Herbicidal efficacy of 4-ethyl-3-(3-fluorophenyl)-1-(3-trifluoromethylphenyl)pyrrolidin-2-one (MT-141) in the control of graminaceous and broad-leaved weeds in cotton
Journal of pesticide science
Diphenylpyrrolidinones have been reported to cause bleaching in plants.    The mechanism of bleaching was shown to be the inhibition of phytoene desaturase (PDS), 4) by using a cell-free assay with plant-type PDS prepared from cloned Escherichia coli transformants. 5,6) PDS, which catalyzes the dehydrogenation of phytoene to zetacarotene, is the major target enzyme of herbicides in the carotenoid biosynthesis pathway. The structural requirements of substituents on the
... e diphenylpyrrolidinone molecule for interaction with PDS were determined by enzyme kinetic studies. 4, 7, 8) The study of enzyme kinetics also revealed a non-competitive inhibition of diphenyl-pyrrolidinones with respect to the substrate phytoene, and competitive inhibition of the cofactor NADP ϩ , suggesting an interaction of diphenylpyrrolidinones at the cofactor-binding site of PDS. 4) PDS inhibitors such as norflurazon, fluridone, fluorochloridone, diflufenican and flurtamone are commercial herbicides. 9) The PDS-inhibitoty activity for some of these herbicides was determined 4) ; pI 50 ϭ6.82 for norflurazon, pI 50 ϭ7.55 for diflufenican and pI 50 ϭ6.06 for fluorochloridone. Herbicidal usages of these compounds are as follows 9) : Norflurazon is used pre-emergence (PRE) at 1-8 kg a.i./ha to control annual grasses and broadleaved weeds in cotton and soybeans; Fluridone and fluorochloridone are applied PRE at 0.3-0.6 and 0.5-2 kg a.i./ha, respectively, to control annual weeds in cotton; Diflufenican is used at 0.125-0.25 kg a.i./ha PRE or early post-emergence (EPOST) in cereals to control grass and broadleaved weeds; and flurtamone is applied PRE or EPOST The herbicidal activity and properties of a diphenylpyrrolidinone, MT-141 [4-ethyl-3-(3-fluorophenyl)-1-(3-trifluoromethylphenyl)pyrrolidin-2-one], were examined. MT-141 controlled barnyardgrass (Echinochloa crusgalli), johnsongrass (Sorghum halepense), green foxtail (Setaria viridis), large crabgrass (Digitaria sanguinalis), fall panicum (Panicum dichotomiflorum), goosegrass (Eleusine indica), and broadleaf signalgrass (Brachiaria platyphylla) at 300 g a.i./ha when applied pre-emergence (PRE), and provided greater than 90% control of these weed species at 500 g a.i./ha when applied post-emergence (POST). MT-141 was less effective against broadleaved plants such as velvetleaf (Abutilon theophrasti ) and ivyleaf morningglory (Ipomoea hederacea), but two other broad-leaved plants, hemp sesbania (Sesbania exaltata) and prickly sida (Sida spinosa), were slightly susceptible to MT-141. MT-141 applied PRE at 500 g a.i./ha did not injure cotton. The most significant herbicidal symptom for this compound was bleaching. Residual activity of MT-141 applied PRE to barnyardgrass and johnsongrass lasted at least 5 weeks. Planting depth or soil type did not affect the herbicidal activity of MT-141 at 300 g a.i./ha. MT-141 applied PRE increased the herbicidal activity of glyphosate against hemp sesbania and morningglory without injuring glyphosate-resistant cotton. Also several surfactants increased the herbicidal efficacy of this compound on POST application. MT-141 seems to be an effective herbicidal compound for controlling graminaceous weeds when applied PRE in cotton production.