Oxadiazon Applied as a Pre-Emergence
for Poa Annua with Reference to
Fall Overseeding of Bermudagrass Turf
D.M. Kopec and J.J. Gilbert
Abstract
Ronstar was applied at three rates (1.0, 2.0 and 4.0 lbs. AI/A) at 12, 10, 8, 6 and 4 weeks before
overseeding bermudagrass turf with perennial ryegrass on October 20, 1997. On November 7, 1997
(18 DAS) Ronstar treated plots ranged from 20% to 81% for percent plot ryegrass coverage. The
greatest mean ryegrass coverage occurred for the 2.0 lbs. rate/@ 12 WBOS. Among the 4 lbs.
treatments, there was more or less a linear decrease for ryegrass establishment on a visual plot basis
as the application time came closer to the overseeding date. On December 1, Ronstar treated field
plots ranged from a low of 29% ryegrass cover (4 lbs./@ 4 WBOS) to 91% (2 lbs./ @ 12 WBOS).
Among the 4 lbs. treated plots, the 10 and 12 WBOS timing allowed for 82% and 75% mean plot cover
respectively, by December 1 (42 DAS). Of the remaining treatments, the 2 lbs./ @ 4 WBOS had 61%
plot cover (ryegrass) while all other 1 lbs. and 2 lbs. plots had 80% or greater cover at this time. On
December 15, 1997 (56 DAS), mean percent plot scores for percentage ryegrass cover ranged from
53% to 100%. The only plot which had significantly less plot cover was 4 lbs./ @ 4 WBOS (53%). All
other plots had 88% or greater ryegrass cover. Turfgrass color scores showed a significant
Atreatment@ effect on December 15, but not on December 29, January 29, March 11 or on April 11. On
December 29 (70 DAS), overall turfgrass quality scores ranged from 4.0 (unacceptable) to 7.8. Two
treatments which were sub-par included 4 lbs./ @ 6 WBOS (5.7 = marginal) and 4 lbs./ @ 4 WBOS
(4.0 = unacceptable). Treatments which had mean quality values of 7.0 or higher included; 1 lbs./ @
10 WBOS (7.8), 1 lbs./ @ 6 WBOS (7.8), 2 lbs./ @ 10 WBOS (7.5), 1 lbs./ @ 8 WBOS (7.3), 2 lbs./ @ 6
WBOS (7.3), 4 lbs./ @ 12 WBOS (7.3) and 2 lbs./ @ 12 WBOS (7.3).
Weed pressure was inadequate to fully assess pre-emergence control of Poa annua. At the close of the
test on April 11, 1998, weed control ranged from 8% to 100%. Plots with 90% or greater weed control
included 2 lbs./@ 10 WBOS, 1 lbs./@ 4 WBOS, and 4 lbs./@ 12, 8, 6, and 4 WBOS. The 1.0 lbs. AI/A
treatment was safe for perennial ryegrass at 12, 10, 8, 6, and 4 WBOS. The 2.0 lbs. AI/A treatment
was safe for perennial ryegrass at 12, 10, and 8 weeks. The 4.0 lbs. AI/A treatment was safe at 12 and
10 WBOS.
Introduction
Annual bluegrass (Poa annua) is a cosmopolitan and perhaps the most troublesome cool season grassy weed in turfgrass
systems. Its control is limited by herbicide tolerances of the desired turfgrass species, application timing, or both. As a
prolific seed producer under closely mowed turf management programs, annual bluegrass is best controlled by consistent
yearly applications of pre-emergence herbicides when and where applicable. A ten month test was conducted to evaluate
the effectiveness and safety of oxadiazon (Ronstar) applied as a pre-emergence herbicide coupled with a standard early
fall overseed program on desert golf course turf (perennial ryegrass over bermudagrass). The test was designed to
measure the effects of application rates and timing data on weed control efficacy and acceptability of overseeding
establishment and turf performance.
Materials and Methods
A common bermudagrass area known to have large infestations of Poa annua was selected for the test site at Moon
Valley Golf Course in Phoenix, Arizona. The area selected was 100% common bermudagrass adjacent to a fairway.
_____________________________
This is a part of the University of Arizona College of Agriculture 2001 Turfgrass and Ornamental Research Report,
index at: http://ag.arizona.edu/pubs/crops/az1246/
Treatments included three application rates as 1.0, 2.0 and 4.0 lbs. AI/A of Ronstar 2G. (Treatments are hereby referred
to as lbs./A). Treatments were applied to separate plots at the following intervals: 12 weeks, 10 weeks, 8 weeks, 6 weeks
and 4 weeks before overseeding with perennial ryegrass (WBOS). The first application date was July 25, 1997 and the
last was on September 19, 1997. Overseeding took place on October 20, 1997.
