17. Lesion nematode
Control Methods
s Rotation but few non-hosts grown.
s Granular insecticide eg. Counter 15G
18. Maize dwarf mosaic (virus)
Symptom/Sign
s Yellow stripes between veins on youngest
leaves
s Stunting
s Shortened internodes
s Sporadic distribution in field
24. Maize chlorotic dwarf (virus)
Conditions favoring development
s Johnsongrass alternate host
s Leafhopper transmits to corn
25. Maize chlorotic dwarf (virus)
Control Methods
s Resistant variety
s Control Johnsongrass
26. Northern corn leaf blight (fungus)
Symptom/Sign
s Gray green elliptical (cigar-shaped) spots,
2-6 inches long on hybrids with no
resistance.
s Lesion size can be affected by hybrid.
s Can be confused sometimes with Stewart’s
wilt if certain resistance genes are present.
28. Northern corn leaf blight (fungus)
Conditions favoring development
s Moderate temperature--65-85 F
s Long dew periods
s Overwinters on plant debris
s Windborne
29. Northern corn leaf blight (fungus)
Control Methods
s Resistant hybrids
s Crop rotation
s Tillage
30. Southern corn leaf blight (fungus)
Symptom/Sign
s Spots on leaf smaller and more numerous
than Northern corn leaf blight
s Spots vary in size and shape due to the
genetic background of the hybrid.
s Common race “O” produces tan, elongated
spots between the veins that have limited
parallel margins and possibly buff to brown
borders.
32. Southern corn leaf blight (fungus)
Conditions favoring development
s Warmer temperature--68-90 F
s High humidity
s Overwinters on plant debris
s Windborne
s Splashed by water
33. Southern corn leaf blight (fungus)
Control Methods
s Resistant hybrids
s Crop rotation
s Tillage
34. Carbonum(Northern corn) Leaf Spot
(fungus)
Symptom/Sign
s Race 3 produces very narrow spots often
resembling “beads on a string”.
s Lesion (spot) type varies with the hybrid
s Often spreads after leaf tissue matures
36. Carbonum(Northern corn) Leaf Spot
Conditions favoring development
s Moderate temperatures and high humidity
s Spores are abundantly produced on old spots on
mature leaves
s Minor importance, small impact on yield.
37. Carbonum leaf blight (fungus)
Control Methods
s Resistant hybrids
s Crop rotation
s Tillage
38. Gray leaf spot (fungus)
Symptom/Sign
s Rectangular lesions with sharp parallel edges,
restricted by veins with yellow margin
s Window pane look, and old lesions are opaque.
s Early lesions are small necrotic spots with
chlorotic halos.
s Often symptoms are worse along the edges of
fields
40. Gray leaf spot (fungus)
Conditions favoring development
s High humidity
s Near water ways
s Overwinters in residue
s Reduced tillage or no-till
41. Gray leaf spot (fungus)
Control Methods
s Resistant hybrids
s Tillage is recommended but is questionable where
the disease is well established.
s Rotation
42. Common Rust (fungus)
Symptom/Sign
s Golden brown to cinnamon brown pustules on
both sides of the leaf.
44. Rust
Conditions favoring development
s Spores are wind blown from the south.
s Moderate temperatures (61-80) and high humidity
s Infections often occur in the whorl where
moisture and humidity are high
46. Fusarium stalk rot (fungus)
Symptom/Sign
s Cottony white mat of fungus at base of plant
or at internodes
s Soft rotted stalk
s Red discoloration inside of stalk
s Lodging
s Yield loss
48. Fusarium stalk rot (fungus)
Conditions favoring development
s Reduced tillage or no-till
s Fungus overwinters in crop residue
s Warm, wet conditions
s Can enter through wounds or directly ( corn
borer interaction)
s Same organism causing scab in cereals
49. Fusarium stalk rot (fungus)
Control Methods
s Hybrid selection
s Tillage
s Proper fertility
s Rotation
s Early harvest
50. Fusarium ear rot (fungus)
Symptom/Sign
s White fungus growing on kernels
s Pink discoloration
s “Starburst” symptom on infected kernels
52. Fusarium ear rot (fungus)
Conditions favoring development
s Reduced or no-till
s Fungus overwinters in crop residue
s Warm, wet conditions
s Insect damage to ear
s Can produce mycotoxin “fumonison”
53. Fusarium ear rot (fungus)
Control Methods
s Tillage
s Proper fertility
s Rotation
s Early harvest
61. Phytophthora root rot (fungus)
Conditions favoring development
s Poorly drained areas
s Heavy soils
s Flooding
62. Phytophthora root rot (fungus)
Control Methods
s Resistant variety
s Seed treatments using Apron, Apron
XL, or Allegiance control the damping-
off stage.
63. Rhizoctonia root rot (fungus)
Symptom/Sign
s Seedlings emerge and die
s Brown, red-brown, or red sunken lesion on
roots or base of the seedling stem.
