Made available in DSpace on 2014-06-11T19:27:55Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-01-03Bitstream added on 2014-06-13T18:32:12Z : No. of bitstreams: 1 ferrucio_b_me_botfm.pdf: 329941 bytes, checksum: 21a4acf2de1c777f8001f2276591fbf4 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Toxicam / Diuron [3-(3,4-dichlorophenyl)-1,1-dimethyl urea] is a herbicide with carcinogenic activity in rats and mice which have developed respectively urothelial and mammary gland tumors in long-term studies. Accordingly, diuron has been categorized as a “likely human carcinogen” by the USEPA. Although the carcinogenesis initiating activity of diuron has been reported in an early initiation-promotion mouse skin study, its genotoxic potential has been disputed. It is necessary to clarify the mode of action through which it has caused rodent neoplasia and verify its relevance to humans. Herein, two experiments were developed to verify the initiating and promoting potentials of diuron in a 23- and a 21-week long mouse skin carcinogenesis protocol. In one, dimethylsulphoxide (DMSO) was the solvent for the herbicide; in the other, acetone was the alternative solvent in order to verify if DMSO had inhibitory influence on a potential cutaneous carcinogenic activity. The adopted schedule for the tumor promoting agent 12-O-tetradecanoylphorbol 13-acetate (TPA) resulted in skin ulcers, evidencing the need for careful selection of TPA dose levels and frequency of application in this model. In both studies diuron did not exert any influence on the skin carcinogenesis process, in contrast with results already reported in the literature.

Made available in DSpace on 2014-06-11T19:28:32Z (GMT). No. of bitstreams: 0 Previous issue date: 2002-03-25Bitstream added on 2014-06-13T18:34:46Z : No. of bitstreams: 1 timossi_pc_me_jabo.pdf: 3782790 bytes, checksum: 441e4bf288bd58405257aa8d2b409197 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / O presente trabalho foi conduzido em Jaboticabal, SP, no ano agrícola de 2000/01. Objetivou-se estudar a possibilidade de redução na dosagem da mistura herbicida (fluazifop-p-butil + fomesafen), aplicada em pós-emergência, no controle de plantas daninhas. Foram instalados três experimentos de campo em novembro, dezembro e janeiro, sobre Latossolo Vermelho eutrófico típico, de textura argilosa. O delineamento foi de blocos ao acaso, num esquema de parcelas sub-divididas, com quatro repetições. Os cultivares IAC- Foscarin31 e o MG/BR46-Conquista, respectivamente, constituíram as parcelas e as dosagens de 100% (1,6 l p.c./ha.), 75% e 50% do herbicida, juntamente com as testemunhas infestada e capinada, as sub-parcelas. A distância entrelinhas foi de 0,45 m. Na aplicação do herbicida utilizou-se pulverizador costal, à pressão constante de 35 lbf.pol-2, com consumo de calda de 200 l/ha. Na semeadura da soja em novembro, obteve-se baixa densidade de plantas (11/m). No entanto, devido ao grande desenvolvimento, para ambos os cultivares, características de produção analisadas, como número de vagens/planta, número de grãos/vagem e massa de 100 grãos, não foram significativamente afetadas pela presença de plantas daninhas. O cultivar IAC- Foscarin31 foi mais sensível à ação fitotóxica do herbicida, baseando-se nos sintomas visuais de intoxicação. Para os experimentos com semeaduras mais tardias, verificou-se influência do fotoperíodo, além das plantas daninhas, proporcionando reduções no crescimento e produtividade da cultura. Nestas épocas, o cultivar IAC- Foscarin31 mostrou maior sensibilidade ao fotoperíodo e à interferência de plantas daninhas. Em todos os experimentos constataram-se produções semelhantes entre os manejos químicos e o com capinas. / The research was carried out in Jaboticabal, SP, in 2000/01 crop year. The aim was study the possibility of reduction in doses of herbicide mixture, in postemergence to weed control. The tests were installed in November, December and January, on Red Latossoil eutrofic of clayish texture. It was used a randomized blocks experimental design with four replications, in split-plot scheme. Cultivars, IAC- Foscarin31 and MG/BR46-Conquista, constituted the plot and the herbicide doses at 100% (1.6 l p.c.ha-1), 75% and 50%, together with the checks (with and without weeds), the split-plot. The row spacing was 0,45 m. The herbicide application was done using knapsack sprayer, with constant pressure (35 lbf.pol-2 ), and volume of application of 200 l.ha-1. When soybean was sowned in November, low stand of plants (11/m) was obtained. Due the great plants development, the agronomic characteristics analyzed as number of pods.plant-1, number of grains.pod-1 and weight of 100 grains were not affected by weed interference. The cultivar IAC- Foscarin31 was more susceptible to fitotoxicity action, estimated by visual symptoms. The tests sowned late were influenced by fotoperiod and weeds, causing reduction in growth and yield. At this time, cultivar IAC-Foscarin31 showed higher sensibility to fotoperiod and weed interference. For all the tests were possible to obtain same yields among chemicals managements and check without weeds.

