Date of Award

1982

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Abstract

Field and greenhouse studies were conducted in 1981 and 1982 to evaluate acifluorfen {5-{2-chloro-4-(trifluoromethyl)phenoxy}2-nitrobenzoic acid} efficacy in controlling morningglory (Ipomea spp.) and common cocklebur (Xanthium pennsylvanicum Wallr.) in soybeans {Glycine max (L.) Merr.}. Repeated low rate applications of 0.2 kg/ha active ingredient acifluorfen were compared to single applications for control of ivyleaf morningglory {Ipomea hederacea (L.) Jacq. var: hederacea}. In field studies two applications of 0.2 kg/ha acifluorfen increased control compared to a single application of 0.6 kg/ha, based on visual ratings and fresh weight reductions in ivyleaf morningglory. In the response of ivyleaf morningglory to increasing rates of acifluorfen, maximum control under greenhouse conditions was achieved at rates of 0.6 to 0.9 kg/ha. Deviation from 100% control at higher rates was due to regrowth at the axillary buds of the lower nodes of treated plants. In one field study, conducted under dry conditions, the rate of increase in percent control as acifluorfen rates increased from 0.3 to 1.2 kg/ha was low compared to results from an experiment conducted under favorable conditions. Since fresh weight measurements often reflected regrowth at the nodes of treated plants, studies on the effect of acifluorfen rate of application on translocation to the leaf node and lower stem was quantified. Differences in ('14)C-acifluorfen translocation to the lower stem was observed between 24, 48, and 72 hour analysis periods. Rates ranging from 0.15 to 1.2 kg/ha of ('14)C-acifluorfen were applied to ivyleaf morningglory leaves in a similar study. The amount of ('14)C-acifluorfen equivalent translocated increased linearly with increasing field rates. Larger amounts of ('14)C-acifluorfen accumulated in the nodes of the treated leaves compared to the lower stem area. In other field studies the potential of mefluidide {N-{2,4-dimethyl-5-{{(trifluoromethyl)-sulfonyl}amino}phenyl}acetamide} applied in combination with acifluorfen to increase control of pitted morningglory {Ipomea lacunosa (L.)} and common cocklebur was examined. All treatments with mefluidide in combination with acifluorfen improved both pitted morningglory and cocklebur control compared to acifluorfen applied alone. The sequential applications of acifluorfen following mefluidide increased control of both weeds compared to the tank-mix combinations.

Pages

131

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