Limitations to broadleaf weed management options in chickpea present obstacles for stable production. Even with low weed incidence, chickpea yield can be severely affected, creating need for an integrated weed management system. Due to zero-tillage commonly practiced in Saskatchewan, there is heavy reliance on herbicides. The chickpea breeding program at the Crop Development Centre, University of Saskatchewan, has developed chickpea cultivars with resistance to imidazolinone (IMI) class of herbicides. The objectives of this study were: (i) to examine the reaction of four chickpea cultivars – CDC Luna, CDC Corinne, CDC Alma, and CDC Cory - to imazamox, imazethapyr, and a combination of imazamox and imazethapyr under field conditions; and (ii) to examine cultivar responses to IMI applications at different growth stages: 2-4 node, 5-8 node, and 9-12 node stage. Field experiments were conducted over five site years in Saskatchewan, Canada in 2012 and 2013. For each experiment, visual injury ratings, plant height, node, and internode length were recorded at 7, 14, 21, and 28 days after each herbicide application (DAA). Days to flowering (DTF), days to maturity (DTM), number of primary branches, pods per plant, harvest index, and seed yield were additional measurements for elucidating physiological responses. Conventional cultivars, CDC Luna and CDC Corinne, had moderate to severe visual injury scores compared to resistant cultivars, CDC Alma and CDC Cory, with minimal to no visual injury after IMI treatment. Height stopped increasing and node development slowed for conventional cultivars treated with IMI herbicides. This susceptibility to IMI herbicides was also recognized with a delay in the DTF and DTM. Despite significant negative response, CDC Luna and CDC Corinne were able to recover throughout the field season, resulting in no yield loss from IMI treatments. Resistant cultivars CDC Alma and CDC Cory demonstrated no negative response from IMI herbicide application compared with the untreated controls. Growth, in terms of height and node development, DTF, DTM, and yield were not significantly different between IMI treated and control treatments. Resistant cultivars tolerated IMI herbicide at all growth stages tested. These results demonstrate potential for use of IMI herbicides in chickpea, expanding the currently limited options for broadleaf weed control.