Plot size was 5'x10'. Each plot received the respective Ronstar treatment by use of a calibrated Gandy 2.5' drop spreader.
Plots were irrigated before the next mowing event occurred. The turf was mowed at 2.0 inches 2-3 times weekly using a
triplex mower with clippings returned to the plots. The turf was overseeded at the rate of 16 lbs./1000 ft2 after being
double scalped with a reel mower with clippings removed. After seed was dropped, the plots were uniformly topdressed
with 1/4 inch of washed topdressing sand and irrigated for germination.
Plots were evaluated for germination and establishment (percent ryegrass cover, relative vigor, visual density, turfgrass
performance of color, quality and vigor) and percent plot Poa annua throughout the test.
Data values were assigned to both halves of the plots (treated and individual plot control halves) for all variables. Data
were analyzed using the analysis of variance technique using SAS software (ANOVA). Each treatment was replicated
four times using a randomized complete block field design. Missing data from seven of the sixty plots was estimated
using the GLM option in SAS (iteration). Mean separation values were calculated using LSD values only when the P
value for the treatment effect was significant at the 0.05 level, or less. Linear contrasts were not used since an ideal
application/rate combination was the main objective relative to weed control efficiency, germination establishment, and
subsequent turf performance. Weed control was calculated by the formulation 1-(treatment/control) * 100, which is
expressed as a percentage of the background control infestation level. Turfgrass response variables were analyzed as the
performance of the treated plots as the best indication of biological field performance and expression.
Results and Discussion
Turfgrass Overseed Tolerance and Turf Performance
The plots were evaluated for percent ryegrass plot cover (indicator of relative emergence) and turfgrass vigor on five
dates from November 17, 1997 to January 29, 1998 to measure the performance of rate/timing treatment combinations for
the critical establishment and early post establishment performance of the overseed ryegrass. Table 1 includes the mean
performance values for the fifteen treatments for percent cover (ryegrass) and turfgrass vigor.
On November 7, 1997 (18 DAS) Ronstar treated plots ranged from 20% to 81% for percent plot ryegrass coverage. The
greatest mean ryegrass coverage occurred for the 2.0 lbs. rate/@ 12 WBOS. The 1.0 lbs. rate/@ 12 WBOS had
significantly less establishment at 55%. This discrepancy could not be explained. Two other field treatments resulted in
high ryegrass establishment; 2 lbs./@ 10 WBOS (75%) and 1 lbs./@ 10 WBOS. Untreated turfs averaged 69% ground
cover on November 7.
Among the 4 lbs. treatments, there was more or less a linear decrease for ryegrass establishment on a visual plot basis as
the application time came closer to the overseeding date. This was noted as the following results occurred respectively:
12 WBOS (59%), 10 WBOS (63%), 8 WBOS (29%), 6 WBOS (58%) and 4 WBOS (20%). Among the 1.0 lbs.
treatments, the percent ryegrass increased with the number of weeks the material was applied, with the previously noted
exception of the 12 WBOS treatment, which had the lowest establishment (55%) among the 1 lbs. treated plots.
Turfgrass vigor was assigned to plots using the 1-6 scale with 1 = dead, 4 = moderate and 6 = greatest possible. Treated
field plots which demonstrated the least amount of vigor (in terms of relative seedling height and size) were plots that
scored values of 3.0 or less. These plots would be easily detectable to the average lay person as having noticeably less
vigor. These treatments included 2 lbs./ @ 6 WBOS, 4 lbs./ @ 6 WBOS, 2 lbs./ @ 4 WBOS, 4 lbs./ @ 8 WBOS and 4
lbs./ @ 4 WBOS. The 4 lbs./ @ 12 WBOS had moderate vigor (3.7 mean score), while at 4 lbs./ @ 10 WBOS the mean
vigor value was 4.3. At this date, combinations of 2 lbs. applied at either 4, 6, or 8 WBOS and 4 lbs. applied at either 4,
6, or 8 weeks visually stunted the grass appreciably.
