A field experiment was conducted in 1998 to determine the efficacy of Puma and Hoelon for littleseed canarygrass control in durum wheat. The herbicide treatments consisted of three rates of Puma, 0.83, 1.24, and 1.66 oz a.i./A, and one rate of Hoelon, 6.8 oz a.i./A, that were applied at two application timings. The early-postemergence (EPOST) applications when canarygrass had 2.2 leaves per plant did not result in commercially acceptable control due to water stress. Increasing rates of Puma applied mid-postemergence (MPOST) when canarygrass had 5 leaves per plant provided increasing canarygrass control (70 to 90 %) with the two higher rates of Puma providing commercially acceptable control. The two highest rates of Puma also resulted in better weed control than the commercial standard, Hoelon, which did not provide commercially acceptable weed control. No herbicide injury symptoms were observed on the wheat at any of the evaluation dates. Grain yield also increased as the rate of Puma applied MPOST increased and yields overall reflected the degree of weed control observed earlier in the season. These data indicate that the combination of Puma applications that killed or stunted emerged canarygrass combined with later season crop competition that suppressed stunted and later emerging canarygrass plants was sufficient to protect grain yields. The highest yielding Puma treatment was equivalent to 4150 lb/A compared to the Hoelon and control treatments which yielded the equivalent of 2753 and 1946 lb/A, respectively.

Master of Science / Department of Horticulture, Forestry, and Recreation Resources / Steven Keeley / Common dandelion (Taraxacum officinale Weber) is an important perennial weed in turfgrass. Fall is considered the optimal time for postemergence herbicidal control of dandelions; however, applications in spring, when volatility damage to surrounding plants is an additional concern, are often needed. Therefore, we conducted research to determine the volatility of common broadleaf herbicides, and their efficacy when applied at spring and fall application timings. Volatility was determined by applying herbicides to turfgrass and using potted tomatoes as indicator plants. Tomatoes exposed to turfgrass treated with Trimec Classic, Confront, Surge, Escalade 2, and Imprelis exhibited little or no volatility damage, while exposure to Speedzone, 4 Speed XT, and Cool Power caused significant damage. In general, herbicides causing little or no damage were amine formulations. Two field studies determined the effect of spring and fall application timing on dandelion control with several herbicides. Herbicide applications in the spring coincided with dandelion anthesis stages: pre-bloom, peak bloom, and post-bloom. Results were dependent on dandelion pressure in the studies. In 2010, with lower pressure, there were no differences among herbicides at any spring timing when dandelion control was evaluated after one year; all herbicides gave ≥ 80% control. In 2011, with higher dandelion pressure, Imprelis SL and 4 Speed XT provided ≥ 96% dandelion control at the spring pre- and post-bloom timings, which was better than Surge, Escalade 2, Cool Power, and Confront. The best choices for spring efficacy combined with minimal to no volatility were Escalade 2 and Trimec Classic. Finally, because interest in organic dandelion control is increasing, we compared several organic weed control tactics with a conventional herbicide. In a two-year field study, the conventional herbicide gave much better control (> 96%) than any organic method. Horticultural vinegar corn gluten meal, and fertilizer-only gave < 25% control, while hand-weeding gave 58 to 71% control. While hand-weeding was the best of the organic tactics, the time required was considered prohibitive for turfgrass managers, unless initial weed levels were very low.

Mechanical weed control, chisel plow tillage and organic fertilization are important components of sustainable agriculture that can contribute to the preservation and improvement of soil and water resources. These practices can each affect weed communities, crop weed interactions and crop yields. Little is known about their combined effects on weed populations and weed community dynamics in common cropping systems. The main objective of this project was to determine the effects of crop rotation, weed control, tillage and nutrient source and their interactions on weed communities and weed emergence. The field experiment was conducted on a Sainte-Rosalie clay and a Duravin loam in Saint-Hyacinthe, Quebec, Canada, in 1996 and 1997. Mechanical control was not as effective as chemical control in controlling weed populations. Weed density increased after the second pass of the rotary hoe in soybean. Cultivation in corn triggered flushes of weed emergence, but corn yield was not affected by the increase in weed density. Chisel plow tillage reduced the efficacy of mechanical weed control in both crops. Reduced soybean yields were partly attributed to the large quantities of corn residues under chisel plow tillage. Nutrient source had no effect on weed densities. However, environmental stress conditions experienced in spring 1997 resulted in reduced crop growth and increased weed biomass under organic fertilization. Seed production of dominant residual weed species was greater under mechanical compared with chemical weed control, but was unaffected by tillage and nutrient source. Particular attention to weed management will be required when including both chisel plow tillage and organic nutrient source in a corn-soybean rotation, especially when resorting to mechanical weed control only.

No description available.

The two herbicides currently registered for the control of canarygrass in Arizona work by inhibiting lipid biosynthesis. The levels of control with these herbicides have been variable, ranging from 60 to 90 percent. Crop safety has been good. Two newer herbicides utilizing a different mode of action have provided more consistent and higher levels of weed control but with increased crop injury. These are numbered compounds (MKH6561 and F130060) and they are ALS inhibitors.