Master of Science / Department of Animal Sciences and Industry / K C Olson / The largest intact remnant of the tallgrass prairie, the Flint Hills ecoregion, is currently under threat from the invasive weed sericea lespedeza (Lespedeza cuneata [Dumont] G. Don; SL). The objectives of this research were to evaluate the efficacy of late-season prescribed burning and fall herbicide application, alone and in concert, for comprehensive control of sericea lespedeza and to assess their broader treatment impacts on native plant communities. A 31-ha native tallgrass pasture with a light to moderate infestation of SL was divided into 16 subunits for this experiment. Each subunit was randomly assigned to 1 of 4 treatments: negative control, spray-only, burn-only, or burn-plus-spray. A prescribed burn was conducted on burn-only and burn-plus-spray subunits in early September 2016. Following the re-emergence of SL, spray-only and burn-plus-spray subunits received a broadcast application of metsulfuron methyl (Escort XP, DuPont, Wilmington, DE) at a rate of 70.1 g ˖ ha⁻¹ in late September. Frequency and vigor of SL, total forage biomass, soil cover, and plant species composition were measured along permanent 100-m transects in each subunit prior to treatment application and again 12 mo later, in 2017 (i.e., 1 YAT). In 30 x 30-cm plots at 1-m intervals along each transect, the presence or absence of SL was noted. Where SL was present, crown maturity and maximum stem length of the SL plant nearest to the transect were recorded. Presence of multiple stems in plots was also recorded. Prior to treatment application, SL comprised 1 ± 2.0% of total basal cover and was not different between treatments (P = 0.38). One YAT, SL was more abundant (P ≤ 0.02) in negative control subunits than in spray-only, burn-only, or burn-plus-spray subunits, which were not different (P ≥ 0.95) from one another. Aerial frequency of SL, abundance of mature SL crowns, and incidence of plots with multiple SL stems were greatest (P ≤ 0.03) for negative controls, although not different (P ≥ 0.50) between the other 3 treatments. The change in forage biomass production 1 YAT did not differ (P = 0.16) between treatments. A tendency (P = 0.06) for a shift from litter cover to bare soil was noted when the spray-only, burn-only, and burn-plus-spray treatments were compared to the negative control. Graminoid basal cover was greater (P < 0.01) in the spray-only and burn-plus-spray treatments than in the negative-control and burn-only treatments 1 YAT. Conversely, forb basal cover was less (P = 0.01) in spray-only and burn-plus-spray treatments than in negative-control and burn-only treatments. The evenness component of diversity decreased in the burn-plus-spray treatment relative to the negative control (P ≤ 0.01). These data indicate that each of these strategies were effective in reducing SL populations. Although late-summer prescribed burning produced no detected negative responses within the native plant community, fall herbicide application, alone or in conjunction with prescribed burning, resulted in collateral damage to forb populations. A late-summer prescribed burn alone is recommended for low-cost comprehensive control of a light to moderate sericea lespedeza infestation.

