The lack of adequate weed control is one of the major problems encountered in soybean production. Johnsongrass presents one of the most serious weed control problems in the Southeastern United States. numerous herbicides are used in an effort to control johnsongrass, and research is still being conducted to find new herbicides for this purpose. Two of these herbicides are BAS 9021 [6,6-dimethyl-2,4-dioxo- 3[1-[2-(propenyloxy)amino]butylidene]-cyclohexane] and BAS 9052 [2-(n-ethoxybutyrimidoyl)-5-(2-ethylthiopropy1)-3- hydroxy-2-cyclohexen-1-one]. In 1978, johnsongrass control with BAS 9021 at 1.1 and 1.7 kg/ha in sim-le early postemergence or late postemergence applications, or in each of two split applications, was evaluated using the herbicide alone, with a nonionic surfactant, or a nonphytotoxic crop oil. The split applications gave johnsongrass control ranging from 49, to 81,. Late postemergence applications of 1.7 kg/ha of BAS 9021 were as Food as split applications. As a group, the addition of oil or surfactant gave increased control over the herbicide alone. In 1979 BAS 9021 and BAS 9052 were compared with mefluidide [N-[2,4-dimethyl-5[[(trifluoromethyl)sulfonyl]amino]phenyl]acetamide]and alachlor (2-chloro-2'6'-diethyl-N-(methoxymethyl)acetamide] for seedling johnsongrass control. The BAS materials were compared with mefluidide, trifluralin]α, α, α trifluoro-2,6-dinitro-N,N-dipropyl-p-toliuidine], fluchloralin [N-(2-chloroethyl)-2,6-dinitro-n-propyl- 4-(trifluoromethyl)aniline] and trifluralin plus vernolate [S-propyl dipropylthiccarbamate] for rhizomic johnsongrass control. In both experiments BAS 9021 was applied at 1.1 and 1.7 kg/ha in each of two applications. BAS 9052 was applied at rates of 0.6 to 1.1 kg/ha early postemergence, late postemergence or in split applications. Mefluidide was applied at rates of 0.3 to 0.6 kg/ha either early postemergence or in split applications. All postemergence herbicide applications contained an oil concentrate at a rate of 2.4 L/ha. Alachlor for seedling control was applied preemergence at 3.4 and 4.5 kg/ha. Preplant incorporated applications of trifluralln and fluchloralin were made at rates of 2.2 kg/ha and vernolate at 2.8 kg/ha was combined with —1 and 2.2 kg/ha of trifluraiin for rhizomic johnsongrass control. In the seedling area, all BAS treatments gave 88% or better johnsongrass control. In the rhizomic area split applications of BAS 9052 tended to result in the best johnsongrass control. Ratings were taken both 8 and 11 weeks after planting. Soybean yields were generally better with higher johnsongrass control. Mefluidide caused apparent soybean injury, resulted in poor johnsongrass control and lowered soybean yields. All preplant incorporated treatments gave poor johnsongrass control and low soybean yields. Alachlor gave fair johnsongrass control but resulted in high soybean yields.

With the introduction of herbicide resistant Palmer amaranth into Kentucky during the past 10 years there has been an increasing concern for effective control measures in grain production. Field trials were performed in 2016 and 2017 near Barlow and Paris, KY to determine efficacy of chemical control programs targeting herbicide resistant Palmer amaranth. Percent visual control, effects on plant density and plant height were measured in 2016 to determine treatment effectiveness. Treatments containing four different sites of herbicide activity achieved an average of 98% control. Treatments containing only 3, 2 or 1 site of activity only achieved 64%, 45% and 33% control, respectively. Within the long-chain fatty acid inhibitors herbicides in this study, pre-emergent applied pyroxasulfone provided greater control than S-metolachlor or acetochlor. Pyroxasulfone also provided greater control than the photosystem II herbicides atrazine and metribuzin. In 2017 PRE treatments consisting of three-way mixtures of flumioxazin + pyroxasulfone + chlorimuron or S-metolachlor + metribuzin + fomesafen followed by a POST herbicide treatment provided > 90% suppression of Palmer amaranth 4 weeks after trial initiation. Post-emergence treatments containing glyphosate + dicamba or glyphosate + 2,4-D following a soil-applied pre-emergent treatment achieved the most effective season-long control of Palmer amaranth.

