Vol. 51—1997 - NorthEastern Weed Science Society

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I 41
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EFFECT OF fSOXABEN APPLIED POSTEMERGENCE FOR BROADLEAF WEED
CONTROL
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Rakesh S. Chandran I and Jeffrey F. Derr
Broadf af weed control continues to be an important aspect of turfgrass
management. soxaben, used primarily as a preemergence (PRE) broadleafherbicide,
was recently r ported to possess postemergence (POST) activity on certain broadleaf
weeds pertine t to agronomic crops. Two greenhouse experiments were conducted to
determine the OST activity ofisoxaben on dandelion (Taraxacum officinale Weber.),
white clover (, rifolium repens L.), buckhorn plantain (Plantago lanceolata L.), common
yellow wood~rrel (Oxalis stricta L.), common lespedeza (Lespedeza striata Thunb.),
black medic ( edicago lupulina L.), spotted spurge (Euphorbia maculata L.), and
Florida beton, (Stachys floridana Shuttlew.). Isoxaben applied at 0.56, 1.12, and 2.24 kg
ai/ha, and a 3 way tank mix of isoxaben, 2,4-0 amine, and dicamba at 1.12, 1.12, and
0.37 kg/ha, re pectively, were compared to a 2-way tankmix of 2,4~D amine plus
dicamba at 1. 2 and 0.37 kg /ha, for broadleafweed control. Percent reduction in
regrowth ofF orida betony following shoot harvest wasalso assessed. Isoxaben applied
POST at all r es provided poor to no control of all the weed species mentioned above,
except Flori betony, based on weed control ratings taken 3 weeks after treatment
(WAT) and soot fresh weights taken 6 WAT. Florida betony control increased with
increasing ra1s ofisoxaben, ranging from 40% control at 0.56 kg/ha to 75% control at
2.24 kg/ha, I oxaben at 2.24 kg/ha reduced Florida betony shoot regrowth by 90%. The
combination f2,4-D plus dicamba gave at least 75% control of white clover, lespedeza,
black medic, d dandelion in both studies based on control ratings taken 3 WAT.
However, thi treatment gave poor to fair control (10-60%) of yellow woodsorrel and
spotted spurg . The 3-way tankmix ofisoxaben with 2,4-0 and dicamba exhibited a
complemen effect, numerically improving control of common lespedeza, buckhorn
plantain, yell w woodsorrel, Florida betony, and dandelion by 13, 12, 11,9 and 8%,
respectively, ompared to 2,4-D plus dicamba applied alone. Although isoxaben is not
effective as a OST herbicide for the weed species studied in this experiment, the effect
of tankmixin this herbicide with growth regulator type herbicides may prove beneficial
for POST an PRE broadleaf weed control.
I Grad. Res. sst., Dept. of Plant Pathol., Physiol., and Weed Sci., VPI&SU, Blacksburg,
VA 24061, Visiting Scientist, Dept. of Plant Sci., Rutgers Univ., New Brunswick, NJ
08903