Foliar Wheat Disease Management with Fungicides: Stillwater, Oklahoma, 2023

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:  11-Nov-2022 at 90 lb/ac


  • 28-Mar-2023 @ Feekes’ growth stage 6 (GS6: 1st node detectable at base of main tiller)
  • 19-Apr-2023 @ 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.


Fertilizer: Based on a soil test with a 50 bu/ac yield goal, 150 lbs/acre of Urea and 150 lbs/ac of DAP for a total of 96 lbs/acre of actual Nitrogen were applied prior to planting. In spring (Feb, 2023), an additional 50 lb/acre of Urea was applied to enhance disease development.

Herbicide:  None applied

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

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 15 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.

DATA ANALYSIS: Data were analyzed using R version 4.1.3.  Mean separation (LSD) test was conducted only if ‘F’ test was significant (Table 1).


Drought was prevalent through most fall 2022 and spring 2023 (October 2022 – March 2023). This suppressed fungal foliar diseases in fall and early Spring.  The highest levels of rainfall in spring of 2023 were recorded during late April-May 2023 (8.07 inches in April-May 2023), which favored some fungal foliar diseases such as powdery mildew and leaf spotting diseases (spot blotch, Septoria leaf blotch and Stagonospora nodorum blotch).

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. No diseases were observed in the fungicide trail until May. Powdery mildew (PM) occurred at moderate levels in mid-May. Spot blotch (caused by Bipolaris sorokiniana) was present at low levels around mid-May to late May. The rain in May also favored different leaf spotting diseases (spot blotch, Septoria nodorum blotch) that occurred at high levels during the third week of May. Foliage senesced quickly toward end of May and no more ratings could be made after May 25. There was no indication of phytotoxicity by any fungicide treatment.


Results from this trial demonstrated the efficacy of fungicide treatments in reducing severity of powdery mildew and leaf spotting (Table1).  Powdery mildew severity of the untreated check reached 15% on average on May 15 (on the upper canopy; flag leaf and F-1). Spot blotch occurred at low levels on May 15 (Table 1). On May 23 (34 days after flag leaf application), leaf spotting diseases (spot blotch, Septoria nodorum blotch) occurred at high severity reaching 63% on untreated check. However, powdery mildew and leaf spotting occurred late in the growing season (soft dough stage). On May 25, the stay green percent was significantly lower in untreated check (12.5%) compared to most fungicide treatments.

Table 1.  Summary of foliar wheat disease management with fungicides in Stillwater, Oklahoma 2023.

CompanyTrt #Fungicide 1Powdery mildew (%) May 15Spot blotch (%) May 15Leaf spotting (%) 2 May 23Stay green (%) 3 May 25
Syngenta1Alto at 4 floz/Ac + 0.125% v/v NIS @ GS 6 fb Trivapro at 13.7 floz/Ac + 0.125% v/v NIS @ GS 10.12.0  def1  cde41.25  hij47.5  cdef
Syngenta2Trivapro at 13.7 floz/Ac + 0.125% v/v Induce @ GS 10.10.25  f0  e20  l70  ab
BASF3Nexicor @ 9 fl oz/A + 0.125 % v/v NIS at GS10.12.0  def0.25  e40  ij50  cde
BASF4Priaxor @ 2 fl oz/A applied at GS 5-6 fb Sphaerex @ 4 fl oz/A + Headline @ 6 fl oz/A at GS10.12.75  cdef0  e28.75  k60  abc
UPL5Zolera FX @ 5 fl oz/a + 0.125% v/v NIS at GS10.10  f4  ab55  bcde35  efgh
UPL6Evito 480 SC @ 4 floz/a +  0.125% v/v NIS  at GS10.16.75  bcde4  ab61.25  abc32.5  fgh
UPL7Evito 480 SC @ 1 floz/a +  0.125% v/v NIS at GS5-611.25  ab5  a67.5  a15  ij
UPL8Evito 480 SC @ 1 floz/a +  0.125% v/v NIS applied at GS 5-6 fb Zolera FX @ 5 fl oz/a + 0.125% v/v NIS at GS10.17.5  bcd4  ab61.25  abc42.5  defgh
FMC9Adastrio 5 fl oz/A at GS10.13.75  cdef5  a66.25  a32.5  fgh
FMC10Adastrio 7 fl oz/A at GS10.17.75  bc3  abc56.25  bcde42.5  defgh
FMC11Topguard 5 fl oz/A at green up fb Adastrio 5 fl oz/A GS10.12.75  cdef3.75  ab42.5  hij57.5  bcd
FMC12Topguard 5 fl oz/A at green up fb Adastrio 7 fl oz/A GS10.11.75  ef0.75  cde45  ghij50  cde
FMC13Topguard 5 fl oz/A at green up fb Topguard 5 fl oz/A at GS10.14  cdef4  ab56.25  bcde45  cdefg
FMC14Topguard 5 fl oz/A at green up fb Topguard EQ 5 fl oz/A at GS10.12.75  cdef2  bcde46.25  fghi47.5  cdef
Albaugh15ALB4003B + ALB5018 (7.0 oz/acre + 0.10% vol/vol @GS5-6) fb ALB4003B + ALB5018 (@ 10.0 oz/acre + 0.10% vol/vol at GS10.1)3.75  cdef1.75  bcde52.5  defg50  cde
Albaugh16ALB4020 + ALB5018 ( 4.0 oz/acre + 0.10% vol/vol at GS5-6) fb ALB4020 + ALB5018 (5.0 oz/acre + 0.10% vol/vol at GS 10.1 )5  cdef5  a62.5  ab27.5  hij
Albaugh17ALB4010 +  ALB5018 (3.0 oz/acre + 0.10% vol/vol at GS5-6) fb ALB4010 +  ALB5018 (3.0 oz/acre + 0.10% vol/vol at GS10.1)5  cdef4  ab60  abcd37.5  efgh
Albaugh18Propi Star @ 4.0 oz/acre at GS 5-6) FB Propi Star @ 4.0 oz/acre at GS 10.12.75  cdef2  bcde57.5  bcd30  ghi
Albaugh19ALB4020 @ 4.0 oz/acre at GS5-6 FB  ALB4020 + ALB4010B ( 4.0 oz/acre + 3.0 oz/acre at GS10.1)1.25  ef2  bcde52.5  defg55  bcd
Albaugh20Prozio 4SC (@5.0 oz/acre at GS5-6) fb Prozio 4SC + Propi Star (5.0 oz/acre + 4.0 oz/acre at GS10.1)1.25  ef2.75  abcd48.75  efgh57.5  bcd
Albaugh21ALB4003B + ALB5013 (7.0 oz/acre + 64.0 oz/100 gal at GS5-6) fb ALB4003B + ALB5013 at 10.0 oz/acre + 64.0 oz/100 gal  at GS10.11.25  ef0.5  de37.5  j75  a
 —22Tilt @ 4.0 oz/ac + 0.125% v/v NIS at GS 10.15.5  cdef2  bcde53.75  cdef50  cde
 —23Untreated check15  a3  abc62.5  ab12.5  j
    LSD (P = 0.05)5.582.428.0915.44

1fb=followed by.

GS (growth stage) is reported according to Feekes’ scale.

GS5-6 (green up) application was on 28-Mar-2023 and GS10.1 (heads just starting to emerge from boot with only awns visible) application was on April 19, 2023.

For all measured traits, treatments with different letters are considered significantly different at 95% level of confidence based on LSD test.

2Leaf spotting includes spot blotch, Septoria nodorum blotch (confirmed with fungus culturing in lab).

3Percent of green tissue