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Title:Weed control efficacy and biodegradation characteristics of imazethapyr
Author(s):Cantwell, John Robert
Doctoral Committee Chair(s):Liebl, Rex A.
Department / Program:Crop Sciences
Discipline:Crop Sciences
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:Ph.D.
Genre:Dissertation
Subject(s):Agriculture, Agronomy
Abstract:The soybean herbicide imazethapyr (2-(4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl) -5-ethyl-3-pyridinecarboxylic acid) was evaluated in the field for weed control in soybean (Glycine max) during 1985 and 1986. Imazethapyr at 0.05, 0.07, 0.10, and 0.14 kg ai/ha was applied preplant incorporated (PPI), preemergence (PRE), or postemergence (POST). Imazethapyr controlled 90% or more smooth pigweed (Amaranthus hybridus) regardless of application method or herbicide rate. Imazethapyr control of jimsonweed (Datura stramonium) at 0.5 kg/ha was 30% better POST compared to soil applications. Imazethapyr at 0.10 kg ai/ha controlled 90% or more velvetleaf (Abutilon theophrasti) regardless of application method.
Biodegradation of $\sp{14}$C-imazethapyr and $\sp{14}$C-imazaquin (2- (4,5-dihydro-4-methyl-4-(1methylethyl)-5-oxo-1H-imidazol-2-yl) -3-quinolinecarboxylic acid) in soil was measured in an invitro system which allowed 90% recovery of applied herbicide. Triallate, (S-(2,3,3,-trichloroallyl) diisopropylthiocarbamate was used as a standard. Herbicide degradation was compared on two soils, a Cisne silt loam with 14% sand, 74% silt, 12% clay, 1.3% organic matter, and cation exchange capacicity (CEC) of 12 meq/100g, and a Drummer silty clay loam with 9% sand, 57% silt, 34% clay, 5.8% organic matter, and a CEC of 40 meq/100g. Herbicide degradation in gamma radiation sterilized soil was compared to fresh soil. $\sp{14}$CO$\sb2$ evolution, extractable parent, metabolites, and inextractable residue were measured. After 12 weeks of incubation, 95% of the radioactivity could be extracted as parent from sterilized soil. Imazaquin and imazethapyr degraded at a similar rate in unsterilized soil which was dependent upon soil type. All herbicides degraded slower in the Drummer soil, however triallate degraded 2-3 times faster than the imidazolinones on either soil. Evolution of $\sp{14}$CO$\sb2$ from an imazethapyr treated Cisne soil, containing a serial dilution of activated charcoal, demonstrated that adsorption of herbicide was negatively correlated with degradation. Therefore the amount of herbicide in soil solution as determined by soil characteristics will regulate imidazolinone microbial degradation.
Issue Date:1989
Type:Text
Language:English
URI:http://hdl.handle.net/2142/21435
Rights Information:Copyright 1989 Cantwell, John Robert
Date Available in IDEALS:2011-05-07
Identifier in Online Catalog:AAI8916220
OCLC Identifier:(UMI)AAI8916220


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