Transcript diseases - Gaurav Kumar Pal

MAIZE DISEASES
Dr. Jamba Gyeltshen
01/04/2010
Maize Diseases
1. Turcicum leaf blight (Northern
leaf blight) (Exserohilum
turcicum syn.
Helminthosporium turcicum)
2. Grey leaf spot (Cercospora
zeae-maydis)
1. Turcicum leaf blight
Northern Corn Leaf Blight
(Exserohilum turcicum)
Syn. Helminthosporium turcicum
TLB Pathogen
Anamorph (asexual phase)
• Exserohilum turcicum (syn.
Helminthosporium turcicum)
Teliomorph (sexual phase)
• Setosphaeria turcica
1. Turcicum Leaf Blight (TLB)
Conidia are 3 - 8 septate, spindle-shaped, and have a protruding hilum.
TLB
• Major constraint to maize production
where humidity is high and temperatures
moderate (17 to 27°C).
• Cause yield losses as high as 70%
TLB Distribution
TLB Symptoms
• Cigar shaped lesions that are 3 to 15 cm long
• Lesions are elliptical and tan in color,
developing distinct dark areas as the fungus
sporulates
• Lesions typically first appear on lower leaves
and spread upwards.
• Under severe infection, lesions may coalesce,
blighting the entire leaf.
TLB Symptoms
Disease cycle
• Overwinters as mycelium and chlamydospores in
infected crop debris.
• Fungi in crop debris sporulate in response to higher
temperatures and humidity.
• Spores (conidia) are then disseminated by wind and rain
splash to freshly planted maize. Conidia can be carried
vast distances in the wind.
• They germinate in temperatures ranging from 17 to 27°C
and during periods of extended leaf wetness (6 to 18
hours), infecting host tissue.
• Secondary cycles of disease occur where conidia
produced in disease lesions are disseminated within the
crop and to other fields by rain splash and wind.
Damage
• Mechanism of damage: Yield loss is caused
predominantly through loss of photosynthetic
leaf area due to blighting. Under severe
infestation, sugars can be diverted from the
stalks for grain filling leading to crop lodging.
• When damage is important: If Turcicum leaf
blight establishes before silking and spreads to
upper leaves during grain filling, severe yield
losses can occur.
• Economic importance: Yield losses as high as
70% have been recorded but typically range
from 15 to 30%.
Disease management
• Grow resistant varieties: Yangtsepa
• Management of overwintering infected crop
residue will reduce the amount of available
inoculum at the onset of the subsequent growing
season.
• Fungicide application can effectively control
Turcicum leaf blight when applied at the right
time.
• Fungicide should be applied when lesions first
become visible on the lower leaves.
2. Grey leaf spot
Pathogen: Cercospora
zea-maydis and
Cercospora zeina
• Gray leaf spot (GLS)
is a serious foliar
disease of maize in
many temperate and
tropical highland
regions of the world.
GLS Symptoms
• GLS has characteristic rectangular, tan-colored lesions
that are contained within leaf margins, as the fungi is not
able to penetrate sclerenchyma tissue in the leaf veins.
• As lesions mature they assume a graying cast due to
sporulation of the fungi. Lesions are typically 2-4 × 1060mm in size and usually develop on the lower leaves,
gradually spreading upwards on the plant during the
season. Under severe disease pressure, entire leaves
can be blighted and lesions can develop on cob sheaths.
Symptoms of GLS caused by Cercospora zeae-maydis
and C. zeina are indistinguishable.
Symptoms as seen against light
GLS symptoms
GLS symptom severity
GLS conidia
Disease development
• In spring, conidia (spores) are produced
and disseminated to corn plants by wind
and rain splashing. They require several
days of high relative humidity to
successfully germinate and infect corn
leaves. Several weeks may be needed for
the development of mature lesions on
leaves. Conidia for secondary spread are
produced from two to four weeks after
initial leaf infection
Management
• Damage, disease cycle and management
are same as TLB
References
• http://www.apsnet.org/online/feature/grayle
af/gallery.htm
• http://www.ars.usda.gov/sp2UserFiles/Plac
e/36021000/dunkle7.jpg
Glyphosate Effects on
Diseases of Plants
Symposium: Mineral Nutrition and Disease Problems
in Modern Agriculture: Threats to Sustainability
O
O
||
||
HO-C-CH2-NH-CH2-P-OH
|
OH
N-(phosphonomethyl)glycine
D. M. Huber, Emeritus Professor
Botany & Plant Pathology Department
Purdue University, West Lafayette, IN 47907
Glyphosate Effects on
Diseases of Plants
 Background - review
 Interacting
factors for disease
 Some cultural factors affecting nutrition and disease
 Glyphosate
 Characteristics
 Glyphosate resistance
 Reported effects of glyphosate
Effect of glyphosate on disease
 Take-all root and crown rot of cereals
 Corynespora root rot
 Marasmius root rot of sugarcane
 Fusarium head scab of cereals
 Citrus variegated chlorosis (CVC)
 Rust diseases
 Rice blast
 Mechanisms to reduce disease
 Conclusions
INTERACTING FACTORS DETERMINING
DISEASE SEVERITY
Vigor, Stage of Growth, Root Exudates
Resistance PLANT Susceptibility
TIME
PATHOGEN
ABIOTIC
ENVIRONMENT
Nutrients
Moisture
Temperature
pH (redox potential)
Density, gases
Population
Virulence
Activity
BIOTIC ENVIRONMENT
Antagonists, Synergists
Oxidizers, Reducers
Competitors, Mineralizers
[Fe, Mn, N, S]
Changes in Agricultural Practices
Change the Interactions
Crop Sequence
Tillage/No-till
Fertilization
Biotic environment
Nutrition
Nitrification
Organic matter
Residue break down
Soil density/aeration
Pathogen survival
Nutrient distribution
Denitrification
Rate/form
Time applied
Source/assoc. ions
Inorganic
Organic
Effect of crop residue on
nitrification
% NO3
100 Alfalfa
80 Soya
Pea
60 Corn
Crop sequence effect on Mn+2
Sufficient
Excess
Extractable Mn Metabolism of different
130 ppm forms of nitrogen
64 pp,
Soybean, wheat, corn
91 ppm
Wheat, corn, soybean
79 ppm
Fallow Trachypogan
Rotation
Wheat Brachiaria Continuous Corn
Oat
Conifers
Continuous soybeans
Barley
40
20
0
0
2
Weeks
Deficient
4
6
8
Fall chissel
No-till
126 ppm
80 ppm
Factors Affecting N Form, Mn Availability
and Severity of Some Diseases*
Soil Factor or
Cultural Practice
Nitrification
Low Soil pH
Effect on:
Mn Availability Disease Severity
Decrease
Green Manures(some) Decrease
Ammonium Fertilizers Decrease
Irrigation (some)
Decrease
Firm Seed bed
Decrease
Nitrification Inhibitors Decrease
Soil Fumigation
Decrease
Metal Sulfides
Decrease
Increase
Increase
Increase
Increase
Increase
Increase
Increase
Decrease
Decrease
Decrease
Decrease
Decrease
Decrease
Decrease
Decrease
High Soil pH
Lime
Nitrate Fertilizers
Manure
Low Soil Moisture
Loose Seed bed
Decrease
Decrease
Decrease
Decrease
Decrease
Decrease
Increase
Increase
Increase
Increase
Increase
Increase
Increase
Increase
---Increase
Increase
Increase
Increase
*Potato scab, Rice blast, Take-all, Phymatotrichum root rot, Corn stalk rot
Glyphosate Started Changing
Agriculture 30+ Years Ago
The most widely used agricultural chemical!
