Disease forecast 2011:
Viruses and stripe rust
Dr. Mary Burrows
Montana State University Bozeman, MT
Virus diseases in MT
• Occur sporadically
• Difficult to predict
Host
Vector
Pathogen
Environment
Wheat streak mosaic virus
• Infects both winter and spring wheat
• Earlier infection = greater yield loss
• Grassy weeds, volunteer wheat, corn,
etc. can harbor both WSMV and the mite
vector
Disease cycle of WSMV
2010: Distribution of WSMV
Weed Host: Volunteer Wheat
Table 2. Capacity of prevalent grassy weeds in Montana to serve as mite and virus hosts.*
Common name
Scientific name
Life cycle Mite host WSMV host
Jointed goatgrass
Aegilops cylindricae
Annual
Yes
Yes
Crested wheatgrass
Agropyron cristatum
Perennial Unknown Unknown
Wild oat
Avena fatua
Annual
No
Yes
Smooth brome
Bromus inermis
Perennial
Yes
No
Bromus japonicus
Japanese brome
Perennial
No
Unknown
Downy brome/Cheatgrass Bromus tectorum
Annual
Yes
Yes
Persian darnell
Lolium persicum
Annual
Unknown Unknown
Western wheatgrass
Pascopyrum smithii
Perennial
Yes
No
Feral rye
Secale cereale
Annual
Unknown Unknown
Yellow foxtail
Setaria glauca
Annual
No
No
Green foxtail
Setaria viridis
Annual
Yes
Yes
*data taken from literature cited in text
Average yield loss (%) due to mechanically inoculated
WSMV in winter wheat, 2008-2010, Bozeman
Variety
2008*
CDC Falcon
Genou
Jagalene
25.1
-24.9
-10.3
Jerry
Ledger
2009
-23.8
-14.3
-14.5
-13.0
31.2
Mace
Morgan
-24.2
-20.4
-37.1
-42.5
14.4
-15.6
-19.0
-40.9
-13.7
-13.1
-18.9
-32.9
-14.0
1.7
-10.7
-17.7
-17.3
-16.3
MT0552 (Decade)
MTV0734
Neeley
Pryor
Rampart
Rocky
Tiber
Yellowstone
Average
2010*
0.7
5.0
-18.1
0.3
-17.7
-3.3
-9.6
-16.5
-21.1
18.0
1.0
-11.3
-6.0
*Hail damage
Average yield loss (%) due to mechanically inoculated
WSMV in spring wheat, 2008-2010, Bozeman
% Yield reduction due to WSMV inoculation
Variety
Amidon
Choteau
Conan
Corbin
Ernest
Fortuna
Hank
McNeal
Reeder
Scholar
Haxby
Metcalfe
2008
8.8
33.6
24.2
18
34.7
32.7
21.8
39.9
22.8
45.9
N/A
N/A
2009
38.7
51.9
32.5
31.9
57.3
42.2
28.4
50.4
34.2
44.3
13.3
16.7
Mean
28.2
36.8
2010
2010
WSMV-CI WSMV-HI
47.8
46.7
74.7
67.2
36.6
46.6
41.5
54.7
70.4
73.8
59.8
57.3
39.2
33.8
66.0
60.3
52.0
51.9
46.9
48.1
36.2
42.3
41.6
48.2
51.1
52.6
Insecticides/Acaracides: NONE!
Chemical
Trade Name
Status
Carbofuran
Furadan 4F
Delisted by EPA as of Jan 2010
Clorpyrifos
Lorsban
Not labelled for WCM, no efficacy
(WCM protected in leaves/whorl)
Imidacloprid
Gaucho
Not labelled for WCM, no efficacy, may
increase WCM
(Harvey. 1998. J. Agric. Urban Ent. 20:7-10)
Thiamethoxam
Cruiser
Not labelled, no efficacy
Spiromesifen
Oberon
May have efficacy, not labelled for wheat
(Sec. 3 is pending)
C. Tharp, Southern Ag Research Center, Huntley, MT, 2010
Barley yellow dwarf virus: The Host
• Infects barley, wheat, oats, rye, corn, triticale,
rice
• Resistance has been developed, but
predicting the virus and aphid populations
from year to year can be difficult (no
resistance in Montana varieties)
Barley yellow dwarf virus
(BYDV)
• Family Luteoviridae
– Genera Luteovirus, Polerovirus, Enamovirus
• First classified by primary aphid vector
MAV: Macrosiphum (Sitobion) avenae
PAV: Rhopalosiphum padi and S. avenae
RMV: Rhopalosiphum maidis
SGV: Schizaphis graminum
RPV: Rhopalosiphum padi (& S. graminum)
(Cereal yellow dwarf virus – RPV)
Russian wheat aphid
RWA is NOT a
vector of BYD
Note leaf
damage
caused by
feeding toxins
(RWA and
greenbug)
Corn leaf aphid
English grain aphid
Greenbug
2010: Distribution of BYD
majority of samples tested negative, even in the counties with confirmed BYD
Control of WSMV vs. BYDV
• Insecticides are effective against BYD, but
generally not economical; no acaracides are
available for WCM/WSMV control
• Plant resistance can be effective, but viruses
and mites evolve rapidly; none available in
MT
• Prevent movement from volunteer plants by
getting rid of volunteers before planting
(green bridge)
The rusts
Stripe
Stem
Leaf
Jim Berg, MSU
Stripe rust: gen’l WA or Canada
Leaf rust, stem rust:
‘Puccinia pathway’
What qualifies as excitement
for a plant pathologist:
Aecia on barberry
Uredinia on Kentucky
bluegrass
Pycnidia on
barberry
Aecia on barberry
Jin, Szabo and Carson, Plant Dis., 2010
Uredinia
on wheat
Fall 2010: Distribution of stripe rust
Does occur on spring wheat, but generally too late to be significant
Fall infection by stripe rust, 2010
WSMV and stripe rust: lucky guy!