64. Rhizoctonia root rot (fungus)
Conditions favoring development
s Cool, damp conditions
s Fertility, soil conditions and the amount of
fungus in the soil can all influence the
degree of infection.
65. Rhizoctonia root rot (fungus)
Control Methods
s Fungicide seed treatments
s Later planting date
66. Septoria leaf spot
(Brown spot)
Symptom/Sign
s Irregular dark brown spots
on unifoliate leaves
progressing to trifoliates
later in the season.
s Infected unifoliate leaves
turn brown and drop
s Black fruiting bodies
(pycnidia) of the fungus
form in old spots.
67. Septoria leaf spot
Conditions favoring development
s Fungus overwinters on old infected plant debris
s Unifoliate infection provides inoculum for later
infection
s Warm, wet weather conditions especially later in
the season influences brown spot in the canopy.
68. Septoria leaf spot
Control Methods
s Rotation
s Plant less susceptible varieties
s Plow under crop residues
69. Charcoal rot
Symptom/Sign
s Usually after midseason, plants appear stunted in
irregular areas of the field.
s Leaves may turn yellow and wilt
s Lower stem and taproot develop a gray to silvery
discoloration
s Microsclerotia develop in epidermis on root and
lower stem and inside pith resembling charcoal
dust
71. Charcoal rot
Conditions favoring development
s Low soil fertility
s Continuous cropping of soybeans.
s Low soil moisture and hot temperatures
increase disease severity.
72. Charcoal rot
Control Methods
s Plant later maturing varieties late group IV’s and
group V’s.
s Rotate with small grains, corn and sorghum for at
least 3 years in severely infected fields.
s Do not overplant, causes seedling stress
s Good fertility practices
73. Sclerotinia white mold (fungus)
Symptom/Sign
s Wilting and death of the upper leaves of the
plants during early pod development
s Often occurs in patches in low areas
s White mat of fungus on stem at nodes often seen
s Stem lesions often girldle the stem and the uper
portions die and produce no pods.
s Large sclerotia on stem and sometimes in pith
75. Sclerotinia white mold (fungus)
Conditions favoring development
s Cool, wet conditions that favor germination
of sclerotia within the upper 2 inches of soil.
s Narrow row spacing
s Dense canopy structure
s Fields with history of white mold on crops
of peas, beans, and soybean
76. Sclerotinia white mold (fungus)
Control Methods
s Avoid planting soybeans after other
susceptible crops such a peas, snap and lima
beans, and sunflowers.
s Choose varieties that are shorter, more open
77. Pod and stem blight (fungus)
Symptom/Sign
s Rows of black fruiting bodies (pycnidia) on
stems, petioles and pods late in season
s Infected seeds are decayed which leads to
direct yield loss
79. Pod and stem blight (fungus)
Conditions favoring development
s Disease of senescing soybeans
s Seed infection favored by delayed harvest
s Warm, rainy weather during pod
development through maturity.
s Low potash levels favor more seed
infection.
80. Pod and stem blight (fungus)
Control Methods
s Rotation
s Tillage
s Resistant variety
s Maintain high level of potash fertility
81. Anthracnose
Symptom/Sign
s Often appears in early reproductive stages on
stems, petioles and pods as an irregularly shaped
brown areas. Often resembles pod and stem
blight.
s Fruiting bodies of the fungus are randomly
scattered on infected plants tissues and produce
black spines called setae that can be seen.
s Can produce cankers on petioles and stems
causing severe defoliation.
83. Anthracnose
Conditions favoring development
s Overwinters on debris and can infect seed.
s Moist, warm weather during reproductive stages.
s Plants are most susceptible from bloom to pod fill
s Need wet periods of 12 hours or more for infecton
to occur.
84. Anthracnose
Control Methods
s Plant disease free seed
s Plow down old soybean residues
s Rotation
85. Soybean cyst nematode
Symptom/Sign
s Stunted yellow plants in patches or large
areas
s Poorly developed roots
s Suppressed nodulation
s Lemon shaped cysts (females) on roots.
96. Tobacco Ringspot Virus
Symptom/Sign
s Primarily seedborne at a low level in the
field
s This results in scattered infected plants.
s Maturity is delayed so they remain green
until killed by frost
s Pods are underdeveloped, tops of plants
have shortened internodes, and leaves are
distorted
98. Tobacco Ringspot
Conditions favoring development
s Nearby crops that may harbor the virus
s Insect vectors are possible and disease is
often found near the edges of fields.
s Dagger nematode (Xiphinema) may cause a
low level of transmission.
