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
FUNGICIDE APPLICATION DATE(S):
- 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.
CULTURAL PRACTICES:
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).
GENERAL OBSERVATIONS:
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.
SUMMARY:
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.
| Company | Trt # | Fungicide 1 | Powdery mildew (%) May 15 | Spot blotch (%) May 15 | Leaf spotting (%) 2 May 23 | Stay green (%) 3 May 25 |
| Syngenta | 1 | Alto at 4 floz/Ac + 0.125% v/v NIS @ GS 6 fb Trivapro at 13.7 floz/Ac + 0.125% v/v NIS @ GS 10.1 | 2.0 def | 1 cde | 41.25 hij | 47.5 cdef |
| Syngenta | 2 | Trivapro at 13.7 floz/Ac + 0.125% v/v Induce @ GS 10.1 | 0.25 f | 0 e | 20 l | 70 ab |
| BASF | 3 | Nexicor @ 9 fl oz/A + 0.125 % v/v NIS at GS10.1 | 2.0 def | 0.25 e | 40 ij | 50 cde |
| BASF | 4 | Priaxor @ 2 fl oz/A applied at GS 5-6 fb Sphaerex @ 4 fl oz/A + Headline @ 6 fl oz/A at GS10.1 | 2.75 cdef | 0 e | 28.75 k | 60 abc |
| UPL | 5 | Zolera FX @ 5 fl oz/a + 0.125% v/v NIS at GS10.1 | 0 f | 4 ab | 55 bcde | 35 efgh |
| UPL | 6 | Evito 480 SC @ 4 floz/a + 0.125% v/v NIS at GS10.1 | 6.75 bcde | 4 ab | 61.25 abc | 32.5 fgh |
| UPL | 7 | Evito 480 SC @ 1 floz/a + 0.125% v/v NIS at GS5-6 | 11.25 ab | 5 a | 67.5 a | 15 ij |
| UPL | 8 | Evito 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 GS10.1 | 7.5 bcd | 4 ab | 61.25 abc | 42.5 defgh |
| FMC | 9 | Adastrio 5 fl oz/A at GS10.1 | 3.75 cdef | 5 a | 66.25 a | 32.5 fgh |
| FMC | 10 | Adastrio 7 fl oz/A at GS10.1 | 7.75 bc | 3 abc | 56.25 bcde | 42.5 defgh |
| FMC | 11 | Topguard 5 fl oz/A at green up fb Adastrio 5 fl oz/A GS10.1 | 2.75 cdef | 3.75 ab | 42.5 hij | 57.5 bcd |
| FMC | 12 | Topguard 5 fl oz/A at green up fb Adastrio 7 fl oz/A GS10.1 | 1.75 ef | 0.75 cde | 45 ghij | 50 cde |
| FMC | 13 | Topguard 5 fl oz/A at green up fb Topguard 5 fl oz/A at GS10.1 | 4 cdef | 4 ab | 56.25 bcde | 45 cdefg |
| FMC | 14 | Topguard 5 fl oz/A at green up fb Topguard EQ 5 fl oz/A at GS10.1 | 2.75 cdef | 2 bcde | 46.25 fghi | 47.5 cdef |
| Albaugh | 15 | ALB4003B + 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 cdef | 1.75 bcde | 52.5 defg | 50 cde |
| Albaugh | 16 | ALB4020 + 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 cdef | 5 a | 62.5 ab | 27.5 hij |
| Albaugh | 17 | ALB4010 + 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 cdef | 4 ab | 60 abcd | 37.5 efgh |
| Albaugh | 18 | Propi Star @ 4.0 oz/acre at GS 5-6) FB Propi Star @ 4.0 oz/acre at GS 10.1 | 2.75 cdef | 2 bcde | 57.5 bcd | 30 ghi |
| Albaugh | 19 | ALB4020 @ 4.0 oz/acre at GS5-6 FB ALB4020 + ALB4010B ( 4.0 oz/acre + 3.0 oz/acre at GS10.1) | 1.25 ef | 2 bcde | 52.5 defg | 55 bcd |
| Albaugh | 20 | Prozio 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 ef | 2.75 abcd | 48.75 efgh | 57.5 bcd |
| Albaugh | 21 | ALB4003B + 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 GS10.1 | 1.25 ef | 0.5 de | 37.5 j | 75 a |
| — | 22 | Tilt @ 4.0 oz/ac + 0.125% v/v NIS at GS 10.1 | 5.5 cdef | 2 bcde | 53.75 cdef | 50 cde |
| — | 23 | Untreated check | 15 a | 3 abc | 62.5 ab | 12.5 j |
| LSD (P = 0.05) | 5.58 | 2.42 | 8.09 | 15.44 |
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