On December 1, 1997 the grand mean of all Ronstar treated plots increased from 58% (7 Nov) to 74% at this time. The
untreated controls had 85% cover at this time. Note that the treatments ranked almost identically for percent plot ryegrass
between the first two evaluation dates which took place at 18 DAS, 42 DAS, respectively. On December 1, Ronstar
treated field plots ranged from a low of 29% ryegrass cover (4 lbs./@ 4 WBOS) to 91% (2 lbs./ @ 12 WBOS). Among
the 4 lbs. treated plots, the 10 and 12 WBOS timing allowed for 82% and 75% mean plot cover respectively, by
December 1 (42 DAS). Of the remaining treatments, the 2 lbs./ @ 4 WBOS had 61% plot cover (ryegrass) while all other
1 lbs. and 2 lbs. plots had 80% or greater cover at this time (Table 1).
Relative vigor of the turf increased for Ronstar treated turfs from 3.3 (7 Nov) to 4.2 (1 Dec). Ronstar treated field plots
ranged in vigor scores from 2.0 (4 lbs./ @ 4 WBOS) to 5.0 (2 lbs./ @ 10 WBOS). The relative ranking for visual
turfgrass vigor was fairly consistent for both the November 7 and December 1 dates (18 DAS and 42 DAS, respectively).
The least vigorous treated plots included the treatments of 4 lbs./ @ 8, 6, and 4 WBOS, which had mean scores of 3.5,
3.3 and 2.0, respectively. At 4 lbs. at either 10 WBOS or 12 WBOS, relative vigor was 4.7. Also note that the treatments
which had the greatest vigor (determined by unmowed height at evaluation date) tended also to have the greater plot
cover percentages as well. Again, the greatest mean vigor scores (4.8 or greater) were realized from the following
treatments: 2 lbs./ @ 10 WBOS, 1 lbs./ @ 6 WBOS, 1 lbs./ @ 10 WBOS, and 2 lbs./ @ 12 WBOS (Table 1).
On December 15, 1997 (56 DAS), mean percent plot scores for percentage ryegrass cover ranged from 53% to 100%.
The only plot which had significantly less plot cover was 4 lbs./ @ 4 WBOS (53%). All other plots had 88% or greater
ryegrass cover. The 4 lbs./ @ 6 WBOS and 2 lbs./ @ 4 WBOS had 88% and 89% percent ryegrass cover, respectively
(Table 1).
For visual relative plot vigor, three treatments had full vigor (mean = 6.0), which included the treatments of 1 lbs./ @ 10
WBOS, 1 lbs./ @ 6 WBOS and 2 lbs./ @ 6 WBOS. At this time, all field treatments of Ronstar had fully acceptable vigor
except for the 4 lbs. treatments at either the 6 or 4 week before overseeding (Table 1).
On December 29, 1997 (70 DAS), percent plot ryegrass coverage ranged from 64% to 100%. All plots had 95% or
greater coverage at this time except for the following field treatments; 2 lbs./ @ 4 WBOS (84%), 4 lbs./ @ 6 WBOS
(78%), 4 lbs./ @ 4 WBOS (64%). Plots should have had at least 95% cover by this time. All 1.0 and 2.0 lbs. treatments
had 95% or more cover at this time with the single exception of 2 lbs./ @ 4 WBOS (84%). Among the 4 lbs. treatments,
the application timings of 10, 12 and 8 WBOS were now acceptable while 6 and 4 WBOS were not (Table 1).
For year end vigor, mean scores ranged from 3.5 to 5.8 on December 29. All treatments scored from 5.0 or greater except
the three treatments as follows: 2 lbs./ @ 4 WBOS, 4 lbs./ @ 6 WBOS, and 4 lbs./ @ 4 WBOS. These treatments had
mean vigor scores of 4.8, 4.6 and 3.5, respectively. A lay person would be able to identify the 4 lbs./ @ 4 WBOS as
Aweak@ (Table 1).
On January 29, 1998, percent plot cover ranged from 75% to 100% with only the 4 lbs./ @ 4 WBOS still showing the
lowest performance of 75% cover at 101 days after overseeding (101 DAS). Two remaining treatments which had less
than 95% mean ryegrass coverage included the following; 4 lbs./ @ 6 WBOS (93%) and 2 lbs./ @ 4 WBOS (92%),
respectively. For vigor, only three plots had moderate vigor or less. These included the treatment of 1 lbs./ @ 8 WBOS
(4.7), 2 lbs./ @ 4 WBOS (4.5) and 4 lbs./ @ 4 WBOS (3.5). All others had values of 5.0 or greater (maximum =
6.0)(Table 1).
