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Weed resistance to different herbicide modes of action is driven by agricultural intensification
Get PDFContext or problem: The continued increase in numbers of herbicide-resistant weed species in field crops constrains sustainable agricultural practices worldwide. Countries differ markedly in numbers of herbicide-resistant weed species in field crops yet the extent this reflects global variation in agricultural intensification is not known.
Objective or research question: To what extent does the global variation in the number of herbicide resistant weeds reflect differences in the magnitude of direct measures of agricultural intensification such as agrochemical inputs, indirect measures such as per capita GDP, or non-agronomic factors such as research intensity?
Methods: Best-subset regression analysis quantified whether national scale estimates of agricultural intensification such as per capita GDP, cropland area, as well as inputs of N-fertilizer and herbicide explained variation in numbers of herbicide-resistant weed species in field crops worldwide. The number of publications addressing herbicides was used as a proxy for sampling effort, while the time since the first record of resistance estimated the window of opportunity for weed species to become resistant. Analyses were undertaken across all herbicides as well as separately for four herbicide modes of action (ACCase, ALS, PSII and EPSPS inhibitors).
Results: Over 70% of the global variation in numbers of herbicide-resistant weed species was explained by national scale estimates of herbicide inputs, cropland area, per capita GDP as well as measures of research effort and the time since the first resistant weed was recorded. The explanatory ability of models for individual herbicide modes of action ranged from 40% (ACCase inhibitors) to 68% (PSII inhibitors), with per capita GDP and time since first record the most consistent explanatory variables.
Conclusions: Agricultural intensification, as captured by herbicide inputs and per capita GDP, was associated with increased numbers of herbicide-resistant weed species worldwide but the limited herbicide expertise in many countries means the scale of the problem is underestimated. The number of resistant weed species depended on how long resistance had been observed suggesting for many countries the problem will increase in the future, especially as different modes of action become more widely used.
Implications or significance: Many countries that have only recently recorded herbicide resistance in weeds are already on a trajectory for future increases but have limited capability to address this problem. Implementation of integrated weed management strategies to reduce the risk of herbicide-resistant weeds evolving should therefore be implemented proactively before the problem gets worse rather than reactively as has occurred in other countries
Sharing energy poverty: The nexus between social interaction-oriented gift expenditure and energy poverty in rural China
Get PDFThis study examines how social interaction-oriented gift expenditure affects the energy poverty of rural households in China, accounting for energy inaccessibility, unaffordability, and multidimensional energy poverty. A conditional mixed process model was used to estimate the 2016 and 2018 China Family Panel Studies survey data and address the endogeneity of gift expenditure. The results suggest that social interaction-oriented gift expenditure could crowd out rural residents' energy expenditures and drive them to energy poverty. Specifically, every 100 Chinese yuan per capita increase in gift expenditure increases the probability of energy inaccessibility by 2.1 % and energy unaffordability by 1.5 %–1.6 %. This increase also increases the likelihood of rural households being trapped in multidimensional energy poverty by 1.9 %. Furthermore, household deposits mediate the positive associations between gift expenditure and rural energy poverty. Our findings suggest that regulating rural residents' behaviors of giving monetary gifts could help alleviate rural energy poverty
Forests from the grass: Natural regeneration of woody vegetation in temperate marginal hill farmland under minimum interference management
