Дисертації з теми "Crop and pasture protection (incl. pests, diseases and weeds)"
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Leathwick, D. M. "Applied ecology of the Tasmanian lacewing Micromus tasmaniae Walker (Neuroptera : Hemerodiidae)." Lincoln College, University of Canterbury, 1989. http://hdl.handle.net/10182/1044.
Повний текст джерелаWhelan, Helen G. "The effect of crop yield potential on disease yield loss relationships in barley (Hordeum vulgare L.)." Lincoln University, 1992. http://hdl.handle.net/10182/1980.
Повний текст джерелаDickson, Ross L. "The effect of water stress, nitrogen and gibberellic acid on the phytotoxicity of post-emergent herbicides to Avena spp." Lincoln University, 1990. http://hdl.handle.net/10182/1283.
Повний текст джерелаMorton, J. D. "The effect on protein synthesis in barley of infection with P. hordei." Lincoln College, University of Canterbury, 1989. http://hdl.handle.net/10182/1950.
Повний текст джерелаBithell, S. L. "An evaluation of Solanum nigrum and S. physalifolium biology and management strategies to reduce nightshade fruit contamination of process pea crops." Lincoln University, 2004. http://hdl.handle.net/10182/1160.
Повний текст джерелаBalasubramaniam, Rengasamy. "The effects of foliar diseases and irrigation on root development, yield and yield components of wheat (Triticum aestivum L.)." Lincoln College, University of Canterbury, 1985. http://hdl.handle.net/10182/1514.
Повний текст джерелаMerfield, C. N. "Predator interactions within a trophic level : Phalangium opilio L. (Arachnida: Opiliones) and mites (Arachnida: Acari)." Diss., Lincoln University, 2000. http://hdl.handle.net/10182/21.
Повний текст джерелаKean, J. M. "Metapopulation theory in practice." Lincoln University, 1999. http://hdl.handle.net/10182/1372.
Повний текст джерелаYamoah, Emmanuel. "A model system using insects to vector Fusarium tumidum for biological control of gorse (Ulex europaeus)." Phd thesis, Lincoln University. Bio-Protection and Ecology Division, 2007. http://theses.lincoln.ac.nz/public/adt-NZLIU20080131.114607/.
Повний текст джерелаChng, Soon Fang. "Microbial factors associated with the natural suppression of take-all in wheat in New Zealand : a thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Lincoln University, Canterbury, New Zealand /." Diss., Lincoln University, 2009. http://hdl.handle.net/10182/863.
Повний текст джерелаViljanen-Rollinson, S. L. H. "Expression and detection of quantitative resistance to Erysiphe pisi DC. in pea (Pisum sativum L.)." Lincoln University, 1996. http://hdl.handle.net/10182/1657.
Повний текст джерелаLaubertie, Elsa. "The role of resource subsidies in enhancing biological control of aphids by hoverflies (Diptera: Syrphidae)." Diss., Lincoln University, 2007. http://hdl.handle.net/10182/984.
Повний текст джерелаBerndt, Lisa A. "The effect of floral resources on the leafroller (Lepidoptera: Tortricidae) parasitoid Dolichogenidea tasmanica (Cameron)(Hymenoptera: Braconidae) in selected New Zealand vineyards." Lincoln University, 2002. http://hdl.handle.net/10182/1045.
Повний текст джерелаPeacock, Lora. "Eco-climatic assessment of the potential establishment of exotic insects in New Zealand." Lincoln University, 2005. http://hdl.handle.net/10182/1530.
Повний текст джерелаRobinson, K. A. "Use of floral resources by the lacewing Micromus tasmaniae and its parasitoid Anacharis zealandica, and the consequences for biological control by M. tasmaniae." Diss., Lincoln University, 2009. http://hdl.handle.net/10182/823.
Повний текст джерела(12298370), Alison S. Jensen. "Redefining pachymetra root rot management strategies and cultivar resistance in commercial sugarcane fields." Thesis, 2020. https://figshare.com/articles/thesis/Redefining_pachymetra_root_rot_management_strategies_and_cultivar_resistance_in_commercial_sugarcane_fields/19426862.