Master of Science / Department of Agronomy / Dallas E. Peterson / During 2015 and 2016, five site years of research were implemented in double crop soybean after winter wheat at experiment fields in Kansas near Manhattan, Hutchinson, and Ottawa to assess various non-glyphosate herbicide treatments at three different application timings for control of Palmer amaranth (Amaranthus palmeri S. Wats.) and common waterhemp (Amaranthus rudis Sauer). Spring-post (SP) treatments with residual control of Palmer amaranth and waterhemp were applied in the winter wheat at Feekes 4 and resulted in less than 50% control of Palmer amaranth and waterhemp at the time of double crop soybean planting. Pre-harvest treatments were applied two weeks before winter wheat harvest. 2,4-D resulted in highly variable Palmer amaranth and waterhemp control whereas flumioxazin resulted in comparable control to PRE treatments that contained paraquat plus a residual herbicide. Excellent Palmer amaranth and waterhemp control was observed at 1 week after planting (WAP) double crop soybean with a preemergence (PRE) paraquat application; however, reduced control of Palmer amaranth and waterhemp was noted at 8WAP due to extended emergence. Palmer amaranth and waterhemp control was 85% or greater at 8WAP for most PRE treatments that included a combination of paraquat plus residual herbicides. PRE treatments that did not include the combination of paraquat and residual herbicides did not provide acceptable control. A second set of field experiments were established in 2015 and 2016 near Manhattan, Hutchinson, and Ottawa to assess residual Palmer amaranth and waterhemp control with very-long-chain-fatty acid (VLFCA) inhibiting herbicides. Acetochlor (non-encapsulated and encapsulated), alachlor, dimethenamid-P, metolachlor, S-metolachlor, and pyroxasulfone as well as the microtubule inhibiting herbicide pendimethalin were applied at three different field use rates (high, middle, and low) based on labeled rate ranges for soybean as PRE treatments in a non-crop scenario after the plot was clean tilled with a field cultivator. The experiment was conducted one time in 2015 and four times in 2016 at two different locations for a total of five site years of data. PRE applications were made June 1, 2015, near Manhattan. PRE applications in 2016 were made in April at locations near Hutchinson and Ottawa; the second run of the experiment was applied in June at the same locations on a different set of plot areas. At Manhattan pyroxasulfone, S-metolachlor, and dimethenamid-P resulted in the highest Palmer amaranth control at 4WAT. At Hutchinson, pyroxasulfone resulted in superior Palmer amaranth control compared to dimethenamid-P and pendimethalin at 4WAT and 8WAT. At Ottawa, acetochlor, S-metolachlor, and pyroxasulfone resulted in higher waterhemp control than alachlor and pendimethalin at 4WAT and 8WAT.

Studies were conducted in 1996 through 1999 to: (1) evaluate the responses of one imidazolinone (IMI)-susceptible (S) and four -resistant (R1, R2, R3, and R4) smooth pigweed populations to various acetolactate synthase (ALS)-inhibiting herbicides, (2) determine the mechanism of resistance, and (3) evaluate the relative growth and competitiveness of each population. Field studies were conducted in 1996 near Marion, MD, in a field with a history of repeated imazaquin use. Smooth pigweed control with IMI herbicides was < 8 percent, but control with sulfonylurea (SU) herbicides ranged from 73 to 99 percent. Follow-up greenhouse studies were used to confirm IMI resistance in the Marion, MD smooth pigweed population (R4) as well as three others (R1, R2, and R3). R populations were 730- to 1350-fold more tolerant to imazethapyr than the S population. Based on resistance ratios, all R populations displayed low-level cross-resistance to chlorimuron and negative cross-resistance to thifensulfuron, pyrithiobac, and cloransulam-methyl with R2 being the most sensitive of the R populations to pyrithiobac and cloransulam-methyl. Absorption, translocation, and metabolism of ¹⁴C-cloransulam-methyl in S and R2 populations were generally similar. Three metabolites of cloransulam-methyl with ratio of front (Rf) values approximately 0.83, 0.65, and 0.45 were isolated. The metabolite with a 0.83 Rf value increased over time as the parent molecule decreased indicating that it plays a major role in cloransulam-methyl metabolism in smooth pigweed. The other metabolites did not change significantly over time and never represented more than 5 percent of the extracted radioactivity. The identity of these metabolites has not been determined. Using enzyme assays, it was determined that IMI resistance in R populations was due to an altered ALS that was no longer susceptible to inhibition by these herbicides. ALS from S, R1, and R2 populations responded similarly to chlorimuron and thifensulfuron, but reductions in enzyme activity by chlorimuron and thifensulfuron were significantly greater for R3 ALS than for S, R1 or R2 ALS. ALS from R2 and R3 was significantly more sensitive to inhibition by pyrithiobac compared to S ALS. Based on resistance ratios, R2 and R3 ALS were also more sensitive to inhibition by cloransulam-methyl than S ALS. Negative cross-resistance to thifensulfuron, pyrithiobac, and cloransulam-methyl in some R populations at the whole-plant level can be explained by increased sensitivity at the enzyme level. Under noncompetitive conditions in the greenhouse, S produced 17, 23, 25, and 44 percent more biomass than R1, R2, R3, and R4 populations, respectively. S plants were also taller than R plants 17 and 21 d after planting (DAP) and displayed a faster initial rate of leaf area increase compared to all R populations. The net assimilation rate of S was significantly higher than R2 and R3 populations 24 DAP. R3 and R4 populations had significantly less chlorophyll per g of plant tissue compared to S; therefore, reduced growth in some R populations compared to S may be linked to chlorosis that generally appears early in seedling development. Biomass production in the field under competitive conditions was similar for all populations using both monoculture and mixed populations. For this reason, the differences in growth observed in the greenhouse in the S population may not confer a competitive advantage over R populations in the field. / Ph. D.

