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Gail Ruhl
Department of Botany and Plant Pathology
Purdue University
West Lafayette, IN 47907
Email: ruhlg@purdue.edu
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This web page address is:
http://www.btny.purdue.edu/Extension/Pathology/CropDiseases/Wheat/Wheat1.html
Search for a Disease Name
LEAF DISEASES
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WHEAT
Disease Name: Powdery Mildew
Pathogen: Fungus. Erysiphe graminis f. sp. tritici
Symptoms: White or gray-brown powdery or cottony patches
of mycelium (fungal threads) on the upper surface of lower leaves.
Tiny, brown-black specks (cleistothecia) are visible in older
gray-brown areas. Yellowing is usually visible on the undersides
of leaves opposite the powdery patches.
Conditions: Disease development is favored by early canopy
closure, heavy nitrogen fertilization, high plant populations,
high humidity, and cool temperatures.
Inoculum Survival: Infected crop residues.
Inoculum Dispersal: Airborne spores.
Management: Crop rotations, resistant cultivars, destruction
of residues, proper fertilization, foliar fungicides. Do not plant
susceptible cultivar prior to fly-free date. |
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WHEAT
Disease Name: Leaf Rust
Pathogen: Fungus. Puccinia recondita f. sp. tritici
Symptoms: Dry, yellow (chlorotic) flecks to red or
brown-black necrotic spots on upper leaf surfaces.
Conditions: Infection favored by moisture and cool temperatures
(59-72 F).
Inoculum Survival: Does not survive in Indiana.
Inoculum Dispersal: Airborne spores from south and southwest.
Management: Resistant cultivars, fungicides. Plant early-maturing
cultivars. |
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WHEAT
Disease Name: Septoria Leaf Blotch
Pathogen: Fungus. Leaf and glume blotch: Septoria nodorum
(Leptosphaeria nodorum), and leaf blotch: S. tritici (Mycosphaerella
graminicola)
Symptoms: Chlorotic (yellow) water-soaked flecks
becoming dry, yellow, then red-brown lesions. S. nodorum lesions
are round. S. tritici lesions are blocky with tiny
black specks (pycnidia) visible in rows in mature lesions.
Conditions: Cool, wet, windy weather favors S. tritici development.
Warm, wet weather favors S. nodorum.
Inoculum Survival: Infected residues, seed, voluteer wheat,
some grassy weed hosts.
Inoculum Dispersal: Airborne spores.
Management: Resistant cultivars, pathogen-free seed, crop
rotation. Destruction of infested straw, stubble, and volunteer
wheat. Foliar fungicides, fungicide seed treatment. |
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WHEAT
Disease Name: Tan Spot or Yellow Leaf Spot
Pathogen:Fungus. Helminthosporium tritici-repentis
(Drechslera tritici-repentis, Pyrenophora tritici-repentis)
Symptoms: Tan-brown, flecks on upper and lower leaf
surfaces expanding to blotches 12 mm long (often with yellow
borders). Fungal fruiting bodies (pseudothecia) are visible as
dark raised specks on wheat straw.
Conditions: Disease is favored by prolonged wet periods.
Inoculum Survival: Infected crop residues.
Inoculum Dispersal: Airborne spores.
Management: Crop rotation, tolerant or resistant cultivars,
destruction of wheat stubble, fungicides. |
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ROOT DISEASES
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WHEAT
Disease Name: Fusarium Foot Rot
Pathogen: Fungus. Fusarium sp.
Symptoms: Seedling blight, root rot. Crown and lower nodes
turn brown.
Conditions: Disease is favored by stress conditions.
Inoculum Survival: Soil, seed.
Inoculum Dispersal: Soilborne and seedborne spores.
Management: Crop rotation, planting after fly-free date,
good soil nutrition, proper planting depth. |
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WHEAT
Disease Name: Rhizoctonia Spring Blight
Pathogen: Fungus. Rhizoctonia cerealis
Symptoms: Large, irregular lesions on dormant leaves.
If plants are dormant or stressed after infection, the fungus
may develop into crown tissue and plants may die. Severely infected
plants fail to green-up in spring, or may be green for a short
period and then die.
Conditions: Favored by fluctuating late winter or early
spring temperatures, wet conditions, and heavy nitrogen applications.
Inoculum Survival: Fungal mycelia and sclerotia in the soil.
Inoculum Dispersal: Soilborne propagules.
Management: Use granular formulations of nitrogen in late
winter or early spring over light snow or wet frozen ground that
will thaw within a few hours of application. Or use split nitrogen
applications. |
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WHEAT
Disease Name: Take-all
Pathogen: Fungus. Gaeumannomyces graminis var. tritici
Symptoms: Infected plants appear mildly chlorotic
and have fewer tillers. Severely infected plants are stunted,
develop white (bleached) heads, and die prematurely. Roots are
few, black, and brittle.
Conditions: Favored by cool temperatures (50-68 F) and wet
soil conditions , neutral to alkaline soils, nitrogen- and phosphorous-deficient
soils. More severe where wheat follows wheat or with no-till.
Inoculum Survival: Soil.
Inoculum Dispersal: Soilborne mycelial fragments.
Management: Tolerant cultivars, crop rotation. Avoid planting
before the fly-free date. Avoid nitrogen stress. Add ammonia or
slow-release forms of nitrogen in fall. |
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