Foliar Wheat Disease Management with Fungicides – 2022: Report 2

COOPERATORS: Meriem Aoun1, Brian Olson1, & Tyler Pierson2; Departments of Entomology & Plant Pathology1, Field Research Services Unit2; Oklahoma State University, Stillwater, OK

PURPOSE:  To determine the efficacy of fungicides for controlling foliar diseases when applied to hard red winter wheat in Oklahoma.

LOCATION:  Entomology & Plant Pathology Research Farm; Stillwater, Oklahoma (Google Maps coordinates:  36.1266690, -97.1047885)

VARIETY:  ‘OK Bullet’                     

SOIL TYPE:  Norge loam

PLANTING DATE & RATE:  15-Oct-2021 at 90 lb/ac       

FUNGICIDE APPLICATION DATE(S):

A total of 12 fungicide treatments ( from Albaugh LLC) were applied on 30-Apr-2022 at Feekes’ growth stage 10.1 (wheat heads (awns) just starting to emerge from the boot). There was an untreated check.

TARGET DISEASES: Powdery mildew, leaf rust, stripe rust, Septoria leaf blotch, spot blotch, and tan spot.

PLOT DESIGN: Plots were 49 in. (7 rows; 7 in. spacing) by 20 ft, replicated four times in a randomized block design. Data were analyzed using R version 4.1.3.  Mean separation (LSD) was conducted only if ‘F’ test was significant.

CULTURAL PRACTICES:

Fertilizer:  Fertilizer was applied to the soil with a 50 bu/ac yield goal.

Herbicide:  None applied

Insecticide:  Gaucho 600 (2.4 fl oz/cwt) applied as a seed treatment

Irrigation:  No irrigation provided

METHOD OF APPLICATION:  Fungicides were applied with a CO2 wheelbarrow sprayer as a broadcast foliar application using flat fan nozzles (8003EVS) spaced 18 inches apart.  The sprayer was calibrated to deliver fungicides at a rate of 20 GPA.

DISEASE ASSESSMENT: When sufficient foliar disease was present, plots were evaluated for type of disease and rated for percent infection using modified keys based on, “A Manual of Assessment Keys for Plant Disease. 1971. Clive James. Canada Department of Agriculture Publication No. 1458.” In this rating system, the percentage of leaf surface area covered by a disease was rated as 0=no disease; 1=1% infection; 5=5% infection; 10=10% infection; 15=15% infection;25=25% infection; 40=40% infection; 65=65% infection; 80=80% infection; 90=90% Infection; 99=99% infection.

GENERAL OBSERVATIONS:  Drought was prevalent through most fall 2021 and spring 2022. The accumulated rainfall in spring of 2022 was 15 inches in March-May 2022. Prior to planting (July-September 2021), the accumulated rainfall was 4.2 inches.  Moisture in October-November (5.37 inches) promoted emergence and stand development.  During spring, the highest levels of moisture were recorded in May 2022 (10.55 inches) which helped crop development and seed fill.

Low levels of barley yellow dwarf (BYD; confirmed with ELISA testing) infections were present but scattered randomly across the trial.  Although BYD may have slightly impacted yield it was not a major concern.  Powdery mildew (PM) was the most prevalent disease in April and May and was severe especially in lower and mid-canopy. PM was rated on 19-April (before fungicide application ( Table1, Figure 1) and on 19-May (after fungicide application, which was on 30-April) (Table 1, Figure 2).  Leaf spot, mainly spot blotch (confirmed by isolation to be caused by Bipolaris sorokiniana), was observed in May and at low to moderate severity and was rated on 19-May (Table 1, Figure 3).  Leaf rust was noted on the upper canopy (flag leaf and F-1) after the rain in May, but it was at low levels that did not exceed 5% severity on the untreated check. Foliage senesced quickly after 19-May and no more ratings could be made. No indication of phytotoxicity by any fungicide treatment was observed.

Figure 1. Powdery mildew (PM) disease distributions (in %) in the plots before fungicide application.

Figure 2. Powdery mildew (PM) disease distributions (in %) in the plots 19 days after fungicide application.

Figure 3. Leaf spot (mainly spot blotch) disease distributions (in %) in the plots 19 days after fungicide application.

Table 1. Summary of foliar wheat disease management with fungicides in Stillwater, Oklahoma 2022.

