Completed Research
Reproductive biology of Nassella neesiana (Chilean Needle Grass); a threat to the sustainability of prime lamb production - Mark Gardener (PhD). Chilean needle grass is a widespread and serious weed in pastures and environmentally sensitive lands in south eastern Australia. By using CLIMATE, the climate matching software, Mark showed that the potential distribution of Chilean needle grass is nearly 40 million hectares in temperate Australia. In a year of good rainfall, Chilean needle grass can produce up to 22,203 seeds/m2 Chilean needle grass flowers from November to February and produces seeds in two ways: seeds develop from the panicle (flower head); and at the nodes of flowering stems. The seeds within the flowering stem are known as cleistogenes. These cleistogenes are self fertilised and account for approximately 24% of the total seed production.
Four dispersal mechanisms of Chilean needle grass were investigated: in the wool of sheep; through ingestion by cattle; by wind; and predation by ants. Of the Chilean needle grass seeds picked up in the wool of grazing sheep, 25% remained in the fleece after 5 months. Seeds fed to Angus cattle were tested for viability after they had been digested. Less than 50% of the seeds that remained intact after they had passed through the cattle, were viable. By wind, the majority of seeds are dispersed within 1 m of the parent plant and there was no conclusive evidence of seed predation by ants.
The seedbank of Chilean needle grass is large and long-lived. In plots cleaned up annually with herbicide, the seedbank declined from 4,676 to 1,323 seeds/m2 after 3 years without seed input. The seed decline was similar in vegetated plots (also without seed input). It was predicted that the seedbank would reach 10 seeds/m2 after 12.4 years without seed input. These seedbank data didn't include cleistogenes. In a separate experiment, cleistogenes were found to contribute a further 2,963 seeds/m2 to a seedbank of 8,335 seeds/m2. Only a small proportion (maximum of 5.6%) of viable seeds in the seedbank emerged in any one six month period from bare ground. However, seedling survival was high, with 77% of those germinating from bare ground surviving over a 20 month period.
Mark's findings indicate that the eradication of well establised and large infestations of Chilean needle grass from pastures is impossible so its usefulness as a pasture species was assessed. As a pasture plant, it grows in winter and the tussocks are long-lived with a high survival rate. The crude protein of Chilean needle grass green leaves ranged from 12.7 to 16.6% while digestible dry matter ranged from 58 to 66%. On a whole paddock basis, average green leaf production of Chilean needle grass was calculated to be 2,395 kg/hectare/year. These results indicate that Chilean needle grass can produce a large amount of reasonable quality feed. Grazing strategies aimed at making Chilean needle grass a more productive component of pastures and reducing its abundance are the only viable alternatives. Short duration, high intensity grazing pressure in summer to remove flower stalks followed by a long rest period may achieve this end.
Ecology, population dynamics and management of Saffron thistle, Carthamus lanatus L. - Blair Grace (PhD). Saffron Thistle (Carthamus lanatus) is a huge problem in much of NSW, however, very little is known about the basic biology of the plant. We are aiming to understand and model the plants survival at various stages of its life cycle at several sites. We want to know how competition affects plant survival, and what are the consequenses of having very large seeds with a high degree of dormancy. Supervisors: Assoc Prof Brian Sindel, Assoc Prof Wal Whalley, and Dr Andy Sheppard (CSIRO - Entomology).
For further information on this project
Using crop residues to control weeds - Anne Hoult (PhD). Sustainable cropping systems will in future require reductions in the use of synthetic chemicals; naturally occurring herbicides in crop residues could be useful in this context. Our aims are to (a) screen a range of crop residues for allelopathic effects on weed germination and growth and, (b) make use of this information by developing rotations which will use allelopathic effects to reduce weed problems and determine the chemistry involved. It is hoped that the project will resolve some of the conflict regarding the effect of crop residues on the growth of subsequent crops and weeds. Implicit in these aims is the need to identify the chemicals and mechanisms involved. A reduction in the use of herbicides is also anticipated. If herbicide usage was reduced, as a result of this work, by only 1 application in 10 and adopted by 40% of farmers, the savings would be $1.74 million per year to wheat farmers in the northern region alone; with a 1 in 4 reduction over all crops, the savings would be $7.25 million per year. Supervisors: Prof Acram Taji, Assoc Prof Robin Jessop and Assoc Prof Brian Sindel. Liz Jones (a previous student involved with the project) made two reports from this work: (a) Utilising crop residues to control weeds - view full text article as pdf, and (b) The potential of summer crops to affect weed growth.
