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Evaluations of Proxy/Primo tank mixes,
timing, and rates for
Poa annua seedhead suppression - 2003 Results
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We have completed our third year of testing products for springtime
suppression of seedhead formation by Poa annua. For an overview
of the topic and previous year results, see our articles published
in the USGA Green Section Record (Volume 41, Number 4, July-August
2003, pages 21-26), USGA Turfgrass and Environmental Research
Online (click
here to view), and on InteractiveTurf.com (click
here to view). In 2003, we looked primarily at
timing and rates of Proxy (ethephon) + Primo (trinexepac-ethyl)
tank mixes. The research was sponsored once again by a USGA Green
Section Regional Grant and by Bayer Crop Sciences.
Tests were conducted on Chicago, IL area golf courses (Aurora
CC, Orchard Valley GC) under green and fairway management conditions.
The Aurora CC site is a practice putting green consisting of 50-60%
Poa annua, with the remaining turf comprised of various types
of creeping bentgrass. Mowing height for this green is approximately
.125" or less year-round and receives standard fertilization
and irrigation. Test applications were made on April 11&18,
and May 15. The first seedheads were noted on the site on the
May 9 rating day. The entire plot was oversprayed with .125 oz/1000
of Primo on June 6 (beginning the regular maintenance cycle of
Primo applications through the summer). Application rates, timing
and results are presented in Table
1 below (means only).
The Orchard Valley tests were conducted on a portion of the ninth
fairway, which consists of approximately 30-40% Poa annua, with
the remainder primarily Penncross creeping bentgrass. The fairway
is mowed 2-3 times per week at 0.5" and receives standard
fertility and irrigation applications. Test applications were
made on April 22 and May 30, 2003. The first seedheads were noticed
on this site on May 2nd. Application rates, timing and results
are presented in Table
2 below (means only).
Individual treatment plots at both sites were 5x8 feet and were
replicated three times in a randomized block design. Growth regulators
were applied using a CO2 sprayer and handheld boom with Turbo
TeeJet nozzles (TT110015VP) delivering approximately 900 CC per
120 sq ft (roughly 2 gal/1000 sq ft). Poa annua seedhead production
was rated visually as percent of Poa plants with visible flowering,
not percent of total plot area with visible flowering. Since both
plots were mowed frequently, seedheads were constantly being removed
and limited the total % seedheads visible at any one rating date.
The Poa seedhead prediction model is triggered to alarm when
the number of base 50 degree days reaches 50. In every
year at this site, the model has alarmed approximately 2 weeks
before the first notice of seedhead emergence (see
Table 3 below). In 2003, applications at Aurora
CC were made early (4/11) or approximately (4/18 and 4/22) on
the date when the prediction model first went off (4/19).
Peak seedhead production at Aurora CC occurred around May 15,
then lingered through most of June. Embark and the earlier application
of Proxy/Primo gave the best suppression on that date (~80%);
other treatments with Proxy or Proxy/Primo gave about 65% suppression
compared to the untreated checks. Treatments with the follow-up
application of Proxy/Primo continued to provide noticeable suppression
well into June, whereas the single Embark treatment was starting
to fade. Embark and Trimmit had noticeable deleterious effects
on turf quality on the Aurora CC putting green height plot until
mid-June. The earlier application of Trimmit at this site did
not improve seedhead suppression.
Results on the fairway height turf at Orchard Valley GC were
not nearly as impressive, although by the June ratings, the repeat
applications of Proxy+Primo were showing very good suppression.
There was a phytotoxic response when the repeat applications were
made in conjunction with a wetting agent. The turf recovered by
the end of the study.
Thanks to our cooperators and supporters for these studies:
- John Gurke, Supt., Aurora CC
- Jim McNair, Supt., Orchard Valley GC
- USGA Green Section - Regional Grants
- Paul Vermeulen, Director, Mid-Continent Region
- Bayer Crop Sciences
- John Smith, Senior Product Development Specialist
Table 1. Results of treatments at Aurora CC on
a practice putting green
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|
appl.
rate
|
|
MEAN PERCENT Poa annua WITH
SEEDHEADS
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TURF QUALITY
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|
Treatment
|
oz/M
|
appl.