Get PDFMarginal hill farmland is a key target for the restoration of temperate indigenous forest, which can help mitigate climate change and biodiversity loss. Reliance on natural regeneration and minimum interference management (MIM) is a low-cost restoration strategy for farmers, with the transition from pasture to woody scrub vegetation (whether indigenous or exotic) an important early successional phase. However, few studies have determined the key factors that influence the regeneration of woody vegetation on pastoral farmland, nor the rate at which regeneration occurs. Using a geospatial analysis of a New Zealand pastoral hill farm subject to variable grazing and MIM, this study found that only 3.8% of grassland experienced detectable regeneration of woody vegetation over 16 years. The key factor influencing natural regeneration was proximity to existing woody vegetation, with the probability of regeneration decreasing as distance increased. Cattle grazing had a significant negative impact, with regeneration more likely to occur in areas free from cattle. Sheep grazing exhibited no significant positive or negative relationship with regeneration. To support natural regeneration of woody vegetation, landowners should prioritize areas with a higher presence of existing woody vegetation and exclude cattle. To increase the rate of regeneration, landowners should consider active management regimes and supplemental restoration strategies, such as applied nucleation and the introduction of nurse species. Given the increased cost and complexity of such approaches, effective government incentive programmes may be needed to provide landowners with financial support and expertise
Linocin M18 protein from the insect pathogenic bacterium Brevibacillus laterosporus isolates
Get PDFBrevibacillus laterosporus (Bl) is a Gram-positive and spore-forming bacterium. Insect pathogenic strains have been characterised in New Zealand, and two isolates, Bl 1821L and Bl 1951, are under development for use in biopesticides. However, growth in culture is sometimes disrupted, affecting mass production. Based on previous work, it was hypothesised that Tectiviridae phages might be implicated. While investigating the cause of the disrupted growth, electron micrographs of crude lysates showed structural components of putative phages including capsid and tail-like structures. Sucrose density gradient purification yielded a putative self-killing protein of ∼30 kDa. N-terminal sequencing of the ∼30 kDa protein identified matches to a predicted 25 kDa hypothetical and a 31.4 kDa putative encapsulating protein homologs, with the genes encoding each protein adjacent in the genomes. BLASTp analysis of the homologs of 31.4 kDa amino acid sequences shared 98.6% amino acid identity to the Linocin M18 bacteriocin family protein of Brevibacterium sp. JNUCC-42. Bioinformatic tools including AMPA and CellPPD defined that the bactericidal potential originated from a putative encapsulating protein. Antagonistic activity of the ∼30 kDa encapsulating protein of Bl 1821L and Bl 1951 during growth in broth exhibited bacterial autolytic activity. LIVE/DEAD staining of Bl 1821L cells after treatment with the ∼30 kDa encapsulating protein of Bl 1821L substantiated the findings by showing 58.8% cells with the compromised cell membranes as compared to 37.5% cells in the control. Furthermore, antibacterial activity of the identified proteins of Bl 1821L was validated through gene expression in a Gram-positive bacterium Bacillus subtilis WB800N
Transforming freshwater politics through metaphors: Struggles over ecosystem health, legal personhood, and invasive species in Aotearoa New Zealand
No full text1. Metaphor, defined as the linguistic substitution of one phenomenon for another, is ubiquitous in environmental science and policy. In science, when used well, metaphors help to make complex and abstract ideas familiar and relatable, while also helping people orient ethically to the natural world. In freshwater science, metaphors structure many aspects of scientific and lay understanding.
2. Yet, while metaphors are often used in environmental science and advocacy, there is a need to join up our currently diffuse understandings about how metaphors can help achieve social transformation for sustainability. Here, we focus on how metaphors are enshrined into institutions, giving them permanence and force as tools for social transformation.
3. We explore three examples of metaphors in environmental science and activism that have ‘gone public’ to shape freshwater politics and governance in Aotearoa New Zealand (henceforth Aotearoa NZ). We focus on the origins, strategic purposes and limitations of the metaphors, the ways they have been institutionalised, and the roles that scientists in particular have played in shaping metaphorical meanings.
