The benefits and potential of pre-emptive weed biological control: Three case studies in Queensland, Australia

Invasive weed species can have significant impacts on agriculture, biodiversity and livelihoods. The cost and feasibility of managing these species using conventional means can be prohibitive depending on the size of the infestations or the habitats in which they invade. Under these conditions, biological control is seen as a viable, sustainable means to manage many weeds. However, biological control can take many years and at considerable cost to achieve the desired level of control, due to the numerous steps that are involved, including native range surveys and host-specificity testing of potential agents. Pre-emptive biological control targeting particularly high-risk species prior to their arrival in a country or emerging weeds can be cost-effective, especially if the respective biological control agents have been utilized in other countries. While pre-emptive biological control of arthropods has been investigated previously, there are few examples of pre-emptive biological control of weed species. The invasive weed species, Chromolaena odorata, Mikania micrantha and Coccinia grandis have all been or are currently targets of pre-emptive biological control in Australia. Research on the gall fly Cecidochares connexa was initiated prior to its host, C. odorata being detected in Australia. Cecidochares connexa was eventually released in Australia to control C. odorata, after initial research on the agent found it to be suitably host specific and effective against the target weed. Cecidochares connexa has also been released in numerous other countries in Africa, Asia and the Pacific, where it is providing very good control. Australia funded research on the rust Puccinia spegazzinii as part of a project involving Fiji and Papua New Guinea while the target weed, M. micrantha was a target for eradication in Queensland. The rust was later approved for release in Australia to control M. micrantha following additional host-specificity testing. However, research funded by Australia overseas suggests that the rust may not be able to suppress M. micrantha populations below current levels. Consequently, while P. spegazzinii has been released in numerous countries now, it has not yet been field released in Australia. Biological control research in Australia on C. grandis is relatively new as the weed is relatively minor and not yet declared a target for biological control. Consequently, no biological control agents have yet been released in the country. Pre-emptive biological control of C. odorata and M. micrantha has been particularly cost-effective, not just for Australia, but subsequently for numerous other countries where these weeds were well-established and problematic and the respective biological control agents were later released

Proposed plant host test list for assessing the risk of biological control agents for Clidemia hirta (L.) D.Don.

Background The following proposed plant host list is for the testing of potential biological control agents of Clidemia hirta (L.) D. Don (Melastomataceae). Post-release evidence from other countries suggests a promising outlook for biological control of C. hirta in Australia. Seven agents have already been released in Hawaii for this purpose, with six of these becoming established (Nakahara et al. 1992). Liothrips urichi Karny (Thysanoptera: Phlaeothripidae) is the first candidate biological control species proposed to undergo testing in Australia. The thrips have been released as a biological control agent for C. hirta in Fiji (1930), the Solomon Islands (1938, 1973 and 1975), Hawaii (1953), Palau (1960 and 1972), and American Samoa (1974) (Conant 2009). Liothrips urichi has established in all but the Solomon Islands and appears to be effective in open, sunny areas (Conant 2009). Host specificity of this insect has been demonstrated both within its native range and within countries where it has been introduced as a biological control of C. hirta (Table 1)

Prediction of disability-free survival in healthy older people

Prolonging survival in good health is a fundamental societal goal. However, the leading determinants of disability-free survival in healthy older people have not been well established. Data from ASPREE, a bi-national placebo-controlled trial of aspirin with 4.7 years median follow-up, was analysed. At enrolment, participants were healthy and without prior cardiovascular events, dementia or persistent physical disability. Disability-free survival outcome was defined as absence of dementia, persistent disability or death. Selection of potential predictors from amongst 25 biomedical, psychosocial and lifestyle variables including recognized geriatric risk factors, utilizing a machine-learning approach. Separate models were developed for men and women. The selected predictors were evaluated in a multivariable Cox proportional hazards model and validated internally by bootstrapping. We included 19,114 Australian and US participants aged ≥65 years (median 74 years, IQR 71.6–77.7). Common predictors of a worse prognosis in both sexes included higher age, lower Modified Mini-Mental State Examination score, lower gait speed, lower grip strength and abnormal (low or elevated) body mass index. Additional risk factors for men included current smoking, and abnormal eGFR. In women, diabetes and depression were additional predictors. The biased-corrected areas under the receiver operating characteristic curves for the final prognostic models at 5 years were 0.72 for men and 0.75 for women. Final models showed good calibration between the observed and predicted risks. We developed a prediction model in which age, cognitive function and gait speed were the strongest predictors of disability-free survival in healthy older people. Trial registration Clinicaltrials.gov (NCT01038583

Biological control of parthenium weed: field collection and redistribution of established biological control agents

