Robust Barley Response to Silwet X-77 Adjuvant Rate in
5.2 and 19.2 GPA Spray Volume with AMS 21619 Fungicide
S. Halley,Langdon Research Extension Center-North Dakota State University, Box 310 Hwy 5 E Langdon, North Dakota 58249
*Corresponding author PH: (701) 256-2582, E-mail: shalley@ndsuext.nodak.edu
OBJECTIVES
To determine if efficacy of fungicide, AMS21619 (Bayer
experimental), can be enhanced by differing rates of Silwet X-77 adjuvant at
5.2 or 19.2 gpa spray volume to Robust Barley.
Introduction
Barley producers in traditional barley producing areas
have been frustrated by the inconsistent performance of fungicides applied to
barley. As a result barley acreage has shifted to different regions of the
state where diseases have not been as prevalent. However, diseases are
developing in these regions and disease levels increasing when environmental
conditions are appropriate.
Barley is particularly difficult to research because
obtaining adequate disease levels for effective fungicide evaluation has been
inconsistent. The extended period of heading among barley main stem and
tillers, lack of yield loss due to FHB, and an inability to distinguish losses
between leaf diseases and FHB, and near zero tolerance for the presence of the
toxin deoxynivalenol (DON) by the malting industry complicate prioritization
of research goals.
Adjuvants are recommended additions to some fungicide
solutions to improve consistency of performance. Often recommendations are for
additions based on volume for volume relative to the tanks solution (1 pt/ 100
gallons of tank solution). Fungicide applicators are recommended to use water
volumes greater than most herbicide application volumes. Wide range of volumes
is used, as low as 3 gpa with aerial application to 20 gpa, ground application
on small grains. The variability in solution volume means total adjuvant
amounts applied can vary widely depending on application choices. One class is
the organosilicates. This particular class, specifically Silwet L-77, reduces
the tension of the spray droplet. Too much adjuvant will move the fungicide
off target and directly to the soil negating the benefit of the fungicide.
MATERIALS AND METHODS
The barley cultivar Robust was planted for fungicide
evaluation in a field at the Langdon Research Extension Center in spring 2002.
An area was planted with a Melroe double-disk grain drill, disks spaced
6-inches apart. The area was divided to plots 12 ft. wide by 20 ft. long in a
RCB design with six replicates arranged as a Silwet X-77 Rate x GPA
factorial. Recommended production practices for Northeast North Dakota were
followed. Three weeks prior to heading a Fusarium spawn grown on spring
wheat was hand broadcast at a rate of approximately 200 grams/plot.
Silwet X-77 rates were:
1.
Untreated
2.
0
3.
1.5 ml/acre.
4.
4.8 ml/acre
5.
23 ml/acre
6.
46 ml/acre
Treatments were applied by a modified SPRAYAIR™ tractor
sprayer. The sprayer was modified to distribute the solution from orifices
angled 30 degrees downward from horizontal oriented forward and backward to
maximize spike coverage. The solution carrier was CO2 delivering
volumes of 5.2 and 19.2 gpa into the air stream. The tractor traveled on the
left half of the plot area. This area also provided border to reduce off
target drift between treatment areas. Visual estimation FHB incidence and
field severity, 20 samples per plot, (spikelet count per individual head
multiplied times FHB infected spikes per head) were determined 20 days after
fungicide application. Each plot was harvested with a Hege plot combine and
the grain sample cleaned and processed for yield, test weight, and plump
measurement. Data was analyzed with SAS GLM.
RESULTS AND DISCUSSION
FHB field severity was reduced by fungicide application
but there were not differences between adjuvant rates and fungicide with no
adjuvant. All fungicide treatments increased test weight over the check.
Silwet L-77 at 1.5 ml/acre also had greater test weights than no adjuvant and
46 ml/acre adjuvant. Test weight was also increased when gpa was 19.2.
At the 5.2 gpa application volume yield was increased
when the adjuvant rate was 46 ml/acre giving an 11.3 bu yield increase over
the untreated. At 19.2 gpa yields were decrease at the 23 and 46 ml/acre rates
compared to no adjuvant and the 1.5 ml/acre adjuvant rate. Most
recommendations for adjuvant are based on a % of the tank volume. This trial
would tend to indicate that increased application volume requires decreasing
adjuvant amounts.