Повний текст джерела(13157903), Earl Sparkes. "Development of herbicide control options for Prosopis velutina as part of an integrated control strategy." Thesis, 2003. https://figshare.com/articles/thesis/Development_of_herbicide_control_options_for_Prosopis_velutina_as_part_of_an_integrated_control_strategy/20380371.
Повний текст джерелаProsopis spp. are prolific seeders with estimates of seed production reaching from 630,000 to 980,000 seeds per mature tree per annum (Felker 1979; Harding 1988). Prosopis velutina shrubs have been recorded to produce up to 5,000 seeds per year (Glendening and Paulsen
1955). The plant has the ability to establish on disturbed or bare soil and can develop into very dense infestations. The plant often grows on scalded areas devoid of other vegetation and out-competes native herbage for moisture and light.
The plant is armed with long axillary spines; it branches from the base and has long arching stems. Its leaves are not commonly eaten by sheep and bovine breeds. Consequently, it forms dense stands that restrict the movement of stock, particularly around watering points, and this interferes with mustering.
There are many options for control of mesquite with herbicide application being integral in a management suite of mesquite control initiatives. Other control methods, which limit its distribution and spread, include mechanical removal, grazing management, competitive pasture
establishment, biological control, and a burning regime where adequate fuel is available.
The thesis discusses merits of the Prosopis species. Commonly known as mesquite or prickly bush, the Australian pest plant is endemic in the southern United States. The description then turns to how the weed was introduced into Queensland at both Quilpie and Hughenden in the north of the state. Some detail is given to its distribution and the effects on primary producers and the environment, and on the cost of control initiatives conducted through the Queensland Department of Natural Resources and Mines.
Scientific findings from the research process are considerable given the base knowledge when the mesquite research project was revived in 1989. Initially, a research review of available literature was conducted revealing a large pool of knowledge from the United States of America. Their research findings on foliar applied herbicides have resulted in a high utilization of tank mixes principally containing triclopyr + clopyralid formulations sometimes with hydrocarbon additives. A more comprehensive summary of field research findings for Queensland is compiled as part of this thesis (Chapter 8) and presents some herbicide control options and constraints that may qualify their performance. Basal stem research in North America has produced many adopted recommendations. There have been numerous experiments on controlling mesquite with herbicides with many referred to in Control of Mesquite in the USA (Chapter 1).
Chapter 2 presents a comparative analysis conducted to determine the different effects of applied herbicides to targeted young mesquite when applied in early summer compared to application in autumn. Formulations of fluroxypyr as well as metsulfuron methyl did not prove
efficacious in this trial. For the first time glyphosate proved to be a valuable herbicide in controlling mesquite when applied in autumn. Triclopyr + picloram and triclopyr alone proved to be more effective following wet conditions when applied in the early summer compared to the autumn application. However, treated plants growing adjacent to continuous paddock ponding were able to recover. Clopyralid exhibited high efficacy in both early summer and autumn treatment applications.
Following poor control of Prosopis velutina at Quilpie by treatments recommended for control
of Prosopis pallida, a potted plant pilot trial was conducted to determine if the two species responded similarly (Chapter 3). The results indicated that Prosopis velutina was ineffectively controlled by herbicide application, at standard rates, compared to the control of Prosopis pallida. The follow-on replicated trial detail in Chapter 4 indicates a similar response for both
species. The effects of the treatments indicated differing susceptibility between the two species,
with metsulfuron, fluroxypyr, 2,4-D + picloram and triclopyr + picloram demonstrating the most pronounced differences compared to the glyphosate formulations here negligible difference occurred. A re -application of all herbicides to the surviving plants, and to a control
group, indicated that susceptibility can decrease when a follow-up application is in autumn and the time since initial application is short. This trend was particularly noticeable for P. velutina where previous sub -lethal damage prevented effective herbicide action.
More fieldwork was conducted following this shade -house work as a prolific growth phase occurred in Quilpie mesquite in the early summer of 1999 (Chapter 5). Four glyphosate, and four triclopyr tank mixes and a control set out in each of three habitats made up the 27 plots evaluated in this aerial herbicide experiment. The triclopyr + picloram formulations at 5 and 7 L ha -1 with the addition of paraffinic oil (582 g L-1) and non-ionic surfactants (208 g L-1) produced the most efficacious and uniform results although triclopyr treatment with the addition of 1000 g L-1 alcohol alkoxylate produced similar results. However, the long-term effect was compromised because of the lack of a residual component in this formulation.
