The Weed's News Digest

The Weed's News email digest contains a summary of activity for the time period May 5, 2015 through June 1, 2015.
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The Weed's News Articles

Perth non-chemical weed management attracts record attendance

David Low / WeedsNews5444 / June 1, 2015 / 1:50:47 PM EST / 0 Comments
[The Weed's Network 08 April 2015] — The Weed’s Network is convening a series of ‘ChemFree Weed Management Workshops’ around Australia in 2015. On the 15th of May we partnered with the Eastern Metropolitan Regional Council (EMRC) to convene a ChemFree weeding workshop in Perth. Almost ninety weed and vegetation stakeholders attended, a record number for a seminar devoted entirely to learning about viable and cost-effective non-chemical methods. The day-long workshop featured eleven speakers who presented the latest practical knowledge on proven approaches to weed management without chemicals. Participants also gained insight into current public perceptions of the herbicide pollution and health issues, and joined in roundtable peer discussion to share their opinions and ideas with other participants. Interest in non-chemical weeding and vegetation is growing rapidly in Western Australia due to the widespread development of herbicide resistance and growing public concerns over the health and environmental effects of using herbicide. Thank you to all our excellent presenters and to the great group of non-chemical weeding professionals and conservation volunteers who attended. A special thank you to the EMRC who so generously supported the event. Registrations are now open for The Weed's Network's Adelaide workshop to be held at the Waite Campus of the University of Adelaide on the 3rd of July -- for more information on The Weed's Network's approach to working with weeds, or to organise a workshop in your region, please contact The Weed's Network's General Manager Dr David Low. Comment.

Non-chemical weeding trial a success

David Low / WeedsNews5442 / June 1, 2015 / 11:51:55 AM EST / 0 Comments
[Canning Times 12 May 2015 by Natalie Nazzari] — EIGHT people and four canoes were involved in a new trial to help combat the aquatic weed hydrocotyle at Wilson Lagoon near Perth Australia. Wilson Wetlands Action Group (WWAG) chairman Russell Gorton headed the hand weeding expedition, which was aimed at removing weeds without using herbicides. Mr Gorton said canoes were used to reach the aquatic weed, which could not be reached from shore. “We are in the early stages of understanding this weed and it characteristics,” he said. “We believe that a combination of several types of control will ultimately bring the best results but our goal is to use less herbicide over this conservation wetland so as to minimize any possible impacts on native fish and other important creatures that rely on the health of the wetland.Mr Gorton said the trial was successful and would be ongoing. Information gained from the trial will be used to help improve activities and treatment control in the future. “At the moment it (hydrocotyle) is quite bad and growing quickly across the Wilson lagoon, however with the State Natural Resource Management funding recently released to WWAG now, we can start to do regular work on the project, which is well funded for the next two years through his program,” Mr Gorton said. “Hopefully with funding, WWAG will be volunteering often with the aim of eradicating this declared weed. Comment

Toxic pressure of herbicides on microalgae in Dutch estuarine and coastal waters

David Low / WeedsNews5440 / June 1, 2015 / 11:36:21 AM EST / 0 Comments
Abstract: For several decades now, there has been an increase in the sources and types of chemicals in estuarine and coastal waters as a consequence of anthropogenic activities. This has led to considerable concern about the effects of these chemicals on the marine food chain. The fact is that estuarine and coastal waters are the most productive ecosystems with high primary production by microalgae. The toxic pressure of specific phytotoxic chemicals now poses a major threat to these ecosystems. In a previous study, six herbicides (atrazine, diuron, irgarol, isoproturon, terbutryn and terbutylazine) were identified as the main contaminants affecting photosynthesis in marine microalgae. The purpose of this study is to investigate the toxic pressure of these herbicides in the Dutch estuarine and coastal waters in relation to the effective photosystem II efficiency (ΦPSII) in microalgae. Temporal and spatial variations in the concentrations of these herbicides were analyzed based on monitoring data. Additionally, a field study was carried out in which chemical analysis of water was performed and also a toxicity assessment using the Pulse Amplitude Modulation (PAM) fluorometry assay that measures ΦPSII. The toxic pressure on ΦPSII in microalgae has decreased with 55–82% from 2003 to 2012, with the Western Scheldt estuary showing the highest toxic pressure. By combining toxicity data from the PAM assay with chemical analysis of herbicide concentrations, we have identified diuron and terbutylazine as the main contributors to the toxic pressure on microalgae. Although direct effects are not expected, the toxic pressure is close to the 10% effect level in the PAM assay. A compliance check with the current environmental legislation of the European Union revealed that the quality standards are not sufficient to protect marine microalgae. [Petra Booija et al. (2015).Toxic pressure of herbicides on microalgae in Dutch estuarine and coastal waters. Journal of Sea Research Volume, 102: 48–56] Comment

Innovative strategies and machines for physical weed control in organic and integrated vegetable crops