A rapid primary herbicide screening experiment was conducted to determine if synergism or antagonism occurs with imazapyr(Arsenal&#174;) plus triclopyr ester (Garlon 4®) and imazapyr plus glyphosate(Accord®) mixtures applied to woody weed seedlings. Using a booth sprayer, 66 herbicide treatments were applied to greenhouse grown black cherry (Prunus serotina), winged elm (Ulmus alata), sweetgum (Liquidambar styraciflua), red maple (Acer rubrum), black locust (Robinia psuedoacacia), loblolly pine (Pinus taeda), water oak (Quercus nigra) and cabbage palmetto (Sabel palmetto). The seedlings were rapidly screened and percent mortality, height and dry weight measurements were obtained five months after treatment. The sweetgum, red maple and black locust experienced unacceptable mortality in the control treatments, and were excluded from further analysis. A determination of synergistic or antagonistic interactions was made using response surface analysis, the nonlinear blending method, the isobologram method, and the Colby method. Imazapyr plus triclopyr ester mixtures were found to be synergistic on black cherry (p < 0.05), with antagonism occurring at high rates of both herbicides. Imazapyr plus triclopyr ester was additive on the remaining species. The imazapyr plus glyphosate mixtures were found to be additive for all tested species. / Master of Science

Field studies conducted in Missouri and Mississippi, in 2017 and 2018, respectively, indicated no droplet size effect on PRE herbicide efficacy, regardless of the herbicide, weed, soil, crop residue and weather conditions during spraying. Nozzle type enhanced herbicide efficacy for one location and herbicide. The TTI60 dual fan nozzle increased pendimethalin weed control, up to 91%, in a high organic matter (OM) soil with large clods and substantial weed pressure. Pendimethalin efficacy was reduced under high OM soils (> 2%) while metribuzin efficacy was reduced under low OM (< 0.7%), low cation exchange capacity (<13.1%) soils and 12.2 mm of rain three days after application. The greenhouse studies indicated that increasing crop residue levels reduced velvetleaf control by 7%. Simulated rainfall eight days after herbicide application decreased johnsongrass dry weight reductions by 29% in comparison to two day rainfall.