• Broad-spectrum (non-selective) weed control
– Paraquat, Tordon, Spike, salt
•
•
•
•
Short “direct” residual activity
Low direct mammalian toxicity
Economical use
TRANSGENIC PROTECTION - selectivity
A very strong metal chelator with
Potential interaction with all life
Through mineral deprivation
“All flesh is grass”
Isaiah 40:6, 800 BC
Some Characteristics of Glyphosate
Chelating stability constants
of glyphosate
• A chemical chelator
Small amount needed
Metal ion
Tightly bind mineral elements
Immobilizes Mn, Fe
• Non-specific herbicidal effect
[ML]
[M][L]
Mg2+
Ca2+
Mn2+
Fe2+
Cu2+
Fe3+
3.31
3.25
5.47
6.87
11.93
16.09
[MHL]
[M][H][L]
[ML2]
[M][L2]
12.12
11.48
12.30
12.79
15.85
17.63
5.47
5.87
7.80
11.18
16.02
23.00
• Tank mix impairs herbicidal activity
•
•
Glyphosate
Glyphosate + Zn tank mix
Some Chemical Chelators
in Agriculture
• Mn, Fe chelating compounds
– Piricularin, alpha-picolinic acid - rice blast toxin
– Glyphosate - non-specific herbicide
– Reducing activity - photosynthesis
• Cu chelating compounds
– Nitrapyrin, methyl pyrazole - inhibit nitrification
– Tordon herbicide - specific to broad-leaved plants
– Oxidizing activity - (lacases, oxidases)
• Various plant root exudates
– Induced with nutrient deficiency
Source of Chelators
• Natural metabolites
Plant root exudates - organic acids, siderophores
Microbial metabolites - organic acids, toxins
Soil organic matter
• Synthetic compounds
Herbicides - glyphosate, Tordon
Nitrification inhibitors - nitrapyrin
EDTA, DTPA, citric acid, amino acids
---------------------------------• Important because micronutrients are the:
Activators
Inhibitors
Regulators of plant physiological functions
Characteristic Effects of
Glyphosate
• Systemic in plants
Transient Mn immobilization
with glyphosate
A modified essential amino acid
Concentrates in meristematic tissues
Shoot and root tips
Reproductive structures
• Distributed throughout the
rhizosphere in root exudates
• Non-specific herbicidal effect
• Toxic to some soil microbes; stimulates others
– Changes nutrient availability
– Changes virulence of some pathogens
Some Microbial Interactions
with Glyphosate
• Changes the soil microbial “balance”
• Toxic to beneficial organisms:
- Rhizobium, Bradyrhizobium
- Inhibits N-fixation
- Mn reducing organisms (Biocontrol)
Root nodules reduced
with glyphosate
- Trichoderma spp, Bacillus spp
Manganese Availability
- Mychorrhizae
- Glomus mossea - Zn, P uptake
• Stimulates:
- Mn oxidizing organisms
- Fusarium, other fungi
pH 5.2 to pH 7.8
Rhizosphere biology
Fungal Mn oxidation in soil
Mn oxidizers from soil
- K sink immobilization
• Increases pathogens:
Control Glyphosate
Roundup Ready® Gene
[Greatly expanded usage of glyphosate]
• Confers “tolerance” to glyphosate
Alternate metabolic pathway introduced
Slows down some physiologic processes
Provided selective herbicidal activity
There are several “modifiers” possible
• Changes physiology of the plant (N metabolism)
• Incomplete “protection” of meristematic
and reproductive tissues - depends on:
Time of application
Method of application
Crop species
• Often causes a “Yield Drag”
Mis-shaped cotton boll
from glyphosate
Normal
Glyphosate
“Glyphosate” Gene Effect on Mn Uptake
Soybean micronutrient concentrations
Corn micronutrient concentrations
Mn Efficiency of Isogenic soybeans - after Gordon, 2007
Isoline:
Mn applied
KS4202
KS4202 RR
Yield Tissue Mn Yield Tissue Mn
Difference*
Yield Tissue Mn
(lb./a)
(bu/a)
(ppm)
(bu/a)
(ppm)
(bu/a)
(ppm)
0
2.5
5.0
7.5
76.9
76.1
74.9
72.6
75
80
92
105
64.9
72.8
77.6
77.6
32
72
87
95
-12.0
- 4.1
+ 0.7
+ 0.7
- 43
-3
+ 12
+ 10
* Difference compared with 0 Mn of normal
Residual Chelation Effect of Glyphosate on Mn
PPM Mn in tissue
40
25
20
15
10
5
Mn “sufficient” soil
30
0
None
- 4 days Same time + 4 days +9 days
Time Mn Applied Relative to Glyphosate (UltraMax®)
REPORTED EFFECTS OF GLYPHOSATE
• Reduced Mn & Fe uptake*
Normal corn
Glyphosate
resistant corn
Root & foliage
[K reduced also)
• Immobilization of Mn*
Mn
Deficient
Sufficient
Translocation
Reduced physiological efficiency
• Reduced root nodulation & N-fixation*
• Soil Microflora changes - Root exudates
Normal soybean
Glyphosate
100
resistant soybean
50
Stimulatory to Fusaria, oxidizers, etc.