Turfgrass Performance
Percent plot ryegrass was rated into the spring on a continual basis on February 12, March 11 and April 11, 1998 (data
not shown). On these dates, the Atreatment effect@ (rate/timing combinations) were not significant in the analysis of
variance, with P values for the F statistic which ranged from 0.22 to 0.80. At these time, percent plot ryegrass cover
ranged from 90-100%, while noting only that the 4 lbs./ @ 4 WBOS treatment always had the lowest plot cover
(maximum was 95% on April 11, 173 DAS).
Turfgrass color and overall quality scores were assigned to plots on 5 of 6 dates, starting on December 15, 1997 and
ending on April 11, 1998. Scores were assigned using the National Turfgrass Evaluation Program/American Society of
Agronomy System using a scale of 1 - 9, 1 = dead grass and 9 = possible/achievable (Table 2).
Turfgrass color scores showed a significant Atreatment@ effect on December 15, but not on December 29, January 29,
March 11 or on April 11 (Table 2).
On December 15 (56 DAS), mean color scores ranged from 4.8 to 7.0. All Atreatments@ (rate/timing combinations) had
mean color scores of 6.0 or greater with the exception of the following four treatments; 1 lbs./ @ 10 WBOS (5.8), 2 lbs./
@ 4 WBOS (5.5), 4 lbs./ @ 4 WBOS (4.8) and 4 lbs./ @ 6 WBOS (4.7). Again the anomaly of the 1 lbs./ @ 10 WBOS
showing a relatively lower score than the 2 or 4 lbs. applications at 10 WBOS could not be explained. Quite noticeable
however, were the 4 lbs. treatments at both 6 and 4 weeks before overseed. These had lighter colored turf. The 4 lbs.
treatments at 12 WBOS had the best color among the 4 lbs. treated turfs (mean = 6.3).
On December 29, 1997 (70 DAS), color scores ranged from 4.8 to 6.7 among Ronstar treated turfs. The lightest color turf
occurred for the 4 lbs./ @ 4 WBOS application. All other treatments had acceptable turfgrass color (Table 2).
On January 29 (101 DAS), color scores for all Ronstar turfs ranged from 6.3 to 7.0 as all plots appeared quite similar and
fully acceptable in color. Although the effect was not significant, plot evaluations showed that four of the four A4 lbs.@
rates appeared last in rank in color. Again, all plots had fully acceptable color (Table 2).
By March 11, 1998 (142 DAS), color scores ranged from 5.6 to 6.8, again showing only a narrow range in color
response. Oddly enough, the A4 lbs.@ treatments all had mean color scores of 6.0 or higher, and the 4 lbs./ @ 4 WBOS
ranked numerically first for color (6.8). This often occurs as a latent response among previously stunted or damaged turf
from chemical applications (herbicides/PGRs). Again, all plots had acceptable color and the range was marginal in effect
(Table 2).
April 11, 1998 was the last color rating (173 DAS). Again, the treatment effect was non-significant and mean color
scores for Ronstar treated turfs ranged from 6.3 to 7.3, all within a narrow range of fully acceptable values. Once again,
the 4 lbs./ @ 4 WBOS ranked numerically highest for color (mean 7.3).
Turfgrass quality is a visual estimate of turfgrass density, smoothness, texture, mowing performance and uniformity.
Turfgrass quality scores were significant only on December 29 and not on the remaining five evaluations ending May 21,
1998 (Table 2).
On December 29 (70 DAS), overall turfgrass quality scores ranged from 4.0 (unacceptable) to 7.8. Two treatments which
were sub-par included 4 lbs./ @ 6 WBOS (5.7 = marginal) and 4 lbs./ @ 4 WBOS (4.0 = unacceptable). Treatments
which had mean quality values of 7.0 or higher included; 1 lbs./ @ 10 WBOS (7.8), 1 lbs./ @ 6 WBOS (7.8), 2 lbs./ @
10 WBOS (7.5), 1 lbs./ @ 8 WBOS (7.3), 2 lbs./ @ 6 WBOS (7.3), 4 lbs./ @ 12 WBOS (7.3) and 2 lbs./ @ 12 WBOS
(7.3) (Table 2).
By January 29, 1998 (101 DAS), mean quality scores ranged from 4.8 to 6.3. Only the 4 lbs./@ 4 WBOS had poor turf
quality, with a mean score of 4.8.
