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Alterations in transmission of vector-borne zoonoses are often linked to environmental change. However, ecological processes that determine variability in potential for transmission are generally not well understood. Ross River virus (RRV, Togoviridae: Alphavirus) is a mosquito-borne zoonosis in Australia with a significant human disease burden. The inland southwest (Wheatbelt) of Western Australia (WA) is substantially affected by an anthropogenic salinization of agricultural land (dryland salinity). Aedes camptorhynchusThomson (Diptera: Culicidae) is the dominant vector of RRV in southwest WA and is halophilic. As such, dryland salinity may influence potential for RRV transmission by influencing interactions between Ae. camptorhynchusand mammalian hosts. We surveyed areas of the Wheatbelt with varying salinity impacts and found Ae. camptorhynchuswas more abundant in saline areas, whereas sheep Ovis aries(Linnaeus 1758, Bovidae) declined with increasing salinity. We used a deterministic model to examine interactions between Ae. camptorhynchusand mammals, and we assessed potential for RRV transmission. We found variation in potential for RRV transmission was positively related to increasing salinity and abundance of Ae. camptorhynchusand negatively associated with increasing abundance of Macropus fuliginosus(Desmarest 1817, Macropodidae). Abundance of Ae. camptorhynchusdetermined more variation in potential for RRV transmission than other variables. Accordingly, dryland salinity increases the zoonotic potential for RRV transmission primarily by facilitating abundance of Ae. camptorhynchus. Human RRV notifications do not currently reflect the salinity-RRV transmission potential in the Wheatbelt but appear to be associated with RRV activity in the enzootic coastal zone. We speculate dryland salinity is a determinant of potential for RRV transmission but not activity. Dryland salinity is predicted to expand two- to four-fold by 2050. Preservation and restoration of freshwater ecosystems may ameliorate the potential for transmission of RRV and possibly incidence of human disease. [ABSTRACT FROM AUTHOR]

Abstract??A leaf beetle,Criocerissp. (Coleoptera: Chrysomelidae), was introduced into Australia as a biological control agent of bridal creeper (Asparagus asparagoidesL. Druce) during October 2002. Rearing ofCriocerissp. is labour intensive therefore all releases ofCriocerissp. have been under 1000 individuals, which may be too low to ensure establishment if high mortality and high competition with other agents occurs. The aim of this study is to understand how the presence of two well-established biocontrol agents, a rust fungus (Puccinia myrsiphylli(Thuem) Wint [Basidiomycota: Uredinales]) and a leafhopper (Zyginasp. [Hemiptera: Cicadellidae]), might influenceCriocerissp. establishment.Criocerissp. neonate larvae were placed on bridal creeper plants with or without the leafhopper and/or rust. The number of larvae that pupated was reduced by 38 and 65% in the presence of the rust fungus and leafhopper, respectively and by 45% in the presence of both agents. As the area infected by the rust increased the area damaged by the leafhopper decreased. The rust appeared to be negatively impacted by the presence of the leafhopper. In a second experiment, femaleCriocerissp. adults were given a choice between uninfested bridal creeper plants and those infested with the rust or the leafhopper. The females preferred to lay their eggs on plants without leafhoppers but did not seem to be deterred by the presence of the rust. Consequently, the performance and impact ofCriocerissp. on bridal creeper may be reduced if populations overlap with the other biocontrol agents in the field. [ABSTRACT FROM AUTHOR]

A new species of wasp, Stethynium sp. (Hymenoptera: Mymaridae), was found parasitizing eggs of an introduced weed biological control agent, Zygina sp. (Hemiptera: Cicadellidae), a leafhopper released against bridal creeper (Asparagus asparagoides L. Druce). A series of laboratory experiments was conducted to determine the development time and longevity of the wasp under different temperatures and the oviposition preference of the wasp for leafhopper eggs of different ages. Parasitized leafhopper eggs were placed in controlled temperature rooms set at either 15, 20, or 25°C and monitored for adult emergence. It was determined that development time of Stethynium sp. from egg to adult eclosion decreased as temperature increased and female wasps took longer to develop than males. Adult male and female wasps were placed in controlled temperature rooms set at these same temperatures and provided either water, a 10% sugar solution, or no food at all. Female wasps lived longer than males and sugar solution increased longevity significantly over no food or water alone, but this effect decreased with increasing temperature. Adult female wasps, given a choice between 1-, 2-, 3-, 5-, and 7-d-old eggs, showed no preference, and all progeny were able to develop and emerge at the same rate from any aged egg. Adult females also laid eggs in 8- and 9-d-old host eggs. There was a slight decrease in emergence rate from 9-d-old host eggs compared with 8-d-old eggs. [ABSTRACT FROM AUTHOR]

Aphids and related insects feed from a single cell type in plants: the phloem sieve element. Genetic resistance to Acyrthosiphon kondoi Shinji (bluegreen aphid or blue alfalfa aphid) has been identified in Medicago truncatula Gaert. (barrel medic) and backcrossed into susceptible cultivars. The status of M. truncatula as a model legume allows an in-depth study of defense against this aphid at physiological, biochemical, and molecular levels. In this study, two closely related resistant and susceptible genotypes were used to characterize the aphid-resistance phenotype. Resistance conditions antixenosis since migratory aphids were deterred from settling on resistant plants within 6 h of release, preferring to settle on susceptible plants. Analysis of feeding behavior revealed the trait affects A. kondoi at the level of the phloem sieve element. Aphid reproduction on excised shoots demonstrated that resistance requires an intact plant. Antibiosis against A. kondoi is enhanced by prior infestation, indicating induction of this phloem-specific defense. Resistance segregates as a single dominant gene, AKR (Acyrthosiphon kondoi resistance), in two mapping populations, which have been used to map the locus to a region flanked by resistance gene analogs predicted to encode the CC-NBS-LRR subfamily of resistance proteins. This work provides the basis for future molecular analysis of defense against phloem parasitism in a plant model system. [ABSTRACT FROM AUTHOR]