Successful weed control is essential for economical cotton production in Uganda. Weeds compete with cotton for moisture, nutrients and light. The greatest competition usually occurs early in the growing season. Therefore, post emergence herbicides such as fluazifop-butyl and sethoxydim were used in this study to control the grass weed species which grow faster than cotton during its initial growth stage. Field trials were conducted on the sandy loam/loam soils at Namulonge Research Institute and Bukalasa Technology Verification Centre in Uganda during the 1995/96 and 1997/98 cotton seasons to investigate the control of the tropical couch grass (Digitaria abyssinica (A. Rich. ) Stapf) using the post emergence herbicides. This weed is a rhizomatous grass and difficult to control. The efficacy of the reduced dose rates of the grass selective post emergence herbicides sethoxydim and fluazifop-butyl was investigated for the control of D. abyssinica and other grass weed species in cotton so as to determine the appropriate dose rate(s). The herbicides were supplemented with two hand weedings. Hand weeding (5 times) during the growing season was included in the treatments. The results obtained from the field trials showed the potential of reduced dose rates in the control of grasses. The application of fluazifop-butyl (138,162 and 188 g a. i. ha 1) and sethoxydim (405,502 and 579 g a. i. ha 1) gave a significant density reduction of D. abyssinica and other annual grasses at 35 days after herbicide application. No significant differences were observed amongst the dose rates of both herbicides in the percentage weed control of D. abyssinica and other grass weed species in the two seasons. The percentage weed control ranged between 79-96%. The assessment showed that fresh and dry weights of D. abyssinica shoots/foliage were reduced by 70-80% irrespective of the dose rates for both herbicides at the two sites during the two seasons. Reduced dose rates below half of the full dose rates were investigated in the greenhouse in UK. A markedly reduction of D. abyssinica shoots and rhizomes was noted following the application of fluazifop-butyl (38,66,94,188 g a. i. ha 1) and sethoxydim (116,203, 290,579 g a. i. ha 1) compared to the control. An average percentage reduction of 43.2- 62% for fresh and dry shoots, and 65.9-78% for fresh and dry rhizomes was observed. Although analysis of variance indicated that there were no significant differences amongst dose rates, low percentage reduction was noted from the lowest dose rate of fluazifopbutyl (38 g a. i. ha 1). 1 As part of the plant stress assessment, results indicated that sethoxydim and fluazifopbutyl inhibited chlorophyll accumulation in the treated leaves of D. abyssinica. A reduction of 40-70% of chlorophyll content was noted. It was noted that sethoxydim had higher inhibitory effect on chlorophyll content than fluazifop-butyl. Results obtained from the measurements of fluorescence parameters showed significant reduction of Fv/Fm in the leaves of D. abyssinica due to sethoxydim and fluazifop-butyl, suggesting significant alteration of the normal fluorescence yield. Interference with the normal fluorescence of D. abyssinica was associated with the inhibition of the flow of electron transport which resulted to plant stress. Further investigation on plant stress was studied by comparing the activity levels of the intracellular proteases of D. abyssinica and cotton plants after the application of sethoxydim. The activity level of alanyl aminopeptidase was not affected by the herbicide both in D. abyssinica and cotton. It was however noted that there was significant decrease in the activity levels of argninyl aminopeptidase (arginyl-ap) (36.1%) and tripeptidyl aminopeptidase (Tap) (51.8%) in the treated plants of D. abyssinica with time after herbicide application. While in cotton, significant increase was observed in the activity level of and tripeptidyl aminopeptidase with time after herbicide application. Therefore it can be assumed that the activity levels of these enzymes in the two plant species may have an influence on their responses to the herbicide. Data on crop performance indicated that seedcotton yields realised from herbicides dose rates combined with two hand weedings were high as or higher than the yields obtained from the hand weeding (5 times). Seedcotton yields were noted high (1793-2993 kg/ha) in 1995/96 compared to 1997/98 (665.1-1184.2 kg/ha). The present study has indicated that integration of reduced dose rates with two hand weeding supplements can reduce the number of weedings and improve cotton production.

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Field experiments were conducted from 1989 to 1991 to evaluate several sulfonylurea herbicides, glyphosate and clopyralid for the control of bunchberry and other hexazinone tolerant weeds in lowbush blueberry. Broadcast applications of chlorosulfuron, metsulfuron and glyphosate reduced bunchberry densities at all application dates, though crop damage and subsequent yield reductions were unacceptable. Glyphosate was very effective in controlling a large number of plant species when applied as a spot spray treatment. Tribenuron and DPX R9674 were effective in suppressing bunchberry stem densities at all application dates, without major adverse effects on blueberry, and also controlled a large number of hexazinone tolerant weeds when applied as a spot spray treatment. Clopyralid, at rates as low as 100 g a.i. ha$ sp{-1}$, was very effective as a broadcast treatment for the control of tufted vetch, although problems with crop tolerance and yield reductions were evident in some instances. Clopyralid did not control a large number of hexazinone tolerant species when applied as a spot spray treatment.

Two field studies assessed sward dynamics to legume removal with and without Canada thistle and other broadleaf plants (i.e. forbs). When grown in mixtures with grass, alfalfa had a more consistent negative yield response to legume removal compared to clover swards. Within established pastures, total forage (i.e. legume and grass) had little association with Canada thistle, but was instead associated with perennial forbs such as dandelion. Grass responses (biomass and protein yield) in established swards were unable to compensate for legume removal up to 2 years after spraying. Relative yield ratios were used to identify weed and legume thresholds, and indicated the removal of legume and Canada thistle did not always negatively impact forage production. Instead, select positive yield responses were observed depending on the initial composition, growing conditions and abundance of weed and legume. / Rangeland and Wildlife Resources

