague locust, Chortoicetes terminifera, are strongly linked to the timing and distribution of heavy rainfall events in semiarid and arid environments. While the effects of insufficient rainfall on survival are relatively well understood, little information exists on the effects of excessively wet conditions. This study aimed to quantify the survival of first-instar C. terminifera nymphs to a range of water-immersion periods and temperatures. Results show that survival is strongly dependent on immersion temperature whereby survival times ranged from time to 50% mortality (LT50)≤8.12±0.26h at 15°C to 4.93±0.30h at 25°C. Nymphs entered a coma-like state within 2min of immersion. Post-immersion recovery times were greater for longer immersion periods and longer at higher temperatures for immersion periods of >3h. These findings suggest that first-instar nymphs would be able to survive most instances of transient, localised pooling of water associated with heavy rainfall in the field. However, flooding that could trap individuals for >5h (including nymphs still underground within the egg pod before emergence to the soil surface) has the potential to cause high mortality, particularly during summer and early autumn when water temperatures may be high. © 2013 CSIRO.


Woodman J.D.,Australian Plague Locust Commission
Bulletin of Entomological Research | Year: 2015

The Australian plague locust, Chortoicetes terminifera (Walker), is an important agricultural pest and oviposits into compacted soil across vast semi-arid and arid regions prone to irregular heavy summer rainfall. This study aimed to quantify the effects of flooding (control, 7, 14, 21, 28 and 35 days) at different temperatures (15, 20 and 25°C) and embryonic development stages (25 and 75%) on egg viability, hatchling nymph body mass and survival to second-instar. Egg viability after flooding was dependent on temperature and flood duration. Eggs inundated at 15°C showed ≥53.5% survival regardless of flood duration and development stage compared with ≤29.6% for eggs at 25°C for ≥21 days early in development and ≥14 days late in development. Hatchling nymphs did not differ in body mass relative to temperature or flood duration, but weighed more from eggs inundated early in development rather than late. Survival to second-instar was ≤55.1% at 15 and 20°C when eggs were flooded for ≥28 days late in development, ≤35.6% at 25°C when flooded for ≥28 days early in development, and zero when flooded for ≥21 days late in development. These results suggest that prolonged flooding in summer and early autumn may cause very high egg mortality and first-instar nymph mortality of any survivors, but is likely to only ever affect a small proportion of the metapopulation. More common flash flooding for ≤14 days is unlikely to cause high mortality and have any direct effect on distribution and abundance. © Cambridge University Press 2015 This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/3.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited..


Deveson E.D.,Australian Plague Locust Commission | Deveson E.D.,Australian National University | Woodman J.D.,Australian Plague Locust Commission
Journal of Insect Physiology | Year: 2014

The Australian plague locust Chortoicetes terminifera (Walker) exhibits facultative embryonic diapause during autumn. To approximate natural photoperiod changes during late summer and autumn, locust nymphs were reared under different total declines in laboratory photophase (-0.5, -0.75, -1.0, -1.25, -1.5, -1.75, -2. h each lowered in 15. min steps) in a 24. h photoperiod to quantify any effect on the subsequent production of diapause eggs. Induction of diapause eggs was significantly affected by accumulated photoperiod decline experienced by the parental generation throughout all development stages from mid-instar nymph to fledgling adult. The incidence of embryonic diapause ranged from nil at -0.5. h to 86.6% diapause at -2. h. Continued declines in photoperiod for post-teneral locusts (transitioned from -1. h until fledging to -1.75. h) produced a further increase in the proportion of diapause eggs. The results were unaffected by time spent at any given photoperiod, despite a previously indicated maximal inductive photoperiod of 13.5. h being used as the mid-point of all treatments. Implications for the seasonal timing processes of photoperiodism in C. terminifera, which has a high migratory capacity and a latitudinal cline in the timing of diapause egg production across a broad geographic range, are discussed. © 2014 Published by Elsevier Ltd.


Deveson E.D.,Australian Plague Locust Commission | Deveson E.D.,Australian National University
Journal of Applied Remote Sensing | Year: 2013

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. © 2013 The Authors.


Woodman J.D.,Australian Plague Locust Commission | Woodman J.D.,Australian National University
Journal of Insect Physiology | Year: 2012

The cold tolerance of overwintering adult Spur-throated locusts, Austracris guttulosa, was examined using measures of supercooling point relative to gender, environmental acclimation and feeding state as well as mortality for a range of sub-zero temperature exposure treatments. Freezing was lethal and supercooling points ranged from -6 to -12.8°C, but were statistically independent of fresh mass, body water content, acclimation, and/or gut content in fed and starved individuals. A significant interaction effect of gender and feeding status showed that the larger bodied females had decreased supercooling capacity with increased food material in the digestive tract. Post-freezing dissections revealed differences in the amount of freshly consumed and retained food material in the digestive tract between fed and starved individuals of each gender, which could explain this effect based on inoculation of ice crystallisation by food particles. Above supercooling temperatures, neither gender nor the rate of cooling had a significant effect on mortality. When cooled from 25°C at 0.1 or 0.5°Cmin -1 to a range of experimental minimum temperatures held for 3h, survival was ≥74% to -7°C, but declined sharply to ≤37% when cooled to -8°C or lower. Although the laboratory experiments reported here suggest that A. guttulosa is not freeze tolerant and unable to rapidly cold harden, exposure to typical cold and frosty nights that very rarely reach below -8°C as a night minimum in the field would be unlikely to cause mortality in the vast majority of overwintering aggregations. © 2012.


Deveson T.,Australian Plague Locust Commission | Woodman J.D.,Australian Plague Locust Commission
Austral Entomology | Year: 2014

Scelio fulgidus (Crawford) is a widely distributed egg endoparasitoid of the Australian plague locust, Chortoicetes terminifera (Walker) that can cause high levels of host mortality in some locust outbreak situations. We assessed S.fulgidus parasitism from 23 locust egg bed sites in the New South Wales Riverina over a sequence of three host generations during the 2010-2011 C.terminifera plague cycle. Parasitism was locally variable but relatively high in each generation, with >90% egg parasitism during the summer 2010 host generation, exceeding previously reported data. There was evidence to support facultative diapause of up to one-third of S.fulgidus larvae in host eggs laid during March-May, with temporal change in proportions similar to diapause incidence in host eggs. © 2013 Australian Entomological Society.

Loading Australian Plague Locust Commission collaborators
Loading Australian Plague Locust Commission collaborators