4. Metaphors perform diverse political tasks, from mobilising popular support for species removal, to reorienting human obligations to rivers, through to expanding the scope of vision for river management. Scientists play key roles in shaping both regulatory institutions as well as informal norms that affect metaphor implementation. Finally, what makes a ‘good’ metaphor needs to be evaluated in context of who is mobilising the metaphor and what their broader sustainability values and objectives are
Semi-arid irrigation farm dams are a small source of greenhouse gas emissions
No full textSmall artificial waterbodies are larger emitters of carbon dioxide (CO₂) and methane (CH₄) than natural waterbodies. The Intergovernmental Panel on Climate Change (IPCC) recommends these waterbodies are accounted for in national emission inventories, yet data is extremely limited for irrigated landscapes. To derive a baseline of their greenhouse gas footprint, we investigated 38 irrigation farm dams in horticulture and broadacre cropping in semi-arid NSW, Australia. Dissolved CO₂, CH₄, and nitrous oxide (N₂O) were measured in spring and summer, 2021–2022. While all dams were sources of CH₄ to the atmosphere, 52% of irrigation farm dams were sinks for CO₂ and 70% were sinks for N₂O. Relationships in the linear mixed effect models indicate that CO₂ concentrations were primarily driven by dissolved oxygen (DO), ammonium, and sediment carbon content, while N₂O concentration was best explained by an interaction between DO and ammonium. Methane concentrations did not display any relationship with typical biological variables and instead were related to soil salinity, trophic status, and size. Carbon dioxide-equivalent emissions were highest in small (< 0.001 km²) dams (305 g CO₂-eq m−² season−¹) and in those used for recycling irrigation water (249 g CO₂-eq m−² season−¹), with CH₄ contributing 70% of average CO₂-eq emissions. However, irrigation dams had considerably lower CH₄ emissions (mean 40 kg ha−¹ yr−¹) than the IPCC emission factor (EF) of 183 kg CH₄ ha−¹ yr−¹ for constructed ponds and lower N₂O EF of 0.06% than the indirect EF for agricultural surface waters (0.26%). This synoptic survey reveals existing models may be severely overestimating (4–5 times) farm dam CH₄ and N₂O emissions in semi-arid irrigation areas. Further research is needed to define these artificial waterbodies in emissions accounting
Seed treatment options for New Zealand carrot production : A thesis submitted in partial fulfilment of the requirements for the Degree of Master of Science at Lincoln University
No full textThe New Zealand carrot industry currently uses fungicide seed coatings, rather than using some of the biological options available for disease control. The industry standard seed treatment has been in use since at least 2008. This research had the aim of comparing the current seed treatment with a pre-commercial biological (Trichoderma) seed treatment under a variety of conditions to determine the best approach. Data were gathered to show the effects of the various seed treatments on the carrots’ emergence, harvest weights, disease severity, and storage ability. A total of four experiments were conducted, two in the field and two in the glasshouse. A further experiment assessed the effects of all the pesticides applied to the crop or seed on Trichoderma conidia germination.
A field trial was established in a commercial crop at Waiuku with five different seed treatments, including the combination of chemical and biological seed treatments. Unfortunately, due to covid restrictions, no data could be gathered until final carrot harvest, and harvested carrots were used in a cool store based storage trial. The Trichoderma alone treatment significantly increased yield over the industry standard seed treatment but there was no difference in storage performance among the treatments.
A second field trial at Lincoln compared between chemical and Trichoderma seed treatments and untreated seed. These carrots were grown at a site known to contain soil-borne pathogens, and the crop received no pesticide applications. The aim was to investigate whether Trichoderma could provide long term disease control and increase marketable carrot yield. The carrots were also ground stored for a month after harvest to further test any long term disease suppression. However no significant differences were recorded among the treatments for any of the parameters measured.
The glasshouse trials used soil from major carrot growing areas of New Zealand and looked at how chemicals and Trichoderma could help reduce the impact of the pathogens present compared to untreated seed. Additional data related to growth promotion such as foliage, taproot, and fine root weight were also recorded. Both trials tended to show that both the Trichoderma and chemical seed treatment had comparable performance in emergence and disease control and that this exceeded that of untreated seed. No growth promotion effects were recorded based on the dry weights of the foliage, taproots, or fine roots.
To test Trichoderma conidia germination in the presence of pesticides, conidia were incubated at 25°C in the presence of pesticides at label rate concentrations. Glyphosate, difenoconazole, and mancozeb completely inhibited conidia germination but the seed treatment fungicides did not.