Stripe Rust: variety resistance is very
effective at reducing yield losses
Yellowstone
Promontory
Johnston & Grey, 2006
Susceptible variety
Resistant variety
Influence of fungicide application on
two stripe-rust infected WW varieties
c
b
b
c
c
b
N
(Quilt, 14oz, Bozeman 2007; P < 0.001, LSD = 6.3)
g
er
in
Bo
ot
Ti
lle
ri n
g
Fl
ow
o
fu
ng
ic
id
e
g
er
in
Bo
ot
a
Fl
ow
o
N
c
Big Sky (Susceptible)
Ti
lle
ri n
g
100
95
90
85
80
75
70
65
60
55
50
fu
ng
ic
id
e
Yield (bu/a)
Yellowstone (Resistant)
Influence of fungicide application on
susceptible SW variety, McNeal
70
Yield (bu/a)
68
66
64
62
60
58
No fungicide
Tillering
Boot
Fungicide application
Quilt, Bozeman 2007, P = 0.50
Flowering
Stripe rust variety evaluation: Winter wheat
Bozeman, 2006
Note:
Jagalene is
susceptible
to the new
strain, had
high disease
severity at
Huntley,
2010
% Stripe rust
(June 28)
Variety
Yield (Bu/a)
Yellowstone
99
7
Promontory
93
9
Jerry
89
10
NuFrontier
85
10
Rampart
80
18
Pryor
80
42
Jagalene
79
12
CDC Falcon
78
55
Genou
71
36
Ledger
70
41
Neeley
70
72
NuSky
66
82
NuWest
65
83
Correlation = -0.749 p < 0.001
Grey, 2006
Yield of control Yield loss (%) Yield Inc. (%)
Cultivar
(bu/A)
by stripe rust by fungicide
AP700CL
116.76
-1.43
-1.41
Resistant
check
Madsen
110.12
1.06
1.07
Chuckar
106.62
7.14
7.68
Rod
104.87
-1.63
-1.61
Stephens
102.07
12.34
14.08
Brundage 96
98.37
11.36
12.82
Westbred 528
97.44
9.95
11.05
Bruehl
95.27
6.65
7.12
Buchanan
93.32
-4.77
-4.56
ORCF-102
90.04
12.22
13.92
Masami
86.10
14.44
16.88
Eltan
85.99
10.48
11.71
ORCF-103
83.07
14.67
17.19
Cashup
78.78
10.59
11.84
Tubbs 06
78.75
23.03
29.93
Eddy
71.37
22.87
29.65
Xerpha
70.49
26.15
35.40
Bauermeister
67.28
20.61
25.96
Farnum
66.43
2.22
2.27
Lambert
64.43
33.34
50.01
Paladin
63.72
20.38
25.60
Finley
61.70
5.04
5.31
Declo
42.15
44.00
78.58
PS 279 Susceptible check 29.88
54.17
118.19
Mean
81.88
14.79
21.61
Mean (Excl. PS 279)
84.14
13.07
17.41
Xiangming Chen, WSU, 2010
Stripe rust would have caused
54% yield loss in WA without
fungicide application in 2010 if
all varieties were as
susceptible as PS279
If all resistant cultivars were
grown, 1% yield loss with no
fungicide application
Acknowledgements
Dai Ito, Zach Miller,
Matt Moffet, Linnea Skoglund
GPDN: Jim Stack & all state reps
and diagnosticians
MSU County Extension Agents
Ug99
First reported in Uganda in 1999
--Pretorius et al. 2000 Plant Dis 84:203
Virulent on Sr31
Sr31 is located on 1BL.1RS translocation
Also carries Lr26, Yr9
Increased adaptation and higher yield. As a result,
widely spread in wheat worldwide
Helped to reduce stem rust population worldwide
Virulence to Yr9, originated in the eastern Africa
in mid 80s, caused worldwide epidemics
TTKS
In 2002 and 2004, CIMMYT nursery planted in Njoro,
Kenya were severely infected by stem rust.
In 2005, we identified Kenyan isolates from 2004 were
race TTKS.
