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Senecio madagascariensis Poir. (fireweed) is a rapidly invading, poisonous weed of temperate and subtropical pastures across several continents and islands worldwide. While the geographic spread of pasture weeds, such as fireweed, can be relatively readily monitored, it is often farmer perceptions of weed impact that form the imperative for their management. Moreover, it is important to assess the types of adaptive changes that farmers may consider to the continued invasion of weeds in pasture-based systems. Therefore, in 2011 we repeated a published 1985 farmer survey in fireweed-impacted regions in Australia to investigate: its continued spread; changes in the perceptions of its importance; and resulting changes in management. Fireweed had spread to new regions and was better established in previously lightly infested regions. It was less likely to be considered troubling by respondents when it was new on their farms, or had been present for an extended period. The effectiveness of a control method was only one of several factors driving adaptive changes in pasture weed management amongst survey respondents. Use of some approaches had declined alongside a perception that they were relatively ineffective, while the level of use of other reportedly successful techniques remained static, indicating major impediments to adoption. Weed invasions are by definition dynamic, and landholder perceptions of pasture weeds appear equally dynamic. As poisonous Senecio species spread around the world, the findings of this Australian research emphasise the need to understand how farmers adapt to weed invasion. Policymakers and landholders can benefit from such research for Senecio and other important weed species, by exploring the perceptions that may drive successful adaptive management of these species on-farm. [ABSTRACT FROM AUTHOR]

Context: Seed germination and seedling emergence are affected by many environmental factors. Knowledge regarding factors affecting seed germination of spiny cocklebur (Xanthium spinosum L.) and common cocklebur (X. strumarium L.) could help determine their potential distribution and control strategies. Aims: The present study was conducted to investigate the effect of key environmental factors on seed germination and seedling emergence of spiny cocklebur and common cocklebur. Methods: Seed germination of spiny cocklebur and common cocklebur was tested at various constant and alternating temperatures, pH, salinity and moisture stress. The effect of flooding height, burial depth and soil type on seedling emergence was also investigated. Key results: The optimum constant temperature for germination of spiny cocklebur was 25°C, and 35°C and higher for common cocklebur. Under alternating temperature, maximal germination was at 25/15°C and 35/15°C for spiny cocklebur and common cocklebur, respectively. Maximum germination of both spiny cocklebur and common cocklebur was at neutral pH. Spiny cocklebur germination was not suppressed as much by lower and higher pH or by an increasing salinity as was common cocklebur germination. Conclusions: Common cocklebur appears to be better adapted to warmer environments than is spiny cocklebur, but less so to a broad range of soil pH and salinity stress. Implications: The different germination responses of common cocklebur and spiny cocklebur to the environmental factors of temperature, pH and salinity imply that the two species may occupy different niches across the landscape. Our knowledge of these responses can help in identifying potential areas for invasion for increased monitoring and management. Information on factors affecting spiny cocklebur (Xanthium spinosum) and common cocklebur (X. strumarium) seed germination could help us determine their potential distribution in different regions and their effective control strategies. Maximum germination of both spiny cocklebur and common cocklebur was at neutral pH. Spiny cocklebur germination was less sensitive to high and low pH, salinity, flooding and surface burial than was common cocklebur germination, indicating that it may be better adapted to the broader range of conditions. Image by Faezeh Zaefarian. [ABSTRACT FROM AUTHOR]

Weeds have a significant impact on vegetable production worldwide. These intensive cropping systems feature frequent tillage, fertilization and irrigation, providing ideal growing conditions for crops as well as certain weeds. Integrated weed management (IWM) can reduce reliance on herbicides by encouraging a systems approach to weed management. Using insights from global research and industry literature, we investigated the effectiveness of prevailing weed control methods, and evaluated emerging management practices and technologies for ongoing research and adoption. Weed control relies primarily on a relatively narrow range of herbicides as well as frequent tillage. Herbicides have negative impacts on soil, water and human health, while tillage impacts soil quality and function. Intensive cropping on smaller plots facilitates IWM, relying on multiple strategies including hand weeding, mulches, cover crops and cultural methods (e.g., crop rotations, timing). New herbicide options are suggested as an industry priority but are constrained by the lack of new chemistry and potential herbicide resistance. Refinement and adoption of non‐herbicide and emerging precision control methods into farm IWM in vegetables is more likely to be sustainable. This review is relevant to advanced vegetable production systems globally, but also to smallholder vegetable production in developing economies. [ABSTRACT FROM AUTHOR]

