Vol. 51—1997 - NorthEastern Weed Science Society

108
CGA-77102: A New Herbicide for Preemergence Weed Control
in Corn and Soybeans
. B. Vitolo, M. G. Schnappinger, T. A. Bauer, B. S. Manley, and S. W. Pruss 1
ABSTRACT
CGA-77102, the S-chiral isomer of metolachlor, is a new acetamide herbicide
being eveloped by Ciba Crop Protection for preemergence grass and broadleaf weed
contro in com (Zea mays L.) and soybeans (Glycine max L.). Metolachlor is an
acet .de herbicide first registered for use in com by Ciba-Geigy Corp. in November,
1976. Since then, it and various formulations of Dual and Bicep brand herbicides have
contin ed to grow in use. Metolachlor is currently the second highest volume herbicide
used' the u.s. Metolachlor is a mixture of isomers, and these isomers, depending on
their nfigurations, can be grouped into R- and S- forms. The majority of the herbicidal
activi ofmetolachlor comes from the S-isomer, designated CGA-77102, while the R­
isome is relatively inactive. Synthesis technology now allows for the selective
produ tion of the active isomer.
Replicated field trials were conducted in New York, Maryland, Pennsylvania,
Ohio, d Indiana from 1994-1996 to evaluate efficacy, duration of activity and crop
toler ce across soil types on yellow nutsedge (Cyperus esculentus L.), and a wide range
of grass and broadleafweeds. These trials, and others conducted across the U.S.,
show an equivalency of CGA-77102 to metolachlor at a ratio of 0.625:1. Com
tole ce trials utilizing rates up to four times the normal use rate were conducted to
dete ine the optimum CGA-77102:benoxacor ratio. These trials indicated a ratio of
20: 1, hich utilizes the same benoxacor rate per acre as in the current Dual II and Bicep
II br ds.
1Res arch Station Manager, Senior Scientist, Senior Research Representative, Research
Repr sentative and Regional Research Manager, respectively, Ciba Crop Protection,
Huds n, NY, 12534