A more manageable result was obtained when larger older plants were foliar overall sprayed using truck -mounted high pressure equipment (Chapter 6). A total of 33 treatments were assessed after each of four assessments of various herbicide mixtures. A blocking factor was plant density. Glyphosate tank formulations were consistently more efficient than other treatments, at all densities, except in combination with metsulfuron methyl. In the low density plots flumetsulam 0.10 g L-1 + glyphosate 3.60 g L-1 tank mix performed significantly better
than other treatments between the second and third applications and the third and fourth applications. Treatments containing clopyralid also showed high efficacy.
A further experiment using the most common method of control (basal stem application technology) was conducted using dieseline as the herbicide carrier in March 1995 (Chapter 7).
The higher strength treatments with dicamba and triclopyr formulations showed the most activity irrespective of plant size (> 1.5 m or < 1.5 m) or water availability with the higher strength of each formulation, dichloromethoxybenzoic amine @ 10 g a.i. L-1 and triclopyr butoxyethyl ester 10 g a.i. L-1, being the most efficacious and not showing significant differenc from each other.
In conclusion a three-year cycle planner was developed incorporating best control strategies researched within this thesis (Chapter 8). Suggestions were also put forward covering grazing management to enhance the effect of control strategies.
(9829109), Donna Rayner. "Spiders in central Queensland mango orchards: Diversity, diel activity and impact of pesticides." Thesis, 2000. https://figshare.com/articles/thesis/Spiders_in_central_Queensland_mango_orchards_Diversity_diel_activity_and_impact_of_pesticides/13424552.
Повний текст джерела(9133244), Wyatt Steven Petersen. "Weed Control in Cover Crop No-Till Corn Systems." Thesis, 2020.
Знайти повний текст джерелаOther field experiments were conducted at the same locations in 2017 through 2018 and 2018 through 2019 to determine the effect of cover crop species, termination timing, and chemical cover crop termination strategies on weed control and corn yield. Crimson cover (Trifolium incarnatum L.), cereal rye, and a cereal rye/crimson clover mix were terminated two weeks before, at, and two weeks after corn planting. All plots were terminated using glyphosate and atrazine, however others were also terminated with dicamba and acetochlor. The addition of acetochlor generally reduced early-season weed biomass or density, but not in cereal rye and cover crop mix treatments that were terminated at or after corn planting. Late-season summer annual grass biomass was reduced when cover crop biomass at termination was over 8000 kg ha-1. Late-season common cocklebur density in 2018 was 450% to 800% higher in cover crops containing cereal rye, compared to crimson clover treatments. Corn yield was reduced by 23% to 67% in cereal rye and cover crop mix treatments in two out of three site-years in 2018, however corn yield was not reduced by crimson clover in either year, nor by cereal rye or the cover crop mix in 2019.
(9802976), Madaline Healey. "The population dynamics of the thrips species assemblage in French bean, lettuce, tomato and zucchini agro-ecosystems." Thesis, 2017. https://figshare.com/articles/thesis/The_population_dynamics_of_the_thrips_species_assemblage_in_French_bean_lettuce_tomato_and_zucchini_agro-ecosystems/13443155.
Повний текст джерела(9780491), Karina Griffin. "Copper tolerance in Pseudomonas syringae pv. tomato isolates from tomato crops in Eastern Australia." Thesis, 2019. https://figshare.com/articles/thesis/Copper_tolerance_in_Pseudomonas_syringae_pv_tomato_isolates_from_tomato_crops_in_Eastern_Australia/13409477.
Повний текст джерела(5929796), Joseph T. Ikley. "The Role of Alternative Hosts and Herbicides in the Management of Clavibacter nebraskensis, Causal Agent of Goss’s wilt of Corn." Thesis, 2019.
Знайти повний текст джерела(9844922), Daniel White. "Phytoplasma diseases of papaya (Carica papaya L.) in Australia: Phytoplasma classification, pathology and transmission." Thesis, 2001. https://figshare.com/articles/thesis/Phytoplasma_diseases_of_papaya_Carica_papaya_L_in_Australia_Phytoplasma_classification_pathology_and_transmission/13426598.