Toxic to manganese reducers and Rhizobium
• Increased drought stress*
• Earlier maturity*
• Interaction with some diseases*
0
Effect of the glyphosate
resistance gene on Mn
*Can be modified by Mn or other micronutrient application uptake efficiency
Some Diseases Increased by Glyphosate
Host plant
Disease
Pathogen
Apple
Banana
Barley
Beans
Bean
Bean
Canola
Canola
Citrus
Cotton
Cotton
Cotton
Grape
Melon
Soybeans
Soybeans
Soybeans
Sugarcane
Tomato
Various
Weeds
Wheat
Wheat
Wheat
Wheat
Wheat
Canker
Panama
Root rot
Root rot
Damping off
Root rot
Crown rot
Wilt (New)
CVC
Damping off
Bunchy top
Wilt
Black goo
Root rot
Root rot
Target spot
SDS
Decline
Wilt (New)
Canker
Biocontrol
Bare patch
Glume blotch
Root rot
Head scab
Take-all
Botryosphaeria dothidea
Fusarium oxysporum f.sp. cubense
Magnaporthe grisea
Fusarium solani f.sp. phaseoli
Pythium spp.
Thielaviopsis bassicola
Fusarium spp.
Fusarium oxysporum, F. avenaceum
Xylella fastidiosa
Pythium spp.
Manganese deficiency
F. oxysporum f.sp. vasinfectum
Phaeomoniella chlamydospora
Monosporascus cannonbalus
Corynespora cassicola
Corynespora cassicola
Fusarium solani f.sp. glycines
Marasmius spp.
Fusarium oxysporum f.sp. pisi
Phytophthora spp.
Myrothecium verucaria
Rhizoctonia solani
Septoria spp.
Fusarium spp.
Fusarium graminearum
Gaeumannomyces graminis
Some Diseases Reduced by Glyphosate
Host plant
Disease
Soybean
Wheat
Rust
Rust
Pathogen
Phycopsora pakyrhiza
Puccinia graminis
Plant Pathogens Affected by Glyphosate
Pathogen
Increase:
Botryospheara dothidea
Corynespora cassicola
Fusarium avenaceum
F. graminearum
F. oxysporum f. sp cubense
F. oxysporum f.sp (canola)
F. oxysporum f.sp. glycines
F. oxysporum f.sp. vasinfectum
F. solani f.sp. glycines
F. solani f.sp. phaseoli
F. solani f.sp. Pisi
Gaeumannomyces graminis
Magnaporthe grisea
Marasmius spp.
Pathogen
Monosporascus cannonbalus
Myrothecium verucaria
Phaeomoniella chlamydospora
Phytophthora spp.
Pythium spp.
Rhizoctonia solani
Septoria nodorum
Thielaviopsis bassicola
Xylella fastidiosa
Decrease (obligate pathogens):
Phykopsora pakyrhiza
Puccinia graminis
Abiotic increase: Mn deficiency diseases
Physiologic Roles of Manganese
Mn
Photosynthesis
Glycolysis (energy reactions)
Mn
Shikimic Acid
Mn
Carbohydrate, hormone &
Amino Acid Synthesis
CHO
Root Growth
Amino Acids
Cyanoglycosides
Phenylalanine
Mn
ammonia-lyase
COUMARINS
LIGNINS FLAVANOIDS = Defense materials
“Lignituber” formed
in response to cell
Penetration.
Wheat
Triticale
(After Skou, 1975)
Take-all of Cereals
- the Pathogen
• Gaeumannomyces graminis var tritici
• Common soilborne fungus - endemic world-wide
– 600 “world” isolates were almost identical in peptidase profiles
– Can distinguish Gaeumanomyces graminis var tritici from G. graminis var
graminis
• Virulence associated with manganese oxidation
• Very high tolerance for Mn
15C
Mn oxidation No oxidation to
Virulent
Avirulent 25C
25C
to
15C
Temperature 15 C
25 C
Isolate X A B C
X A B C
Mn Oxid. 0
0 + +
0
+ +
0
VIRULENCE AND MANGNAESE OXIDATION
A
The Pathogen
Gaeumannomyces graminis
A. Ectotrophic growth on root
“Runner” hyhae on wheat root
B. Extracellular oxidation of Mn
Ectotrophic growth of Ggt on wheat root
B
C. Dispersive X-ray microanalysis
of ectotrophic mycelium on root
C
Hyphal networks in soil
Gaeumannomyces oxidizes Mn in
Soil, rhizosphere, and root tissue
MnO2 in wheat root hair cell
XANES - MnO2 distribution
More intense with high soil moisture
Severe take-all spots in wheat
Severe Mn deficiency in double-crop
Spybeans after severe take-all
Factors Affecting N Form, Mn Availability
and Severity of Some Diseases*
Soil Factor or
Cultural Practice
Nitrification
Low Soil pH
Effect on:
Mn Availability Disease Severity
Decrease
Green Manures(some) Decrease
Ammonium Fertilizers Decrease
Irrigation (some)
Decrease
Firm Seed bed
Decrease
Nitrification Inhibitors Decrease
Soil Fumigation
Decrease
Metal Sulfides
Decrease
Increase
Increase
Increase
Increase
Increase
Increase
Increase
Decrease
Decrease
Decrease
Decrease
Decrease
Decrease
Decrease
Decrease
High Soil pH
Lime
Nitrate Fertilizers
Manure
Low Soil Moisture
Loose Seed bed
Decrease
Decrease
Decrease
Decrease
Decrease
Decrease
Increase
Increase
Increase
Increase
Increase
Increase
Increase
Increase
---Increase
Increase
Increase
Increase
*Potato scab, Rice blast, Take-all, Phymatotrichum root rot, Corn stalk rot
A
Effect of N form & inhibiting
nitrification on take-all and
rhizosphere Mn oxidizers
A. N form on Take-all
B. Manganese oxidizers
C. -/+ Nitrification inhibitor
B
Mn oxidizers / reducers
C
C
Nitrate BEAU Ammonium
Nitrate AUBURN Ammonium
Ammonia
Ammonia + nitrapyrin
Effect of Cultural Practices on Tissue Mn
and Take-all
Cultural Condition
Mn*
TA index
Loose Seedbed
11.2
Firm Seedbed
19.3
3.0
2.4
Nitrification (normal)
8.9
Inhibiting Nitrification 17.2
3.2
2.0
Wheat-wheat-wheat
Wheat-oats-wheat
Oats-oats-wheat
4.8
1.4
0.5
20.0
55.0
76.0
No press wheel Press wheel
*Wheat tissue Mn, PPM; Take-all index = 1-5 (severe
Take-all and
Populations of
Mn-oxidizing
Rhizosphere
Bacteria
Cattle
dung
(manure)
Impact of Glyphosate on Take-all
Take-all of wheat after
glyphosate to RR beans
After
glyphosate
No
glyphosate
Soybean herbicide plots
Transient Mn immobilization
In tissue with glyphosate
Wheat after soybeans
After
glyphosate
No
glyphosate
