D.Sc. / Please refer to full text to view abstract

M.Sc. (Botany) / Please refer to full text to view abstract

Horseweed (Erigeron canadensis) is a competitive winter or summer annual broadleaf weed. When uncontrolled, horseweed can reduce soybean (Glycine max) yields by 93%. Research was conducted to advance our knowledge on horseweed growth stage response to foliar-active and residual herbicides, fall applications, and the utility of differing herbicide technologies. Greenhouse results determined that herbicide efficacy was greatest when applied to early rosette horseweed providing an average control of 70% across herbicide treatments. Field trials determined that preventing new emergence with flumioxazin, added with dicamba or paraquat to kill existing plants in the fall, increased control to 99% the following spring. Field trials also determined that dicamba, applied PRE or POST, provided excellent horseweed control and was an effective soybean technology system for horseweed-infested fields. Saflufenacil controlled existing plants, but residual benefits were unclear. Further research must be done to investigate residual activity of PRE herbicides applied before horseweed emergence.

Common integrated vegetation management (IVM) practices including herbicide and mowing applications on right-of-ways and forages were evaluated on green antelopehorn populations near Starkville, MS. Live stems in each plot were counted prior to treatment application and approximately one year after treatment (YAT). Analysis of the stem counts 1YAT indicated aminopyralid+metsulfuron, imazapyr, picloram+2,4-D, maximum rates of triclopyr ester or choline, glyphosate, imazapyr+aminocyclopyrachlor+metsulfuron reduced the number of green antelopehorn stems compared to the untreated. Aminocyclopyrachlor, aminocyclopyrachlor+chlorsulfuron, aminopyralid, aminopyralid+2,4-D, dicamba+2,4-D, foramsulfuron+iodosulfuron+thiencarbazone, fluroxypyr, hexazinone, metsulfuron, metsulfuron+chlorsulfuron, nicosulfuron+metsulfuron, sulfometuron, sulfosulfuron or low rates of triclopyr did not reduce the stem count 1YAT when compared to the untreated. Mowing timing and frequencies applications were initiated May through July and evaluated through August. Mowing early in the season increased milkweed stems one month after treatment versus late season mowings. Majority of milkweed plants developed mature seed pods and senesced by early August.

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This investigation is concerned is concerned with how a commercial herbicide, dimethyl 2, 3, 5, 6-tetrachloroterephthalate (DCPA) affects the growth, morphology, and physiology of foxtail millet (Setaria italica (L.) Beav.). The objectives were to examine the nature of morphological changes, to determine what physiological and chemical changes accompanied the morphological alterations and to obtain information about the mechanism by which DCPA is herbicidal.

No description available.

No description available.

No description available.

No description available.