Nick Christians
December 8, 2015
nchris@iastate.edu
The following is a report on a dollar spot trial conducted at the research station this past summer. The primary objective of the work was to evaluate the effect of an experimental adjuvant on disease control, but there is a lot of good information comparing the different fungicides. We had a great year for dollar spot at the station.
KALO
FUNGICIDE/ADJUVANT TRIAL-2015
Nick Christians and
Dan Strey
Iowa State University
Objective
To compare the control of Dollar Sport caused by the fungi Sclerotinia homeocarpa on creeping
bentgrass turf with 7 commercial fungicides applied with and without Kalo’s KA-9107 experimental adjuvant.
Materials and Methods
The trial was conducted at the Iowa State University Horticulture
research station near Gilbert, Iowa.
Plots were located on a mature stand of creeping bentgrass and were
arranged in a randomized complete block design with 3 replications. Each
plot measured 5 x 5 ft, for a total of 25 ft2 per plot. Bentgrass was a mixed sward of ‘1019’,
‘1020’, and ‘Penncross’ maintained at 0.5”.
Soil at the site was a 1:1:1 mix
of sand:peat:soil with a particle size of 13.7% sand, 56.9% silt, and 29.5%
clay. Soil pH was 7.6 with soil P and K
contents of 17 and 58 ppm, respectively.
Soil type was a Nicollet clay-loam (fine-loamy, mixed, mesic, Typic Hapluldoll).
The full list of treatments appears
in Table 1. All products were applied through TeeJet 8002VS nozzles in a spray
volume equivalent to 2 gallons/1000 ft2 powered by carbon dioxide
supplying 40 pounds per square inch. The products were generally applied
on 14 day intervals.
Results
The two week interval of application was too long to get
satisfactory control of dollar spot with chlorothalonil (Table 2). The addition
of the KA-9107 to chlorothalonil did provide numerically better control in most
data collection dates. These differences
were significant on Sept. 2, Sept. 24, Oct. 2 and for the grand mean of all
dates. Fathom 14.3 MEC, Briskway, and Renown
also provided less than desirable control. Control with Briskway was improved
by KA-9107 on July 8 and July 27, as was the control with Renown. The control with Fathom 14.3 MEC was
improved by the adjuvant on August 25.
Emerald, Secure, and Velista were the most effective controls of dollar
spot. While at most dates, there was a
numerical advantage to adding KA-9107 to these materials, there control was so effective,
that none of these differences were significant.
Overall means comparing fungicides with adjuvant and those
without adjuvant were calculated and orthogonal contrasts were performed to
compare the means (Table 2) (Figure 1).
Significant improvement in activity of all fungicides that included
KA-9107 were observed on July 8 and July 27.
The grand mean of all treatments over all dates showed a decrease of
from 22 % dollar spot to 18 % dollar spot when KA-9107 was used as an
additive. The level of significance for
this difference was 0.08.
It is apparent that KA-9107 can boost the activity of some fungicides
for the control of dollar spot on creeping bentgrass turf. Future studies could include the application
of KA-9107 without a fungicide to determine if it provides any suppression on
dollar spot development by itself. It
would also make sense to test the most effective materials with and without the
adjuvant at longer intervals between treatments to determine if KA-9107 extends
the activity of these products.
Table 1.
Treatments in the 2015 Kalo Fungicide/Adjuvant trial.
|
||||||||
Product
|
Adjuvant
|
Product
|
Adjuvant
|
App
|
||||
Trt #
|
Treatment
|
Rate (/1,000 ft²)
|
Rate (/1,000 ft²)
|
Rate
(ml/25 ft²)
|
Rate
(ml/25 ft²)
|
Interval
|
||
1
|
Control
|
-
|
-
|
-
|
-
|
|||
2
|
Chlorothalonil
|
1.8
dry oz.
|
-
|
1.277
g
|
-
|
14
days
|
||
3
|
Chlorothalonil + adj
|
1.8
dry oz.
|
1.3
fl. oz.
|
1.277
g
|
0.96
ml
|
14
days
|
||
4
|
Emerald
|
0.13
dry oz.
|
-
|
0.092
g
|
-
|
14
days
|
||
5
|
Emerald + adj
|
0.13
dry oz.
|
1.3
fl. oz.
|
0.092
g
|
0.96
ml
|
14
days
|
||
6
|
Secure (Fluazinam)
|
0.5
fl. oz.
