Vol. 51—1997 - NorthEastern Weed Science Society

116
RESULTS AND DISCUSSION
GI fosinate provided rapid bumdown of all of the weeds in the treated areas (Table 1).
There was ittle regrowth in these areas, even where glufosinate alone was used. There was
apparently orne herbicide residue in this area from prior applications by the Pennsylvania
Departme of Transportation. No conclusions can be reached on the effectiveness of the
preemerge ce herbicides used in this part of the study.
Ini 'ally, all of the treatments including glyphosate provided good to excellent control of all
weeds. H wever, by August 22 it appeared that applying glyphosate prior to the treatments
containing oxyfluorfen resulted in better control than applying glyphosate and oxyf1uorfen
together. he rating on October 24 confirmed this. The oxyfluorfen must injure the weed foliage
before the lyphosate can be absorbed and translocated. Perennial weeds were burned down by
the combi ation, but were able to regrow if the oxyfluorfen interfered with the activity of the
glyphosat .
In is study, adding thiazopyr to the oxyfluorfen did not consistently improve the level of
preemerge ce weed control obtained. In the area to which glyphosate was applied prior to
treatment, xyfluorfen alone or in combination with thiazopyr provided better control than the
glyphosat alone. The control provided by thiazopyr at O:Slb/aalone was no better than that
provided glyphosate alone. Thiazopyr at 1.0 and 2.0 lb/a alone provided a level of control
between g phosate alone and the treatments including oxyf1uorfen
Th roadside environment is extremely variable. Soils are mixed, gravel and grit are added
in variable amounts, and highly active, long residual herbicides are periodically added. In
addition, wide mixture of annual and perennial weeds may be present. Several years of testing
on a varie of sites is necessary to determine the suitability of a herbicide for use along roadsides.