Corynespora Root Rot of Soybeans
 Caused by Corynespora cassiicola
 Dark brown to black rotted small lateral roots & hypocotyl
Generally considered “root nibbler” - limited economics
 Can be severe & also as a foliage pathogen (target spot)
Control
Inoculated
Long, multiseptate spores
Corynespora cassiicola
Inoculated Healthy
Predisposing Effect of Glyphosate on
Corynespora Root Rot of Soybean
Control
Inoculated
Inoculated
+ foliar glyphosate
Effect of Glyphosate from Root Exudates
• Stunted soybean plants adjacent to
glyphosate-killed giant ragweed plants
• Very severe Corynespora root rot
• Dead ragweed is not a host for Corynespora
Dead ragweed plant
Surviving ragweed plant
4-6”
18” away
Citrus Variegated Chlorosis
Predisposition to CVC (Xylella fastidiosa) by glyphosate
Tissue nutrients
Typical glyphosate
weed control
After T. Yamada
CVC with the
Alternative mulch program
glyphosate program
of T. Yamada
Fusarium Head Scab and Root Rot
• Caused by Fusarium graminearum & other F.
spp.
- Soilborne fungi
- Stimulated by glyphosate
• Disease “requires” three “cardinal” conditions
- Flowering (center of head outwards)
- Moisture
- Temperature > 26 C
• Temperature changes C:N ratio (physiology)
• Glyphosate induces similar changes
• New “Cardinal” conditions:
- Flowering
- Moisture
- Previously applied glyphosate
(Mn, Fe, etc.)
Predisposition of Bean to Root Rot
• Non-nodulating isolines of beans are more
resistant to root rot
• Glyphosate reduces nodulation and
increases root rot
• Glyphosate increases manganese
deficiency
Manganese and N
deficiency
After
Burndown
RR corn
Manganese “Forms” in Blast Infected Rice
Rice blast, caused by
Pyricularia grisea
(Magnaporthe grisea)
Only oxidized Mn in lesion area
Magnaporthe grisea is a strong
Mn oxidizer
A
A. Mycelium on leaf surface
B
B. Micro XANES of MnO2 in A
C. Blast lesion on leaf
D. XANES of MnO2 in lesion
MnO2
C
E. Lesion produced by toxin
D
E
Glyphosate is Reported to Control
Rust Diseases
• Increases resistance
-Specific N nutrients withheld
Glycine, phenylalanine, etc.
- Amino acid inhibitors increased
• Provides a 20-25 day effect
• Blocks specific peptidase activity
• May account for the more limited damage from
soybean rust than anticipated in the U. S.
Mechanisms by which Nutrients
Reduce Disease
• Increased Plant Resistance
– Physiology - phytoalexin, CHO, phenolic production
– Defense- callus, lignituber, cicatrix formation
• Disease Escape, Increased Plant Tolerance
– Increased growth - roots, leaves
– Shortened Susceptible stage
– Compensation for disease damage
• Modifying the environment
– pH, other nutrients
– Rhizosphere interactions, nitrification, biological balance
• Inhibited Pathogen Activity
– Reduced virulence
– Direct effect on survival and multiplication
– Biological control
Strategies to Reduce Mn Immobilization
 Amendment
Micronutrient
Timing/formulation
Biological amendment
Bacillus, Trichoderma
 Detoxification
Calcium chelation - gypsum
Manganese
 Cultural practices
Increase Mn availability
Ammonium sources of N
Inhibit nitrification
Crop sequence - after corn
Alternative weed control
Mulch
Reduce usage - chemistry
Reduce rates
30
25
20
15
10
5
0
-
- 4 Same
days time
+4
days
+9
days
Time Mn applied relative
to glyphosate (UltraMax®)
Interaction of Micronutrients with Glyphosate*
Micronutrient
Rate
Yield
Untreated control
Glyphosate** control
Gly+MnCO3
Gly+MnSO4
Gly+MnEDTA
Gly+Mn-AA
Gly+ZnO
Gly+ZnChelate
Gly+Zn+P
None
46 a
24 oz/a
57 b
0.5 #Mn/a
75 d
0.5 #Mn/a 70 cd
0.25 #Mn/a 72 cd
0.25 #Mn/a 67 c
0.5 #Zn/a
49 ab
0.25 #Zn/a
40 a
0.5 #Zn/a
41 a
% Weed control
0a
100 e
91 de
93 e
100 e
85 d
33 c
40 c
20 b
* Glyphosate WeatherMax® formulation at 24 oz/a + AMS
Biological Amendments to Increase Mn
Microbes: Bacillus (cereus), Trichoderma (konigii)
Concerns (other than Mn activity):
Tolerance of glyphosate
Timing
Method of application
Formulation
Safety
Treatment
None
Bio # 1
Bio # 2
Corn yield (bu/a)
Rainfed Irrigated
176a
186a
181ab
187a
185b
186a
Detoxifying Glyphosate
 In meristematic/reproductive tissues
Mn, Si+Mn, Mn+Cu foliar fertilization
 In root exudates in soil
 Approach:
Broadcast:
Lime
Gypsum
Phosphorus
In furrow treatment:
Gypsum (CaSO4)
Lime
Manganese
Ca + Mn
Effect of in-furrow treatments
on Soybean tissue Mn
Treatment
Rainfed Irrigated
Lime
32a
29a
Gypsum
38b
36b
Modify Cultural Practices to Affect Mn Availability
 Crop sequence
Residual effect of NH3 for corn
on Mn availability for soybean*
 Firm seedbed
 Grass mulch
Lower pH
 Moisture management
Tissue
Mn
Bean Yld
(bu/a)
None
12.1
22
NH3 only
14.3
26
NH3+Mn
---
39
NH3+NI
30.1
44
---
44
Treatment
NH3+NI+Mn
*NH3 on 15” centers
 Ammonium N
- inhibiting nitrification
NH3 +
N-serve
(30” centers)
Control
GLYPHOSATE: A simple Compound with
Profound Effects on Nutrients & Disease
Vigor, Stage of Growth, Root Exudates
Health PLANT Nutrient efficiency
Resistance
Susceptibility
Pathogen
Quantity
Activity
Virulence
TIME
ABIOTIC
ENVIRONMENT
Moisture
Temperature
pH (redox potential)
Density, gases
Nutrients
Organic matter (sinks)
RHIZOSPHERE ENVIRONMENT
Oxidizers, Reducers, Antagonists
Competitors, Mineralizers, Synergists
Interacting Factors Influencing
Summary of Glyphosate
Effects
• Physiology of the plant
- Nutrient composition
- Inorganic micronutrients
- Organic - N compounds (amino acids, etc.)