Seed germination studies are often used to predict the potential of plants to extend their global distribution. In this research, the effect of gibberellic acid (GA3) concentrations, pre-chilling, temperature, water and salt stresses, pH, high-temperature pretreatment, planting depth, and flooding on seed germination and seedling emergence of three Amaranthus retroflexus L. populations was investigated. GA3 concentration significantly affected seed germination of all three A. retroflexus populations grown under light/dark conditions. All three populations germinated under constant (10, 15, 20, 25, and 30 °C) and alternating (20/15, 25/18, and 35/25 °C (day/night)) temperatures. The optimum alternating temperature for germination of all three populations was 18/25 °C day/night. Seed germination was severely reduced under moisture and salt stresses. Seedling emergence was reduced on the soil surface by increasing the planting depth from 2.5 to 7.5 cm, and no seedlings emerged when the planting depth of seeds was more than 10 cm. The results of this research help us to understand the germination capacity and requirements of A. retroflexus in different environments and also provide information to help better control the weed. [ABSTRACT FROM AUTHOR]

Conservation agriculture (CA) is being promoted as an energy efficient and cost-effective farming system that conserves soil and water and improves crop yields. Adoption of this farming system can contribute to attainment of Sustainable Development Goal (SDG) 2: end hunger, achieve food security and improved nutrition, and promote sustainable agriculture. However, the adoption rate of this new farming technique by smallholder farmers in sub-Saharan Africa (SSA) is low. The trade-offs and synergies related to the three pillars that anchor CA have not, however, been investigated in the context of Botswana. Farmers are faced with trade-offs in the use of crop residue in CA as mulch with traditional use as feed for livestock. This paper reviews the components of CA with a view to contribute to the development of CA strategies for Botswana. We show that adoption of CA in SSA is challenged by lack of weed control measures, the lack of a market for grain legumes and competing uses of crop residue. The paper highlights the discrepancy between CA methods and current government subsidies, issues that may restrain the adoption of CA in Botswana. The paper concludes by making recommendations for research and policy development for sustainable CA practices in Botswana. [ABSTRACT FROM AUTHOR]

The Antarctic is an extreme environment for plants. Several invasive plant species, however, have invaded the sub-Antarctic Southern Ocean islands and increasingly threaten the vulnerability of maritime and continental Antarctica, particularly with changes in climate. We provide an overview of issues to consider with regard to the impact, ecology and management of non-native plants in the Antarctic, focusing on knowledge gained and recent research results from the sub-Antarctic with possible application to Antarctica. We provide a brief review of literature and bring together experience and previously unpublished research with Poa annua and Stellaria media on Macquarie Island. While no one set of biological characteristics predicts plant invasiveness in the sub-Antarctic, all are adapted to survive extreme cold conditions and persistence is enabled through large and long-lived soil seed banks. Ecological drivers for invasion include accidental human introductions and continuing movement, along with animal and other disturbance to soil. The invasive cold-tolerant plant species now prevalent on sub-Antarctic islands also pose a threat to Antarctica due to a warming climate and so efforts should continue to prevent further spread, while developing effective, low-impact control and eradication options to protect these high-value extreme ecosystems. [ABSTRACT FROM AUTHOR]

Eradication of alien plants is notoriously challenging, however eradication projects reap great biodiversity benefits, particularly on islands. To date only individual plants or small restricted populations have been successfully eradicated from the Southern Ocean Islands (SOI). The next phase in conservation for the region is tackling more widespread, abundant alien plant species. Several on-going and proposed control programs for such weeds exist in the SOI and Antarctic regions. If eradication of a widespread species is to be successful, a number of factors need to be considered. 'Organisational' factors such as management agency capacity, resources and the availability of effective control methods are critical to the success of an eradication. 'Site and species' factors such as infestation extent, number of discrete populations, dispersal processes and detectability typically show a cumulative effect on success. We assessed the site and species factors for Stellaria media, an alien species on sub-Antarctic Macquarie Island, to determine the feasibility of its eradication from the island. Organisational factors can successfully be met with adequate funding. Site and species factors which reduce the likelihood of eradication included large gross infestation areas, large plants with high reproductive output (precocity or fecundity), dense seed banks, short pre-reproductive period, extended seed longevity and vegetative reproductive capacity. We recommend a small-scale eradication trial for restricted, easily accessible populations of S. media on Macquarie Island to further evaluate the likelihood of broader eradication. [ABSTRACT FROM AUTHOR]

