No description available.

No description available.

Weed control is typically achieved by broadcast spraying postemergence herbicides on the entire orchard floor which wastes chemical by spraying bare ground. Growers can account for spatial variation in weed density and only spray weedy areas instead of applying herbicide to entire fields by using the automatic spot-sprayer, WeedSeeker sprayer. We conducted field experiments in flood- and microsprinikler-irrigated lemon orchards, and flood- and sprinkler-irrigated pecan orchards to measure the amount of herbicide applied, weed control, tree yield, and the economic value of adopting the WeedSeeker sprayer compared to conventional boom spray technology. The WeedSeeker sprayer reduced cumulative herbicide use by at least 36% compared to the conventional boom sprayer at all sites. Weed control obtained using the WeedSeeker sprayer was usually similar to the conventional boom sprayer. There were no effects of the treatments on yield at any location. The partial budget analysis, used to determine the economic value of adopting the technology, showed that as the area of the orchard and the cost of the herbicide increased, the time to recover the initial investment in the WeedSeeker sprayer decreased. The investment in the technology can typically be recovered in less than five years in Arizona lemon and pecan orchards.We also conducted greenhouse experiments to determine the effect of various sensitivity settings and leaf area on the operational efficiency of the WeedSeeker sprayer. The WeedSeeker sprayer did not detect and spray all broadleaf and monocot plants unless a sensitive setting was used. The WeedSeeker sprayer was more efficient when detecting broadleaf plants compared to monocot plants. Our results indicate that operating the WeedSeeker sprayer using a sensitive setting (sensitivity level 2) will result in the most efficient detection of weeds.Finally, field studies were conducted in a non-bearing pecan orchard to evaluate weed management systems using various postemergence and preemergence herbicides. Most postemergence herbicides controlled the weed species present in the orchard. Tank mixing the herbicides generally resulted in greater control compared to applying them alone. All preemergence herbicides reduced the weed emergence compared to not using a preemergence herbicide. No pecan tree damage was observed in any treatment.

There is little information published on red sorrel (Rumex acetosella L.), a perennial weed that is considered a serious problem in wild blueberry production. Hexazinone, a photosystem II inhibitor, has been used in wild blueberry fields for more than 30 years. Hexazinone efficacy on red sorrel has declined over time. Therefore, a two year study was conducted to examine hexazinone alternatives that can be sprayed in wild blueberry fields. Red sorrel ramets from mature blueberry fields were tested to determine whether long-term spraying of hexazinone selected for resistant red sorrel. The results show that hexazinone+rimsulfuron/nicosulfuron may be a alternative for hexazinone. Red sorrel from some blueberry fields is hexazinone-resistant and the resistance is caused by a Phe255 to Val mutation in the psbA gene.

In recent years global concern over the development of herbicide resistant (HR) weeds has lead to interest in integrated weed management (IWM) strategies. IWM seeks to relieve selection pressure for herbicide resistance by utilizing mechanical and cultural controls in addition to herbicides. The situation experienced by Saskatchewan lentil growers with large populations of group 2 herbicide resistant wild mustard provides an ideal model system to test our hypothesis that IWM strategies can provide robust weed management and maintain crop yields. The first study evaluated an IWM method targeting HR wild mustard in lentil. This study was conducted for 3 years between 2011 and 2013 at 2 locations at Saskatoon and Scott, Saskatchewan. It was a randomized two way factorial with weed control method and seeding rate as the main effects. Weed control treatments tested consisted of a control treated with a glyphosate burnoff, saflufenacil (Heat ™) herbicide, rotary hoeing, half rate metribuzin (Sencor ™) herbicide, a fully integrated treatment, and a full herbicide treatment. Three seeding rates representing 1, 2, and 4 times the recommended seeding rate were tested. The integrated treatment relied on increased seeding rate to reduce mustard biomass and produce yield, and at the highest seeding rate it was able to provide equivalent yield to the full herbicide system. The results of this study show that an integrated system utilizing an increased seeding rate can control resistant weeds and maintain yields to a similar level as a strategy that relies only on herbicides for weed control. The cultural practice of increasing crop seeding rate has been identified as having potential to provide non-chemical weed control and enhance the effects of herbicide application. The objective of the second study was to examine the interaction between increasing seeding rate and the dose response relationship of weeds to herbicide application. The experiment was a factorial design with four levels of lentil seeding rate and seven levels of fluthiacet-methyl herbicide application rate. The study was conducted at two locations near Saskatoon, Sk. in 2012 and 2013. Results of the experiment show that increasing lentil seeding rate decreased the total mustard biomass when herbicides were not applied or were applied at low rates. In addition increasing lentil seeding rate lowered the herbicide dose required to result in a 50% reduction in mustard biomass in 2012, though it had little effect in 2013. These results suggest that the practice of increasing seeding rate can work with herbicide application to reliably and effectively control weeds, even in situations where herbicides alone may not achieve good control.

Soil samples were collected from several corn fields with history of atrazine (herbicide) application. Samples were inoculated into Erlenmeyer flasks each containing 50m1 of minimal basal salts medium amended with 100 ppm atrazine as sole nitrogen source. Flasks were shaken at 200 rpm at ambient temperature and were examined daily for one week for microbial growth and/or disappearance of atrazine. Promising consortia were subcultured for further additional enrichments before characterization of potentially active protein (enzyme)fractions. Proteins from cell-free and cellbound fractions were compared for ability to denature atrazine. Following gel permeation chromatography, isolated protein fractions were examined for atrazinefound in the cell-bound fractions capable degrading degradation. Two were found in the cell-free fractions (approx. Mol. wts. 55kDa and 180kDa) and one (55 kDa) atrazine to hydroxyatrazine. Atrazine and its breakdown products (hydroxyatrazine in particular) were detected via HPLC using C18 and C8 columns with absorbance at 229 nm. / Department of Biology

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.

Graduation date: 1993

Thesis (Ph. D.)--University of Adelaide, Dept. of Crop Protection, 1994. / Includes bibliographical references (leaves 143-161).

Thesis (M.S.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on April 10, 2009) Includes bibliographical references.