date
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May
9
|
May
15
|
May
22
|
May
30
|
June
6
|
June
20
|
June
30
|
|
Apr
25
|
May
2
|
Jun
20
|
|
UT Check
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- -
|
- -
|
7.0
|
20.9
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5.4
|
10.2
|
9.5
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4.9
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4.7
|
|
6.0
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5.5
|
7.8
|
|
Proxy
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5.0
|
4/18
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3.7
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7.3
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0.7
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5.0
|
1.3
|
2.0
|
1.3
|
|
6.3
|
6.3
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8.0
|
|
Proxy
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3.0
|
"
|
1.3
|
7.7
|
3.3
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3.0
|
2.3
|
1.0
|
1.3
|
|
5.3
|
5.3
|
7.0
|
|
Proxy +
Primo
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5 +
1/8
|
"
|
1.7
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6.7
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1.3
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4.3
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3.0
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1.7
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0.7
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|
6.3
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6.3
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7.3
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|
Proxy +
Primo
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3 +
1/8
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"
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3.7
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6.7
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5.3
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9.0
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5.7
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1.3
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1.3
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|
6.3
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6.0
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7.7
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|
Proxy +
Primo
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5 +
1/8
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4/18
5/15
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1.3
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7.3
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0.3
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0.1
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1.0
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1.0
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0.3
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6.3
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6.0
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6.8
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|
Proxy +
Primo
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3 +
1/8
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4/18
5/15
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2.3
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10.7
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2.0
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2.3
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0.7
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1.0
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0.3
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6.3
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5.7
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8.0
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Embark + Fe
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1.0
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4/18
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2.3
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3.3
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1.0
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2.3
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1.7
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4.7
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2.0
|
|
6.0
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4.7
|
7.7
|
|
Early:
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|
|
|
|
|
|
|
|
|
|
|
|
|
|
Proxy +
Primo
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5 +
1/8
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4/11
5/15
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2.7
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4.3
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0.7
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0.3
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0.7
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0.3
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0.0
|
|
6.7
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5.7
|
7.5
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|
Trimmit
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1/4,
1/8
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4/11
5/15
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15.0
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20.0
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8.3
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18.3
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14.0
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11.7
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5.0
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4.7
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4.7
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8.0
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Table 2: Results of treatments at Orchard Valley GC on a fairway
turf.
|
|
appl.
rate
|
|
MEAN PERCENT Poa annua WITH
SEEDHEADS
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TURF QUALITY
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|
Treatment
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oz/M
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appl.
date
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May
9
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May
15
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May
22
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May
30
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June
6
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June
20
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|
June
6
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June
20
|
|
UT Check
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- -
|
- -
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8.3
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15.0
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11.7
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13.3
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11.7
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7.0
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|
7.7
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8.2
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|
Proxy
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7.5
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4/22
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4.7
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18.3
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7.3
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6.7
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4.0
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2.0
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7.0
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8.0
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Proxy +
Primo
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5 +
1/8
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4/22
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5.0
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13.3
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8.3
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6.7
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6.7
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4.3
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|
8.0
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7.8
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|
Proxy +
Primo
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7.5 +
1/8
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4/22
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4.3
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10.0
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6.0
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13.3
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7.3
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4.7
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|
8.0
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8.3
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|
Proxy +
Primo
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5 +
1/8
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4/22
5/30
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3.3
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5.7
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4.0
|
6.7
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1.7
|
0.0
|
|
6.3
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8.3
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|
Proxy +
Primo
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7.5 +
1/8
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4/22
5/30
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4.3
|
8.3
|
4.7
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4.0
|
7.3
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0.0
|
|
5.7
|
7.5
|
|
Proxy +
Primo
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7.5 +
1/4
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4/22
5/30
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5.0
|
5.0
|
4.0
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2.3
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5.0
|
0.0
|
|
6.0
|
7.5
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|
Proxy +
Trimmit
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7.5 +
1/4
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4/22
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11.7
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8.3
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6.3
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11.7
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4.7
|
1.3
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|
7.0
|
8.0
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Table 3. Comparison of Growing Degree Day base 50
Model to first visible flowering in Poa annua over the
last five years (Aurora site). .
| Year |
Date that GDD50 >=50 |
1st Visible Flowering |
| 2003 |
April 19 |
May 9 |
| 2002 |
April 15 |
April 24-28 |
| 2001 |
April 12 |
April 27-29 |
| 2000 |
April 7 or April
24 |
May 3-7 |
| 1999 |
April 4 |
April 15 |
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