Agricultural production has observed many changes in technology over the last 20 years. Producers are able to utilize technologies such as site-specific applicators and remotely sensed data to assist with decision making for best management practices which can improve crop production and provide protection to the environment. It is known that plant stress can interfere with photosynthetic reactions within the plant and/or the physical structure of the plant. Common types of stress associated with agricultural crops include herbicide induced stress, nutrient stress, and drought stress from lack of water. Herbicide induced crop stress is not a new problem. However, with increased acreage being planting in varieties/hybrids that contain herbicide resistant traits, herbicide injury to non-target crops will continue to be problematic for producers. With rapid adoption of herbicide-tolerant cropping systems, it is likely that herbicide induced stress will continue to be a major concern. To date, commercially available herbicide-tolerant varieties/hybrids contain traits which allow herbicides like glyphosate and glufosinate-ammonium to be applied as a broadcast application during the growing season. Both glyphosate and glufosinate-ammonium are broad spectrum herbicides which have activity on a large number of plant species, including major crops like non-transgenic soybean, corn, and cotton. Therefore, it is possible for crop stress from herbicide applications to occur in neighboring fields that contain susceptible crop varieties/hybrids. Nutrient and moisture stress as well as stress caused by herbicide applications can interact to influence yields in agricultural fields. If remotely sensed data can be used to accurately identify specific levels of crop stress, it is possible that producers can use this information to better assist them in crop management to maximize yields and protect their investments. This research was conducted to evaluate classification of specific crop stresses utilizing hyperspectral remote sensing.

White clover (Trifolium repens) is a common and difficult weed to control in turfgrass as it is a highly visible and unsightly weed that disrupts the uniformity of the turfgrass surface. This weed is a serious problem in the turfgrass industry in California and there is a need for better methods of control. With more regulations on pesticides and less information about efficient application techniques, controlling white clover with available herbicides can be difficult. Compatibility trials were conducted during the summer of 2005 to determine the compatibility of the herbicides and adjuvants planned for use in subsequent greenhouse and field trials. A greenhouse trial was conducted in the spring of 2006, followed by field trials in fall of 2006 and spring of 2007 to determine the efficacy of two herbicides on white clover when combined with each of three adjuvants and two nozzles. Results showed the nozzles to have no significant effect on phytotoxicity to white clover in the greenhouse trial, while some of the herbicides and adjuvants significantly increased phytotoxicity to white clover. In the field trials, adjuvants had no effect on phytotoxicity, while some herbicides and nozzles significantly increased phytotoxicity to white clover, perennial ryegrass and common bermudagrass. Information about the combination of herbicides, adjuvants and nozzles will help turfgrass managers to improve their management of white clover in turfgrass.

Flowering rush (Butomus umbellatus L.) is a perennial wetland/aquatic plant that is native to Eurasia but has invaded North America and spread across Southern Canada and the Northern U.S. where it thrives along wetlands, shallow shorelines, and in submersed habitats of lakes, ponds, streams, rivers, and reservoirs. Little is known about the life cycle of flowering rush in its invaded range as only one study has investigated flowering rush phenology in Minnesota, USA. As flowering rush continues to expand its range southward in the U.S. it is imperative that resource managers 1) better understand the plants life cycle, 2) identify more aggressive and 3) selective herbicide strategies, and 4) utilize adaptive management protocols. In a mesocosm experiment, flowering rush grown in southern climates produced less overall biomass but produced more buds than recorded in northern populations. A second mesocosm study using one to four biweekly sequential diquat (0.37 mg L-1) treatments reduced flowering rush biomass and rhizome bud density by 62 to 100% one year after treatment. Additionally, there were no differences among diquat treatments suggesting that more aggressive diquat protocols may not be useful. In field trials, flowering rush was selectively reduced 92 to 99% by diquat treatments over two years, while hardstem bulrush was not affected. In mesocosms, flowering rush and hardstem bulrush were exposed to the contact herbicides diquat, endothall, copper, carfentrazone-ethyl, and flumioxazin; endothall (3.0 mg L-1) selectively reduced aboveground biomass of flowering rush by 69% and diquat (0.19 mg L-1) selectively reduced belowground biomass by 77%. None of the other herbicides affected flowering rush. In a Minnesota field project to identify adaptive control strategies, treatment sites were designated as having very-low, low, or high flowering rush prevalence with each receiving no, one, or two diquat treatments (0.37 mg L-1), respectively. Flowering rush did not increase after single diquat applications in low prevalence sites while prevalence declined in high prevalence sites. This suggests that single diquat applications are suitable to maintain control of sites with low flowering rush prevalence allowing resource managers to allocate unused resources elsewhere.