UNL Studies Effect of Foliar Fungicides and Insecticides on Soybean Disease Severity and Yield

UNL Studies Effect of Foliar Fungicides and Insecticides on Soybean Disease Severity and Yield

January 12, 2012

Foliar fungicide trials were conducted at four locations in Nebraska to determine the effects on disease control and yield. The sites, part of the the Soybean Management Field Days, were near Bancroft (northeast), Clay Center (south central), Cortland (southeast), and Elba (central).

Two of the sites, Bancroft and Cortland, showed yield differences from fungicide treatments. Adding insecticide to the fungicide showed an increased yield compared to fungicide alone for each company’s products.

How the Trial was Conducted

The study included 9 treatments and an untreated control.

  • Planting population at all sites was 150,000 seeds/ac.
  • Weed control was accomplished through a preemergence application of Warrant (acetochlor) and post applications of Roundup (glyphosate).
  • Additional site details are listed in Tables 1-4.

Plots were 4 rows wide (10 feet) by 25 feet long. Treatments were applied with a CO2 pressurized backpack sprayer and arranged in a randomized complete block design. The spray boom was 10 ft wide with 20-inch nozzle spacings and was pressurized to 40 psi. Fifteen gallons per acre of spray volume from Teejet XR11002 nozzles provided adequate canopy penetration and coverage of soybean leaves.

All applications were made at the R3 (beginning pod development) growth stage. Disease was assessed at approximately 11-22 days after treatment and again later in the growing season. Leaf retention was assessed shortly before harvest when less than 50% of the leaves were remaining in non-treated control plots. Prior to harvest, the ends of each plot were cut to minimize edge effects in yield data. All yields were adjusted to 13% moisture content.

Findings

  • Septoria brown spot was reduced in fungicide-treated plots at Bancroft and Elba. A different soybean variety was planted at these sites than at Clay Center and Cortland, where there was no difference in disease severity. The difference in varieties needs to be taken into account when looking at these results. Each variety can have different susceptibility levels to brown spot and respond differently to fungicides.
     
  • At Clay Center and Cortland, fungicide-treated plots tended to have lower disease severity than the control plots, but the differences were not significant.
     
  • Generally, all fungicides in this trial at all locations increased leaf greenness and leaf retention over the control.
     
  • Only the Bancroft and Cortland sites showed statistical yield differences from applying fungicide.  All treatments at these sites yielded more than the control. The Stratego YLD + Leverage 360 and Quilt Xcel + Warrior II treatments had the highest yields at Bancroft and Cortland, respectively.
     
  • There was no significant bean leaf beetle or soybean aphid feeding observed at these locations. Adding an insecticide to each fungicide increased yield in most cases as compared to applying the fungicide alone for each company’s products.

Loren Giesler
Extension Plant Pathologist
Travis Gustafson
Technologist, Department of Plant Pathology


Table 1. Effects of fungicide and insecticide applications on disease severity and yield at Bancroft.  All products were applied at R3 growth stage on July 27. Herbicides for weed control were applied on May 18. Location was planted on May 9 with variety Pioneer 93M11 and harvested on October 8.
Treatment and Rate/Acre % Brown Spot Severity  
Yield (bu/ac)
 
22 DAT*
42 DAT
   
Untreated
5.0
12.0
 
58.5
Headline SC 6 fl oz/ac
0.5
5.0
 
60.0
Headline SC 6 fl oz/ac + Respect 3 fl oz/ac
0.5
4.0
 
63.2
Quilt Xcel 14 fl oz/ac
0.4
7.5
 
59.7
Quilt Xcel 14 fl oz/ac + Warrior II 1 fl oz/ac
1.0
12.0
 
62.2
Stratego YLD 4 fl oz/ac
0.4
8.8
 
61.2
Stratego YLD 4 fl oz/ac + Leverage 360 2.8 fl oz/ac
0.1
6.5
 
64.9
Evito 2 fl oz/ac
0.9
9.5
 
60.1
Evito 2 fl oz/ac + Mustang Max 3 fl oz/ac
1.4
10.8
 
62.1
Mustang Max 3 fl oz/ac
3.5
14.5
 
60.6
LSD (α=0.1)
0.8
4.9
 
1.5

*DAT = Days After Treatment

 

Table 2.  Effects of fungicide and insecticide applications on disease severity and yield at Clay Center.  All products were applied at R3 growth stage on July 28.  Herbicides for weed control were applied on May 17.  The site was planted on May 4 with Pioneer 93Y70 soybeans and harvested on October 19.

