Vol. 54—2000 - NorthEastern Weed Science Society

WEED CONTROL PROGRAMS WITH GLUFOSINA TE- AND
GLYPHOSATE-RESISTANT FIELD CORN
P.J. Stachowski and R.R. Hahn'
ABSTRACT
Field experimentswere establishedin 1999to evaluatethe effect of applicationtimingof
glufosinateandglyphosatetreatmentson weedcontrolandcom (Zea mays L.) yields andto
evaluate the effect of residual herbicides with glyphosate. A preemergence (PRE) standard of s­
metolachlor/atrazineplus pendimethalinwasappliedin all experiments. Applicationsof 1.34tb
ailA of glufosinatelatrazine (Liberty ATZ) were made early, mid- and late postemergence
(EPOST, MPOST, and LPOST) at one location. Glyphosate applications of lib ailA were made
EPOST, MPOST, and LPOST at threelocations. In addition, EPOST applications of glyphosate
weremadein combinationswith residualherbicides.
All glufosinatelatrazine applications provided excellent (94%+) velvetleaf (Abuti/on
theophrasti Medicus) and green foxtail (Setaria viridis (L.) Beauv.) control except the MPOST
applicationwhichcontrolled65%of thevelvetleaf. Controlof velvetleaf andgreenfoxtailwas
only 9 and 33% respectively with the PRE standard due to limited rainfall for herbicide
activation. With limited rainfall throughout the season, silage com yields with the EPOST,
MPOST, and LPOST glufosinatelatrazine applications were only 10.1, 8.I and 6.9 T/A
respectively. The PRE standard yielded 6.3 T/A and the untreated check 3.3 T/A. Although
application timing in an adjacent glyphosate-resistant com experiment planted the same day
affected velvetIeaf control, it did not affect green foxtail control or grain com yields. In a second
experiment planted 10 days later, velvetleaf control was 96, 80, and 47% for the EPOST,
MPOST, and LPOST glyphosate applications respectively. Green foxtail control was 94, 98, and
30% and com yields were 108,98, and 44 buiA respectively. By compatison, the PRE standard
controlled 60 and 89% of the velvetIeaf and foxtail respectively and yielded 91 bu/A. The yield
from the untreated check was 20 bulA. An experiment with heavy velvet1eaf and redroot
pigweed (Amaranthus retroflexus L.) pressurewas conductedwith glyphosate-resistantcom.
Velvetleaf and pigweed control were 60 and 90'/0 respectively with the PRE standard. The three
POST glyphosate applications controlled an average of 97 and 96% of the velvet1eaf and
pigweed respectively. The average yield for the threeglyphosate treatments was 181 bulA
compared with 173 and 107 bulA for the PRE standard and untreated check respectively.
Finally, in an experiment with triazine-resistant common lambsquarters (Chenopodium album L.)
and fall panicum (Panicum dichotomiflorum Michx.) control averaged 97 and 98% respectively
for the three POST glyphosate treatments compared with 89 and 97% respectively for the PRE
standard.Therewere no significantdifferencesincom yield amongthese treatments. The
addition of residual herbicides to EPOST glyphosate treatments had little impact on weed control
ratingsor graincom yields inthese experiments.
'Res. Supp. Spec. and Assoc. Prof., Dept. of Crop and Soil Sci., Cornell Univ., Ithaca, NY
14853.
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