Understanding the DON-Wheat Head Scab Connection. Don Hershman Extension Plant Pathologist University of Kentucky, Princeton, KY

Size: px

Start display at page:

Download "Understanding the DON-Wheat Head Scab Connection. Don Hershman Extension Plant Pathologist University of Kentucky, Princeton, KY"

Alaina Burns
6 years ago
Views:

1 Understanding the DON-Wheat Head Scab Connection Don Hershman Extension Plant Pathologist University of Kentucky, Princeton, KY

2 Understanding the DON-Wheat Head Scab Connection and Impact of Corn Residue on Head SCAB/DON Risk. Don Hershman Extension Plant Pathologist University of Kentucky, Princeton, KY

5 Head Scab (A.K.A Fusarium Head Blight) 1. Significant about 1 year in Epidemic about once every 8-10 years. 3. Impacts yield and grain quality (including seed quality) = $ lossed. 4. Can be successfully managed in most years: *Plant multiple varieties to encourage escape. *Resistant varieties. *Fungicides. *Crop Uniformity

6 Optimal Timing of Fungicide Application Crop most susceptible when flowering (anthers protruding) on 50% of main tillers.

7 Despite our best efforts, we occasionally have failures

8 Some failures are not failures at all: Reality Check!

9 Some failures are not failures at all: Reality Check! Up to 75% control can be achieved when a resistant variety is sprayed with a properly timed fungicide.

10 Despite our Best Efforts, We Occasionally Have Failures Inability to get crop sprayed in a timely fashion. Rain prohibits spaying at desired timing (anthesis). Rains within an hour of making an application. Non-uniform crop results in variable tillering and extended flowering window. Sometimes we do everything right and still have failures. High disease pressure overwhelms current management program. Disease favorable conditions during grain fill (= late infections).

11 Limited or no FHB head symptoms DON: 11.7ppm DON: 4.2ppm

13 What is DON? Deoxynivalenol; also called vomitoxin. The most common trichothecene toxin associated with FHB in U.S. and Canada. Is produced by Fusarium graminearum during infection and disease development.

14 DON in Grain Scabby grain is always contaminated with DON at some level. Is present in seed coat (bran component) of kernel. Especially concentrated in milled bran fraction and chaff.

15 Typical DON levels in Grain 274 ppm in pink tombstones 174 ppm in white tombstones 2-40 ppm in shriveled grain 0-4 ppm in asymptomatic grain* Actual observed DON level is average of all the above and sample quality. *Associated with late infections and cool-wet grain fill period.

16 Impact of DON? Not a known carcinogen or poison. Feed refusal and poor weight gain in animals is the main concern in animals. Animal death in extreme cases (especially swine). End Market: Humans Perceived impact (fear). Flavor and processing performance.

17 DON DOES NOT Kill or injure seedlings when contaminated grain is planted. Increase the risk of head scab the following spring. Does indicate the seed is compromised by Fusarium. Seed testing!

18 FHB Susceptibility Crop most susceptible when flowering (anthers protruding).

19 FHB Susceptibility Actual window of infection is from head emergence until late milk. Extruded, spent anthers are frequently retained on heads well into early grain fill and serve as primary infection site for late infections.

20 DON Accumulation DON accumulation in grain following infection is impacted by multiple factors Weather before, during and after grain fill Wheat cultivar Crop health FHB fungal isolates involved Timing of infection relative to crop stage Timing of crop harvest Use of strobilurin-based fungicides after flag leaf extension.

21 High DON and Low FHB Symptoms: Usually has a reasonable explanation if you analyze the unique scenario that occurred.

22 Impact of Corn Residue on Head Scab/DON Risk.

23 FHB (AKA Head Scab) Disease Cycle

24 Fusarium graminearum in corn stubble

25 Corn Residue Head Scab Planting wheat following corn. Increased corn production in areas where wheat is also a major crop is thought to be the reason for the increase in head scab epidemics since late 1990 s. Historically, Planting wheat no-till following corn is considered to be the worse-case scenario for head scab risk. 99% of KY wheat is planted no-till, into corn stubble and we are making it just fine!

26 Corn Residue Head Scab Planting wheat following corn. Increased corn production in areas where wheat is also a major crop is thought to be the reason for the increase in head scab epidemics since late 1990 s. So what is going on? Historically Planting wheat no-till following corn is considered to be the worse-case scenario for head scab risk. 95% of KY wheat is planted no-till, into corn stubble and we are making it just fine!

27 KY Survey of 300 Wheat Fields, Looked at wheat planted behind corn. Measured surface coverage by corn residue in the fall, after wheat planting, using standardized a NRCS protocol. Measured head scab incidence and severity in the spring, during early grain fill. Collected grain and tested it for DON content.

28 KY Survey of 300 Wheat Fields, FHB Variable % Corn Residue Cover (fall) Incidence P < (r 2 = 0.17) Severity NS Index P <0.001 (r 2 =0.11) DON NS

29 KY Survey of 300 Wheat Fields, FHB Variable % Corn Residue Cover (fall) Incidence P < (r 2 = 0.17) Conclusion: Severity NS Corn residue does impact FHB risk, but there are many Index more important factors, P <0.001 as indicated (r 2 =0.11) by the highly variable relationship between FHB and corn DON residue cover. NS

30 HERETIC! Some Breeders and plant pathologists Me

31 Effects of Local Corn Debris Management on FHB and DON Levels in Seventeen U.S. Wheat Environments in 2011 to 2013 Project Investigators Gary C. Bergstrom, Jaime A. Cummings, Katrina D. Waxman, Carl A. Bradley, Stephen N. Wegulo, Ann L. Hazelrigg, Donald E. Hershman, Martin Nagelkirk, and Laura E. Sweets

32 Effects of Local Corn Debris Management on FHB and DON Levels in Seventeen U.S. Wheat Environments in 2011 to 2013 Significant differences (P = 0.05) between treatment means for a location are indicated by *.

33 Explanation for Findings In wheat production areas with widely scattered corn production: F.g. spores are abundant no matter where you farm in the area. Spores generated outside one s field are just as, or more, abundant than spores generated within a field. With this scenario, the previous crop and tillage regime are not very important because abundant spores will be produced as long as conditions favor FHB.

34 HERETIC!

35 Questions?

Wheat Management. Anthony Ohmes University of Missouri Extension

Wheat Management. Anthony Ohmes University of Missouri Extension Wheat Management Anthony Ohmes University of Missouri Extension Wheat Yield Components Head Size Feekes 3 (tillering) # of Heads and Kernels - Feekes 6 (jointing) Kernel Size Feekes 8 Feekes Scale Wheat