Fungicide; rate (oz/ac) 1 Date of fungicide application: 30-Apr Growth stage of application: 10.1Powdery Mildew (%) (before fungicide application) 2Powdery Mildew (%) (after fungicide application) 3Leaf Spot (%) (Mainly spot blotch) 4
Dates of disease ratings19-Apr19-May19-May
ALB4010B @ 2 oz/A16.255.00 bcd3.75 bcd
ALB4010B @ 3 oz/A16.2510.00 ab0.00 d
ALB4010B @ 4 oz/A22.508.75 bc5.00 bcd
ALB4024B @ 4 oz/A13.757.50 bcd3.75 bcd
ALB4024B @ 7 oz/A30.006.25 bcd3.75 bcd
ALB4024B @ 10 oz/A22.503.75 bcd2.50 cd
Propi-Star @ 2 oz/A17.501.25 d6.25 bc
Propi-Star @ 3 oz/A17.5010.00 ab8.75 ab
Propi-Star @ 4 oz/A21.257.50 bcd5.00 bcd
Quilt Xcel @ 4 oz/A16.251.25 d3.75 bcd
Quilt Xcel @ 7 oz/A17.502.50 cd1.25 cd
Quilt Xcel @ 10 oz/A17.503.75 bcd1.25 cd
Untreated Check18.7516.25 a12.50 a
LSD (p=0.05)7.245.88

1Plus 0.125% Induce (v/v) added to all treatments.

2Powdery mildew rated on leaves in lower canopy on 19-Apr

3Powdery mildew rated on leaves on flag leaves on 19-May

4Leaf spot rated on flag leaves on 19-May

SUMMARY:  Results from this trial demonstrated the value of fungicide to manage foliar fungal diseases (powdery mildew and leaf spot).  Fungicide application (growth stage 10.1; 30-April) managed powdery mildew and leaf spot development. For the four used fungicides, the rate did not have significant effect on the severity of powdery mildew and leaf spot. 

Foliar Wheat Disease Management with Fungicides – 2022

COOPERATORS: Dr. Meriem Aoun1, Dr. Amanda de Silva Oliveira2, Brian Olson1, & Tyler Pierson3

Departments of Entomology & Plant Pathology1, Plant & Soil Science2, and Field Research Services Unit3; Oklahoma State University, Stillwater, OK

PURPOSE:  To determine the efficacy of fungicides for controlling foliar diseases when applied to hard red winter wheat in Oklahoma.

LOCATION:  Entomology & Plant Pathology Research Farm; Stillwater, Oklahoma (Google Maps coordinates:  36.1266690, -97.1047885)

VARIETY: ‘OK Bullet’ hard red winter wheat              

SOIL TYPE:  Norge loam

PLANTING DATE & RATE:  15-Oct-2021 at 90 lb/ac

FUNGICIDE APPLICATION DATE(S):

16-Mar-2022 @ Feekes’ growth stage 6 (GS6: 1st node detectable at base of main tiller)

30-Apr-2022 @ Feekes’ growth stage 10.1 (GS 10.1: heads (awns) just starting to emerge from the boot)

TARGET ORGANISMS (DISEASES): Blumaria graminis f. sp. tritici (wheat powdery mildew), Puccinia triticina (wheat leaf rust), and P. striiformis (stripe rust), Zymoseptoria tritici (Septoria leaf blotch)

PLOT DESIGN: Plots were 49 in. (7 rows; 7 in. spacing) by 20 ft, replicated four times in a randomized block design. Data were analyzed using R version 4.1.3.  Mean separation (LSD) test was conducted only if ‘F’ test was significant.

CULTURAL PRACTICES:

Fertilizer: Based on a soil test with a 50 bu/ac yield goal, 26 lb/acre of nitrogen, 107 lb/acre of phosphorus, and 233 lb/acre of Potassium were applied.

Herbicide:  None applied

     Insecticide:  Gaucho 600 (2.4 fl oz/cwt) applied as a seed treatment

     Irrigation:  No irrigation provided

METHOD OF APPLICATION:  Fungicides were applied with a CO2 wheelbarrow sprayer as a broadcast foliar application using flat fan nozzles (8003EVS) spaced 18 inches apart.  The sprayer was calibrated to deliver fungicides at a rate of 20 GPA.

