Effect of foliar herbicides on the germination and viability of Siam weed (Chromolaena odorata) seeds located on plants at the time of application.

This paper reports a field study undertaken to determine if the foliar application of herbicides fluroxypyr (150 mL 100 L-1 a.i.) and metsulfuron-methyl (12 g 100 L-1 a.i.) were capable of reducing the germination and viability of Chromolaena odorata (L.) R.M.King & H.Rob. (Siam weed) seeds at three different stages of maturity. After foliar application of fluroxypyr germination of mature seeds was reduced by 88% and intermediate and immature seeds were reduced by 100%, compared to the control. Fluroxypyr also reduced the viability of mature, intermediate and immature seeds by 79, 89 and 67% respectively, compared to the control. Metsulfuron-methyl reduced germination of intermediate and immature seeds by 53 and 99% respectively compared to the control. Viability was also reduced by 74 and 96% respectively, compared to the control. Mature seeds were not affected by metsulfuron-methyl as germination and viability increased by 2% and 1% respectively, as compared to the control. These results show that these herbicides are capable of reducing the amount of viable seed entering the seed bank. However depending on the treatment and stage of seed development a percentage of seeds on the plants will remain viable and contribute to the seed bank. This information is of value to Siam weed eradication teams as plants are most easily located and subsequently treated at the time of flowering. Knowledge of the impact of control methods on seeds at various stages of development will help determine the most suitable chemical control option for a given situation.

Defect Sensitization of Combustion and Thermal Decomposition of Ammonium Perchlorate: Effect of Pelletizing Pressure and Dwell Time

A systematic study was undertaken on the combustion and thermal decomposition of pelletized Ammonium Perchlorate (AP) to investigate the effects of pelletizing pressure and dwell time. At constant pressure, increasing the dwell time results in an increase in the burning rate up to a maximum and thereafter decreases it. The dwell time required for the pellets to have maximum burning rate is a function of pressure. The maximum burning rate is the same for all the pressures used and is also unaffected by increasing, to the range 90-250 μ, the particle size of AP used. In order to explain the occurrence of a maximum in burning rate, pellets were examined for their thermal sensitivities, physical nature and the changes occurring during pelletization with dwell time and pressure. The variations are argued in terms of increasing density, formation of defects such as dislocations leading to an increase in the number of reactive sites, followed by their partial annihilation at longer dwell times due to flow of material during pelletization.

The adoption of sustainable grazing land management practices in the Burdekin Rangelands of northern Australia.

The Burdekin Rangelands is a diverse area of semi-arid eucalypt and acacia savannah covering six million hectares in north eastern Australia. The major land use is cattle grazing on 220 commercial cattle properties (average size 26,000 ha) each carrying on average 2600 adult equivalents. Production was the focus of the beef industry and support agencies prior to the mid 1980's. Widespread land degradation during the 1980's led to a grassroots realisation that environmental impacts, including water quality had to be addressed for the beef industry to attain sustainability. The formation of a series of producer based landcare gropus and the support of several Queensland and Australian government research and extension agencies led to a greater awareness and adoption of sound grazing land management practices (Shepherd 2005).

The effect of data sources and quality on the predictive capacity of CLIMEX models: an assessment of Teleonemia scrupulosa and Octotoma scabripennis for the biocontrol of Lantana camara in Australia

Understanding the effects of different types and quality of data on bioclimatic modeling predictions is vital to ascertaining the value of existing models, and to improving future models. Bioclimatic models were constructed using the CLIMEX program, using different data types – seasonal dynamics, geographic (overseas) distribution, and a combination of the two – for two biological control agents for the major weed Lantana camara L. in Australia. The models for one agent, Teleonemia scrupulosa Stål (Hemiptera:Tingidae) were based on a higher quality and quantity of data than the models for the other agent, Octotoma scabripennis Guérin-Méneville (Coleoptera: Chrysomelidae). Predictions of the geographic distribution for Australia showed that T. scrupulosa models exhibited greater accuracy with a progressive improvement from seasonal dynamics data, to the model based on overseas distribution, and finally the model combining the two data types. In contrast, O. scabripennis models were of low accuracy, and showed no clear trends across the various model types. These case studies demonstrate the importance of high quality data for developing models, and of supplementing distributional data with species seasonal dynamics data wherever possible. Seasonal dynamics data allows the modeller to focus on the species response to climatic trends, while distributional data enables easier fitting of stress parameters by restricting the species envelope to the described distribution. It is apparent that CLIMEX models based on low quality seasonal dynamics data, together with a small quantity of distributional data, are of minimal value in predicting the spatial extent of species distribution.