By March 11, 1998 (142 DAS), quality was not affected by Ronstar treatments and overall quality mean treatment scores
ranged from 5.8 to 6.8. Only the 4 lbs./ @ 4 WBOS had a slightly sub-par score (5.8). All remaining plots were very
similar for overall turf quality (Table 2).
The treatment effect was again non-significant on April 11, 1998 (173 DAS) and treated plots had a mean range of
performance from 6.3 to 7.0. All turfs were very similar in appearance.
At the close of the test on May 21, 1999 (213 DAS), there was again no significant treatment effect for overall turfgrass
quality. The treatment mean scores ranged from 5.3 to 7.0 with two treatments (both at 1 lbs. rates applied at either 12 or
8 WBOS having submarginal appearance. This would not be attributable to former treatments, but most likely to position
affects in the test area (mowing, irrigation, etc.) (Table 2).
Turfgrass density scores were assigned twice (December 15 and May 21), while texture (relative leaf width of turfgrass
plants) was assigned once on May 25 (Table 3).
Turfgrass density (visual estimate of overall plot shoot density) showed a significant Atreatment@ effect in the late fall
(December 15), but not in the spring (May 21). In the late fall, treatment mean scores for Ronstar treated turfs ranged
from 4.0 (low density) to 8.0 (very high density). The turf that received the 4 lbs./@ 4 WBOS showed a decreased plot
density (indicative of a Athin@ condition). The 2 lbs./ @ 4 WBOS treatment scored 6.5 which is fully acceptable. All other
treatment combinations produced a visible thick turf at this time (56 DAS) (Table 3).
On May 21, all Ronstar treated turf plots had mean treatment density scores from 6.0 to 7.0, all of which were most
acceptable (Table 3).
Turfgrass texture on May 21 (close of the test) showed no effect from treatments, as all turfs that received Ronstar the
previous summer had mean texture scores of 6.0 to 7.0.
At the close of the test, the percent plot bermudagrass was assigned visually (0-100%) to see if any latent affect was
realized for transition. The treatment affect was not significant. Percent plot bermudagrass present by the third week of
May 1998 ranged from 15% to 25% plot cover. Plot scores were not related to previous rates/timing which started 10
months previously (Table 3).
Weed Control
Weed pressure at the test site was inadequate to discern effectiveness of the treatments. There was simply not enough Poa
present with the overseed ryegrass. Surrounding areas had large patches of Poa, but it unfortunately proved difficult to
find Poa within and between plots. Note that each plot was split in half to afford a background control for each plot.
Therefore Poa pressure was inadequate. On February 12, the number of Poa plants in check plots ranged from 0-10. On
March 11, 0-14 and on April 11, 0-12 (Table 4). All weed control values were positive, showing less weeds among
treated plots than the controls. Even so, the weed counts were not distributed normally (due to small numbers of plants).
For perusal only are the calculated weed control values for February 11, March 11 and April 11, 1998. F values for
Atreatment@ combinations were less than 1.0, indicating more variation within plots of the same treatment than between
treatments themselves. Corresponding large P values arose accordingly. This was true for the February and March
ratings.
The April ratings were significant at the P = 0.04 level, with an F value of 2.17 (ration of treatment mean squares to
experimental error mean square). Therefore the April rating offers some interpretation, noting however, that low weed
pressure existed (range 0-12 plants/plot, average = 3).
Table 4 lists the results for weed control. Note that only the April 11, 1998 rating has some validity.
Conclusion
1.
Ronstar was applied at three rates (1.0, 2.0 and 4.0 lbs. AI/A) at 12, 10, 8, 6 and 4 weeks before overseeding
bermudagrass turf with perennial ryegrass on October 20, 1997.
2.
On November 7, 1997 (18 DAS) Ronstar treated plots ranged from 20% to 81% for percent plot ryegrass
coverage. The greatest mean ryegrass coverage occurred for the 2.0 lbs. rate/@ 12 WBOS.
Among the 4 lbs. treatments, there was more or less a linear decrease for ryegrass establishment on a visual plot
basis as the application time came closer to the overseeding date.
3.
4.
On December 1, Ronstar treated field plots ranged from a low of 29% ryegrass cover (4 lbs./@ 4 WBOS) to
91% (2 lbs./ @ 12 WBOS). Among the 4 lbs. treated plots, the 10 and 12 WBOS timing allowed for 82% and
75% mean plot cover respectively, by December 1 (42 DAS). Of the remaining treatments, the 2 lbs./ @ 4
WBOS had 61% plot cover (ryegrass) while all other 1 lbs. and 2 lbs. plots had 80% or greater cover at this
time.