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Made available in DSpace on 2014-06-11T19:29:39Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-02-28Bitstream added on 2014-06-13T18:39:27Z : No. of bitstreams: 1 paula_cs_me_ilha.pdf: 334753 bytes, checksum: fcd8aee2a013e0a21c4a8de75c837120 (MD5) / A ocorrência de plantas daninhas em pastagens é um dos fatores responsáveis pela queda na produtividade das plantas forrageiras e, a espécie Mimosa pudica L. (malícia) é uma das mais frequentes infestantes na região centro-oeste brasileira. O trabalho constou de dois experimentos e foi desenvolvido com o objetivo de analisar a eficácia de herbicidas hormonais recomendados para pastagens, no controle de M. pudica, considerando as doses normais e doses reduzidas dos herbicidas. O primeiro experimento foi desenvolvido no município de Inocência, MS, onde o trabalho foi realizado em campo sobre a forrageira Brachiaria decumbens Stapf, analisando-se os dados submetidos aos tratamentos sob o aspectos de eficácia. Os tratamentos utilizados foram: 2,4-D + picloran (2,0; 3,0 e 4,0 L/ha), fluroxypyr + picloran (1,0 e 2,0 L/ha), aminopiralide + 2,4-D (1,0 e 2,0 L/ha), aminopiralide + fluxipir metílico (0,5 e 1,0 L/ha), 2,4-D (2,0 L/ha) e testemunha sem herbicida. O segundo experimento foi desenvolvido em laboratório no município de Ilha Solteira, SP, onde o trabalho foi realizado em laboratório e os herbicidas foram aplicados sobre a espécie daninha M. pudica cultivada em vasos. Os tratamentos para esta fase foram os seguintes: 2,4-D + picloran (2,0; 3,0 e 4,0 L/ha), fluroxypyr + picloran (1,0 e 2,0 L/ha), aminopiralide + 2,4-D (1,0 e 2,0 L/ha) e aminopiralide + fluxipir metílico (0,5 e 2,0 L/ha). Neste experimento analisou-se também o efeito dos tratamentos sobre as plantas daninhas em relação à sua sensibilidade ao toque e em relação à taxa de ETR (taxa de caminhamento de elétrons) utilizando-se um fluorômetro. Observou-se que, no primeiro experimento, todos os tratamentos, exceto o 2,4-D isolado, controlaram eficazmente a planta daninha. No segundo experimento, os tratamentos utilizados controlaram 100% a planta daninha... / The occurrence of weeds in pastures is one of the factors responsible for the decline in productivity of forage plants and the species Mimosa pudica l. (malice) is one of the most common weeds in the central-western Brazil. The study consisted of two experiments and was developed with the aim of analyzing the efficacy of hormonal herbicides recommended for pastures to control M. pudica, considering the normal doses and low doses of herbicides. The first experiment was conducted in the municipality of Inocência, MS, where the field work was carried out on the grass Brachiaria decumbens analyzing treatments under the aspects of efficacy. The treatments for this step were as follows: 2,4-d + picloran (2.0, 3.0 and 4.0 L / ha) + fluroxypyr picloran (1.0 and 2.0 l / ha), aminopyralid + 2,4-D (1.0 and 2.0 L / ha) + aminopyralid fluxipir methyl ester (0.5 and 2.0 L/ ha), 2,4-D (2.0 L / ha) and witnesses in the bush and clean. The second experiment was conducted in single Ilha Solteira, SP, where the work was performed in the laboratory and were sprayed on the weed M. Pudica cultivated in pots. The treatments for this step were as follows: 2,4-D + picloran (2.0, 3.0 and 4.0 L / ha) + fluroxypyr picloran (1.0 and 2.0 L/ ha), aminopyralid + 2,4-D (1.0 and 2.0 L / ha) + aminopyralid and fluxipir methyl ester (0.5 and 1.0 L / ha). This experiment also examined the effect of treatments on weeds in relation to their sensitivity to touch and relative to ETR rate (rate of traversal of electrons) using a fluorometer apparatus. It was observed that in the first experiment, all treatments except 2,4-D alone, effectively controlled the weed. In the second experiment, the treatments used 100% controlled the weed and no differences in the rate of ETR and sensitivity to touch, to 3 days after application. It was also found that lower dose in all treatments that... (Complete abstract click electronic access below)

