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Studies relating to seeding depleted range in undisturbed residues of weedy vegetation killed by herbicidesOke, Jagannath Ganesh. January 1959 (has links)
Call number: LD2668 .T4 1959 O38
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Integrated control of water hyacinth using a retardant dose of glyphosate herbicideJadhav, Ashwini Mohan 23 February 2012 (has links)
Ph.D, Faculty of Science, University of the Witwatersrand, 2011 / Abstract
Eichhornia crassipes (Martius) Solms-Laubach (Pontederiaceae) (water hyacinth), a neotropic
noxious weed of South American origin, is counted among the “big five” aquatic
weeds in South Africa. The weed causes dramatic ecological and economic losses in
infested areas. Its control is facilitated by the release of biocontrol agents, mainly
Neochetina eichhorniae (Warner) and Neochetina bruchi Hustache (Coleoptera:
Curculionidae). Control efforts via biocontrol are hampered, mainly by the climate
incompatibility of the agents, aggravated further by the indiscriminate use of lethal doses
of glyphosate based herbicides. The lethal doses interfere with the successful
establishment and persistence of the biocontrol agents, thus undermining their impact.
Continued use of herbicide kills the water hyacinth mat and as a result, the immature
stages of the agents are killed. If biocontrol is to succeed as a control strategy, then low
doses of the herbicide need to be advocated. It was hypothesized that a low dose will
constrain the vegetative and reproductive capacity of the weed, while maintaining the
habitat for the biocontrol agents. Consequently, this study was conducted to identify a
retardant dose of glyphosate herbicide and test its effect on the Neochetina weevils. A
concentration of 0.8% (0.11g m-² or 2880mg a.i /L) glyphosate based herbicide, sprayed
at 150 L ha-1 was proved to retard the vegetative and the reproductive growth of the
weed, in terms of leaf and ramet production. Further, the retardant dose did not have any
detrimental effects on the adult weevils and its larval stages. Weevil herbivory was also
enhanced by the retardant dose. Furthermore, the retardant dose did not have any
detrimental effects on ‘plant quality’ as evidenced by % nitrogen level in plant tissues
such as crown and leaves. Contrary to expectation however, the combined effects of the
retardant dose and Neochetina herbivory (0.8%+Ne) did not result in the production of
lower number of ramets or leaves than water hyacinth plants dosed with 0.8% herbicide
alone. Water hyacinth biocontrol agents in South Africa are subjected to frosty winters
with low temperatures which cause the biocontrol agents to decline to an overwintering
larval population that fails to catch up with the weed as it rebounds from the frost in
spring. This hypothesis was tested in this study at 12 water hyacinth infested sites, which
were grouped as temperate and sub-tropical sites. At both the temperate and subtropical
sites, water hyacinth plants produced ramets (daughter plants) through autumn and
increased biomass during summer. However, weevil numbers were very low at these
sites, as evidenced by adult counts and feeding scars, indicating a marked seasonal
asynchrony between the phenologies of the weevils and water hyacinth. Hence,
intervention by seasonal applications of the herbicide is crucial to constrain weed growth.
Herbicidal applications during autumn and spring inhibited the growth of the weed
without adversely affecting the adult weevils or immature, immobile stages. Continued
use of herbicides raises concerns of effect on non-target species, such as amphibians.
Results from this study indicate that a direct application of a retardant dose of glyphosate
did not kill or affect the growth of the Xenopus larvae, as determined by survival and
body lengths. However, under laboratory conditions, this study has shown for the first
time that an invasive aquatic weed (water hyacinth) was more lethal to an aquatic
vertebrate (Xenopus larvae) than a herbicide advocated for its control. This study
conclusively shows that retardant dose of glyphosate herbicide can be integrated with
biocontrol to provide a sustainable and eco-friendly technique with which to combat
water hyacinth infestations in South Africa.
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Economic and efficacy evaluations of napropamide, DCPA, and hand-weeded treatments in newly established strawberries (Fragaria x ananassa duch. "redchief")Henning, Susan Faye January 2011 (has links)
Typescript (photocopy). / Digitized by Kansas Correctional Industries
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The effect of tillage systems on weed control and botanical composition in forage corn /Sampson, D. L. January 1988 (has links)
No description available.
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Chemical weed control : options in fibre flaxMühleisen, Martin Bernd. January 2000 (has links)
There is an ongoing and increasing interest in the significant and essential role that food plays in the health and survival of all people. As masticatory efficiency diminishes drastically in edentulous patients, many researchers in the past two decades have been studying how dietary intake varies when different types of oral rehabilitation are provided. Since the use of implants to support prostheses in edentulous mandibles has been shown to significantly improve masticatory performance, the question remains as to whether this improvement will influence nutritional status. In the present study, we used several nutritional markers to compare the nutritional status of edentulous patients who randomly received either mandibular conventional dentures or implant-supported overdentures one year previously. Although the conventional denture wearers reported having more difficulty chewing hard foods, no significant differences were detected in any of the nutritional markers. Therefore, even though chewing is more difficult for the patients wearing conventional dentures, it appears that the nutritional status of these two groups is similar.
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Development and validation of a theoretical method to evaluate the efficacy of mechanical cultivatorsPortillo Nuñez, David. January 1996 (has links)
The methods currently used to evaluate cultivator weed control are imprecise and often biased. A new method was tested. An experiment was carried out at two sites in 1993 and again in 1994, using a split-plot design with four repetitions. Cultivation was carried out on weed populations simulated with rye grass (Lolium spp L.) and mustard (Sinapis alba L.) in 1993 and on both simulated and natural weed population in 1994 with Rabe Werk, Hiniker and Kongskilde cultivators. Weed control was assessed by the effective weed kill and the percentage of the area of the simulated weed population which was affected, and by counts and visual observations on the natural weed population. The new method provided an objective assessment of the cultivation treatments, especially by the effective weed kill index. The area affected approach was not suitable for all cultivation treatments. There was agreement between the proposed method and the conventional methods. This validated the proposed new method. Overall, the Hiniker with ridgers performed the best. The Hiniker without ridgers, and the Kongskilde with or without ridgers performed similarly. The Rabe Werk without goosefoot attachment resulted in the poorest weed control. The degree of weed displacement varied among the cultivators and was associated with weed density. The degree of weed displacement onto the crop row from the inter-row area was low ($<$1% in 1993 and up to 3.4 in 1994). The weed displacement distance was related to weed density and the degree of weed uprooting produced by cultivation.
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Mechanism of resistance to paraquat in the weedy grasses Hordeum leporinum and H.glaucum / Hassan Mohammad Alizadeh.Alizadeh, Hassan-Mohammad January 1998 (has links)
Bibliography: leaves 126-143. / x, 143 leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--Adelaide University, Dept. of Applied and Molecular Ecology, 2001
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The Effects of Brassica Cover Crops on Weed DynamicsHaramoto, Erin R. January 2004 (has links) (PDF)
No description available.
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Chemical weed control : options in fibre flaxMühleisen, Martin Bernd. January 2000 (has links)
No description available.
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The effect of tillage systems on weed control and botanical composition in forage corn /Sampson, D. L. January 1988 (has links)
No description available.
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