5.
On December 15, 1997 (56 DAS), mean percent plot scores for percentage ryegrass cover ranged from 53% to
100%. The only plot which had significantly less plot cover was 4 lbs./ @ 4 WBOS (53%). All other plots had
88% or greater ryegrass cover.
6.
Turfgrass color scores showed a significant Atreatment@ effect on December 15, but not on December 29,
January 29, March 11 or on April 11.
7.
On December 29 (70 DAS), overall turfgrass quality scores ranged from 4.0 (unacceptable) to 7.8. Two
treatments which were sub-par included 4 lbs./ @ 6 WBOS (5.7 = marginal) and 4 lbs./ @ 4 WBOS (4.0 =
unacceptable). Treatments which had mean quality values of 7.0 or higher included; 1 lbs./ @ 10 WBOS (7.8),
1 lbs./ @ 6 WBOS (7.8), 2 lbs./ @ 10 WBOS (7.5), 1 lbs./ @ 8 WBOS (7.3), 2 lbs./ @ 6 WBOS (7.3), 4 lbs./ @
12 WBOS (7.3) and 2 lbs./ @ 12 WBOS (7.3).
8.
Weed pressure was inadequate to fully assess pre-emergence control of Poa annua. At the close of the test on
April 11, 1998, weed control ranged from 8% to 100%. Plots with 90% or greater weed control included 2
lbs./@ 10 WBOS, 1 lbs./@ 4 WBOS, and 4 lbs./@ 12, 8, 6, and 4 WBOS.
9.
Ronstar applied at 1.0 lbs. AI/A was safe for perennial ryegrass at 12, 10, 8, 6, and 4 WBOS.
10.
Ronstar applied at 2.0 lbs. AI/A was safe for perennial ryegrass at 12, 10, and 8 weeks. At 6 WBOS, cover was
adequate compared to the control plots, but the turf was noticeably stunted until late December.
11.
Ronstar applied at 4.0 lbs. AI/A was safe at 12 and 10 WBOS.
Table 1. Mean turfgrass percent plot cover1 and relative vigor2 of perennial ryegrass on five evaluation dates in 1997 and 1998 after previous treatment with
Ronstar herbicide applications before fall overseeding. University of Arizona, 1997-1998.
EVALUATION DATE/# DAYS AFTER SEEDING
1
% RYE
VIGOR
% RYE
VIGOR
% RYE
VIGOR
% RYE
VIGOR
% RYE
VIGOR
Rate lbs.
AI/A
Weeks before3
Overseed (WBOS)
07 NOV
(18 DAS)
07 NOV
(18 DAS)
01 DEC
(42 DAS)
01 DEC
(42 DAS)
15 DEC
(56 DAS)
15 DEC
(56 DAS)
29 DEC
(70 DAS)
29 DEC
(70 DAS)
29 JAN
(101 DAS)
29 JAN
(101 DAS)
1.0
12
55
3.5
81
4.5
98
5.5
98
5.0
97
5.0
2.0
12
81
3.8
91
4.8
99
5.5
100
5.3
99
5.5
4.0
12
59
3.7
75
4.7
97
5.6
97
5.7
98
5.3
1.0
10
74
4.3
86
4.8
99
6.0
99
5.3
100
5.5
2.0
10
75
4.0
88
5.0
98
5.6
99
5.5
99
6.0
4.0
10
63
4.3
82
4.7
98
5.3
96
5.3
98
5.3
1.0
8
63
3.7
82
4.7
98
5.3
99
5.7
98
4.7
2.0
8
65
3.3
83
4.7
96
5.8
99
5.5
98
5.3
4.0
8
29
1.8
51
3.5
96
5.3
98
5.0
99
5.3
1.0
6
65
4.3
83
5.0
100
6.0
100
5.8
98
5.3
2.0
6
65
2.7
82
4.0
98
6.0
99
5.7
99
5.8
4.0
6
58
2.7
73
3.3
88
4.7
78
4.7
93
5.0
1.0
4
65
3.5
79
4.5
98
5.5
98
5.0
97
5.3
2.0
4
40
2.5
61
3.8
89
5.3
84
4.8
92
4.5
4.0
4
20
1.5
29
2.0
53
3.0
64
3.5
75
3.5
Control Mean4
69
4.2
85
5.6
98
5.9
99
5.7
99
5.5
Test Mean5
58
3.3
74
4.2
93
5.3
94
5.1
96
5.2
LSD Value6
28
1.4
20
1.4
16
1.1
18
1.1
8
1.5
Percent plot cover from overseed ryegrass (0-100%). Values are the mean of 4 replications.