--Wanyera, Kinyua, Jin, Singh 2006 Plant Dis 90:113
Broad virulence of TTKS
to North American spring wheat
 US spring wheat CVs of the Northern Great Plains,
known to have broad-based resistance to stem rust,
were mostly susceptible (84%).
 500 CIMMYT CVs released
since 1950’s, 84% were
susceptible.
Conclusion:
Ug99 possesses a unique
virulence combination that
renders many resistance
genes ineffective.
Jin & Singh, 2006, Plant Dis:90:476-480
Ramification of Sr24/Sr36 virulence to US Wheat
based on testing of 2007 elite breeding germplasm
% of resistance to
Type
Entry
TTKSK
TTKST
TTTSK
(Ug99)
Sr24v
Sr36v
Hard red spring
89
21%
12%
21%
Hard red winter
416
29%
15%
28%
Soft red winter
377
27%
25%
11%
Western wheat
60
3%
3%
3%
Total
942
26%
18%
19%
Current status of Ug99
• New races constantly evolving
• Ug99 stalled in Iran due to long drought
• If moves to Pakistan/India will affect 15% of
world’s wheat crop that feeds 1 billion of the
world’s poorest people
• Strain of stem rust in India that overcomes Sr25
• ‘Likely’ Ug99 has already spread beyond Iran Rick Ward, co-coordinator of the Durable Rust Resistance in Wheat project, based
at Cornell university; http://rustopedia.org/traction/permalink/Resources905
Projected potential pathways for Ug99
based on the migration of Yr9 virulence
Singh et al. 2006. CAB Review 1, 54
Ug99 migration
2007
2006
2006
2003?
2005
1998
2001?
2004
Singh et al. 2008. Advances in Agronomy v98
The good news
• Phil and Luther are both working on it
already!
• Li Huang, PSPP, has identified spring wheat
mutants from a population derived by Mike
Giroux with resistance to leaf, stem, and
stripe rust – including all Ug99 derivatives
• Fungicide trials with great results
• Communication and education ramping up!
Triazole + Strobilurin
Triazoles
Fungicide modes of action: Triazoles
• FRAC group 3
• DMI (demethylation) inhibitors; biosynthesis of sterols
in fungal cell membrane; spore penetration and
mycelial growth
• Provides 14-21 days of protection
• Medium risk of resistance development
• Greater mobility in plant than strobilurin fungicides
• Most widely used class of fungicide in the world
• Control a wide array of fungal diseases
• Protective and curative effects (if applied early in
disease development)
Fungicide movement in the plant
From: Tenuta, A., D.
Hershman, M. Draper and A.
Dorrence. 2007. Using foliar
fungicides to manage
soybean rust.. Land-Grant
Universities Cooperating
NCERA-208 and OMAF.
Available online at
http://www.oardc.ohiostate.edu/SoyRust/
Fungicide modes of action:
Strobilurins
• FRAC group 11
• QoI (quinone outside) inhibitors (respiration); spore germination,
penetration, and mycelial growth
• Provides 14-21 days of protection
• High risk of resistance development because it has a very
specific mode of action (they block electron transfer at the site of
quinol oxidation (the Qo site) in the cytochrome bc1 complex,
thus preventing ATP formation)
• Originally isolated from wood-rotting fungi Strobilurus tenacellus
• ‘Reduced-risk’ pesticide (pose less risk to human health than
other chemical options at the time of registration by EPA)
• Control a wide array of fungal diseases
• Excellent preventative fungicides, but limited curative effects
• “Plant health benefit” independent of disease control?
Figure 1. Mobility of trifloxystrobin, an example of a
QoI fungicide.
http://www.apsnet.org/education/AdvancedPlantPath/Topics
/Strobilurin/top.htm
Stem rust fungicide trial
1. Control
2. Proline 480 SC
3. Prosaro 421 SC
4. Quilt
5. A15590C
6. Alto 100SL
7. Caramba
8. Twinline
9. Headline 2.09EC
10. Gem 500 SC
Rate
Active Ingredient
Company
5.3 oz
7.5 oz
14 oz
14 oz
4 oz
13.5 oz
9 oz
7.5 oz
2.4 oz
Prothioconazole
Tebuconazole + Prothioconazole
Azoxystrobin + Propiconazole
Azoxystrobin + Propiconazole
Cyproconazole
Metconazole
Pyraclostrobin +Metconazole
Pyraclostrobin
Trifloxystrobin
Bayer
Bayer
Syngenta
Syngenta
Syngenta
BASF
BASF
BASF
Bayer
Yield, stem rust fungicide trial
2009, Bozeman
120
bcd
bc
Yield (bu/A)
100
80
60
40
20
0
cd
cd
bc
bc
a
a
d
b
Control (no fungicide), 14 daa
Strobilurin fungicides, 14 daa
Headline
Gem 500 SC
Strobiliurin + Trizole, 14 daa
Quilt
Quilt Xcel
Strobiliurin + Trizole, 14 daa
Twinline
Prosaro
Trizole fungicides, 14 daa
Alto
Caramba
Proline
Compare sprayed and unsprayed plots