Italian ryegrass (Lolium perenne spp. multiflorum) is a common weed management problem in turfgrasses, cereals and non-crop areas in the United States. In Oregon, the number of populations with multiple-resistance continues to increase. To manage these resistant populations, the resistance patterns must be determined. In this study, five Italian ryegrass populations (CT, R1, R2, R3 and R4) from two cropping systems were studied for resistance patterns and mechanisms. The CT population is from a Christmas tree plantation and was resistant to at least six herbicides with four different mechanisms of action: atrazine, diuron (2.4-fold), glyphosate (7.4-fold), hexazinone (3.1-fold), imazapyr (1.8-fold), and sulfometuron. The resistant indices (RI) for sulfometuron and atrazine could not be calculated because 50% growth reduction for the CT population was not reached even with the highest rates applied, 17.6 kg ai ha⁻¹and 16 kg ai ha⁻¹, respectively, which are 16 times the recommended field application rates for this two herbicides. The CT population accumulated less shikimate than the S population. There were two mutations in the CT population, Trp591 to Leu in the ALS gene and Ser264 to Gly in the psbA gene, which explain the ALS and PII cross resistance, respectively. R1, R2, R3 and R4 were collected from annual cropping systems. All four populations were resistant to flufenacet. RIs for two populations, R2 and R4, were 8.4 and 5.9, respectively. R2 and R4 also were resistant to mesosulfuron-methyl, pinoxaden, quizalofop and clethodim. R4 was resistant to diuron, but R2 was not. An Asp-2078-Gly substitution in the ACCase gene was found in both R2 and R4 populations, while another Ile-2041-Asn substitution in the ACCase gene was found in the R4 population. These mutations explain the ACCase cross resistance in the R2 and R4 populations. The mechanisms for the glyphosate resistance in the CT population and the flufenacet resistance in R1, R2, R3 and R4 populations were not identified in this study. None of the five populations were resistant to the herbicide pyroxasulfone. / Graduation date: 2013

This study investigated the possibility of using data, acquired from airborne multi-spectral or hyper-spectral sensors, to detect nitrogen status and presence of weeds in crops; with the ultimate aim of contributing towards the development of a decision support system for precision crop management (PCM). / A 24-waveband (spectrum range 475 to 910 nm) multi-spectral sensor was used to detect weeds in corn (Zea mays L.) and soybean ( Glycine max (L.) Merr.) in 1999. Analysis of variance (ANOVA), followed by Scheffe's test, were used to determine which wavebands displayed significant differences in aerial spectral data due to weed treatments. It was found that the radiance values were mainly indicative of the contribution of weeds to the total vegetation cover in various plots, rather than indicative of changes in radiance of the crops themselves, or of differences in radiance between the weed populations and the crop species. / In the year 2000, a 72-waveband (spectrum range 407 to 949 nm) hyperspectral sensor was used to detect weeds in corn gown at three nitrogen levels (60, 120 and 250 kg N/ha). The weed treatments were: no control of weeds, control of grasses, control of broadleaved weeds and control of all weeds. Imagery was acquired at the early growth, tassel, and fully-mature stages of corn. Hyper-spectral measurements were also taken with a 512-waveband field spectroradiometer (spectrum range 270 to 1072 nm). Measurements were also carried out on crop physiological and associated parameters. ANOVA and contrast analyses indicated that there were significant (alpha = 0.05) differences in reflectance at certain wavebands, due to weed control strategies and nitrogen application rates. Weed controls were best distinguished at tassel stage. Nitrogen levels were most closely related to reflectance, at 498 nm and 671 nm, in the aerial data set. Differences in other wavebands, whether related to nitrogen or weeds, appeared to be dependent on the growth stage. Better results were obtained from aerial than ground-based spectral data. / Regression models, representing crop biophysical parameters and yield in terms of reflectance, at one or more wavebands, were developed using the maximum r2 criterion. The coefficients of determination (r 2) were generally greater than 0.7 when models were based on spectral data obtained at the tassel stage. Models based on normalized difference vegetation indices (NDVI) were more reliable at estimating the validation data sets than were the reflectance models. The wavebands at 701 nm and 839 nm were the most prevalent in these models. / Decision trees, artificial neural networks (ANNs), and seven other classifiers were used to classify spectral data into the weed and nitrogen treatment categories. Success rates for validation data were lower than 68% (mediocre) when training was done for all treatment categories, but good to excellent (up to 99% success) for classification into levels of one or the other treatment (i.e. weed or nitrogen) and also classification into pairs of levels within one treatment. Not one classifier was determined best for all situations. / The results of the study suggested that spectral data acquired from airborne platforms can provide vital information on weed presence and nitrogen levels in cornfields, which might then be used effectively in the development of PCM systems.

No description available.

Call number: LD2668 .T4 1985 L435 / Master of Science

Call number: LD2668 .T4 1985 O77 / Master of Science