Evaluating the effectiveness of weed biocontrol at the local scale

Too many biocontrol programs have focused mainly on the establishment and prevalence of the biocontrol agents, with only limited studies on the impact of biocontrol at the individual plant level. Long-term effectiveness of biocontrol at the population level of the weed, and the resulting social and economic benefits are often not studied. The need for a comprehensive evaluation as an integral part of any biocontrol program, reasons for the limited emphasis on evaluation studies, and the potential role of community organizations in evaluation studies are discussed. Advantages and disadvantages of various valuation methods such as before and after release assessments, simulation experiments, relating damage levels to plant performance, and exclusion methods are compared. Evaluation methods commonly used in weed biocontrol programs in Australia are highlighted, along with an assessment on the success rates achieved. Evaluation protocols for aquatic and terrestrial weeds are suggested

Designs and Materials for Better Coronagraph Occulting Masks

New designs, and materials appropriate for such designs, are under investigation in an effort to develop coronagraph occulting masks having broad-band spectral characteristics superior to those currently employed. These designs and materials are applicable to all coronagraphs, both ground-based and spaceborne. This effort also offers potential benefits for the development of other optical masks and filters that are required (1) for precisely tailored spatial transmission profiles, (2) to be characterized by optical-density neutrality and phase neutrality (that is, to be characterized by constant optical density and constant phase over broad wavelength ranges), and/or (3) not to exhibit optical- density-dependent phase shifts. The need for this effort arises for the following reasons: Coronagraph occulting masks are required to impose, on beams of light transmitted through them, extremely precise control of amplitude and phase according to carefully designed transmission profiles. In the original application that gave rise to this effort, the concern has been to develop broad-band occulting masks for NASA s Terrestrial Planet Finder coronagraph. Until now, experimental samples of these masks have been made from high-energy-beam-sensitive (HEBS) glass, which becomes locally dark where irradiated with a high-energy electron beam, the amount of darkening depending on the electron-beam energy and dose. Precise mask profiles have been written on HEBS glass blanks by use of electron beams, and the masks have performed satisfactorily in monochromatic light. However, the optical-density and phase profiles of the HEBS masks vary significantly with wavelength; consequently, the HEBS masks perform unsatisfactorily in broad-band light. The key properties of materials to be used in coronagraph occulting masks are their extinction coefficients, their indices of refraction, and the variations of these parameters with wavelength. The effort thus far has included theoretical predictions of performances of masks that would be made from alternative materials chosen because the wavelength dependences of their extinction coefficients and their indices of refraction are such that that the optical-density and phase profiles of masks made from these materials can be expected to vary much less with wavelength than do those of masks made from HEBS glass. The alternative materials considered thus far include some elemental metals such as Pt and Ni, metal alloys such as Inconel, metal nitrides such as TiN, and dielectrics such as SiO2. A mask as now envisioned would include thin metal and dielectric films having stepped or smoothly varying thicknesses (see figure). The thicknesses would be chosen, taking account of the indices of refraction and extinction coefficients, to obtain an acceptably close approximation of the desired spatial transmittance profile with a flat phase profil

The Jewel Beetle (Hylaeogena jureceki); a new biocontrol for cat’s claw creeper (Dolichandra unguis-cati) in Queensland

Cat’s claw creeper (Dolichandra unguis-cati (Bignoniaceae) is a serious environmental weed in Queensland and New South Wales. It presents a threat to riparian and rainforest ecosystems and is often found in inaccessible locations that are not suitable for chemical or physical control methods. This makes biological control an important tool for managing this weed. The jewel beetle Hylaeo¬gena jureceki was approved for release in Australia in May 2012. Since approval, approximately 35,000 insects have been released at 53 sites. Multiple and single releases have been made at sites with the number of insects released ranging from 20 to 1590. Post-release monitoring before and after winter found the beetle persisting at 73% of release sites in southeast Queensland. Within the release sites, the beetle appears to disperse widely, up to 100 m over a 15 month period. Based on these early field results, it appears that the beetle will establish and spread in Queensland and New South Wales. In addition to direct field releases, the beetle has been supplied to various community and Landcare groups for breeding and field release. This will hasten the spread of the insect to a wider area. It is expected that the jewel beetle will complement the leaf-sucking tingid (Carvalhotingis visenda) and leaf-tying moth (Hypocosmia pyrochroma) that were released in 2007

Temporal Variation of Phytophagous Insects of Calotropis gigantea (L.) in Southern Province of Sri Lanka

Calotropis gigantea is a native plant to Sri Lanka having an ayurvedic medicinal value. People use the plant to gain fodder, fiber, and fertilizer. Despite its benefits, the plant is considered as an invasive species in Australia, the USA, etc. As the plant is medicinally, agriculturally, and ecologically valuable, the study was designed to investigate phytophagous insects of C. gigantea and their temporal variation. The field visits were conducted fortnightly from August 2015 to August 2016 in eleven sites in Southern Province (SP). During sampling, the number of insect species, their abundance, and the number of Calotropis fruits were recorded in selected trees. Twentynine insect species were recorded from C. gigantea and among them twelve species were phytophagous. Dacus persicus and Paramecops farinosa were destructive phytophagous insects. D. persicus was recorded in all three districts of SP throughout the year and the mean abundance varies significantly (p= 0.002) among districts. P. farinosa was only recorded from Hambantota district. Sphaeroderma sp. was the most abundant phytophagous insect and varied widely across (p = 0.000) districts of Southern Province. Danaus chrysippus larva was observed in all selected sites of SP. None of the insect abundance correlated with Calotropis fruit density, month of year and monthly rainfall

