Vol. 51—1997 - NorthEastern Weed Science Society

55
ISOXAFL
OLE COMBINATIONSWITH PREEMERGENCEHERBICIDES FOR
ANNUALWEEDCONTROLIN FIELD CORN
Frank J. Himmelstein, Robert J. Durgy 1
ABSTRACT
Isoxaf utole (Balance) has been shown to be an effective
weed contro option in Connecticut field corn (Zea mays L.)
trials. Two 1996 field trials conducted in Bolton and Lebanon, CT
evaluated s ven preemergence herbicides applied alone and in
combination with isoxaflutole. The studies were split plot
designs wit three replications. The main plots were isoxaflutole
applied at .75 and 1.5 oz ai/A and the preemergence herbicide
(PRE)treatm nts applied alone. The sUb-plot treatments and
applied rat s were: thiafluamide + metribuzin [(Axiom) 0.32 and
0.64 lb ai/ ], metolachlor [(Dual II) 1 and 2 lb ai/A],
dimethenami [(Frontier) 0.59 and 1.17 lb ai/A], acetochlor
[(Harness) .88 and 1.75 lb ai/A], alachlor [(Lasso MT) 1 and 2
lb ai/A], a etochlor + safener [(Surpass) 0.9 and 1.8 lb ai/A],
and pendime halin [(Prowl) 0.75 and 1.5 lb ai/A]. Herbicides were
applied wit a C02 backpack sprayer delivering 20 gpa at 32 psi.
Weed contro was assessed by visual ratings, and weed biomass
samples tak n from a 2.25 ft 2 quadrat from the center of each
plot. Weed pecies included common lambsquarters [Chenopodium
album L.], edroot pigweed CAmaranthus retroflexus L.), common
ragweed ( rosia artemisiifolia L.], velvetleaf (Abutilon
theophrasti Medik.) and giant foxtail [Setaria faberi Herrm.].
Common ragw ed was the dominant weed at the Bolton site.
Excellent c mmon ragweed control was obtained with the
isoxaflutol treatment combinations as indicated by the weed
ratings and weed biomass samples taken 53 and 90 OAT,
respectivel • Average common ragweed dry matter yields were
reduced 99% with the isoxaflutole combinations, and 5% for the
PRE treatme ts compared to the check. Giant foxtail and redroot
pigweed wer the dominant weeds at the Lebanon site, however,
velvetleaf, common lambsquarters, and common ragweed proliferated
where these weeds were controlled. Weed ratings taken 36 OAT
indicated t e isoxaflutole treatment combinations resulted in
greater co rol (>90%) of all five weed species compared to the
PRE treatme ts alone. Average control of giant foxtail,
velvetleaf, common lambsquarters, redroot pigweed and common
ragweed wi the PRE treatments alone was 85%, 24%, 35%, 73% and
12% respectively. Weed biomass samples taken 79 OAT indicated
there were 0 significant differences in the average giant
foxtail an redroot pigweed biomass between the isoxaflutole
treatment mbinations and the PRE treatments alone. The average
velvetleaf, common lambsquarters, and common ragweed biomass was
significan ly greater for the PRE treatments alone compared to
the isoxafl tole treatment combinations. Isoxaflutole shows great
promise fo broadspectrum weed control alone and in combination
with reduc rates of other preemergence herbicides.
Extension ducator-Integrated Crop Management, and Res. Asst.,
respectivel , University of connecticut, Storrs, CT 06269