Invasive species are often successful and problematic because of their ability to persist in disturbed and undisturbed environments despite weed management practices. Understanding reproduction and dispersal strategies in these species can aid in developing management approaches to help control their spread. Centaurea melitensis, a nonnative invasive with European origins, is found in disturbed areas of southern California. It produces three different types of flower heads that develop at different times and at different locations on the plant during the growing season. The chasmogamous (CH) flower heads are located at the top of the plant, the initial cleistogamous (iCL) heads are located at the base of the plant and at some branch and axillary points, and the final cleistogamous (fCL) heads are located along the stem and at some branch points. This pattern differs from that in Centaurea solstitialis, its most closely related congener, which develops one type of flower head with two morphologically distinct achenes within each flower head: peripheral and center achenes. The overall objective of this study was to examine potential differences between peripheral and center achenes of Centaurea melitensis, including morphological differences in dispersal features, potential differences in response to temperature, tendency to disperse, dormancy and viability. The approach involved selecting whole plants from the field and separating peripheral and center achenes from each of the three head types. Morphological differences were assessed by measuring mass, fruit length, fruit width, pappus length, pappus width, and elaiosome features. Temperature response patterns were evaluated by exposing peripheral and center achenes to temperatures ranging from 5 C to 30 C and measuring germination. Tendency of different achene types to remain in the flower heads was assessed by comparing ratios of peripheral to center achenes in heads immediately after maturation (March to June) to the ratios remaining in heads in early fall (September). Viability and dormancy testing was performed using a cut test and tetrazolium chloride tests in conjunction with germination tests. Results of these studies indicate that peripheral achenes of Centaurea melitensis were lighter and narrower, with shorter pappi and smaller elaiosomes than center achenes. Peripheral achenes responded similarly to their center counterparts in germination response to temperature, but the pattern differed among head types. Broad temperature optima were observed within the fCL and CH heads and a narrow optimum was observed in iCL. There was no evidence that the peripheral achenes remained in the heads longer than the center achenes. Ratios of peripheral to center achenes were 3.8:1 in CH heads, 2.23:1 in iCL heads, and 1.94:1 in fCL heads. Peripheral achenes were more likely to be dormant while maintaining viability than center achenes were. The results of this study, therefore, indicate that peripheral and center achenes of Centaurea melitensis differ morphologically. Dispersal features, such as pappi and elaiosomes, were more highly developed in center achenes than in peripheral achenes, but these differences were not reflected in differences in behavior to the extent we could measure it (i.e., the tendency to remain in heads or the germination responses to temperature). Differences between peripheral and center achenes of Centaurea melitensis trended in the same direction as differences seen in its closely related congener, Centaurea solstitialis, which has center achenes that disperse more readily than peripheral achenes. However, the differences observed in Centaurea melitensis were not as pronounced as those seen in Centaurea solstitialis.

An analysis of the previous method for testing tolerances of noxious weed seeds was performed. Problems of the current techniques were discussed, and the solution to these problems was given. A new technique of testing through the sequential test ratio was developed, and results examined. The sequential test was found to be useful enough to include the use of it in determining tolerances for noxious weed seeds. This study did show that the use of sequential tests does have excellent potential and flexibility as a statistical tool for the tolerances of noxious weed seeds. (75 pages)

It is well known that weeds spread and are perpetuated by means of seed and vegetative reproduction. The seeds in turn are spread by various agencies such as wind, water, animals and man. These agencies are aided by especially adapted seed mechanisms for dissemination.

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Bibliography: leaves 209-254. Experiments detailed in this thesis, evaluate the impact of various herbicides and herbicide mixtures on the growth, nodulation and nitrogen fixation of annual pasture legumes, the efficacy of the herbicides for weed control, and the potential role of mechanical defoliation to replace herbicides, leading to lower cost and more sustainable farming systems.

Bibliography: leaves 82-89. Rampion mignonette is an annual to short-lived perennial agricultural weed from the Mediterranean region, first found in vineyards at Clare, South Australia, in 1986. The biology and ecology of rampion mignonette was studied to provide a basis for its integrated control and management. The study includes a literature review, maps of world and Australian distribution and drawings showing plant habit and details. A field survey found that rampion mignonette showed little migration and that containment and population reduction could be achieved by careful management including both chemical and cultural techniques. Common herbicides were also found to be effective in controlling the weed. An experiment established that it is unlikely to become a major weed of broadacre crops and pastures in the South Australian dryland farming system. It does however have the potential to compete with grapevines and reduce grape yields.

<p>Weed control is nowadays a hi-tech discipline. Inter-row weed control is very sophisticated </p><p>whereas the intra-row weed control lacks a lot. The aim of this pro ject is to implement </p><p>an embedded system of an autonomous vision based intra-row weeding robot. Weed and </p><p>crops can be distinguished due to several attributes like colour, shape and context fea- </p><p>tures. Using an emebedded system has several advantages. The embedded system is </p><p>specialized on video processing and is designed to withstand the needs of outdoor use. </p><p>This embedded system is already able to distinguish between weed and crops. The per- </p><p>formance of the hardware is very good whereas the software still needs some optimizations.</p>