Vol. 51—1997 - NorthEastern Weed Science Society

120
B USB CONTROL PROVIDED BY LOW VOLUME FOUAR APPLICATIONS
Jon M. Johnson, Chad W. Spackman, and Larry J. Kuhnst/
ABSmCf
of a cooperative research project between The Pennsylvania State University and The
ia Department of Transportation, a study evaluating brush control provided by the
ine salt of dicamba (dicamba) alone and in combination with other herbicides was
establish along SR 219 near Ebensburg, PA on September I, 1995. Dicamba was applied alone
at rates of .5 and 2.0 lb/a; in combination with triclopyr1J , imazapyr, and glyphosate; and
compared 0 glyphosate, and fosamine ammonium (fosamine) plus imazapyr (Table 1). Thinvertv
was used' three of the treatments as a carrier instead of water. The plots were approximately 20
by 50 ft, ged in a randomized complete block with three replications. A CO2-powered
backpack prayer equipped with a handgun and a Spraying Systems #5500 Adjustable ConeJet
with a X- tip, operating at 20 psi was used to approximate an application volume of 20 gal/a for
the aqueo s treatments. The Thinvert treatments were applied with the same apparatus except for a
change to Thinvert 71031 tip. All aqueous treatments included a surfactant" and a drift control
agents/ at .125 and 0.25 percent vlv, respectively. Each plot contained several tree species in the
3 to 10 ft eight range with a few up to 15 ft, The predominant species were red maple (Acer
rubrum ), black cherry (Prunusserotina Ehrh.), quaking aspen (PopulustremuloidesMichx.),
white oak Quercusalba L.), red oak (Quercusrubra L.), green ash (Fraxinuspennsylvanica
Marsh.), d staghorn sumac (Rhus typhina L.). Visual ratings of foliar necrosis were taken
Septembe 15, 1995, 14 days after treatment (OAT). Visual ratings of tree injury were taken
August 1 , 1996 (347 DAT). Average tree injury results are reported in Table 1.
Green ash, staghom sumac and a few less notable species are not included on Table 1 due to
lack of sp ceo The average total tree injury rating on the far right side of the table includes these
tree speci s in the statisical analysis, however. Table 1 includes a T Grouping for determining
which tments are statistically different Analyzing the datawith unequal replication made
providing LSD values impractical.
The tments including glyphosate caused the most foliar necrosis 14 DAT. The treatments
providing the highest average tree injury ratings 347 DATwere the 2.00 lb/a dicamba plus 0.25
lbla i pyr, 1.5 lb/a dicamba plus 0.38 lb/a imazapyr in Thinvert, 2 lb/a glyphosate, 3.0 lb/a
fosamine Ius 0.15 lb/a imazapyr, and dicamba at the 2 lb/a rate in combination with glyphosate at
1.5 lblac. Although dicamba alone was significantly better than the untreated check, it did not
provide s tisfactory results.
Two f the three dicamba plus imazapyr combinations evaluated in this trial provided
satisfacto first year injury ratings, but used relatively high rates of imazapyr. Due to the soil
activity 0 imazapyr, combinations with dicamba using lower rates of imazapyr need to be
evaluat to most efficiently use this combination on rights-of-way.
11Project ssistant, Research Technologist, and Professor of Ornamental Horticulture, respectively, The
Penns lvania State University, University Park, PA 16802
21Garlon A, triethanolamine salt oftriclopyr, 3 lb ae/gal, DowElanco, Indianapolis, IN.
3/ Thinve Waldrum Specialties, Doylestown, PA.
4/ QwikW t 357, Exacto Chemical Co., Richmond,!L.
5/ Fonnu 358, Exacto Chemical Co., Richmond, IL.