2
Relative vigor scores (1-6). 1 = none, 2 = slight, 3 = slight/moderate, 4 = moderate, 5 = moderate/extreme, 6 = extreme. Values are the mean of 4 replications.
3
WBOS = Number of weeks Ronstar was applied before overseeding with perennial ryegrass on October 20, 1997.
4
Mean of all non-treated controls. Values are the means of 32 plots.
5
Mean of all Ronstar treated plots.
6
LSD values = Mean separation statistic. Treatments which differ from each other by values greater than the LSD are significantly different from each other.
Table 2. Mean turfgrass color1 and quality2 scores on five evaluation dates in 1997 and 1998 after previous treatment with Ronstar herbicide applications before
fall overseeding. University of Arizona, 1997-1998.
EVALUATION DATE/# DAYS AFTER SEEDING
1
COLOR
QUALITY
COLOR
QUALITY
COLOR
QUALITY
COLOR
QUALITY
COLOR
QUALITY
Rate lbs.
AI/A
Weeks before3
Overseed (WBOS)
15 DEC
(56 DAS)
29 DEC
(70 DAS)
29 DEC
(70 DAS)
29 JAN
(101 DAS)
29 JAN
(101 DAS)
11 MAR
(142 DAS)
11 MAR
(142 DAS)
11 APR
(173 DAS)
11 APR
(173 DAS)
21 MAY
(213 DAS)
1.0
12
6.0
6.5
5.5
7.5
7.0
6.0
6.3
6.8
6.8
5.8
2.0
12
6.3
7.3
6.5
7.3
7.0
6.0
6.0
6.5
7.0
6.8
4.0
12
6.3
7.2
6.3
7.7
6.3
6.0
6.0
6.3
6.7
7.0
1.0
10
5.8
7.8
6.0
7.8
6.8
6.0
6.3
6.8
6.5
6.3
2.0
10
6.3
7.5
6.3
8.7
7.0
6.0
5.6
6.5
7.0
7.0
4.0
10
6.0
6.8
5.8
7.5
6.8
6.0
6.5
6.5
6.7
6.8
1.0
8
6.7
7.3
6.7
7.0
7.0
6.0
6.0
6.3
6.7
5.3
2.0
8
6.8
6.8
6.3
8.3
6.8
6.0
6.0
6.5
7.0
7.0
4.0
8
6.3
6.8
6.0
7.8
7.0
6.3
6.3
6.8
7.0
6.5
1.0
6
6.5
7.8
6.3
7.3
7.0
6.0
5.8
6.5
6.8
6.5
2.0
6
7.0
7.3
6.3
7.7
7.0
6.0
6.5
7.0
7.0
7.0
4.0
6
4.7
5.7
6.0
6.7
6.7
6.3
6.3
7.0
6.3
6.7
1.0
4
6.5
6.5
5.5
7.3
6.8
6.8
6.0
6.8
6.5
6.8
2.0
4
5.5
6.5
5.5
6.5
6.8
6.5
6.5
7.0
7.0
6.0
4.0
4
4.8
4.0
4.8
4.8
6.5
5.8
6.8
6.5
7.3
6.0
Control Mean4
6.3
7.2
6.0
7.9
6.8
6.6
6.0
6.6
6.7
6.6
Test Mean5
6.1
6.8
6.0
7.3
6.8
6.1
6.2
6.6
6.8
6.5
LSD Value6
1.2
1.3
NA
NA
NA
NA
NA
NA
NA
NA
Color scores (1-9). 1 = dead, 9 = darkest possible. Values are the mean of 4 replications.
Quality scores (1-9). 1 = dead, 9 = best possible. Values are the mean of 4 replications.
3
WBOS = Number of weeks Ronstar was applied before overseeding with perennial ryegrass on October 20, 1997.
4
Mean of all non-treated controls. Values are the means of 32 plots.
5
Mean of all Ronstar treated plots.
6
LSD values = Mean separation statistic. Treatments which differ from each other by values greater than the LSD are significantly different from each other.
