Wheat Diseases and Their Control in a No-till Management System

Bob Hunger

Extension Wheat Pathologist

Oklahoma State University

Low- or no-till affects impacts disease incidence/severity via increased residue

on soil surface that affects pathogen inoculum and/or alters the soil

environment (moisture/temperature)

Photo credit: Oklahoma Conservation Commission

The Disease Triangle

Courtesy of J.P. Damicone

Some Diseases – No or little effect

Courtesy Dr. Stephen Harrison, LSU

Stripe rust Loose smut

Common bunt WSMV

Leaf rust

Courtesy Dr. Jeff Edwards, OkSU

WSBM & WSSMV

Aphids:Barley Yellow Dwarf Virus

Aphids:BYDV Decreased disease Increased residue is less attractive to aphids

Photo credit: extension.entm.purdue.edu

ROOT DISEASES Strawbreaker foot/root rot is decreased due

to residue inhibiting spore dispersal to seedlings

Strawbreaker foot root (eyespot)

ROOT DISEASES Dryland root rot is decreased because the soil

environment becomes more cool and moist

Dryland root rot caused by Fusarium

Courtesy of Dr. B. Bowden, USDA-ARS, Manhattan, KS

ROOT DISEASES Sharp eyespot (Rhizoctonia root rot) and

Pythium root rot are increased due to the soil environment becoming more cool/moist &

inoculum is increased

Sharp eyespot caused by Rhizoctonia

Poor seedling stand due to Pythium root rot

Take-all root rot is increased because the soil environment becomes more cool/moist & inoculum is increased

Take all root rot

% GC 14 DAP

% GC 31 DAP

% GC 45 DAP0

10

20

30

40

50

60

70

80

90

Effect of seed treatments on ground cover in Oklahoma in 2009

Drs. Jeff Edwards & Hunger, OkSU

% G

rou

nd

co

ver

*

*

Kingfisher 2008

Cherokee 20080

10

20

30

40

50

60

70

UntreatedRaxil

Gaucho XT

Yield response to Raxil and Gaucho seed treatments in Oklahoma in 2008

Dr. Jeff Edwards, OkSU

Yie

ld (

bu

/acre)

*

Powdery mildew

Foliar Diseases: Powdery Mildew

Powdery mildew

Increased disease Increases pathogen inoculum

FOLIAR DISEASES Septoria leaf & Stagonospora glume blotch

Septoria leaf & Stagonospora glume blotch

Increased disease Increased pathogen inoculum

Septoria leaf blotch – note “pycnidia” (black specks) Stagonospora glume blotch

Foliar Diseases Tan Spot

Resting bodies on straw Lesions on leaves

Tan spot Increased disease Increases pathogen inoculum

Fungicide applied

No fungicide0

10

20

30

40

50

60

70

Percentage (%) tan spot severity as affected by management practices,

cultivars, & fungicide

Carignano, et al. 2008. Agron. J. 100:145-153

2145 = Susceptible Overley = moderately resistant

% t

an

sp

ot

severit

y

Crop Rotation is helpful with No-till

• If do not rotate crops in a no-till system, there likely will be problems over time with tan spot, septoria, powdery mildew, etc

•Even with rotation, a disease such as Fusarium head blight can occur in a wheat-corn rotation

Fusarium head blight (aka scab) Photo credit: Oklahoma Conservation Commission

Plow

Chisel

No-till

0

200

400

600

800

1000

1200

1400

1600

Effect of wheat-sorghum rotation on tan spot severity

Bockus & Claassen. 1992. Agron. J. 100:145-153 A

UD

PC

m

easu

re o

f t

an

sp

ot

severit

y)

Plow

Chisel

No-till

0

5

10

15

20

25

30

35

40

Effect of wheat-sorghum rotation on wheat yield

Bockus & Claassen. 1992. Agron. J. 100:145-153

Wh

eat

yie

ld (

bu

/acre)

Wheat Foliar Fungicides in Oklahoma (Not all are yet labeled for use on wheat)

Rate PHIA Product (oz/A) (days/GS) TRIAZOLE Tilt – Syngenta 4 10.5 Alto – Syngenta 3.0-5.5 30 Folicur – Bayer CropScience 4 30 Prosaro – Bayer CropScience 6.5-8.2 30 STROBILURIN Headline - BASF 6.0-9.0 10.5 Evito – Arysta LifeScience 2-4 40 Aproach – DuPont 6-12 45, 14, 7/10.5 straw, hay, forage MIXTURES Quilt - Syngenta 14 45/10.5 Quilt Xcel - Syngenta 10.5-14 30 Stratego – Bayer CropScience 10 35 Stratego YLD – Bayer CropScience 4 35 TwinLine – BASF 7-9 30/10.5 Priaxor – BASF ?? ?? PYRAZOLE – AMIDE &/or MIXED Vertisan - DuPont ?? ?? APHI = pre-harvest interval; number of days required between last application & harvest

This information is provided only as a guide. It is the responsibility of the pesticide applicator by law to read and follow all current label directions. No endorsement is intended for products listed, nor is criticism meant for products not listed.

Generics are available for Tilt and Folicur

Split Application of a Fungicide – on

spring wheat in North Dakota

Yield increases of 2-7 bushels IF environment favorable for disease; greater return if have wheat stubble present and the it is a susceptible variety

Dr. Marsha McMullen, North Dakota St. Univ

Split Application of a Fungicide

4-5 leaf

Stage =

Feekes 2

Tillering

stage

Dr. Marsha McMullen, North Dakota St. Univ

0

10

20

30

40

50

60

70

80

PM

LR

Wheat Disease Control with Fungicides - 2011

Fungicides -applied on 16-Mar* (GS 6), 05-Apr** (GS9), & 12-Apr (GS 10.1) -PM rated on 01-Apr; LR rated on 19-May

Dis

eas

e S

eve

rity

(%

) P

M=p

ow

de

ry m

ildew

L

R=l

eaf

ru

st

A A A

A A A

B

B

B

B

B B

B

A

A

B

48

50

52

54

56

58

60

62

64

66

Yield

TW

2011 Wheat Disease Control using Fungicides Y

ield

(b

u/A

) &

te

st w

eig

ht

(lb

/bu

)

Fungicides applied on 16-Mar* (GS 6), 05-Apr** (GS 9) and 12-Apr (GS10.1) BUT for Hdline FB Twinline, it was a half rate of Twinline

A

A A A

A

For TW – no differences between fungicides

B B

B

Summary of Effects of Tillage on Wheat Diseases

•No- or low-till increases residue that affects disease by:

-increasing pathogen inoculum

-altering the soil environment (cooler, more moist soil)

•Rotate crops and have a plan for the rotation

-generally a rotation to a legume is best

•Consider reactions of varieties to diseases

-e.g., a variety with some resistance to tan spot, septoria, etc.

•Use a seed treatment to help stand establishment

•Use fungicide to help with foliar disease control,

especially in continuous wheat