Parthenium (Parthenium hysterophorus L.), a noxious weed of grazing areas in Queensland (Qld), is a Weed of National Significance in Australia. Eleven biological control agents (nine insect species and two rust pathogens) have been released against parthenium in Australia. The majority of these agents have become established and have proven effective against the weed in central Qld. Parthenium is spreading further into southern Qld, where many of the widespread and effective biological control agents in central Qld are not present. Hence, a program to redistribute these agents from central Qld to the south and south east of the state has been initiated. The seed-feeding weevil (Smicronyx lutulentus Dietz), the stem-boring weevil (Listronotus setosipennis (Hustache)), and the root-boring moth (Carmenta nr. ithacae Beutenmüller), the winter rust (Puccinia abrupta var. partheniicola Dietel & Holway), and the summer rust (Puccinia xanthii var. parthenii-hysterophorae Seier, Evans & Romero) have been identified as priority agents for redistribution. So far, field collected winter rust, the Listronotus weevil, the Smicronyx weevil, the Carmenta moth and the leaf-feeding beetle (Zygogramma bicolorata Pallister) have been field released at ten sites in south and south east Qld. Field releases of the winter rust from glasshouse cultures were also made at several sites. So far there is evidence of field establishment of the winter rust and the Smicronyx weevil in some of the release sites. Cultures of the summer rust and Listronotus weevil have recently been established at the Ecosciences Precinct for future mass rearing and field releases. Redistribution of field collected and glasshouse cultured biological control agents and monitoring their establishment status in the field will continue over the next three years

Biology, host specificity and varietal preference of the lantana gall fly: lessons learnt in time

Lantana camara L. (Verbenaceae) is a Weed of National Significance in Australia. This aggressive perennial woody shrub invades national parks, forestry, grazing lands, and riparian areas, displacing native species and reducing productivity. Effective control using mechanical or chemical means is both difficult and costly. Lantana was one of the first weeds to be targeted for classical biological control. Thirty agents were deliberately introduced to Australia, of which twenty agents, including a mite and a fungal pathogen, have become established and contribute to seasonal damage of the weed. Despite this, control of the lantana is still not adequate. The lantana gall fly, Eutreta xanthochaeta Aldrich (Tephritidae), which aids control in Hawai’i, was field released in Australia in 1914, and again in 1971. This fly forms monothalamous galls on young shoots of lantana, significantly reducing the production of inflorescences on galled branches. Historically, difficulties mass rearing this agent resulted in only a very limited number of flies ever being released, and at only two locations in Queensland. Ultimately the agent failed to establish, and it was deemed a low priority to pursue further, as other potential agents were investigated. In 2022, E. xanthochaeta was re-imported into quarantine at the Ecosciences Precinct in Brisbane. A colony was successfully established from one female fly and five male flies, the only survivors from imported galls from Hawaii. This paper reports on the optimisation of rearing methods, biology of the lantana gall fly, and preliminary results of supplementary host specificity testing being undertaken

Biological control of parthenium: progress on the redistribution of established agents to southern Queensland

Parthenium (Parthenium hysterophorus L.), a serious weed of grazing areas in central Queensland (Qld) and a Weed of National Significance in Australia, has spread into parts of southern Qld. The isolated nature of the southern Qld infestations, probably resulting from the movement of contaminated stock feed, livestock and machinery, has meant many of the effective biological control agents established in core infested areas of central Qld have not extended their distribution at the same pace as the weed. As a result, a program to redistribute these agents from central Qld to southern Qld was initiated. The seed-feeding weevil (Smicronyx lutulentus Dietz), the stem-boring weevil (Listronotus setosipennis (Hustache), and the root-boring moth (Carmenta nr. ithacae Beutenmuller), the winter rust (Puccinia abrupta var. partheniicola Dietel & Holway), and the summer rust (Puccinia xanthii var. parthenii-hysterophorae Seier, Evans & Romero) were prioritised for redistribution. Since late 2015, prioritised agents have either been bulk collected from central Qld, or reared in glasshouse facilities in Brisbane, and released at 19 sites across 10 geographically isolated areas in southern Qld. Periodic surveys of release sites have indicated strong evidence of establishment of the winter rust and the Smicronyx weevil at most of the sites and preliminary signs of establishment of the summer rust and the Listronotus weevil at a few sites. Redistribution of field-collected and glasshouse-reared agents and monitoring of their establishment status in the field will continue over the next year

Biological control of parthenium (Parthenium hysterophorus): the Australian experience

Parthenium is a Weed of National Significance in Australia. Biological control of parthenium in Australia commenced in 1977 and since then nine insect species and two rust fungi have been introduced and established. Seven of them are widespread, however the time taken for field establishment varied widely between various agents, ranging from one to 15 years. Among them, the stem-galling Epiblema moth, the stem-boring Listronotus weevil, the seed-feeding Smicronyx weevil and the root-feeding Carmenta moth occur in all parthenium-infested areas at high population densities. The leaf-feeding Zygogramma beetle occurs only in central and southern Queensland, and not in northern Queensland. The parthenium summer rust occurs seasonally in central and northern Queensland, while the parthenium winter rust is more widespread in southern Queensland than in central Queensland, but does not occur in north Queensland. The sap-feeding Stobaera planthopper and the leaf-mining Bucculatrix moth established and are widespread, but their damage levels remain very low. The stem-galling Conotrachelus weevil and the stem-boring Platphalonidia moth are believed to be established, but at very low abundance. Biological control has resulted in significant reductions in the abundance and impact of parthenium in Australia. As a result, the area infested with parthenium in central Queensland has declined since the mid-1990s. Due to the absence of many of the effective agents in southern and south-eastern Queensland, agents from central Queensland are being redistributed there. Additionally, based on Australian success, many of these agents have also been introduced into other countries around the world