Ecology and management of the "take-all" weed Polymeria longifolia (Peak Downs curse) in cotton - Stephen Johnson (PhD). Weed control costs the Australian cotton industry $50 million annually. One of the most competitive and difficult to control weeds, which is likely to become more serious under current management practises is Polymeria longifolia. It belongs to the 'take-all' group of weeds, so named because of their perennial, rhizomatous habit and ability to smother the ground and take all the nutrient and water resources available in the soil. Although ranked as one of the ten major weeds of cotton, virtually nothing is known about its ecology or how best to control it. This project endeavours to survey the distribution and spread of Polymeria longifolia; establish its relationship to crop management practises, soil types and seasonal conditions; quantify the competitive impact of Polymeria longifolia on cotton; examine its ecology; and elucidate the principles for effective management. Supervisor: Assoc Prof Brian Sindel.
Further information on this project
Malvaceae weeds in cotton production- Dr Stephen Johnson. Stephen was employed as a UNE post doctoral research fellow, collaborating with NSW Agriculture, the Cotton CRC and the Cotton RDC. He is working on a project that investigates the basic biology and ecology of Malvaceae weeds in cotton (see poster about the project). There appear to be two varieties of bladder ketmia (Hibiscus trionum) in Australia - a native and introduced variety with different phenological and quite probably physiological characteristics. Both Anoda weed (Anoda cristata) and velvetleaf (Abutilon theophrasti) are spreading in the cotton industry. It appears that Anoda weed was first introduced into Australia as a weed in fodder sometime late in the last century. It is a major summer cropping weed (including cotton) in southern Queensland. Velvetleaf may have been introduced into Australia as an alternative fibre plant in the early days of Australian settlement. It has been spreading rapidly in NSW cotton areas in the last two seasons which follows the flooding of winter 1998. Supervisors: Assoc Prof Brian Sindel and Mr Graham Charles (Weeds Research Agronomist, NSW Agriculture - ACRI, Narrabri).
Sustainable Weed Management in Organic Herb and Vegetable Production - Paul Kristiansen (PhD). The general aim of the project is to reduce the impact of weeds in organic herb and vegetable production. A grower survey was conducted, acquiring information about current methods and strategies used by certified organic producers. Field trials are being carried out to determine the relative effectiveness and economics of a range of weed management methods such as cover crops, mulching, cultivation and hand-weeding. Further trials are being done in the field and in glasshouse/laboratory settings to look at the potential weed-suppressive effects of mulches and Brassica cover crops. In addition to details about the research work, the project web site also contains an extensive Sustainable Agriculture Resources site with links to research and information available on the web. Supervisors: Assoc Prof Brian Sindel and Assoc Prof Robin Jessop.
Allelopathic effects of weeds - Lynn Madden (BRurSc Honours). Bachelor of Rural Science student, Lynn Madden, was been granted an Honours Scholarship by the CRC for Weed Management Systems to study the allelopathic effects of certain weeds as a possible control method for other weeds species. Lynn was supervised by Assoc Prof Brian Sindel.
Coolatai Grass (Hypparhenia hirta) Invasion of National Parks - Scott McArdle (Honours)
Coolatai grass (Hypparhenia hirta) has invaded several National Parks in the northern parts of New South Wales. In this project, Scott McArdle is looking to assess the impact of Coolatai grass on floral biodiversity in one such park and to devise appropriate management plans for the weed. Scott is supported by an Honours Scholarship from the Weed CRC. Supervisor: Assoc Prof Brian Sindel.
Temperature effects on the efficacy of Roundup® (glyphosate) for the control of Nutgrass (Cyperus rotundus) in cotton - Keith Penguilly (BRurSc Honours) An Honours project wasl conducted by Keith (4th year of BRurSci, UNE) to examine the effect of temperature on the efficacy of Roundup® (glyphosate) for controlling the growth of nutgrass. Nutgrass is probably the most serious weed of the Australian cotton industry and one that is extremely difficult to control. Research being undertaken by the Cotton CRC at Narrabri has shown that the non-selective herbicide Roundup® (glyphosate) has potential to control this weed, particularly when genetically engineered glyphosate-resistant cotton is introduced to the industry. However, results are sometimes unpredictable, and this appears to be related to lower temperatures early in the cotton season. In order to better refine this technique, the influence of temperature on the efficacy of Roundup on nutgrass needs to be determined. A pot trial was be carried out in temperature-controlled growth chambers at UNE. Supervisors: Dr Brian Sindel and Mr Graham Charles (Weeds Research Agronomist, NSW Agriculture - ACRI, Narrabri)
Roundup Ready Cotton Volunteer Survey - Rebecca Perry (Honours)
With the introduction of the genetically modified Roundup Ready cotton into the Australian industry, there are some concerns that volunteer plants of this variety may be difficult to control because of its tolerance of the herbicide glyphosate, which is commonly used to control cotton volunteer plants. The aim of this project is the determine the incidence of volunteer Roundup Ready cotton in on-farm (e.g. fallow, rotation crops, irrigation channels, head ditches) and off-farm (e.g. roadsides) areas. Surveys are currently being conducted with support from the Cotton CRC. Supervisor: Assoc Prof Brian Sindel.