2
Table 3. Mean turfgrass density1, texture2 and percent3 plot bermudagrass at select evaluation dates in 1997 and 1998 after previous treatment with Ronstar
herbicide applications before fall overseeding. University of Arizona, 1997-1998.
EVALUATION DATE/# DAYS AFTER SEEDING
1
DENSITY
DENSITY
TEXTURE
% BERMUDA
Rate lbs.
AI/A
Weeks before4
overseed (WBOS)
15 DEC
(56 DAS)
21 MAY
(213 DAS)
21 MAY
(213 DAS)
21 MAY
(213 DAS)
1.0
12
7.5
6.0
6.3
18
2.0
12
8.0
6.5
6.5
21
4.0
12
7.3
7.0
6.3
17
1.0
10
7.8
6.0
6.5
18
2.0
10
7.3
6.7
6.7
18
4.0
10
7.3
6.5
6.5
20
1.0
8
7.3
6.5
7.0
25
2.0
8
7.7
6.7
6.7
15
4.0
8
7.0
6.3
6.3
18
1.0
6
8.0
6.5
7.0
17
2.0
6
8.0
7.0
6.3
18
4.0
6
6.3
6.7
6.7
20
1.0
4
7.3
6.8
6.5
18
2.0
4
6.5
7.0
6.7
22
4.0
4
4.0
6.0
6.7
18
Control Mean5
7.7
6.8
6.8
17
Test Mean6
7.1
6.5
6.5
19
LSD Value7
1.4
NA
NA
NA
Density scores (1-9). 1 = dead, 9 = best possible. Values are the mean of 4 replications.
2
Texture scores (1-9). 1 = dead, 9 = best possible. Values are the mean of 4 replications.
3
Percent plot bermuda (0-100%). Values are the mean of 4 replications.
4
WBOS = Number of weeks Ronstar was applied before overseeding with perennial ryegrass on October 20, 1997.
5
Mean of all non-treated controls. Values are the means of 32 plots.
6
Mean of all Ronstar treated plots.
7
LSD values = Mean separation statistic. Treatments which differ from each other by values greater than the LSD are significantly different from each other.
Table 4. Mean percent weed control1 of Poa annua in overseeded turf in 1998 after application of Ronstar herbicide2. University of Arizona, 1997-1998.
FEBRUARY 12, 19983
MARCH 11, 19983
APRIL 11, 19983
RATE LBS.
AI/A
WEEKS BEFORE
OVERSEED (WBOS)
PERCENT WEED
CONTROL
RATE LBS.
AI/A
WEEKS BEFORE
OVERSEED (WBOS)
PERCENT WEED
CONTROL
RATE LBS.
AI/A
WEEKS BEFORE
OVERSEED (WBOS)
PERCENT WEED
CONTROL
4.0
4
100
2.0
10
100
4.0
4
100
2.0
10
100
2.0
12
100
2.0
10
100
1.0
4
100
2.0
4
100
4.0
10
97
4.0
12
100
4.0
4
100
4.0
8
97
4.0
8
100
4.0
6
100
2.0
4
94
4.0
6
100
4.0
10
96
4.0
6
92
4.0
10
100
4.0
8
91
1.0
8
88
2.0
4
100
4.0
12
90
1.0
4
83
1.0
10
80
1.0
10
88
4.0
12
83
2.0
6
70
1.0
8
--4
2.0
8
67
2.0
12
67
1.0
4
87
2.0
6
67
1.0
12
50
2.0
8
67
1.0
10
64
1.0
6
50
2.0
6
50
1.0
6
39
2.0
8
33
1.0
12
50
2.0
12
33
1.0
8
0
1.0
6
40
1.0
12
8
No Weeds Per Control5 (avg/max)
1.5/10
--
--
1.8/14
--
--
3.0/12
Treatment Test Mean6
NA
--
--
NA
--
--
70
LSD Value7
NA
--
--
NA
--
--
65
1
Weed control as percent of control plot weed counts. Values are the mean of four replications.
WBOS = Number of weeks Ronstar was applied before overseeding with perennial ryegrass on October 20, 1997.
3
No interpretation possible for February 12 and March 11 evaluation dates. Proceed with extreme caution on April 11, 1998.
4
Not computable estimates. No weeds in plot.
5
Average number of weeds control plot/Max number weeds realized in controls.
6
Mean of all plots having received Ronstar previously.
7
LSD values = Mean separation statistic. Treatments which differ from each other by values greater than the LSD are significantly different from each other.
2
FN:moonron,wpd q1/99