Vol. 51—1997 - NorthEastern Weed Science Society

E
OF PRE AND POSTEMERGENCEHERBICIDESFOR EASTERNBLACK
GHTSHADE (SolanumptycaothuroDun.) CONTROLIN SOYBEANS
E. L. Werner, W. S. Curran, J. O. Yocum and M. J. VanGessel l
ABSTRACT
-long control of easternblack nightshade(SolanumptycantbumDun.) has been
sporadicemergenceand the lack of effectivesoybean(Glycine.m.M)herbicides.
ucted at Penn Stateon currentavailableandexperimentalherbicidesfor the control
k nightshademay give producersadded options.
Sm plot field research was conductedin southeasternPennsylvaniain 1995and 1996
and Townse d, Delawarein cooperationwith the Universityof Delawarefor the 1996growing
season. Soy s were planted to 30 inch rows for the southeasternPA locationsand in drilled
rowsin DE. mergencetreatmentswere appliedshortlyafter plantingwith a CO 2 backpack
sprayer. In 1 5, postemergencetreatmentswere appliedwhen nightshadewas 1 to 2 inches in
height In 1 6, early postemergencetreatmentswere appliedwhen nightshadewas less than 1
inchtall, whi e postemergencetreatmentswere appliedat 2 inchesor greaterin height. Crop
phytotoxicit ,visual weed control ratings,crop yield, and easternblack nightshadebiomassand
berry produc .on were measured. Greenhouseresearchwas conductedto evaluate the efficacyof
severalcorn d soybean herbicides,and to supporteastern black nightshadefield studies.
Field studies indicatedthat applicationtiminghad no effect in southeasternPA, howeverin
DE, betterc ntrol was achievedwith the early postemergenceapplication. The lack of control
from the late post treatmentswas probablydue to early canopyclosure and poor spray coverage
from the late treatment. Lactofen,acitluorfen,imazethapyr,and fomesafenofferedthe most
consistents on-longnightshadecontrol of all the postemergenceherbicidesexamined.
ChIorimuro + thifensulfuronofferedlittle to no controlat all locations,howeverthe additionof
lactofenoffe excellentseason-longcontrol.
Res ts with preemergencetreatmentswere variablebetweenstudy years and locations. In
1995,meto hlor, alachIor,dimethenamid,sulfentrazone,imazethapyrand tluamide +metribuzin
all gave 90 100%control by the end of the season. Imazaquin,chlorimuron+metribuzinand
tluamide all ffered 80 to 90% control In 1996at the southeasternPA location,metolachlor,
sulfentrazon and imazethapyrprovided80 to 90% controlby the end of the season. All other
preemergen e herbicidestested had less than 50% control. No soybeaninjurywas observedat the
PA location. Early seasonratingsfor the DE locationindicatedexcellentnightshadecontrolwith
all preemer nce herbicidestested,however,CGA277102ll,dimethenamidand chlorimuron+
metribuzin vided only 60 to 80% control.Due to the sandysoils at this site, significantsoybean
injury was 0 served with severalpreemergenceherbicides.
R ch at Penn Stateindicatedthat postemergenceherbicideswereoverallless active
under green ouse conditions. Ratings 1WAA indicatedactivitywith most of the herbicides,
however,d weights 3 WAA indicatednightshaderegrowthfor most of the treatments. Results
from the p mergence greenhousestudy supportfield studieswith sulfentrazone,metolachlor,
dimethen id and alachlorproviding80 to 100%control 8 WAA. However,some herbicides
inclndingi azethapyrand imazaquinwere not as active undergreenhouseconditions.
I Res. Tech, Assoc. Prof. of Weed Science and Senior Res. Assoc., respectively,Dept. of
Agron., Th Pennsylvania State University,UniversityPark, PA 16802and Asst. Prof. of Weed
Science,U iversityof Delaware, Georgetown,DE 19947.