Повний текст джерела(9778178), Lafta Atshan. "Multispectral and thermal imagery approaches to insect pest and disease detection in horticultural crops." Thesis, 2021. https://figshare.com/articles/thesis/Multispectral_and_thermal_imagery_approaches_to_insect_pest_and_disease_detection_in_horticultural_crops/19919891.
Повний текст джерела(10723935), Quincy D. Law. "Buckhorn plantain (Plantago lanceolata) biology and 2,4-D resistance in turf." Thesis, 2021.
Знайти повний текст джерелаHerbicide resistance poses a threat to sustainable vegetation management. Recently, the first report of 2,4-D resistance in buckhorn plantain (Plantago lanceolata L.) as well as the first report of 2,4-D resistance in turf was published. Additional 2,4-D resistant buckhorn plantain ecotypes have been reported in Indiana, Ohio, Pennsylvania, Georgia, and Virginia in the short time since. Thus, the aims of this research were to investigate the mechanism(s) of 2,4-D resistance in a resistant ecotype of buckhorn plantain, screen other potentially resistant ecotypes and measure them for fitness penalties, and identify effective turfgrass cultural control practices for managing buckhorn plantain.
A radiolabeled 2,4-D experiment was conducted to investigate absorption and translocation, and a 2,4-D dose-response experiment was conducted using malathion as a cytochrome P450 inhibitor to assess the potential mechanism of 2,4-D resistance in buckhorn plantain. The clearest difference between the resistant (IN-GW) and susceptible ecotype (IN-WL) was the interaction between ecotype and harvest period for [14C]2,4-D in the non-treated shoots. After 192 hr, the susceptible ecotype had a higher amount of [14C]2,4-D in the non-treated shoots (16.1%) than the resistant ecotype at any of the harvest periods (5.5-7.3%); the amount of [14C]2,4-D in the non-treated shoots was similar across all three harvest periods for the resistant ecotype. Thus, reduced translocation plays an apparent role in 2,4-D resistance in buckhorn plantain. Malathion pre-treatment did not fully revert the resistant ecotype back to susceptible. Thus, if cytochrome P450 metabolism is part of the 2,4-D resistance mechanism of this buckhorn plantain ecotype, it is likely a contributor and not the sole mechanism of resistance.
In total, this research identified four 2,4-D resistant buckhorn plantain ecotypes from Indiana and one from Ohio. Only one report of a failure to control buckhorn plantain was confirmed to be a susceptible ecotype. When compared to susceptible ecotypes in a garden study, no major fitness penalties were identified in resistant ecotypes.
Given that no specific cultural or biological control methods of buckhorn plantain have been recognized to date, two field trials were conducted to investigate the influence of 1) mowing height and nitrogen rate on buckhorn plantain coverage and 2) mowing frequency on buckhorn plantain coverage and seed production. Nitrogen fertilization and low mowing reduced buckhorn plantain coverage after 3 yr, but low mowing also increased crabgrass and dandelion as well as reduced turf quality. Frequent mowing reduced viable seed production, but that did not translate into a reduction in buckhorn plantain coverage after 2 yr.
This research demonstrates the complex mechanism of action of 2,4-D, as the resistance mechanism for buckhorn plantain was not fully elucidated. It also highlights the importance of utilizing best management practices for managing weeds in turf, including rotating herbicide chemistries, high and frequent mowing, and nitrogen fertilization.
(10782717), Brent Coy Mansfield. "Characterization of protoporphyrinogen oxidase (PPO) herbicide resistance in tall waterhemp (Amaranthus tuberculatus)." Thesis, 2021.
Знайти повний текст джерелаTall waterhemp management in agronomic crops continues to be an increasing problem due to widespread resistance to herbicides, including protoporphyrinogen oxidase (PPO)-inhibitors. With limited effective postemergence herbicides, especially in soybeans, research to further understand the selection of PPO-resistant (PPO-R) tall waterhemp and identification of new herbicide resistance mechanisms is crucial for improving weed management decisions in order to slow selection for herbicide resistance and prolong the effectiveness of PPO-inhibiting herbicides.