BACKGROUND Low rainfall is a major limitation to expanding the dairy industry in semi-arid environments in East Africa. In such dry areas, plants need to keep their tissues hydrated and stomata open for carbon exchange and to grow. On this basis, we assessed the productivity of 10 lines of Napier grass ( Pennisetum purpureum Schum.), which formed three yield clusters: low yielding ( LYC), moderate yielding ( MYC), and high yielding ( HYC), in a wet highland (Muguga) and semi-arid lowland (Katumani) of Kenya. Stomatal conductance ( gs), leaf water potential ( LWP) and relative water content ( RWC) were monitored, and water use simulated, over four growth cycles in 2012. These were used with measurements of leaf area index ( LAI) and plant dry weight to explore the possible use of these physiological parameters for assessing productivity potential of Napier grass accessions. RESULTS The plants were less stressed at Muguga, where gs was 700-1000 mmol m−2 s−1, LWP −0.4 to −0.9 MPa and RWC was 82-95%; these values at Katumani were 450-750 mmol m−2 s−1, −0.7 to −1.4 MPa and 74-93%, respectively. Total water use at Katumani was of the order HYC ≈ MYC (390 mm) > LYC (370 mm), and water use efficiency ( WUE, kg ha−1 mm−1) followed the same order HYC (34.3) > MYC (32.6) > LYC (24.9); whereas at Muguga water use averaged 710 mm for HYC and MYC, greater than 676 mm for LYC, and WUE (kg ha−1 mm−1) averaged 29.2 for HYC and MYC, and 19.4 for LYC. CONCLUSIONS The three water stress indices were poor, whereas vigorous early canopy development (determined as LAI) was a more reliable predictor of productivity potential of Napier grasses. In these dry environments, therefore, early rapid canopy development can be an effective indicator of yield potential and a credible selection criterion. © 2016 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Most recently naturalized weeds (invasive non-native plant species. or species growing outside their natural range) in Australia are still only locally distributed, so it is critical to identify the pathways by which these and more widespread species are most likely to spread and to identify the domestic sources from which they are most likely to emerge. Our research sought to identify which weed sources and pathways account for the majority of weed ingress, which pathways pose the greatest risk, how these risks are changing, and how pathway management strategies might be improved. These questions were addressed through a review of literature and a survey of Australian weed experts. Twenty-four sources and 17 natural and human-assisted pathways were identified and assessed. The most significant weed spread pathways in Australia appear to be the trade in ornamental plants and movement of machinery and vehicles, while other important pathways include fodder trade, aquarium plant trade, agricultural produce, and water. Economic and demographic trends, and changing climate, are likely to contribute to growing importance of a range of weed spread pathways in the future. Pathway risk assessment makes it possible to target scarce weed control resources, policy measures, and research efforts by highlighting the pathways that have the greatest potential (in terms of likelihood and potential magnitude) to spread weeds, now and in the future. Similarly, it informs naturat area managers as they instigate control and management tools that address the highest risk means by which weeds might enter and spread through their area of responsibility. [ABSTRACT FROM AUTHOR]

The effects of soil nitrate and the herbicide, isoxaflutole, on chickpea nodulation were examined in a glasshouse experiment. The treatments consisted of one isoxaflutole-tolerant and one isoxaflutole-sensitive chickpea cultivar, five nitrate concentrations (0, 0.75, 1.5, 3.0, and 6.0 mmol L), and three herbicide rates (0, 75 [the recommended rate], and 300 g ha). The sensitive cultivar was more susceptible to isoxaflutole damage with an increasing herbicide rate and nitrate concentration, compared with the tolerant cultivar. Isoxaflutole at the recommended rate reduced the nodule dry weight of the sensitive cultivar by 51% and by 33% in the tolerant cultivar. The nodule dry weight of the sensitive cultivar was reduced by 28%, 40%, 64%, and 76% with the addition of the 0.75, 1.5, 3.0, and 6.0 mmol L nitrate concentrations, respectively. In comparison, the nodule dry weight of the tolerant cultivar was reduced by 50% and 79% at the 3.0 and 6.0 mmol L nitrate concentrations, respectively. In addition, the level of damage from increasing rates of isoxaflutole increased with the highest nitrate concentrations of 3.0 and 6.0 mmol L, regardless of the cultivar. Isoxaflutole at the recommended application rate had a detrimental effect on the nodulation of both chickpea cultivars, but the isoxaflutole-tolerant cultivar suffered less injury than the sensitive one in relation to some growth parameters. The damage to chickpea from the recommended rate of isoxaflutole also increased with soils of higher nitrate content. [ABSTRACT FROM AUTHOR]