|
-
|
0.37
ml
|
-
|
14
days
|
||
7
|
Secure + adj
|
0.5
fl. oz.
|
1.3
fl. oz.
|
0.37
ml
|
0.96
ml
|
14
days
|
||
8
|
Fathom 14.3 MEC (propinozole)
|
0.5
fl. oz.
|
-
|
0.37
ml
|
-
|
14
days
|
||
9
|
(Fathom 14.3 MEC + adj
|
0.5
fl. oz.
|
1.3
fl. oz.
|
0.37
ml
|
0.96
ml
|
14
days
|
||
10
|
Briskway (difenoconozole + azoxystrogin)
|
0.5
fl. oz.
|
-
|
0.37
ml
|
-
|
14
days
|
||
11
|
Briskway + adj
|
0.5
fl. oz.
|
1.3
fl. oz.
|
0.37
ml
|
0.96
ml
|
14
days
|
||
12
|
Renown (chlorothalonil + azoxystrobin
|
4.0
fl. oz.
|
-
|
2.96
ml
|
-
|
14
days
|
||
13
|
Renown + adj
|
4.0
fl. oz.
|
1.3
fl. oz.
|
2.96
ml
|
0.96
ml
|
14
days
|
||
14
|
Velista (penthiopyrad)
|
0.5
dry oz.
|
0.355
g
|
14
days
|
||||
15
|
Velista + adj
|
0.5
dry oz.
|
1.3
fl. oz.
|
0.355
|
0.96
ml
|
14
days
|
||
Table 2. Data from 2015 Dollar Spot Trial.
|
||||||||||
% DOLLAR SPOT INFESTATION
|
||||||||||
TREATMENT
|
8-Jul
|
22-Jul
|
27-Jul
|
8-Aug
|
14-Aug
|
25-Aug
|
2-Sep
|
24-Sep
|
2-Oct
|
MEAN
|
1. Control
|
68
|
68
|
85
|
49
|
38
|
32
|
19
|
42
|
24
|
47
|
2. Chlorothalonil
|
25
|
57
|
75
|
54
|
52
|
83
|
82
|
33
|
15
|
53
|
3. Chlorthalonil + adj
|
13
|
52
|
70
|
30
|
37
|
73
|
75
|
15
|
6
|
41
|
4. Emerald
|
1
|
6
|
1
|
0
|
0
|
3
|
11
|
4
|
2
|
3
|
5. Emerald + adjuvant
|
0
|
2
|
0
|
1
|
1
|
0
|
3
|
1
|
1
|
1
|
6. Secure
|
0
|
1
|
1
|
1
|
2
|
6
|
13
|
3
|
0
|
3
|
7. Secure + adjuvant
|
0
|
1
|
2
|
2
|
0
|
4
|
9
|
4
|
0
|
2
|
8. Fathom 14.3 MEC
|
8
|
38
|
28
|
12
|
12
|
53
|
70
|
27
|
9
|
29
|
9. Fathom + adjuvant
|
3
|
32
|
21
|
6
|
6
|
29
|
67
|
24
|
10
|
22
|
10. Briskway
|
28
|
57
|
29
|
12
|
7
|
27
|
84
|
15
|
3
|
29
|
11. Briskway + adjuvant
|
11
|
37
|
10
|
4
|
4
|
25
|
77
|
18
|
5
|
21
|
12. Renown
|
33
|
53
|
64
|
14
|
8
|
45
|
72
|
14
|
6
|
34
|
13. Renown + adjuvant
|
14
|
52
|
52
|
24
|
15
|
60
|
83
|
30
|
6
|
37
|
14.
Velista
|
0
|
5
|
4
|
2
|
1
|
5
|
12
|
6
|
4
|
4
|
15. Velista + adjuvant
|
0
|
2
|
1
|
1
|
0
|
2
|
7
|
5
|
1
|
2
|
LSD 0.05
|
16
|
21
|
12
|
24
|
26
|
16
|
10
|
15
|
8
|
12
|
ADJ VS NOADJ
|
0.02*
|
0.15
|
0.01**
|
0.37
|
0.57
|
0.16
|
0.10
|
0.77
|
0.34
|
0.08
|
MEAN ADJ
|
6
|
25
|
22
|
10
|
9
|
28
|
46
|
14
|
4
|
18
|
MEAN NOADJ
|
14
|
31
|
29
|
14
|
12
|
32
|
49
|
15
|
6
|
22
|