David Low / WeedsNews5438 / May 31, 2015 / 10:08:58 PM EST / 0 Comments
Abstract: Weed control is one of the most serious problems in vegetable crops, limiting cultivated plants correct development, yields, product quality and farmers income. Therefore, the aim of this work was to set up and improve innovative strategies and machines for physical (mechanical and thermal) weed control in organic or “integrated” vegetables production in many important areas of Northern, Central and Southern Italy. Therefore, on-farm experiments were carried out since 1999 on fresh marketable spinach, processing and fresh market tomato, cauliflower, savoy cabbage, greenhouse cultivated leaf beet, garlic, chicory, fennel and carrot. These research activities started are still ongoing. The traditional farm weed management system was always compared to one or more innovative strategies that were defined according to the characteristics of the environment (i.e. soil type and conditions, water availability, etc.), typology of cultivation, crop rotation, expected technical and economical results. The innovative strategies were the combination among preventive methods (false or stale seed-bed technique), cultural methods (i.e. crop spatial arrangement that was often adjusted in order to improve operative machines effectiveness) and direct control methods (flaming, precision hoeing, etc.). Different kinds of specific implement such as flex tine and rolling harrows (patented by the University of Pisa, patent n. PI/2004/A/000071), and flamers (designed and realized by the University of Pisa) were used to perform false or stale seed-bed technique. Precision hoes equipped with rigid tools and hoeconformed rolling harrows, equipped with elastic tines for selective intra-row weed control, were used to perform post emergence interventions. The use of the innovative weed management systems always resulted in significant weed abundance reductions (from 70 to 100 %), relevant yield increases, high contractions of manpower requirement (from 20 to 80 %) and consequent relevant reductions of costs and increases of farmers gross incomes (from 15 to 75 %) in comparison with those obtained performing the standard systems. The results of these on-farm experiments emphasise that physical weed control can be effectively performed using the innovative machines designed and built at the University of Pisa. These machines can also be easily adjusted in order to be used in other crops and agricultural contexts. Moreover, the present versions of the machines, realized as “low-tech” implement in order to be available on the market at low costs, were recently modified within the RHEA Project, a 7th Framework Programme EU funded research project, in which an automatic and robotized hoeing-flaming machine able to perform VRA cross flaming was designed, fully realized and tested obtaining very promising results. [Marco Fontanelli, Christian Frasconia, Luisa Martelloni, Michel Pirchio, Michele Raffaelli & Andrea Peruzzi (2015). Innovative strategies and machines for physical weed control in organic and integrated vegetable crops. Chemical Engineering Transactions, 44.] Comment

Lethal and sub-lethal chronic effects of the herbicide diuron on seagrass

David Low / WeedsNews5432 / May 29, 2015 / 3:18:41 PM EST / 0 Comments
Abstract: Photosystem II herbicides from agricultural sources have been detected throughout nearshore tropical habitats including seagrass meadows. While PSII herbicides have been shown to inhibit growth in microalgae at low concentrations, the potential impacts of chronic low concentration exposures to seagrass health and growth have not been investigated. Here we exposed two tropical seagrass species Halodule uninervis and Zostera muelleri to elevated diuron concentrations (from 0.3 to 7.2 μg l) over a 79-day period followed by a 2-week recovery period in uncontaminated seawater. PAM fluorometry demonstrated rapid effect of diuron on photosystem II (PSII) in both seagrass species at 0.3 μg l−1. This effect included significant inhibition of photosynthetic efficiency (ΔF/Fm′) and inactivation of PSII (Fv/Fm) over the 11 week exposure period. Significant mortality and reductions in growth was only observed at the highest exposure concentration of 7.2 μg l−1 diuron. However, biochemical indicators demonstrated that the health of seagrass after this prolonged exposure was significantly compromised at lower concentrations. For example, the drop in C:N ratios (0.6 μg l−1) and reduced δ13C (1.7 μg l−1) in seagrass leaves indicated reduced C-assimilation from photosynthesis. Critically, the energetic reserves of the plants (as measured by starch content in the root-rhizome complex) were approximately halved following diuron exposure at and above 1.7 μg l−1. During the 2-week recovery period, the photosynthetic capacity of the seagrass improved with only plants from the highest diuron treatment still exhibiting chronic damage to PSII. This study shows that, although seagrass may survive prolonged herbicide exposures, concentrations ≥0.6 μg l−1 diuron equivalents cause measureable impacts on energetic status that may leave the plants vulnerable to other simultaneous stressors. For example, tropical seagrasses have been heavily impacted by reduced light from coastal flood plumes and the effects on plant energetics from light limitation and diuron exposure (highest in flood plumes) are very similar, potentially leading to cumulative negative effects. [Andrew P. Negri, Florita Flores, Phil Mercurio, Jochen F. Mueller & Catherine J. Collier (2015). Lethal and sub-lethal chronic effects of the herbicide diuron on seagrass. Aquatic Toxicology, 165: 73–83] Comment