Silverleaf nightshade (Solanum elaeagnifolium), a perennial broadleaf weed, has become a serious pest in many semi-arid areas of the world. Control of silverleaf nightshade is confounded by its ability to produce thousands of viable seeds from a single mother plant, a deep and well-developed root system and the ability to propagate vegetatively from creeping lateral roots, root fragments and from rhizomes. Exacerbating factors are longevity of its propagules in soil, particularly under adverse environmental conditions. Currently, in South Africa, it is one of the more serious weeds in cotton (Gossypium hirsutum L.) production, where its interference results in remarkable loss of product quantity and quality. Research has been done on the competition aspect of silverleaf nightshade with cotton but there is a serious lack of information on the allelopathic aspect. In this study, a series of experiments that included laboratory and glasshouse experiments were conducted to evaluate the allelopathic interference of silverleaf nightshade on early growth of cotton. Cotton seeds were exposed to silverleaf nightshade extract solutions or planted in soil into which silverleaf nightshade leaf material or ripe berries were incorporated. In all the experiments attempts were made to avoid or to reduce, at least, the influence of factors that could be potentially confounding. In this regard, PEG-6000 was used to evaluate the sensitivity of crop parameters to the osmolality of test solutions in order to ensure that osmotic inhibition was not a confounding factor in the bioassays where the biological activity (phytotoxicity) of plant extracts were assessed. Competition for growth factors was the other major potentially confounding factor that was considered throughout, and steps were taken to negate its influence. Germination and early seedling growth of cotton cultivars Sicala, CA 223, Siokra V15, Tetra and Delta Opal were inhibited by test solutions (silverleaf nightshade extracts) and by soil-incorporated residues of silverleaf nightshade. Inhibitory effects of silverleaf nightshade solutions were observed when either a layer of filter paper or a thin layer of soil or quartz sand was used as substrate. In both laboratory and pot experiments, it appeared that cotton cultivar Sicala was the most sensitive to allelochemicals contained in extracts and residues of silverleaf nightshade. This finding of differential tolerance of crop cultivars towards allelochemicals contained in a weed is a rare occurrence in allelopathy research. Berries of silverleaf nightshade were generally more inhibitory to cotton than leaf material. For both types of plant material used, residues lost their inhibitory effect over time, probably as decomposition of allelopathic compounds in soil progressed. Information obtained from this study can be viewed as knowledge that contributes to the bridging of the gap between identification and isolation of allelochemicals from silverleaf nightshade, and confirmation of silverleaf nightshade allelopathy under natural conditions. Experiments involving soil as growth medium, in particular fieldwork, are needed to verify the validity of these findings under natural conditions. / Dissertation (MSc(Agric) Agronomy (Weed Science))--University of Pretoria, 2007. / Plant Production and Soil Science / MSc(Agric) / unrestricted

Pyroxasulfone is a VLCFA inhibitor labeled to control grasses and small-seeded broadleaf weeds. Little information is available regarding this herbicide being applied postemergence. Two field experiments were conducted to evaluate the efficacy of pyroxasulfone used postemergence. Pyroxasulfone applied to 2-leaf wheat controlled up to 83% of the green foxtail but had little to no effect on broadleaves. An additional field study was conducted to determine if pyroxasulfone could give supplemental green foxtail control when tank-mixed with ALS inhibitors. Few tank-mix combinations increased control, and the tank-mixes that did had inadequate control, <70%. Greenhouse experiments were also conducted. The first concluded that a wide range of grass species are susceptible to pyroxasulfone applied postemergence. The second demonstrated weed control with pyroxasulfone is almost exclusively due to root uptake. Contradicting levels of control between field and greenhouse experiments suggests more information is needed before pyroxasulfone can be utilized as a postemergence herbicide. / North Dakota State University. Department of Plant Sciences

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