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Agriculture, Agronomy Weed control efficacy and biodegradation characteristics of imazethapyr text Liebl, Rex A. Cantwell, John Robert 2011-05-07T13:08:34Z 2011-05-07T13:08:34Z 10000-01-01 1989 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. Made available in DSpace on 2011-05-07T13:08:34Z (GMT). No. of bitstreams: 2 license.txt: 4922 bytes, checksum: 910b249b4beec47e7ab768910c8f966f (MD5) 8916220.pdf: 1318936 bytes, checksum: ce449f7a1871d3ed7f06cf020c42f425 (MD5) Previous issue date: 1989 Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Howard Ding (hding2@illinois.edu) on 2011-05-07T14:50:45Z Item is restricted indefinitely. Restriction data tranferred 2014-07-01T11:23:13-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: ETDs are only available to UIUC Users without author permission ETDs are only available to UIUC Users without author permission U of I Only AAI8916220 (UMI)AAI8916220 http://hdl.handle.net/2142/21435 eng Copyright 1989 Cantwell, John Robert Crop Sciences Crop Sciences University of Illinois at Urbana-Champaign Dissertation Ph.D.