Pasture Weed Education - Ursula Taylor (ex-Communications Officer for the Pastures Program, CRC for Weeds Managment Systems)
The effects of bromoxynil and glyphosate on two biotypes of bladder ketmia, Hibiscus trionum - Scott Wallace (BRurSc Honours). The prevalence and persistence of bladder ketmia (Hibiscus trionum), a weed closely related to cotton, is increasing throughout the Australian cotton industry. The close phenological and physiological relationship shared between H. trionum and cotton plants makes this weed very difficult to control in post emergent situations. Recently the industry has recognised that two biotypes exist, a narrow leaf biotype that appears to be susceptible to bromoxynil and a broadleaf biotype that appears to be susceptible to glyphosate.
Given that this weed has shown differential susceptibility to these herbidides, that glyphosate resistant cotton has been recently registered, and that bromoxynil tolerant cotton is likely to be introduced, a pot trial was set up to evaluate the effects of these herbicides on both biotypes of H. trionum. The trial was performed in a climate-controlled glasshouse, where either a half label rate, label rate or double label rate for each herbicide was applied to both biotypes of H. trionum, seed of which was sourced from two locations being Narrabri and Warren. Dry weight yield and visual assessments of herbicide injury were measured to evaluate the susceptibility of both H. trionum biotypes to these herbicides.
All glyphosate rates significantly (p<0.05) reduced dry weight yield for both biotypes. All glyphosate rates were also observed to cause significant (p<0.05) visual leaf damage, however only the label and double label rates were found to cause effective plant death. There was no significant effect of any bromoxynil treatments on dry weight yield for either biotype. All bromoxynil treatments caused a significant (p<0.05) visual leaf injury. However, they did not cause plants to die. There was also evidence suggesting that the narrow leaf biotype appeared more susceptible to bromoxynil than the broadleaf biotypes. In contrast, the broadleaf biotype may be more susceptible to glyphosate than the narrow leaf biotype. The use of glyphosate tolerant cotton would be more beneficial for the control of H. trionum than that of bromoxynil tolerant cotton.. Supervisors were Assoc Prof Brian Sindel, Guy Roth (Research Program Manager, Cotton RDC) and Dr Stephen Johnson (Post Doctoral Fellow in Weed Science, Australian Cotton Research Institute).
Effects of night cultivation and tillage method on weed emergence - Greg Stockings (BRurSc Honours). Here is the abstract from a paper presented at the 13th Australian Weeds Conference, Perth, September 2002:
A preliminary investigation into the effects of night cultivation and tillage method on weed emergence Summary: Recent research has suggested conducting tillage operations at night can reduce weed emergence. This has sparked a great deal of interest, particularly overseas, in determining the usefulness and accuracy of these claims. There have been quite mixed results, due to differences in species responses to light exposure. Interactions with environmental conditions also seem to have a large influence on the 'photo-control' of weed species. In this research, we investigated the effects of night and day cultivation on the background weed flora in a weed-infested paddock. This was coupled with the use of two different methods of tillage, which were discing and scarifying. The results showed that there were early trends towards greater emergence of grass and broadleaf weeds in the day cultivations compared with the night. At the conclusion of the experiment there were lower numbers of grass weeds (P=0.05) with greater than four leaves in the night scarify treatment compared with the day scarify treatment. There were similar trends for the night disc treatments. After 57 days, the disc treatments had greater weed emergence (P=0.05) than the undisturbed control. The same trend was seen in the scarify treatments. These preliminary results suggest that photo-control of weeds may hold potential benefits for integrated weed management in Australian cropping systems. Keywords: night cultivation, emergence, tillage, germination |
Integrated Weed Management of Chickpeas (Cicer arietinum) - Jeremy Whish (PhD). The practice of using legumes in wheat rotations to improve soil nitrogen levels, break disease cycles and enable chemical control of grass weeds, is slowly being adopted by wheat farmers in the northern cropping region of eastern Australia. Pulse crops and particularly chickpea can be described as poor competitors; hence, if not grown on clean country or with herbicides, will quickly become infested with weeds, reducing quality and yield. This research examines a number of chemical and agronomic strategies that have been proposed to improve weed control in chickpea and identifies specific research areas that may offer long and short term control. Recent paper (PDF file, 201kb). Supervisors: Assoc Prof Brian Sindel and Assoc Prof Robin Jessop.