Treatment and Rate/Acre
% Brown Spot Severity
Leaf Retention**
Yield (bu/ac)
 
11 DAT*
25 DAT
 
 
Untreated
25.0
43.8
10.0
72.8

Headline SC 6 fl oz/ac

17.5
45.0
28.8
64.5
Headline SC 6 fl oz/ac + Respect 3 fl oz/ac
16.3
45.0
28.8
73.5
Quilt Xcel 14 fl oz/ac
17.5
40.0
28.8
70.6
Quilt Xcel 14 fl oz/ac + Warrior II 1 fl oz/ac
30.0
32.5
18.8
70.6
Stratego YLD 4 fl oz/ac
17.5
33.8
27.5
76.5
Stratego YLD 4 fl oz/ac + Leverage 360 2.8 fl oz/ac
21.3
40.0
30.0
77.0
Evito 2 fl oz/ac
18.8
38.8
25.0
73.2
Evito 2 fl oz/ac + Mustang Max 3 fl oz/ac
23.8
42.5
17.5
74.1
Mustang Max 3 fl oz/ac
22.5
45.0
12.5
69.8
LSD (α=0.1)
NS
NS
6.3
NS

*DAT = Days After Treatment
**Leaf retention rating indicates % leaves remaining and was assessed on September 27

 

Table 3.  Effects of fungicide and insecticide applications on disease severity and yield at Cortland.  All products were applied at R3 growth stage on July 21.  Herbicides for weed control were applied on May 16.  The site was planted on May 2 with Pioneer 93Y70 soybeans and harvested on October 7.

Treatment and Rate/Acre % Brown Spot Severity
Leaf Retention**
Yield (bu/ac)
 
14 DAT*
47 DAT*
   
Untreated
33.8
50.0
35.0
52.3
Headline SC 6 fl oz/ac
33.8
36.3
85.0
54.6
Headline SC 6 fl oz/ac + Respect 3 fl oz/ac
26.3
42.5
90.0
56.4
Quilt Xcel 14 fl oz/ac
30.0
 
77.5
55.8
Quilt Xcel 14 fl oz/ac + Warrior II 1 fl oz/ac
30.0
47.5
87.5
58.1
Stratego YLD 4 fl oz/ac
27.5
45.0
78.8
57.3
Stratego YLD 4 fl oz/ac + Leverage 360 2.8 fl oz/ac
18.8
45.0
81.3
58.0
Evito 2 fl oz/ac
38.8
50.0
66.3
55.9
Evito 2 fl oz/ac + Mustang Max 3 fl oz/ac
25.0
40.0
61.3
55.3
Mustang Max 3 fl oz/ac
30.0
48.8
48.8
54.5
LSD (α=0.1) NS
NS
13.2
2.4

*DAT = Days After Treatment
**Leaf retention rating indicates % leaves remaining and was assessed on September 20

 

Table 4.  Effects of fungicide and insecticide applications on disease severity and yield at Elba.  All products were applied at R3 growth stage on August 3.  The site was planted on May 6 with Pioneer 93M11 soybeans and harvested on October 21.

Treatment and Rate/Acre % Brown Spot Severity
Leaf Retention**
Yield (bu/ac)
 
14 DAT*
40 DAT*
   
Untreated
8.8
50.0
1.3
64.7
Headline SC 6 fl oz/ac
4.3
48.8
10.0
64.8
Headline SC 6 fl oz/ac + Respect 3 fl oz/ac
4.3
53.8
16.3
68.2
Quilt Xcel 14 fl oz/ac
5.5
53.8
7.0
67.4
Quilt Xcel 14 fl oz/ac + Warrior II 1 fl oz/ac
4.8
53.8
10.0
69.6
Stratego YLD 4 fl oz/ac
3.5
50.0
7.5
67.0
Stratego YLD 4 fl oz/ac + Leverage 360 2.8 fl  oz/ac
6.3
51.3
15.0
67.6
Evito 2 fl oz/ac
3.5
52.5
3.3
63.7
Evito 2 fl oz/ac + Mustang Max 3 fl oz/ac
6.3
53.8
7.5
64.9
Mustang Max 3 fl oz/ac
8.8
51.3
6.3
63.1
LSD (α=0.1)
2.7
NS
4.3
NS

*DAT = Days After Treatment
**Leaf retention rating indicates % leaves remaining and was assessed on September 28