Overall the results suggest that, under the conditions used, a Trichoderma seed treatment had a similar performance to the commonly used fungicide seed treatment. There was no best seed treatment in this study, but more options have been identified. The results in glasshouse conditions were not replicated in the field. The results also suggest that this strain of Trichoderma did not provide long term disease control, or promote carrot growth. The compatibility results showed that these strains of Trichoderma are sensitive to some pesticides but they are pesticides that are unlikely to come into direct contact with the conidia. The seed treatment fungicides did not affect conidial germination
Agricultural expansion and trade-off decision making using analytic hierarchy process in Ghana
No full textThe current study sought to investigate the factors influencing the conversion of forest lands to agricultural areas, which is primarily a result of agricultural expansion. This phenomenon is recognized as a significant driver of land use and land cover change in Ghana. Data was collected from land managers (commercial and subsistence farmers) who are major decision-makers on accelerated farm land expansion in districts known for large-scale food and tree crop production. The method used for data collection was the Analytical Hierarchy Process (AHP). APH was used to assess factors that influence farmers' decisions to expand their farms. These are economic, environmental, social, and policy factors that were weighted to determine the most important factors of agricultural expansion. Study results showed that economic factors were weighted above other factors in terms of importance when it came to making decisions on farm expansion. Environmental and social factors were second and third, respectively, while policy factors were weighted as the least important factors. The study provides valuable insight into key factors that influence land managers farm expansion decisions and how land-use change can be addressed. The study concludes that the Analytic Hierarchy Process is a useful method for analyzing multiple factors considered by farmers when expanding their farms, despite its limitations
Peru’s persistent hydraulic development model and shifting water governance regimes
No full textThe 20th century saw a proliferation in national modernization efforts through large hydraulic projects—a trend referred to as the hydraulic mission. In this paper, I analyze Peru’s hydraulic mission and its relationship with different water governance regimes, since the inception of a coastal agricultural development model in the early 20th century, to the present. I draw from analysis of secondary literature, water law and policy, and hydraulic infrastructure project documents. These methods are complemented with interviews in highland and lowland irrigation sites serviced by the Majes-Siguas Special Project (PEMS) in southwestern Peru. I argue that Peru’s hydraulic mission is tied to a sociotechnical imaginary of coastal agricultural development that has persisted through major political-economic and water policy shifts. This persistence is epitomized by the two stages of PEMS. The first stage showcases pro-poor land- and water-distribution policies typical of the 1970s Agrarian Reform. The second stage set water tariffs to ensure full-cost recovery and auctioned large parcels of land to the highest bidder, thereby reflecting the 1990s neoliberal turn. Despite significant political-economic shifts, both stages of the project maintained a spatial model of national development that neglected highland farmers’ water needs in favor of coastal agriculture. This research contributes to geographical debates about water governance transitions in Latin America
No evidence of increased competitive ability among three widespread alien weeds in their introduced range
No full textIt has long been hypothesised that introduced species can evolve to become better competitors, which in turn will enable some of them to become invasive. The evolution of increased competitive ability hypothesis (EICA) gives a possible answer for why some introduced plants become invasive by stating that they can escape natural coevolved enemies (pests, pathogens and herbivores) in their new environment, thus allowing them to shift resource allocation from producing expensive chemical defences, towards a higher growth rate and competitive ability. In order to test if there is evidence for increased competitive ability in introduced populations, we examined the performance of three Rumex species (R. obtusifolius, R. crispus and R. conglomeratus, Polygonaceae) from their native (United Kingdom) and introduced ranges (New Zealand), when grown alone and in competition with a conspecific from the same or a different provenance. Based on the predictions of EICA, we hypothesised that plants from the introduced provenance would: (i) have a faster growth rate and a larger biomass at harvest; and (ii) would perform better in competition with a conspecific from the native provenance than one from the introduced provenance. Intraspecific competition reduced biomass by as much as 50%. However, contrary to expectations, we found no difference between the performance of plants from native and introduced provenances when grown in direct competition with each other. Plant performance when grown with a conspecific from the same provenance was similar to performance when paired with one from a different provenance, showing that there was no provenance effect. These results were consistent for all three Rumex species. Our findings contradict the predictions of the EICA hypothesis suggesting that other factors are needed to explain the success of Rumex species in New Zealand