Growth of Queensland Jatropha gossypifolia biotypes under varying water regimes

Bellyache bush (Jatropha gossypifolia L. (Euphorbiaceae)) is a serious weed of dry tropical regions of northern Australia, with the potential to spread over much of the tropical savannah. It is well adapted to the harsh conditions of the dry tropics, defoliating during the dry season and rapidly producing new leaves with the onset of the wet season. In this study we examined the growth and biomass allocation of the three Queensland biotypes Queensland Green, Queensland Bronze and Queensland Purple) under three water regimes (water-stressed, weekly watering and constant water). Bellyache bush plants have a high capacity to adjust to water stress. The impact of water stress was consistent across the three biotypes. Water stressed plants produced significantly less biomass compared to plants with constant water, increased their biomass allocation to the roots and increased biomass allocation to leaf material. Queensland Purple plants allocated more resources to roots and less to shoots than Queensland Green (Queensland Bronze being intermediate). Queensland Green produced less root biomass than the other two biotypes

Growth of Queensland Jatropha gossypifolia biotypes under varying water regimes

Bellyache bush (Jatropha gossypifolia L. (Euphorbiaceae)) is a serious weed of dry tropical regions of northern Australia, with the potential to spread over much of the tropical savannah. It is well adapted to the harsh conditions of the dry tropics, defoliating during the dry season and rapidly producing new leaves with the onset of the wet season. In this study we examined the growth and biomass allocation of the three Queensland biotypes Queensland Green, Queensland Bronze and Queensland Purple) under three water regimes (water-stressed, weekly watering and constant water). Bellyache bush plants have a high capacity to adjust to water stress. The impact of water stress was consistent across the three biotypes. Water stressed plants produced significantly less biomass compared to plants with constant water, increased their biomass allocation to the roots and increased biomass allocation to leaf material. Queensland Purple plants allocated more resources to roots and less to shoots than Queensland Green (Queensland Bronze being intermediate). Queensland Green produced less root biomass than the other two biotypes

Proposed plant host test list for assessing risk of biological control agents for Navua sedge, Cyperus aromaticus

The following is a draft test list for potential weed biological control agents for Navua sedge, Cyperus aromaticus (Ridl.) Mattf. & Kukenthal (formerly Kyllinga aromatica Ridl. or K. polyphylla Willd. Ex. Kunth). Navua sedge is a perennial grass-like plant with a creeping rhizome and densely set culms. It was first detected in Australia in Cairns in 1979 and has since spread along the coast of northern Queensland between Bamaga and Langdon (west of Mackay) and west to the Atherton Tablelands (DAF 2020). In 2011, it was recorded in south-eastern Queensland (AVH 2020). Navua sedge is particularly prevalent in areas with more than 2500mm rainfall per year and no distinct dry season (Figure 2; Parsons and Cuthbertson, 2001). In lower rainfall areas it is restricted to wetter low-lying areas. In higher rainfall areas of northern Australia, Navua sedge has become a serious pasture weed (DAF 2020). It is an aggressive competitor for nutrients, light, and moisture and can form dense monospecific stands (Vitelli et al. 2010). Reproduction and spread occurs vegetatively by rhizomes and by seed, which are produced in abundance (Parsons and Cuthbertson 2001). Navua sedge has low nutritional value and is avoided by grazing animals (Vitelli et al. 2010)

Application to release Stomphastis sp. nov., an agent for the biological control of Jatropha gossypiifolia in Australia

Jatropha gossypiifolia (Euphorbiaceae), commonly known as bellyache bush, is a serious weed of rangelands and riparian zones of northern Australia, and it has the potential to invade much of northern Australia. Biological control is an important component of the long-term management strategy for J. gossypiifolia in Australia. Biological control of bellyache bush was initiated in 1999. Since then, only one agent, the jewel bug, Agonosoma trilineatum has been released and there is no evidence of its establishment. A renewed biological control effort, involving exploration in South America identified a number of potential biological control agents, the most promising of which, a small leaf-mining moth Stomphastis sp. nova (Lepidoptera: Gracillariidae), was imported from Peru into quarantine in 2014 for further research

The Impact of Parthenium Weed-Amended Substrates on the Germination and Early Growth of a Range of Pasture and Crop Species

Parthenium weed (Parthenium hysterophorus L.) is an internationally important invasive weed native to the tropical and sub-tropical Americas, and invasive in more than 30 countries. This weed has serious adverse influences on rangeland and agricultural crop production, on human and animal health, and on the biodiversity of natural communities. Parthenium weed leaf litter can reduce seedling emergence and affect the early growth of a wide range of pasture and crop species. Soil collected from a heavily infested parthenium weed area was shown to reduce seedling emergence of a wide range of test plants (lettuce (Lactuca sativa L.), maize (Zea mays L.), curly windmill grass (Enteropogon acicularis L.), and liverseed grass (Urochloa panicoides P.Beauv.)) by between 20 to 40%; however, the soil had no effect on the subsequent growth of the surviving test plants. Soil amended with dried parthenium weed leaf litter reduced the emergence of test species by ca. 20 to 40%, but it had no effect on the growth of the surviving test plants. One week after emergence, the growth of all test species was stimulated by 9 to 86% in the leaf litter-amended soil with the increased growth matching the increased amounts leaf litter amended. In parthenium weed-infested landscapes, the substrate (soil) is affected by the plant during the growing season by the release of allelopathic chemicals. However, the plant’s litter can affect the community outside of the growing season, first through a residual allelopathic activity, but also by a fertilizing effect as litter breakdown occurs. This study demonstrates the significant ability of parthenium weed to affect plant communities throughout the year and, when considered over several years, this may lead to the creation of a complete monoculture of the weed. View Full-Tex