- Nutrient efficiency
- Defense compounds
• Environment
- Nutrient availability, form, uptake
- Rhizosphere microbial activity and balance
• Pathogen
- Virulence, biological synergy
Conclusions & Recommendations
1. The glyphosate-resistance gene selectively reduces Mn uptake
Select cultivars with highest Mn efficiency
2. Application of glyphosate reduces Mn translocation in tissues
Apply micronutrients 8+ days after glyphosate
3. Glyphosate formulation and nutrient source influence uptake
Select formulations that are compatible for uptake
4. Changes in rhizosphere biology are accumulative
Use cultural practices that minimize glyphosate impact
Use a non-systemic herbicide
5. Glyphosate reduces root growth
Detoxify glyphosate in roots and rhizosphere
6. Severity of some diseases increase with glyphosate
Use alternate weed control -Minimize glyphosate use
“Rice”
A Cradle to Grave Analysis
Erick Mendoza
MW 10:10-11:50
Race, Poverty, and the Environment
Professor Raquel R. Pinderhughes, Urban Studies Program, SFSU
Public has permission to use the material herein, but only if Erick
Mendoza, Urban Studies 515, SFSU, and Professor Pinderhughes
are credited.
This presentation focuses on Rice. It
is designed to describe the cradle to
grave lifecycle of Rice, paying
particular attention to the social,
environmental, and public health
impacts of the process associated with
the production of Rice.
Rice has been promoted as the cure
to hunger in these regions, this
analysis explores the impacts of such
claims to the farmer, consumer, and
environment.
IRC 2003:1908
Why Rice?
• Four-fifths of rice produced is consumed by small-scale
farmers in most developing countries.
• Alone it supplies over seventy percent of their daily
calories/protein intake.
• Along with grains such as wheat and maize it is consumed by
5.6 billion people world wide. That is four-fifths of the world
population.
• Unlike wheat and maize 80 percent of rice is consumed by
people.
• It contains large amounts of calories, high protein content, it
has high utilization process (vitamin digestion and absorption).
• It contains vitamin A, zinc and iron.
IRRI 2003a:1
IRC 2003:1911
IRC 2003:6323
Other uses for Rice:
• Waxy rice are used for desserts and as salad dressings.
• As baby food, breakfast cereals, rice breads, beer, wines.
• As rice paper.
Juliano 1985:14
IRC 2003:2305
IRC 2003:2305
• The hulls and excess tillers (stems) are used as feed, compost
for the fields, for fuel. Juliano 1985:14
IRC 2003:18433
IRC 2003:18446
IRC 2003:2308
IRC 2003:15490
Rice Cultivation
• Rice is cultivated and eaten mostly in the “rice bowl”
region, which consists of Asia and middle/near east
countries. Juliano 1985:15
IRC 2003:31222
IRC 2003:154888
Rice has been cultivated in these regions for over
nine thousand years, which means that it is highly
variable and adaptable. Its been grown in the
lowlands of India to as high as three thousand
meters in Nepal. Lang 1996:5
IRC 2003:18437
It just needs enough water and solar energy to be
cultivated in most places. Lang 1996:5
IRC 2003:2326
• Rice has been cultivated mostly in tropical areas because it
lives in water.
• Every stage of its growth, it is immersed in water.
• Most rice are cultivated and consumed by small-scale farmers
and local communities.
• Their planting season begin in a month before the monsoon
season, usually in May.
• They plant the seedlings in irrigated paddies, lowland marshes,
or near river beds.
• After one month or so the seeds germinate and begin to grow,
they then transplant them to larger fields, where they are
matured.
• The process lasts about 100-120 days.
Mutters 1998:1
IRC
2003:15363
IRC
2003:2290
IRC 2003:1914
“The Green Revolution”
• Leading scientists postulated in the 1950s that the
world population will grow exponentially and feeding
them will be one of the main issues that will entail
the population boom.
• The International Rice Research Institute was
subsequently founded by the Rockefeller Foundation
along with the Ford Foundation. And with their
success other research organizations had been
spawned: The International Rice Commission, Food
and Agricultural Organization, United Nation
Development Program to name a few.
Lang 1996:xiv
IRC 2003:2321
IRC 2003:2317
• Researchers proposed that in order to increase yields as well
as the quality of the rice, they needed to:
– Cultivate rice that has shorter tillers (stems) to combat the
torrential downpour common in these regions.
– Be resistant to pests.
– Robust enough to handle cultivation.
– Have an earlier maturation stage, achieve better irrigation
methods. Lang 1996:xi, Juliano 1985:11
IRC 2003:2958
• For the most part they were successful in their
goals:
– They increased the yields annually from 203 million tons to
479 millions tons by the nineties. Lang 1996:9
– They produced rice that has higher nutrient contents such
as IR6884 and IR72, which contains higher zinc and iron.
IRRI 2003a:4
– They also have been able to introduce direct seeding
methods that help reduce the cultivation time from 190-220
days to 100-120 days. Lang 1996:3
• They were able to produce hybrid rice that could
withstand the monsoon season, have shorter tillers,
and be able to yield more grain. Juliano 1985:11
IRC 2003:2384
IRC 2003:25244
The Aftermath: environmental and
social effects
• With all their accomplishments there have been set
backs.
