Search Results (4)

Pasture lands, while appearing uniform in species diversity, exhibit notable variations upon closer examination. The study on Pimelea (or riceflower) seedbank dynamics revealed significant variations in seed density and distribution across soil depths, sites, years, and between pasture and cultivated paddocks in the same region of western Queensland. For the total number of germinable riceflower seeds across both the years 2019 and 2020, there is a clear distinction between pasture and cultivated paddocks. Pasture paddocks exhibited a gradual increase in total seed count from 108 seeds m⁻² in 2019 to 121 seeds m⁻² in 2020, resulting in a combined total of 229 seeds m⁻² over the 2 years across both depths. In contrast, cultivated paddocks showed a more substantial increase, with seed counts rising from 146 seeds m⁻² in 2019 to 255 seeds m⁻² in 2020, resulting in a combined total of 401 seeds m⁻² across both depths. Additionally, the Shannon–Wiener index at Site 1 indicated increased species diversity in the topsoil of pasture paddocks in 2020 compared to 2019, while deeper soil diversity decreased. Cultivated paddocks showed a declining trend, while pasture sites exhibited stable or increasing diversity. Pasture management generally maintained or enhanced diversity better than cultivation, especially in the topsoil layer. These findings highlight site-specific differences influenced by soil properties, land management practices, and local environmental conditions, shaping riceflower seedbank dynamics. Understanding these patterns is crucial for developing targeted management strategies to control riceflower in affected areas. Long-term field studies focusing on seedbanks are essential to develop sustainable control strategies. Full article

Pimelea trichostachya Lindl. is a native Australian forb responsible for livestock poisoning and reducing the productivity and sustainability of grazing enterprises. This study was conducted as a pot trial under controlled conditions to investigate an effective chemical management strategy for P. trichostachya, a method that did not leave standing dead plant material, as such material can also be toxic to grazing cattle. Three herbicides, including one pre-emergence (tebuthiuron) and two post-emergence herbicides (2,4-D and metsulfuron-methyl), were tested in pot trials for their efficacy on P. trichostachya. Results showed that tebuthiuron applied as either a granular (10% active ingredient, a.i.) or pelleted (20% a.i.) form efficiently reduced the emergence of P. trichostachya seedlings. Although some seedlings emerged, they perished within 7 days post treatment, leaving no residual plant matter. Testing now needs to be undertaken under field conditions to validate the findings within vegetation communities where potential non-target impacts need to be accounted for as well. The post-emergence application of 2,4-D and metsulfuron-methyl demonstrated that the highest efficacy and reduced application rates were achieved by treating earlier growth stages (i.e., seedlings) of P. trichostachya plants. In addition, the amount of toxic dead plant material was minimized due to the faster degradation of these small plants. These findings offer practical, cost-effective solutions for sustaining grazing lands from P. trichostachya challenges. Full article

Pimelea is a genus of about 140 plant species, some of which are well-known for causing animal poisoning resulting in significant economic losses to the Australian livestock industry. The main poisonous species/subspecies include Pimelea simplex (subsp. simplex and subsp. continua), P. trichostachya and P. elongata (generally referred to as Pimelea). These plants contain a diterpenoid orthoester toxin, called simplexin. Pimelea poisoning is known to cause the death of cattle (Bos taurus and B. indicus) or weaken surviving animals. Pimelea species are well-adapted native plants, and their diaspores (single seeded fruits) possess variable degrees of dormancy. Hence, the diaspores do not generally germinate in the same recruitment event, which makes management difficult, necessitating the development of integrated management strategies based on infestation circumstances (e.g., size and density). For example, the integration of herbicides with physical control techniques, competitive pasture establishment and tactical grazing could be effective in some situations. However, such options have not been widely adopted at the field level to mitigate ongoing management challenges. This systematic review provides a valuable synthesis of the current knowledge on the biology, ecology, and management of poisonous Pimelea species with a focus on the Australian livestock industry while identifying potential avenues for future research. Full article

Pimelea trichostachya Lindl is a little-understood Australian native plant, with irregular field emergence, causing significant poisoning to grazing livestock. The study aims to examine the form of dormancy exhibited by P. trichostachya and determine how key environmental conditions, such as alternating temperature and light conditions, moisture availability, substrate pH and burial depth, affect its germination and emergence. The study concludes that P. trichostachya has a complex dormancy mechanism. This comprises a physical component that can be partly removed by fruit scarification, a metabolic dormancy that can be overcome by gibberellic acid (GA₃), and a suspected third mechanism based on a water-soluble germination inhibitor. The results showed that scarified single seeded fruit (hereafter seed) with GA₃ treatment gave the highest germination percentage (86 ± 3%) at 25/15 °C, with good germination rates at other temperature regimes. Light exposure stimulated germination, but a significant proportion of seeds still germinated in the dark. The study also found that seeds could germinate under water-limited conditions and a wide range of pH levels (4 to 8). Seedling emergence was inhibited when seeds were buried below 3 cm in soil. Pimelea trichostachya emergence in the field commonly occurs from Autumn to Spring. Understanding its dormancy mechanism and recognizing its triggers for germination will enable better prediction of outbreaks. This can help landholders prepare for emergence and help manage seedbank build-up in pastures and crops. Full article