The effect of night sowing on the emergence patterns and competitive impact of weeds on buckwheat (Fagopyrum esculentum) on the Northern Tablelands of New South Wales - David Van Ryswick (BRurSc Honours). Supervisors: Assoc Prof Brian Sindel, Assoc Prof Robin Jessop and Dr Paul Kristiansen. Here is the abstract from his thesis:
Weed management in Australia is continually changing and with these changes comes the need for new innovative management practices, reducing the reliance on traditional methods of weed control such as burning and herbicide usage. Recent overseas research into the effect of night cultivation in some cropping systems has identified that weed seedling emergence is highly variable. A reduction of seedling emergence has been dependent on the response of seed dormancy to light exposure and other environmental factors. The growth and development of seeds is dependent upon the time and location of germination. The response of seed dormancy to light exposure can be influenced by a range of factors including seed size and length of time that it is imbibed. The light receivers that play a major role in the process of overcoming dormancy are called photoreceptors. Phytochrome is the primary group of chemicals responsible for the breaking of dormancy in plants through the interaction of light. The objective of this research project was to identify the effect of night cultivation as a weed management practice to reduce weed populations and their competitive effects within a cropping system. The type of cultivation method used and the degree of soil inversion has been found to alter the number of seeds that are triggered to germinate by a flash-like exposure of light. For this reason the project also involved a comparison between the use of disc tillage and zero tillage systems on potential weed seedling emergence. Buckwheat (Fagopyrum esculentum) was chosen as the crop in which to test these effects because of its ability to be grown in the Armidale region as well as its short life cycle between planting and harvest, allowing for a full season of data to be collected in a shorter period. Another reason was that there has been very little research undertaken on weeds in buckwheat in Australia. The results of the research indicated the potential for short-term reductions in seedling emergence of weeds when light is excluded from the process of cultivation and sowing. The results showed a significant reduction in the number of bladder ketmia (Hibiscus trionum) and amaranth (Amaranthus spp.) seedlings that emerged in the early stages following night soil cultivation and sowing. However, after the initial count at 24 DAS this difference disappeared with the treatments cultivated at night matching the weed densities of those cultivated in daylight at 37 DAS and onwards. It was found that the use of disc tillage had significantly higher weed densities and biomasses throughout the experiment than the zero-tillage treatments. The presence of the crop (buckwheat) was also found to be highly suppressive of the weed populations in the experiment. This project provides potential options to develop night cultivation as an effective management tool to be used in an integrated weed management system. |
Biology, Ecology & Management of Common Sowthistle (Sonchus oleraceus) - Michael Widderick (PhD). Michael is a Weeds Agronomist with Department of Primary Industries at Toowoomba, Queensland and PhD student at UNE. He is focussing on common sowthistle which is increasingly becoming a dominant and herbicide resistant weed over the northern grain growing region of eastern Australia. Its population increase is thought to be associated with the move towards reduced tillage farming systems either through changes in the physical environment for weed establishment and/or through herbicide selection pressures. Current control methods in reduced tillage systems involve the use of in-crop herbicides and several applications of fallow herbicides due to the weed's broad pattern of emergence. The effectiveness of herbicides is variable with some populations now being resistant to all group B herbicides. A series of field and glasshouse experiments will be used to characterise the biology and ecology of sowthistle from across the northern grain region, particularly focussing on germination and plant establishment. The reasons for its emerging dominance under reduced tillage systems will be assessed. Field studies will investigate the impact of increasing sowthistle densities on crop yield and interactions of different fallow management practices and cropping systems on weed emergence patterns. As a result, effective and sustainable management strategies for sowthistle will be developed. Supervisor: Assoc Prof Brian Sindel and Steve Walker (Queensland DPI).