– Mono-culturing was emphasized thus depleting the
nutrients in the soil. FAO 2003:5
– The crops became very susceptible to pests such as
insects, weeds, and fungus. Rola and Pingali 1993:17
– The overuse of pesticides, herbicides to combat these
pests. And the misuse of fertilizers. Rola and Pingali 1993:23
– The stagnation of rice production today, along with the
marginalization of the local farming community. Mutters:
1998:1
• The most important environmental issue that
concern rice production today is the improper use of
pesticides, herbicides and fertilizers to help
increase yields. IRRI 2003a:4
• The pesticides used in combating rice pests are
some of the most toxic in agrochemicals; most are
banned in the U.S. Rola and Pingali:199338
IRC 2003:24777
IRC 2003:2387
• Insecticides such as Methyl parathion are commonly
used because they are cheaper but are classified as
one of the most toxic by the WHO.
– It interferes with the normal functioning of the brain and
nerve cells.
– Exposure to very high levels of methyl parathion for a short
period in air or water may cause death, loss of
consciousness, dizziness, confusion, headaches, difficult
breathing, chest tightness, wheezing, vomiting, diarrhea,
cramps, tremors, blurred vision, and sweating.
USDHS 2001:2,3
• Farmers are commonly unaware of the effects of these
chemicals on themselves as well as others they come into
contact with.
• They normally wear minimal protective gear when spraying.
• They lack the knowledge of proper interval time before
reentering the sprayed areas. Rola and Pingali 1993:38
• They store the chemicals improperly: in their homes near food,
areas where anyone has access to them, and they dispose the
containers in piles near their farms where they leach into the
ground and affect the water base. FAO 2003:3,4, Maranan and
Rapusas 2000:2,3
• Further the overuse of pesticides, herbicides, and artificial
fertilizers leaches into the ground water effectively
contaminating it.
– High levels of nitrates in drinking water can cause health
problems such as stomach pains, cholera, and hepatitis.
– High nutrient content in water are toxic to aquatic life by
encouraging rapid growth of algae, which depletes the oxygen in
the water thus suffocating fish and other aquatic life. FAO 2003:2,3
• The arability of the land is also affected.
– Soil salinity is affected by mono-cropping and depletes the soil
fertility
– Makes the soil too acidic for crops.
– The soil structures are altered and are susceptible to erosion. FAO
2003:5,6
Contemporary Issues:
• Development in production methods to help curtail
the stagnation on current yields:
– The re-introduction of crop rotation in order to increase
yields.
– Methods in reducing the lost of yields in the post production
process. FAO 2002:1
– Research in genetic development of rice to increase yields
as well as their nutrient contents. ISS 2003:2
IRC 2003:3022
IRC 2003:1917
• Data today shows that mono-culturing of rice has
stagnated the production of rice. Further, along with
pesticide use, it has increased rice’s susceptibility to
insects due growing resistance against the
pesticides by the insects through mutation and the
“survival of the fittest” of the insects. Rola and Pingali
1993:17
• Researchers are now trying to incorporate crop
rotation in order to decrease these effects, which
were overlooked at the genesis of the “green
revolution.” Maranan and Rapusas 2000:6, FAO 2002:1
IRC 2003:2319
IRC 2003:2421
• Although the possible losses are tremendous in the
cultivation of rice due to the unpredictable impact of
nature, the majority of losses are actually at the
postproduction level process.
• The losses are about 30 percent and are attributed to
operational, technical, socioeconomic, cultural,
political and environmental factors. Maranan and Rapusas
2000:5
• Dealing with these issues are now part of the
discourse in improving the yields of rice for the
future.
IRC 2003:2737
• The most volatile issue that concern rice production
and research today is the genetic alteration of the
composition of rice in order to add nutrients and
resistance to pests.
– Instead of hybridizing different kinds of rice, researchers
now are attempting to genetically alter their composition,
which has had its success but ultimately have been mired in
problems with such rice. ISSI 2003:2
– It is also very costly: financially as well as environmentally.
– The concentration of research and development by bio tech
industries. ISS 2003:1
• Bio tech firms are funding these research projects and are
monopolizing the outcomes.
– They patent the seeds, making them inaccessible to those who
really need them.
– By the time they are at the finished stage they are very costly,
billions of dollars are funded into their research. FAO 2002:1,2
• The potential environmental effects are grave according to data
on the research so far.
– They contaminate other crops.
– Have been proven to be toxic in humans.
• High contents of vitamin A can cause abdominal pains, nausea,
vomiting, hair loss, weight loss.
• Herbicides infused with rice are harmful; glufosinate was added to rice
and was found that it caused birth defects, behavioral changes, cleft
lips and skeletal defects, and miscarriages.
Jack 2003a:3
• Rice is the most important crop cultivated in the “rice belt”
region. For that reason, I feel that current research on
developing and altering the composition of rice by genetic
modification be hindered and the development and
improvements in traditional ways of integrated farming be put
at the forefront of discussion. Because there are evidence that
the current methods and applications are not surpassing the
advancements achieved during the “green revolution.” Further,
the mishaps of the revolution should be addressed.
• I also want to add that there are aspects of the production
process that I did not cover in detail because of the magnitude
of the research.
Work Cited:
Annotated Bibliography:
Food and Agricultural Organizational of the UN
2002. Concern about rice production practices. Electronic Document,
http://www.fao.org/english/newsroom/news/2002, accessed February 14, 2003.
2003. Environmental Impact Assessment of Irrigation and Drainage Projects. Electronic Document, http://www.dfid-karwater.net/w5outputs, accessed March 1, 2003.
Institute of Science in Society
2003. The ‘Golden rice’ – an Exercise in How Not to Do Science. Electronic Document, http://www.i-sis.org.uk/, accessed February 18,
2003.
Jack, Alex
2003a. GE Rice Update: Organic Rice Surges While GE Rice Falters. Amberwaves. Fall Issue 2001.
2003b. Protecting the Staff of Life: Gene-Altered Rice Coming. Electronic Document, http://www.cybermacro/rice-production/html, accessed
February 18, 2003.
International Research Rice Institute.
2003a Revolutionary Rice: More Nutrition for Women and Children. Electronic Document, http://www.irri.org/Hunger/Nutrition.htm,
accessed March 4, 2003.
2003b The Politics of Rice. Electronic Document, http://www.irri.org/Hunger/Politics, accessed March 4, 2003.