Summary
There were no differences in FHB field severity among
Silwet X-77 rates. The addition of Silwet X-77 at 1.5 or 23 ml/acre increase
test weight over no Silwet X-77, 46 ml/acre and the untreated. Greater water
volume also increased test weight. Yield was increased by using greatest rates
of adjuvant at low water volume but decreased when rates of 23 and 46 ml/acre
were used with greater water volume.
Table 1. FHB disease, yield, test weight, and plump response to Silwet X-77 rate with AMS 21619 fungicide application to Robust Barley Langdon, 2002.
|
GPA |
Silwet L-77 |
FHB |
Yield |
Test |
Plump |
|
|
|
Rate |
Incidence |
Severity |
|
Weight |
|
|
|
|
|
|
|
|
|
|
|
ml/acre |
% |
% |
bu/acre |
lb/bu |
% |
|
|
|
|
|
|
|
|
|
GPA*Silwet L-77 Rates |
|
|
|
|
|
|
|
5.2 |
0 |
76.7 |
11.2 |
80.5 |
46.8 |
87.7 |
|
|
1.5 |
67.5 |
9.8 |
76.2 |
47.3 |
88.4 |
|
|
4.8 |
80.0 |
11.3 |
75.7 |
47.4 |
88.7 |
|
|
23 |
76.7 |
9.9 |
76.0 |
47.1 |
89.1 |
|
|
46 |
71.7 |
10.9 |
91.3 |
47.4 |
89.1 |
|
|
Untreated |
83.3 |
13.7 |
80.0 |
46.4 |
87.7 |
|
|
|
|
|
|
|
|
|
19.2 |
0 |
75.8 |
11.3 |
86.1 |
47.5 |
90.3 |
|
|
1.5 |
74.2 |
9.8 |
86.6 |
48.2 |
89.5 |
|
|
4.8 |
80.8 |
11.1 |
82.2 |
47.4 |
88.3 |
|
|
23 |
70.0 |
10.8 |
76.8 |
48.1 |
89.2 |
|
|
46 |
75.0 |
8.0 |
75.3 |
47.0 |
86.1 |
|
|
Untreated |
85.6 |
20.3 |
82.1 |
46.7 |
87.1 |
|
|
|
|
|
|
||
|
Silwet L-77 Rates averaged over GPA |
|
|
|
|
||
|
|
0 |
76.3 |
11.3 |
83.3 |
47.2 |
89.0 |
|
|
1.5 |
70.8 |
9.8 |
81.4 |
47.8 |
89.0 |
|
|
4.8 |
80.4 |
11.2 |
79.0 |
47.4 |
88.5 |
|
|
23 |
73.3 |
10.4 |
76.4 |
47.6 |
89.1 |
|
|
46 |
73.3 |
9.5 |
83.3 |
47.2 |
87.6 |
|
|
Untreated |
84.2 |
17.0 |
81.0 |
46.6 |
87.4 |
|
|
|
|
|
|
||
|
GPA averaged Silwet L-77 Rates |
|
|
|
|
||
|
5.2 |
|
76.0 |
11.1 |
79.9 |
47.1 |
88.4 |
|
19.2 |
|
76.8 |
11.9 |
81.5 |
47.5 |
88.4 |
|
|
|
|
|
|
|
|
|
Silwet Rate* |
NS |
3.3 |
NS |
0.6 |
NS |
|
|
GPA* |
|
NS |
NS |
NS |
0.4 |
NS |
|
Sil*GPA |
|
NS |
NS |
7.3** |
NS |
NS |
|
%CV |
|
15 |
35 |
12 |
2 |
4 |
*Significant at 0.05
probability level for mean comparisons.
** Significant at 0.1
probability level for mean comparisons.
Figure 1. Yield response to Silwet X-77 rate with AMS 21619 fungicide at 5.2 and 19.2 gpa water volume applied to Robust Barley Langdon, 2002.