DISEASE ASSESSMENT: When sufficient foliar disease was present, plots were evaluated for type of disease and rated for percent infection using modified keys based on, “A Manual of Assessment Keys for Plant Disease. 1971. Clive James. Canada Department of Agriculture Publication No. 1458.” In this rating system, we took the percentage of leaf surface area covered by a disease.

HARVEST METHOD:  Plots were harvested with a Wintersteiger Delta small plot combine. Grain weight, test weight, and moisture content were collected from each plot. Grain moisture at harvest was ~ 8% for all plots. Grain yield of the plots was adjusted to 12% moisture.

GENERAL OBSERVATIONS

Drought was prevalent through most fall 2021 and spring 2022. The accumulated rainfall in spring of 2022 was 15 inches in March-May 2022. Prior to planting (July-September 2021), the accumulated rainfall was 4.2 inches.  Moisture in October-November (5.37 inches) promoted emergence and stand development.  During spring, the highest levels of moisture were recorded in May 2022 (10.55 inches) which helped crop development and seed fill.

      Low levels of barley yellow dwarf (BYD; confirmed with ELISA testing) infections were present but scattered randomly across the trial.  Although BYD may have slightly impacted yield it was not a major concern.  Powdery mildew (PM) was the most prevalent disease in April and May and was severe especially in lower and mid-canopy. PM was rated on 19-April (before fungicide application at GS 10.1) and on 15-May (after fungicide application at GS 10.1). Leaf rust was noted on the upper canopy (flag leaf and F-1) after the rain in May, but it was late during the season and at low levels that did not exceed 5% severity on the nontreated check. Foliage senesced quickly after 15-May and no more ratings could be made. No indication of phytotoxicity by any fungicide treatment was observed.

SUMMARY

Results from this trial demonstrated the efficacy of most fungicide treatments to manage foliar fungal diseases (powdery mildew) (Table1).  The average powdery mildew severity of the nontreated check reached 33% on April 19 (rating on the lower and mid canopy) and 25% on May 15 (on the upper canopy; flag leaf and F-1). Yield (adjusted to 12% moisture) ranged from 50.51 bu/ac to 69.72 bu/ac. Test weight ranged from 59.0 to 60.35 lb/bu. For the nontreated check, yield was 58.20 bu/acre whereas test weight was 59.6 lb/bu.

Most early season fungicide treatments (GS 6; on 16-March) did not manage early season powdery mildew (rated on 19-April) to sufficient levels compared with the nontreated check. Compared to the nontreated check, yield was significantly higher for four treatments (i.e., Topguard fb Topguard, Topguard  fb Topguard EQ, ALB4010B (2.8 fl oz/a) and ALB4010B (4 fl oz/a). For these treatments, powdery mildew severity (15 days after application at GS 10.1) ranged from 8 to 15% (significantly lower than the nontreated check).

Table 1.  Summary of foliar wheat disease management with fungicides in Stillwater, Oklahoma 2022.