Juliano, Bienvedio O., ed.
1985. Rice: Chemistry and Technology. Minnesota. The American Association of Cereal Chemists, Inc.
Lang, James 1996. Feeding a Hungry Planet. North Carolina. The University of North Carolina Press.
Maranan, C.L., R.R. Paz and R.S. Rapusas
2000. National Postproduction Loss Assessment for Rice and Maize. ACIAR Proceedings 100.
Mutters, R.G.
1998. Planting and Production. Electronic Document. http://www.ucdavis.edu/jayoung.ftp, accessed January 29,
2003.
Rola, Agnes C. with Prabhu L. Pingali.
1993. Pesticides, rice productivity, and farmers’ health: An economic assessment. Philippines. International Rice
Research Institute.
U.S. Department of Health and Human Services.
2001. Agency for Toxic Substances and Disease Registry. Atlanta, GA.
Realities of Disease
Management in
Wheat
Paul Esker
Extension Plant Pathologist
UW-Madison
Contact: [email protected], 608-890-1999
Considerations for Disease
Management
• Variety selection
• Field scouting and disease identification
– Today’s emphasis: fungal diseases
– Other things to consider: aphids and viruses
•
•
•
•
•
•
Growth stage identification
Knowledge about disease risk
Crop development
Weather
Fungicides
Commodity prices
Scouting
• Identify the growth stage
• The flag leaf and its importance
• Scout the entire field and make
assessments from different locations
• Identify current diseases and severity
levels
The Flag Leaf
• Fungicide applications are based on the
risk of disease on the flag leaf
• Flag leaf becomes visible during Feekes 8
• Most important leaf for yield, accounting
for upwards of 50% or more of final yield
• Disease on this leaf at scouting may
indicate it is too late for a fungicide to
reduce the effects of disease - scout early!
Scouting the Field
• Scout 10 locations within
field
• Examine 10 plants
selected at random from
each of the locations
• Assess disease
presence/absence
(incidence) and how
much area is infected
(severity)
What Are We
Looking For?
Loose Smut
• Ustilago tritici
• Diseased plants produce
blackened heads
• Most obvious to see just
after wheat has headed
• Reduces yield in proportion
to the percentage of
smutted heads in field
– http://ohioline.osu.edu/a
c-fact/0012.html
Loose Smut
• Survival as dormant mycelia within embryo of
infested seed
• When seed germinates, fungus grows along
wheat shoot apex
• Dispersal to other plants can occur via
rain and insects
• Environmental conditions that favor infection
after deposition on head: light rains or
heavy dew; moderate temperatures (60
to 71 ºF)
• Management: resistance, seed fungicide,
clean and disease-free seed
Fusarium Head Scab
• Fusarium graminearum
• Any part or all of wheat head may appear
bleached
• Often, part bleached, part green
• Infected spikelets and glumes = salmoncolored spore masses of fungus (prolonged
periods of wet weather)
• Immediately below head, stem may be infected
and have brown or purplish discoloration
• Kernels shriveled and lightweight
• Kernels with “tombstone” appearance = dull
grayish or pinkish color (not consistent
symptom)
Fusarium Head Scab
•
•
•
•
•
Inoculum sources = crop residue; organism surviving soil
Same organism that causes Gibberella stalk rot (corn)
Spores wind or rain disseminated
Infection occurs when spores land on heads (florets) of wheat
Infection favored by prolonged periods of rain (or dew), high
relative humidity and temperatures from 65 to 85 ºF
• Toxin concern: deoxynivalenol (DON) and zearalenone
• Management:
– Rotation (avoid wheat after corn)
– Fungicide sprays
– Prediction tool: flowering date, wheat class (spring/winter), production
practices
Wheat Leaf Rust
• Puccinia triticina
• Rust monitoring: Cereal Disease
Laboratory
(www.ars.usda.gov/Main/docs.htm?
docid=9757)
• Reddish-orange spore mass
(pustules or uredinia)
• Approximately 1/32 inch long and
1/64 inch wide
• Initial symptoms in lower canopy
that will progress upwards
Wheat Leaf Rust
• Survival = either in live winter wheat (mycelia) or on
infested dead leaves (urediniospores)
• Infection favored by moisture on leaves (6-8 hours of
dew) and temperatures from 60 to 80 ºF
– In general, cool nights and warm days favor
• Management: resistance; fungicides (timing and severity of
disease); fertility (excess nitrogen increases susceptibility)
Wheat Stripe Rust
• Puccinia striiformis (Puccinia striiformis f.
