Human activities have had an adverse impact on ecosystems on a global scale and have caused an unprecedented redispersal of organisms, with both plants and pathogens moving from their regions of origin to other parts of the world. Invasive plants are a potential threat to ecosystems globally, and their management costs tens of billions of dollars per annum. Rubus anglocandicans (European blackberry) is a serious invasive species in Australia. Herbicide and cultural control methods are generally inefficient or require multiple applications. Therefore, a biological control program using stem and leaf rust strains is the main option in Australia. However, biological control using rusts has been patchy, as host factors, climate, and weather can alter the impact of the rust at different locations. In 2007, Yeoh and Fontanini noticed that blackberry plants on the banks of the Donnelly and Warren rivers in the southwest of Western Australia were dying in areas that were being regularly monitored for the impact of rust as a biological control agent. The symptoms on blackberry became known as the disease “blackberry decline”. Continuous and intensive investigations are required to discover the different biotic and abiotic components associated with specific declines in plant populations. The only agent so far introduced to Australia for the biological control of blackberry is the rust Phragmidium violaceum.

ABSTRACT. The male bushcricket, Requena verticalis, calls with a signal containing two predominant frequencies, 16 kHz and 28 kHz. A synthesized call, made from a template of the natural call, was played to females under conditions of a two‐speaker trial on a flat arena. Orientation pathways to a speaker emitting only a 16 kHz signal were more circuitous than the pathways made by females orientating to a speaker emitting only a 28 kHz signal. Females preferred a signal with both carrier frequency peaks present within the song to a signal with only a 16 kHz or 28 kHz carrier frequency, when the signal containing a double peak was kept at equivalent absolute intensity to that with a single peak. Females chose signals containing a more powerful high frequency peak over a signal in which both peaks were balanced. For the higher peak, they were able to differentiate between frequencies with a separation of 8 kHz but not of 4 kHz. They were unable to differentiate between frequencies with a separation up to 8 kHz in the lower peak when one frequency was held at 16 kHz; however, when this frequency was held at 18 kHz, females were able to distinguish between frequencies with a difference of 4 kHz. (N.B. 18 kHz is 2 kHz above the mean value for this frequency within the natural population.) We conclude that females are choosing males on the amount of power in the higher frequency range of their song and that this may be equivalent to a close calling male in the field.

Development rates of the aphid, Brachycaudus rumexicolens (Patch), a recent arrival in Australia and a potential biological control agent against weeds in the family Polygonaceae, were measured over a range of constant temperatures. The theoretical lower limit for development is 6.4°C and the upper limit 32°C. Maximum fecundity per day was reached at 19°C. The rate of increase peaked at about 28°C giving a population doubling time of less than two days. These values were used with the current distribution to develop a CLIMEX model to predict the potential world distribution of the aphid. The model predicts that the aphid has suitable periods of population growth in autumn and spring, and that survival is unlikely over summer in most of south-western Australia where the aphid has the potential to contribute to the biological control of the polygonaceous weeds, Emex and Rumex species. The model predicts that years with cool summer temperatures and late summer rains in south west Australia, such as in 1990 when the aphid was first abundant, will be particularly suitable for aphid development. These conditions occurred twice between 1985 and 1995. To increase the effectiveness of the aphid as a biological control agent of weeds in other years, augmentation by provision of alternative hosts and/or the release of mass reared individuals during autumn is proposed.

Our aim was to model the current and future potential global distribution of Chloris truncata (windmill grass) based on the plant's biology, soil requirements and colonisation success. The growth response of C. truncata to constant temperatures and soil moisture levels were measured and estimated respectively, to develop parameters for a CLIMEX bioclimatic model of potential distribution. The native distribution in eastern Australia and naturalised distribution in Western Australia was also used to inform the model. Associations with soil types were assessed within the suitable bioclimatic region in Australia. The global projection of the model was tested against the distribution of soil types and the known successful and failed global introductions. The verified model was then projected to future conditions due to climate change. Optimal temperature for plant development was 28°C and the plant required 970 degree-days above a threshold of 10°C. Early collection records indicate that the species is native to Queensland, New South Wales and Victoria. The plant has been introduced elsewhere in Australia and throughout the world as a wool contaminant and as a potential pasture species, but some of the recorded establishments have failed to persist. The CLIMEX model projected to the world reflected effectively both the successful and failed distributions. The inclusion of soil associations improved the explanation of the observed distribution in Australia, but did not improve the ability to determine the potential distribution elsewhere, due to lack of similarity of soil types between continents. The addition of a climate change projection showed decreased suitability for this species in Australia, but increased suitability for other parts of the world, including regions where the plant previously failed to establish.