Previous research has shown that soil-applied applications of PPO-inhibiting herbicides can increase the frequency of the PPO resistance trait (∆G210) in surviving tall waterhemp plants, even when applied in combination at the same ratio with the very long chain fatty acid inhibitor (VLCFA), s-metolachlor. Field experiments were conducted to determine if selection for tall waterhemp resistant individuals to PPO-inhibitors could be reduced when the soil residual activity of s-metolachlor persisted longer than the PPO-inhibitor herbicide. The frequency of ∆G210 in surviving individual plants increased as the fomesafen rate increased, but was independent of the rate of s-metolachlor. Additionally, heterozygosity of ∆G210 in surviving individuals did not change with any rate or combination of fomesafen and s-metolachlor. However, saflufenacil, standard PPO-inhibitor with relatively short soil residual activity, applied alone increased the number of homozygous PPO-R tall waterhemp by 15% compared to the high rate of s-metolachlor and the combination of saflufenacil and s-metolachlor. Furthermore, this research demonstrated that end of season control of tall waterhemp plays a more vital role in delaying a large-scale shift towards herbicide resistance through reduced seed production. This can be achieved through the combination of multiple effective herbicide sites of action, including soil residual PPO-inhibitors. Tall waterhemp control and density were greatest with the high rates of fomesafen plus s-metolachlor, which resulted in the lowest number of PPO-R tall waterhemp that survived herbicide treatment at the end of season.
Prior to the research conducted in this thesis, the only known resistance mechanism to PPO-inhibiting herbicides in tall waterhemp has been the ∆G210 target site mutation. A previously developed TaqMan assay used to determine the presence or absence of the ∆G210 mutation has allowed accurate, high throughput screening of this mutation. However, suspected PPO-R tall waterhemp do not always receive positive confirmation indicating the presence of an alternative resistance mechanism. Identification of additional resistance mechanisms can provide valuable insight in regards to resistance to PPO-inhibiting herbicides as well as cross resistance to other herbicide modes of action, which can lead to improved tall waterhemp management decisions. Of 148 tall waterhemp populations collected across the Midwestern U.S., 84% of the populations sampled contained at least one PPO-R biotype with the ∆G210 mutation, although several individual plants across the Midwest U.S. exhibited phenotypic resistance to fomesafen that could not be explained by ∆G210. The percentage of PPO-R tall waterhemp without ∆G210 was 19, 5, 2, 1, and 2% for Iowa, Illinois, Indiana, Minnesota, and Missouri, respectively. Following the initial greenhouse screening, subsequent tall waterhemp populations were selected that exhibited low-, mid-, and high-level resistance to fomesafen that resulted in resistance ratios from 0.6 to 17X in response to fomesafen. This research documents the variability in fomesafen response to multiple tall waterhemp populations in addition to revealing the presence of additional resistance mechanism(s), other than the previously known ∆G210 mutation that has been the benchmark for resistance to PPO-inhibiting herbicides in tall waterhemp.
Lastly, greenhouse and lab experiments were conducted to investigate the role of antioxidant enzymes with PPO-R tall waterhemp via ∆G210. The objectives of this research were to determine if the variability in resistance ratios for PPO-R tall waterhemp documented in greenhouse and field scenarios could be due to an enhanced antioxidant enzyme pathway. Basal levels of antioxidant enzymes in PPO-S populations were not different from PPO-R populations when pooled together by respective phenotype. However, enzyme activity of tall waterhemp populations varied at the individual level, but independent of the ∆G210 mutation. This indicates that an inherent enhanced antioxidant enzyme pathway does not cause the variability in fomesafen response in tall waterhemp. With the exception of glutathione reductase, antioxidant enzyme activity following fomesafen application was generally the same for PPO-R and PPO-S populations by increasing, decreasing, or remaining unchanged. Glutathione reductase activity in PPO-S populations decreased compared to PPO-R populations from 9 to 36 HAT. By 36 HAT, all antioxidant enzyme activity for PPO-S populations was lower compared to PPO-R populations most likely a consequence of more lipid peroxidation. This research shows that antioxidant enzyme activity correlated with fomesafen application and documents the variability observed within tall waterhemp populations with and without the ∆G210 mutation.