Sonchus oleraceus (common sowthistle) is a dominant weed and has increased in prevalence in conservation cropping systems of the subtropical grain region of Australia. Four experiments were undertaken to define the environmental factors that favor its germination, emergence, and seed persistence. Seeds were germinated at constant temperatures between 5 and 35°C and water potentials between 0 and −1.4 MPa. The maximum germination rate of 86–100% occurred at 0 and −0.2 MPa, irrespective of the temperature when exposed to light (12 h photoperiod light/dark), but the germination rate was reduced by 72% without light. At water potentials of −0.6 to −0.8 MPa, the germination rate was reduced substantially by higher temperatures; no seed germinated at a water potential >−1.0 MPa. Emergence and seed persistence were measured over 30 months following seed burial at 0 (surface), 1, 2, 5, and 10 cm depths in large pots that were buried in a south-eastern Queensland field. Seedlings emerged readily from the surface and 1 cm depth, with no emergence from below the 2 cm depth. The seedlings emerged during any season following rain but, predominantly, within 6 months of planting. Seed persistence was short-term on the soil surface, with 2% of seeds remaining after 6 months, but it increased with the burial depth, with 12% remaining after 30 months at 10 cm. Thus, a minimal seed burial depth with reduced tillage and increased surface soil water with stubble retention has favored the proliferation of this weed in any season in a subtropical environment. However, diligent management without seed replenishment will greatly reduce this weed problem within a short period. [ABSTRACT FROM AUTHOR]

Effects of soil type, time, depth of seed burial and rainfall pattern were investigated on the longevity of glyphosate resistant annual ryegrass ( Lolium rigidum Gaudin) in the northern summer rainfall dominant grain region of Australia in a 16 month experiment conducted under polyhouse conditions. Lolium rigidum seeds placed in nylon bags were buried in pots at 5 and 10 cm depth in either Laureldale (clay) or Kirby (sandy loam) soil receiving simulated rainfall representing a Tamworth (summer) and Hamilton (winter) rainfall environment of Australia. The bags were exhumed every four months and tested for percent viable, germinable, dormant and dead seeds. In the short term (several months), factors such as soil type, rainfall and depth of burial affected the fate and condition of L. rigidum seeds and emergence pattern of seedlings. However, irrespective of treatment, all seeds lost their viability after 16 months of burial. Hence, in the longer term, L. rigidum behaviour in this summer dominant rainfall environment with different soils is likely to be similar to that where the weed occurs more commonly in the southern Mediterranean regions of Australia. Maximum emergence in the polyhouse occurred during mid autumn similar to that in the field. The results from this experiment will allow for the development of management strategies which may enhance the depletion of the soil seedbank of viable L. rigidum seeds in the shortest possible time. [ABSTRACT FROM AUTHOR]

A glasshouse experiment was conducted to investigate the effect of soil pH on chickpea ( Cicer arietinum) tolerance to isoxaflutole applied pre-emergence at 0, 75 (recommended rate) and 300 g a.i. ha−1. For this study, the variables examined were two desi chickpea genotypes (97039-1275 as a tolerant line and 91025-3021 as a sensitive line) and four pH levels (5.1, 6.9, 8.1, and 8.9). The results demonstrated differential tolerances among chickpea genotypes to isoxaflutole at different rates and soil pH levels. Isoxaflutole applied pre-emergence resulted in increased phytotoxicity with increases in soil pH and herbicide rate. Even the most tolerant chickpea genotype was damaged when exposed to higher pH and herbicide rates, as indicated by increased leaf chlorosis and significant reductions in plant height, and shoot and root dry weight. The effects were more severe with the sensitive genotype. The susceptibility of chickpea to this herbicide depends on genotype and soil pH which should be taken into account in breeding new lines, and in the agronomy of chickpea production. [ABSTRACT FROM AUTHOR]

Global climate change and anthropological activities have led to a decline in insect pollinators worldwide. Agricultural globalisation and intensification have also removed crops from their natural insect pollinators, and sparked research to identify alternate natural insect pollinators and artificial technologies. In certain countries such as Australia the importation of commercial insect pollinators is prohibited, necessitating manual labour to stimulate floral pollination. Artificial pollination technologies are now increasingly essential as the demand for food grown in protected facilities increases worldwide. For tomato fruits, precision pollination has the ability to vastly improve their seed set, size, yield, and quality under optimal environmental conditions and has become financially beneficial. Like many crops from the Solanaceae, tomatoes have a unique self-pollinating mechanism that requires stimulation of the floral organs to release pollen from the poricidal anthers. This review investigates various mechanisms employed to pollinate tomato flowers and discusses emerging precision pollination technologies. The advantages and disadvantages of various pollinating technologies currently available in the protected-cropping industry are described. We provide a buzz perspective on new promising pollination technologies involving robotic air and acoustic devices that are still in their nascency and could provide non-contact techniques to automate pollination for the tomato horticultural industry. [ABSTRACT FROM AUTHOR]