Vol. 51—1997 - NorthEastern Weed Science Society

106
C MMONRAGWEEDCONTROLIN FIELD CORNWITH PREEMERGENCE
HERBICIDES
Frank J. Himmelstein, Robert J. Durgy 1
ABSTRACT
Co on ragweed [Ambrosia artemisiifolia L.] infestations
have i reased in field corn [Zea mays L.] in Connecticut where
triazi herbicide use has been reduced or eliminated and
resist ce to these herbicides may have occurred. A field study
conduc d at the Plant Science Research Farm in Storrs, CT. in
1996 e aluated seventeen preemergence herbicide treatments for
common agweed control in field corn. The experimental design was
a spli plot with three replications. The main plots were
pendim thalin (Prowl) applied at 0 and 0.75 lb ai/A. The subplots
reatments and applied rates were: thiafluamide +
metrib zin (Axiom) at 0.64 lb ai/A, isoxaflutole (Balance) at 1.5
oz ail , metolachlor + atrazine (Bicep) at 2.7 lb ai/A,
metola hlor + atrazine (Bicep Lite) at 2.25 lb ai/A, alachlor +
atrazi e (Bullet) at 3.0 lb ai/A, dimethenamid + atrazine
(Guard man) at 2.19 lb ai/A, acetochlor (Harness) at 1.75 lb
ai/A, cetochlor + atrazine (Harness xtra 6.0) at 2.75 lb ai/A,
acetoc lor + atrazine (Harness xtra 5.6) at 2.5 lb ai/A, microencaps
lated alachlor (Lasso MT) + atrazine at 2.0 and 0.75 lb
ai/A r spectively, micro-encapsulated acetochlor (MON8414) at
1.75 I ai/A, imazethapyr (Pursuit) at 0.063 lb ai/A, acetochlor
+ safe er (Surpass) at 1.8 lb ai/A, acetochlor + safener +
atrazi e (Surpass 100) at 3.0 lb ai/A, micro- encapsulated
acetoc lor + safener (Topnotch) at 1.8 lb ai/A, pendimethalin +
atrazi e at 1.5 and 1.0 lb ai/A respectively, and pendimethalin +
cyanaz'ne (Bladex) at 1.5 and 1.0 lb ai/A respectively.
Herbic'des were applied with a CO 2 backpack sprayer delivering 20
gpa at 32 psi. Weed control was assessed by both visual ratings,
and we d biomass samples taken from a 2.25 ft 2 quadrat from the
center of each plot. Field corn 'pioneer 3395 IR' was planted on
June 5 1996. Herbicide treatments were applied on June 6, 1996.
Weed b'omass samples taken 70 OAT indicated there were no
signif cant differences in ragweed control between the main
effect • The Pursuit treatments resulted in poor ragweed control
«50%) The Bicep Lite and Axiom treatments resulted in
unacce table ragweed control (60-65%). The Prowl + atrazine,
Prowl Bladex, and Bicep treatments resulted in fair ragweed
contro (75-85%). The Lasso + atrazine, Harness, Balance, Mon
8414, ullet, Surpass, Guardsman, Topnotch, Surpass 100, and
Harnes xtra treatments resulted in excellent ragweed control
(>90%) The use of several acetolchlor formulations or
isoxaf utole alone provided effective common ragweed control and
may re uce dependence on triazine herbicides for weed control in
areas here either triazine herbicide use rates must be reduced
or eli inated entirely, and where common ragweed resistance to
triazi e herbicides have occurred.
Exten ~on Educator-Integrated Crop Management, and Res. Asst.,
respec ively, University of connecticut, Storrs, CT 06269.