(7041278), Sharon Wanjiru Kinyungu. "Efficacy of pre-harvest Aspergillus flavus biocontrol treatment on reducing aflatoxin accumulation during drying." Thesis, 2019.
Знайти повний текст джерелаMaize is a major calorie source for people living in Sub-Sahara Africa. In this region, Aspergillus flavus causes ear rot diseases in maize, contributing to food insecurity due to aflatoxin contamination. The biological control principle of competitive exclusion has been applied in both the United States and Africa to effectively reduce aflatoxin levels in maize at harvest by introducing atoxigenic strains that out-compete toxigenic strains. The goal of this study was to determine if the efficacy of preharvest biocontrol treatments carry over into the drying period, which is often delayed in Sub-Sahara Africa by the complexities of postharvest drying practices and lack of modern drying machinery. Maize was collected from fields in Texas and North Carolina that were treated with commercial biocontrol, and control fields that were untreated. To simulate moisture conditions similar to those experienced by farmers during drying in Sub-Sahara Africa, we adjusted the grain to 20% moisture content and incubated it at 28 ℃ for 6 days. Although the initial number of infected kernels in most samples were high, less than 24% of kernels were infected with Aspergillus flavus and aflatoxin levels were low (<4ppb). Both toxigenic and atoxigenic strains increased and spread through the grain over the incubation period, and aflatoxin levels increased, even in samples from biocontrol-treated fields. Our molecular analysis suggests that applied biocontrol strains from treated fields migrate to untreated fields. The results also indicate that the population of toxigenic A. flavus in the harvested grain will grow and produce aflatoxin during the drying period when moisture is high. Therefore, any potential postharvest reduction in aflatoxin accumulation will depend on how effective the biocontrol strain was at displacing the toxigenic populations prior to harvest.
(9806690), Lily Ishak. "Soil microbial communities and disease suppression as affected by soil compaction resulting from different management strategies." Thesis, 2017. https://figshare.com/articles/thesis/Soil_microbial_communities_and_disease_suppression_as_affected_by_soil_compaction_resulting_from_different_management_strategies/13449452.
Повний текст джерела(8797730), Rupesh Gaire. "GENOTYPIC AND PHENOTYPIC CHARACTERIZATION OF PURDUE SOFT RED WINTER WHEAT BREEDING POPULATION." Thesis, 2020.
Знайти повний текст джерела(6623615), Jesse A. Haarmann. "The Effect of Herbicide Respray Treatments and Timings on Regrowth of Four Weed Species." Thesis, 2019.
Знайти повний текст джерелаControl of weeds that have survived a postemergence (POST) herbicide often need to be controlled in order to prevent seed production and interference with crops. The most efficacious herbicides and timings used for respray applications has not been determined in many problematic weed species. Previous research has demonstrated that weeds clipped to simulate a failed herbicide application responded differently to herbicide applications to regrowth based on herbicide used and weed species. Other research is conflicting as to the optimum timing of an herbicide respray application with various herbicides. Gaining a better understanding of how to maximize respray herbicide performance will help growers and land managers to preserve crop yield and prevent weed seed production in the event of POST contact herbicide failure. The objectives of this research were to determine the optimum respray herbicide and timing combinations for control of four problematic weed species in the midwestern United States that have survived an application of either glufosinate or fomesafen: waterhemp [Amaranthus tuberculatus (Moq.) J. D. Sauer], Palmer amaranth (Amaranthus palmeri S. Watts), giant ragweed (Ambrosia trifida L.), and horseweed (Erigeron canadensis L). Through a series of field and greenhouse experiments we determined that respray herbicide, respray application timing, initial herbicide, and level of injury from the initial application influence efficacy of the respray herbicide in a species-specific manner. Waterhemp regrowth following a failed glufosinate application was controlled most effectively by applying glufosinate or fomesafen 7 to 11 days after initial treatment. When following fomesafen, applications of 2,4-D 3-7 days after initial treatment or glufosinate 7 to11 days after initial treatment were most effective. Control of Palmer amaranth regrowth following either initial herbicide is best achieved with respray applications of glufosinate, fomesafen, or 2,4-D applied no later than 7 days after initial treatment. The best strategy to control giant ragweed regrowth following a failed fomesafen applications is to apply 2,4-D, dicamba, fomesafen, or glufosinate at any timing between 3 and 11 days after initial treatment. Efficacy of the respray glufosinate application was maximized when applied 11 days after the initial application rather than 3 days after initial application. Horseweed regrowth was best controlled by 2,4-D, dicamba, or glufosinate applied at any timing between 3 and 11 days after the initial application. Where injury from the initial herbicide application is high, there were fewer differences among herbicide treatments and treatment timings. A greenhouse bioassay revealed that as waterhemp injury from an initial glufosinate application increases, control with a respray herbicide also increases. Therefore, complete control of weed regrowth is achieved more easily with increasing injury from the initial application. This research suggests that timing of herbicide respray applications is more urgent than previously thought, so scouting must be done within days of a contact herbicide application to ensure adequate control.