Treatment 1RateCompanyGS applied 2PM rating_19 Apr 3PM rating_15 May 4Yield (bu/acre) 5Test weight (lb/bu)
Alto fb Trivapro4 floz/A fb 13.7 floz/ASyngenta6 fb10.122.50     ef3.75    
fg
59.04 cdef59.85
Trivapro fb Trivapro9.4 floz/A fb 9.4 fl oz/ASyngenta6 fb10.123.75    def5.00   
efg
58.51 cdef60.33
Trivapro13.7 floz/ASyngenta10.137.50     ab7.50   defg54.39
ef
60.25
Nexicor9 fl oz/ABASF10.130.00 abcdef7.50   defg57.97
def
60.35
Sphaerex fb Nexicor3.5 fl oz/A fb 7 fl oz/ABASF6 fb10.121.25     
f
7.50   defg58.92 cdef60.23
Priaxor fb Nexicor2 fl oz/A fb 7 fl oz/ABASF6 fb10.132.50  abcde10.00  cdefg58.94 cdef60.18
Sphaerex6.5 fl oz/ABASF10.127.50  bcdef2.50     
g
61.28 abcde59.3
Zolera FX + NIS (0.125 % v/v)5 fl oz/AUPL10.140.00     
a
6.25   defg50.51
f
59.5
Evito 480 SC + NIS (0.125 % v/v)4 fl oz/AUPL10.132.50  abcde15.00    bcd58.04
def
59.83
Evito 480 SC + NIS (0.125 % v/v) fb Tebuzol + NIS (0.125% v/v)2 fl oz/A fb 4 fl oz/AUPL6 fb10.135.00    abc15.00    bcd54.66
ef
59.65
Evito 480 SC + NIS (0.125 % v/v) fb Zolera FX + NIS (0.125 % v/v)2 fl oz/A fb 5 fl oz/AUPL6 fb10.135.00    abc12.50  bcdef56.05
ef
59.43
Topguard fb Topguard5 fl oz/A fb 5 fl oz/AFMC6 fb10.123.75    def11.25 bcdefg69.11
ab
59.45
Topguard  fb Topguard EQ5 fl oz/A fb 5 fl oz/aFMC6 fb10.122.50     ef8.75  cdefg69.72
a
60.18
Topguard fb Lucento5 fl oz/A fb 5 fl oz/aFMC6 fb10.126.25   cdef13.75   bcde60.058 bcde59.73
Topguard5 fl oz/AFMC626.25   cdef17.50    abc56.35
ef
59.25
Topguard EQ5 fl oz/AFMC10.132.50  abcde12.50  bcdef54.59
ef
60.05
Plain Urea (46-0-0)100 lbs/AFMC637.50     ab20.00     ab54.20
ef
59.00
Topguard Fertilizer GR with Topguard fb Topguard EQ100 lbs/A fertilizer with 5 floz/A fb 5 fl oz/AFMC6 fb10.133.75   abcd17.50    abc59.71
cde
59.08
Topguard Fertilizer GR with Topguard fb Topguard EQ100 lbs/A fertilizer with 7 floz/A fb 5 fl oz/AFMC6 fb10.135.00    abc11.25 bcdefg59.13 cdef59.4
Topguard Fertilizer GR + Topguard fb Topguard EQ100 lbs/A fertilizer + 10 floz/A fb 5 fl oz/aFMC6 fb10.135.00    abc10.00  cdefg56.82
ef
59.83
Cover XL fb Cover XL + NIS (0.125% v/v)10 fl oz/a fb  10 fl oz/aAlbaugh LLC6 fb10.126.25   cdef10.00  cdefg58.72 cdef59.8
ALB4003B fb ALB4003B + NIS (0.125% v/v)7 fl oz/a fb  7 fl oz/aAlbaugh LLC6 fb10.127.50  bcdef11.25 bcdefg60.78 abcde60.00
PropiStar fb Cover XL + NIS (0.125% v/v)4 fl oz/a fb  10 fl oz/aAlbaugh LLC6 fb10.126.25   cdef15.00    bcd61.49 abcde59.93
ALB4010B fb ALB4003B + NIS (0.125% v/v)2.8 fl oz/a fb  7 fl oz/aAlbaugh LLC6 fb10.127.50  bcdef7.50   defg66.73 abcd59.90
ALB4010B + NIS (0.125% v/v)2.8 fl oz/aAlbaugh LLC10.128.75  bcdef15.00    bcd67.35
abc
59.65
ALB4010B + NIS (0.125% v/v) 4 fl oz/aAlbaugh LLC10.128.75  bcdef13.75   bcde60.78 abcde59.83
PropiStar + NIS (0.125% v/v) 4 fl oz/aAlbaugh LLC10.135.00    abc15.00    bcd57.28
ef
60.00
 Tilt 4 fl oz/a —10.132.50  abcde10.00  cdefg57.28
ef
59.88
Folicur 4 fl oz/a —10.135.00    abc13.75   bcde61.40 abcde59.45
Nontreated check —32.50  abcde25.00     
a
58.20
def
59.6
LSD (p=0.05)   11.239.699.11 —

1fb=followed by.

2GS (growth stage) is reported according to Feekes’ scale, where GS 6=first node detectable at base of main tiller;

  GS 10.1=heads just starting to emerge from boot with only awns visible.

3Powdery mildew rated on leaves in lower canopy on 19-Apr (before application at GS 10.1).

4Powdery mildew rated on leaves on flag leaves on 15-May (After application at GS 10.1).

5Yield values adjusted to 12% moisture.