sp. tritici)
• Yellowish, long stripes between veins
(leaves and sheaths) that have masses
(pustules) of yellow spores
• Young plants = pustules appear in blotches
• Older plants = parallel striping that is
distinctive
• Difference from leaf or stem rust =
appearance of reddish brown spore in
those diseases
• Difference from Septoria leaf blotch =
presence of gray leaf blotch with
black fruiting body
Wheat Stripe Rust
•
Life cycle is similar to leaf rust
•
Initial source of inoculum = urediniospores that survive in crop residue
•
Spores are formed during cool, wet weather and are wind-dispersed
•
Infection favored by moisture on leaves (4-6 hours) and temperatures from
50 to 60 ºF
– Disease progression is ceased when temperatures > 70 ºF
– Warmer than normal winters followed by cooler April temperatures favor epidemics
•
Management: resistance; fungicides (timing and severity of disease)
Septoria Leaf Blotch
• Septoria tritici
• Symptoms often part of complex
with Glume blotch
• Light green to yellow spots
between leaf veins on lower
leaves (contact with soil)
• Symptoms elongate: irregularly
shaped lesions that are tan to
red-brown
• Lesions age = black speckles
(pycnidia) can be seen on
lesion (good diagnostic sign)
Septoria Leaf Blotch
• Two phases
– Fall just after wheat sown
– Spring/summer on upper leaves
• Inoculum source = pycnidia on infested residue (survive 23 years) or mycelia in disease live wheat
• Infection favored by cool conditions: 59 to 68 ºF
• Six hours of leaf wetness required (maximum infection
with 48 hours)
• Management: certified disease seed with seed fungicide
treatment; some resistance; rotation of at least 2 years;
foliar fungicides
Glume Blotch
• Stagonospora nodorum
• Symptoms often part of complex
with Septoria leaf blotch
• Brown spots on glumes (outer
chaff), lemmas (inner chaff),
and awns
• Damage later (near maturity)
• Symptoms most common at tips
• Diagnostic indicator = presence
of small, round brown or black
specks (pycnidia) - can be
difficult to see with naked eye
Glume Blotch
•
•
•
•
•
•
•
Similar disease cycle to Septoria leaf blotch
Primary inoculum = seed or crop residue
Spores dispersed via wind or rain
Temperatures for infection: 68 to 81 ºF
Leaf wetness: 6 to 16 hours
Pycnidia can produce spores
Management: certified disease seed with seed fungicide
treatment; some resistance; rotation of at least 2 years;
foliar fungicides
Powdery Mildew
• Blumeria graminis
• Symptoms include powdery
white to gray fungal growth
• Symptoms on leaves, stems and
heads
• Pustules first on lower leaves
• Late symptoms: small, black
fruiting bodes (cleistothecia)
that contain spores
(ascospores)
Powdery Mildew
• Primary inoculum = spores on volunteer wheat or spores
within cleistothecia
• Infections first occur in fall
• Spores dispersed by wind
• Infection favored under cool (50 to 71 °F), wet weather
• High relative humidity
• Management: resistance; fungicide seed treatments; foliar
fungicides when applied between Feekes 6 (1st detectable
node) and 8 (flag leaf is visible); balanced fertility (avoid
high nitrogen)
Tan Spot
• Pyrenophora tritici-repentis
• Symptoms include small tan, spots (lensshaped)
• Tan to brown, round to slightly
elongate spot surrounded by yellow
halo
• Center spot often diamond-shaped
• Plant matures: fungus invades
straw - tiny black, raised fruiting
structures (pseudothecia) formed
• Severe infections: red smudge on seed
(quality downgraded)
Tan Spot
• Highest risk: wheat following wheat
• Primary source of inoculum = ascospores (found in crop
residue)
• Initial infections under cool, cloudy, humid weather and
frequent spring rains
• Infection of wheat seed found to be positively
correlated with severity of tan spot on flag leaf
• Management: resistance (multiple mechanisms); foliar
fungicides (application earlier than for rusts); tillage and
rotation help reduce survival and infection
Management
Tactic
Diseases Affected
Rotation
Fusarium head blight; Septoria leaf blotch; Glume blotch;
Tan spot
Resistance
Wheat leaf rust; Wheat stripe rust; “Septoria leaf blotch”;
“Glume blotch”; Powdery mildew; Tan spot
Seed fungicides
Loose smut; Septoria leaf blotch; Glume blotch
Foliar fungicides
Fusarium head blight; Wheat leaf rust; Wheat stripe rust;
Septoria leaf blotch; Glume blotch; Powdery mildew; Tan
spot
Soil fertility
Wheat leaf rust; Powdery mildew
For Further Information
• Boerboom, C., et al. 2007. Pest
Management in Wisconsin Field Crops,
UW-Extension, A3646.
– Table 5-4, Page 192 = Fungicides for
control of foliar diseases of small grains
– Table 5-5, Page 193 = Seed treatment
fungicides for small grains
– Always consult the label for up-to-date
information
Photo Credits
• Craig Grau, UW-Madison
• Nancy Koval, UW-Madison
• American Phytopathological Society
Image Gallery
• Oregon State University
Wheat Diseases
(Fusarium Head Blight)
Presentation by:
Chad Lee, Grain Crops Extension Specialist
University of Kentucky
Most of the information comes from:
ID-125: A Comprehensive Guide to
Wheat Management in Kentucky
Objectives
• Fusarium Head Blight (Head Scab)
• Management Options
Three Critical Management Issues
1. Seeding: Date, Depth, Rate
2. N Rate and Timing
3. Fusarium Head Blight
Disease Management
• Choose disease-tolerant varieties.
• Rotate Crops
– Reduces Pythium root rot and take-all.
• Other disease are airborne
– Stagonospora, Septoria, Fusarium
– Rotation has less impact on these diseases.
Fusarium Head Blight
Wheat Production
Year
Harvested
2001
Acres
Planted
(x1,000)
550
Acres
Harvested
(x1,000)
Yield per
Acre
Low Disease
360
66
Record High
2002
2003
2004
530
500
530
Kentucky Agricultural Statistics Service
330
350
380
Moderate Disease
53
High Disease
59
High Disease
54
Year
Production
Price
Value
(x1000 bu)
($/Bu)
(x $1000)
2001
23,760
2.50
59,400
2002
17,160
3.01
51,652
2003
21,700
3.25
66,495
2004
20,520
Kentucky Agricultural Statistics Service
Fusarium Head Blight
• Pathogen: Fusarium graminearum
• Host: Wheat
• Disease: Fusaorium Head Blight (head
scab, FHB)
Disease Management: FHB
• Fusarium Head Blight
• Symptoms visible in Feekes 11.1-11.5
• Warm, moist conditions during Feekes
10.51-10.54 favor development of FHB.
Disease Management: FHB
• Fungicides: Folicur, Section 18 in KY
– Moderate suppression of FHB.
– Effective for low levels of FHB, but not for high levels
of FHB.
– Very difficult to overcome favorable weather timed
with crop stage.
• Varying wheat varieties/planting dates may help
avoid FHB in some fields.
Disease Management: FHB
• Probably single-most damaging factor to
wheat yields in Kentucky in 2003 and
2004.
• No apparent differences between
conventional and no-till wheat.
• Airborne spores likely “swamp” most
fields, regardless of tillage history.
Variety Development
Variety Development
• Dr. Van Sanford has an active program
looking for Type II resistance to FHB
– Type II: spread of FHB in the head of wheat is
slowed
• Some developmental lines express Type II
• The goal: combine Type II with yield
Variety Development
• Syngenta has reported to being close to
developing a biotech wheat with
resistance to FHB
– Would produce enzymes to fight off the
pathogen
• Close: 2008? 2009? 2010?
Disease Management
Seed Fungicide Treatments
• Combination mixes such as Raxil-Thiram
or Dividend
– Reduce soil-born pathogens such as Pythium,
Fusarium, Rhizoctonia, Septoria, and
Stagonospora
– Improves germination rates of infected seeds
(i.e. Fusarium-infected seeds) by an average
of 15%
Weed Management
• Burndown Herbicides (no-till)
– Gramoxone
– Glyphosate