Moyo, Clyton. "Improving the efficiency of herbicide application to pasture weeds by weed-wiping and spot-spraying : a thesis presented in partial fulfillment of the requirements for the degree of Doctor of Philososphy in Plant Science at Massey University, Palmerston North, New Zealand." 2008. http://hdl.handle.net/10179/779.
Повний текст джерела(8932271), Connor L. Hodgskiss. "WEED CONTROL SYSTEMS IN SYNTHETIC AUXIN-RESISTANT SOYBEANS." Thesis, 2020.
Знайти повний текст джерелаHerbicide-resistant weed populations have become problematic throughout the Eastern Corn Belt, with 18 unique herbicide-resistant weed biotypes confirmed in Indiana alone. In response to these resistant populations, the agricultural chemical industry has responded by developing glyphosate-resistant crops paired with resistance to synthetic auxin herbicides such as dicamba and 2,4-D.
This research evaluates weed population shifts in cropping systems using row crops that are resistant to synthetic auxin herbicides. Identifying weed population shifts will allow future research to be targeted to weed species that would become more prevalent in cropping systems using synthetic auxin-resistant crops. The use of multiple sites of action will be needed in order to prevent weed shifts in both conventional and no-till corn-soybean production systems. Weed densities and species richness were reduced within field evaluations when six or more herbicide sites of action were implemented with residual herbicides in both corn and soybean years over a seven-year period. Additionally, soil seedbank weed densities and species richness were reduced within 2,4-D-resistant soybean production systems. Additional strategies other than the application of herbicides may be needed to manage weed populations in the future due to the high levels of herbicide-resistant weed populations in the Midwest.
Off-target movement of these synthetic auxin herbicides, has been a concern, and label-mandated buffer areas are required near sensitive areas. Investigation of whether cover crops can be an effective tactic in managing weeds in these label-mandated buffer areas was conducted. Cover crop utilization in buffer areas has not been investigated in Indiana. Additionally, termination timing is becoming more prominent as farm operators are increasingly terminating cover crops after planting. Our results demonstrate that using cover crops that utilize cereal rye and that are terminated at, or after the time of soybean planting will be beneficial in suppressing waterhemp, grasses, and sometimes horseweed within label-mandated buffer areas, but not for suppression of giant ragweed. However, delaying termination of cover crops can result in soybean yield reductions and caution should be used. Terminating cover crops with glyphosate and auxin and a residual herbicide was more effective than glyphosate alone, but would not be permitted within label-mandated buffer areas.L
(6632369), Jodi E. Boe. "Establishing the Value of ALS-Inhibiting Herbicides in Fields with Confirmed Weed Resistance to ALS-Inhibiting Herbicides." Thesis, 2019.
Знайти повний текст джерелаAcetolactate synthase (ALS) inhibitors are a widely used class of selective herbicides used to control grass and broadleaf weeds. The repeated use of ALS-inhibiting herbicides has selected for biotypes of weeds resistant to ALS inhibitors, especially in the weeds most problematic to growers in the Midwest. While ALS inhibitor use seems futile, new mechanisms of herbicide action are not predicted to be commercialized in the near future to solve this problem. This leads to the main objective of this research, determining what value ALS inhibitors provide in controlling populations of weeds with resistance to ALS inhibitors.
