Vol. 51—1997 - NorthEastern Weed Science Society

28
METRIBUZIN COMBINA nONS FOR POSTEMERGENCE
VELVETLEAF CONTROL IN FIELD CORN
Russell R. Hahn!
ABSTRACT
Fie d experiments were conducted in 1993, 1994, and 1996 to compare postemergence
herbicides one and in combination with 1.5 oz ailA metribuzin for velvetleaf (Abutilon
theophrasti Medicus) control in field com (Zea mays L.). Herbicides were applied to lO-by 25-ft
plots usin 80015 flat spray tips in 25 gpa of spray solution in 1993 and 1994 and using 8002 flat
spray tips' 22 gpa of spray solution in 1996. Other annual weeds were controlled with
preemerge ce applications of metolachlor at 1.5 or 2 Ib ailA. A randomized complete block
design wi four replications was used for each experiment.
Ex eriments in 1993 and 1994, in Columbia and Livingston counties respectively,
compared .251b ai/A ofbromoxynil, 0.251b ae/A of2,4-D amine or 2,4-D ester, and 0.251b ai
of dicamb alone and with metribuzin. Treatments were applied early postemergence (EPO)
when velv tleaf was in the 2-to 4-leaf stage both years and mid-postemergence (MPO) when
velvetleaf as in the 4- to 6-leafstage in 1994. The metribuzin combinations provided better
velvetleaf ontrol than the other herbicides applied alone in both years. Velvetleaf control with
bromoxyn I averaged 83% for the two years while the combination with metribuzin improved
control to 7%. The addition ofmetribuzin increased control from 17 to 89% for 2,4-D amine
applied E O. The 2,4-D ester and dicamba provided 63 and 59% control when applied alone and
95 and 94 0 control respectively when applied with metribuzin. MPO applications of
bromoxyn I or 2,4-D ester in combination with metribuzin did not provide better velvetleaf
control when applied alone. The addition of metribuzin increased control from 50 to 85%
and from 5 to 96% with 2,4-D amine and dicamba respectively when applied MPO.
In 996 at the Livingston county site, EPO (cotyledon to 2-leaf velvetleaf) application of
0.251b/A f2,4-D ester alone and with metribuzin resulted in 65 and 75% velvetleaf control
respective y compared with 86 and 99% control for EPO applications of 0.5 lblA of dicamba or
1.5 lb ail of pendimethalin plus lIb ailA of atrazine respectively. MPO (4- to 6-leaf ve1vetleat)
app1icatio of 0.25 Ib/A ofbromoxynil alone and with metribuzin controlled 87 and 97% of the
velvetleaf espectively. MPO application ofO.25lb/A of dicamba controlled 57% of the
velvetleaf hile the combination with metribuzin controlled 97% of the velvetleaf. Little or no
com inj was observed in the three experiments previously discussed, however, there was
significan injury for some of the metribuzin combinations in Columbia County when applied at
the V4 sta e of com in 1996. The combination of 0.25 lblA of bromoxynil with metribuzin
caused 20 0 stunting and 10% chlorosis when evaluated 9 days after treatment. The combination
of 0.25 lb of dicamba plus metribuzin caused 7% stunting but no chlorosis.
'Assoc. P of., Dept. of Soil, Crop and Atmospheric Sci., Cornell Univ., Ithaca, NY 14853.