Field experiments with soil-applied (PRE) applications of ALS inhibitors on horseweed (Erigeron canadensis) and tall waterhemp (Amaranthus tuberculatus var. rudis) exhibited higher efficacy than would be expected given the frequency of the ALS resistance trait in the population. Whereas control of these species with POST-applied applications was similar or less than the proportion of the population characterized as susceptible using molecular techniques. Soil-applied applications, therefore, resulted in relatively greater control than POST applications in populations with known ALS-inhibitor-resistance mechanisms.
Greenhouse experiments showed that overall resistance ratios were higher for PRE applications of ALS inhibitors in horseweed, tall waterhemp, and Palmer amaranth (Amaranthus palmeri). However, GR50 values decreased for both susceptible and resistant biotypes for the PRE applications compared to POST, suggesting the biologically effective dose of these herbicides is lower in soil residual applications. This research found that PRE applications of ALS inhibitors resulted in some level of control on horseweed and tall waterhemp classified as resistant to ALS inhibitors due to the higher efficacy of PRE herbicide applications.
Genetic analysis assessing the amino acid substitutions that confer resistance to ALS inhibitors in tall waterhemp confirmed a difference in selection pressure between PRE and POST applications and between ALS active ingredients in tall waterhemp. Applications of chlorimuron PRE at 11 g ai ha-1 selected for 35% homozygous W574L genotypes and at 44 g ha-1 selected for 70% homozygous W574L genotypes. An increase of homozygous W574L individuals along with a decrease in heterozygous individuals from 65 (11 g ha-1) to 29% (44 g ha-1) suggests that W574L is semi-dominant in tall waterhemp and that high labeled rates of chlorimuron applied PRE can partially overcome the heterozygous W574L-resistance mechanism. In horseweed, no difference in selection pressure was observed between application timing or between chlorimuron or cloransulam. A new mutation conferring ALS-inhibitor resistance in horseweed was discovered, a Pro197Leu amino acid substitution, with resistance ratios of 21X to chlorimuron and 8.6X to cloransulam. These resistance ratios are slightly less than those reported for the Pro197Ala and Pro197Ser amino acid substitutions in conferring ALS-inhibitor resistance in horseweed.
Finally, a survey of 42 populations of tall waterhemp in Indiana counties with confirmed ALS-inhibitor resistant populations of tall waterhemp found that all populations contained at least 16% individuals with the W574L amino acid substitution, 35 populations contained at least 1% individuals with the S653N substitution, and 9 populations contained at least 1% individuals with the S653T substitution. Taking into consideration the three mutations tested, 8 of the 42 populations tested contained <50% ALS-inhibitor resistant individuals within the population. Using the same tall waterhemp populations as collected in the survey, Next-Generation Sequencing was used to determine if other amino acid substitutions conferring resistance to ALS inhibitors existed. Results from WideSeq revealed that 10 other amino acid substitutions in the ALS protein may be conferring resistance in tall waterhemp in Indiana: A122T, A122N, A122S, P197T, P197L, P197H, D376E, and G654F. Further research from this survey also suggests that metabolic resistance to ALS inhibitors is likely a contributor to resistance in tall waterhemp in Indiana.
This research suggests that ALS-inhibiting herbicides, more specifically chlorimuron, would provide the greatest contribution to management of tall waterhemp. Chlorimuron would perform best when used in soil residual applications and in populations of tall waterhemp containing either individuals susceptible to chlorimuron or individuals heterozygous for ALS inhibitor resistance conferred by the W574L mutation. This research also demonstrates the specificity of the amino acid substitutions in the ALS protein and by weed species to realize the benefit of these herbicides for management of weeds resistant to ALS inhibitors. Molecular characterization of target site resistance to ALS inhibitors has traditionally been considered relatively simple. However, we found 11 new amino acid substitutions that confer resistance to ALS inhibitors in horseweed and tall waterhemp. The complexity of ALS inhibitor resistance calls for the use of methods such as NGS to detect all potential resistance mutations in a timely manner and for the use of tests detecting metabolic resistance. Overall, this research demonstrates that ALS inhibitors still provide some utility for management of weed populations classified as resistant to ALS inhibitors and that the resistance mechanisms in horseweed and tall waterhemp are more numerous than previously reported.
(9729146), Kyle David Richardville. "Overcoming Barriers In Urban Agriculture To Promote Healthy Eating On College Campuses." Thesis, 2020.
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