101. Powdery Mildew (fungus)
Symptom/Sign
s Irregular shaped yellow areas on leaf
initailly
s White powdery mass of fungus on upper
surface of lower leaves
s Older PM colonies will have small brown to
black sexual fruiting structures present late
in the spring
103. Powdery Mildew (fungus)
Conditions favoring development
s Optimal powdery mildew development
occurs between 60- 72 F basically cool, wet
conditions
s High nitrogen fertility
s Dense stands of susceptible varieties
s High humidity
104. Powdery Mildew (fungus)
Control Methods
s Resistant varieties
s Rotation is of some value but limited
s Balanced fertility
s Fungicides (seed and/or foliar treatments)
105. Leaf rust (fungus)
Symptom/Sign
s Orange-red pustules mostly on upper leaf surfaces
s Randomly scattered within the canopy
s Usually appears after heading
107. Leaf rust (fungus)
Conditions favoring development
s Temperatures from 59-72 F and free-
moisture. Needs adequate rainfall.
s Overwinters far south
s Spores carried by wind
109. Septoria leaf and glume blotch (fungus)
Septoria nodorum
Symptom/Sign
s Elongate lens-shaped lesions with yellow
margins
s Black fruiting bodies in center of lesion help
distinguish from tan spot. Often found in
orderly rows.
s On the heads a brown to gray -brown
discoloration occurs and pycnidia are found
on the infected glumes
111. Septoria leaf and glume blotch (fungus)
Conditions favoring development
s Optimal development is between 68-82 F
wet, windy conditions.
s Minimal wet periods of 6 hours, but mostly
needs 16 hours of wetness.
112. Septoria leaf and glume blotch (fungus)
Control Methods
s Fungicides
s Tillage
113. Scab (fungus)
Symptom/Sign
s Bleached spikelets on part or all of wheat
head
s Pink or orange spore masses may be seen at
the base of infected spikelets during periods
of high humidity
s Infected heads are sterile or contain white
shriveled grain
s Same as Fusarium on corn (mycotoxins)
115. Scab (fungus)
Conditions favoring development
s Spores from corn, wheat and grass residue
spread to flowering wheat under warm, wet
conditions.
s Temperatures between 77-86 F and
continous moisture at flowering are most
favorable for epidemics.
116. Scab (fungus)
Control Methods
s Tillage prior to planting
s Rotation (limited value in areas with intense
no-till or reduced tillage corn production)
s No resistance
117. Take-all (fungus)
Symptom/Sign
s Infected plants are stunted and ripen prematurely
s Best identified at heading by stunted growth in
patches and heads are bleached white and often
sterile
s Black lesions at base of crown under the lowest
leaf sheath
s Plants pull easily from the soil from extensive rot
rot.
120. Take-all (fungus)
Conditions favoring development
s Continuous wheat production
s High pH, poorly drained soils or wet years
121. Take-all (fungus)
Control Methods
s Rotation
s Maintain good fertility levels
s No good resistant varieties
s Control grassy weeds before cropping to
wheat
122. Barley yellow dwarf (virus)
Symptom/Sign
s Ambiguous often look like nutritional
disorders
s Fall infection results in patches of yellow,
stunted plants. Spring infections usually
result in plants of varying heights and
yellow or purple colored flag leaves after
head emergence
s Occurs in patches of field where aphid
vectors feed
124. Barley yellow dwarf (virus)
Conditions favoring development
s Transmitted by aphids
s Cool, moist conditions (50-65 F)
s Early planted fields attractive to aphids
s Mild winter with aphids
125. Barley yellow dwarf (virus)
Control Methods
s Tolerance
s Later planting date
s Control aphids
126. Wheat spindle streak mosaic (virus)
Symptom/Sign
s Non-distinct yellow streaks can be confused with
early stage powdery mildew
s Often produces yellow-green mottling, dashes
and streaks. The streaks often have tapered ends
forming spindles.
s Entire field affected--not patchy. Low spots in
field can have more severe symptoms.
128. Wheat spindle streak mosaic (virus)
Conditions favoring development
s Soil borne virus
s Transmitted by fungus, in the fall.
s Cool weather (46-53 F) produces the most
symptoms
s “Disappears” as temperatures increase
129. Wheat spindle streak (virus)
Control Methods
s Resistant variety
s Rotation of some value
s Later planting
s Poultry manure may decrease disease
incidence
136. Phytophthora root rot (fungus)
Conditions favoring development
s Cool, wet conditions
s Poorly drained soils
137. Phytophthora root rot (fungus)
Control Methods
s Select well drained sites
s Break up compacted soils to enhance drainage
s Plant resistance varieties
s Use Apron seed treatments to avoid seedling
damping-off
138. Anthracnose (fungus)
Symptom/Sign
s Wilted stems
s Diamond shaped lesions on lower stem
s Lesion gray with red margin
s Scattered in the field
s Infected stems with characteristic diamond
shaped lesion will also produce a typical
shepard’s crook
140. Anthracnose (fungus)
Conditions favoring development
s Warm, humid conditions
s Late summer/ early fall weather can be very
favorable for infection
141. Anthracnose (fungus)
Control Methods
s Resistant variety
s Clean harvesting equipment before first
cutting and when going from a known
infected fields to a healthy field.
142. Sclerotinia crown rot (fungus)
Symptom/Sign
s Fall- planted alfalfa dies in spring during
cool, wet conditions.
s Cottony web-like growth on stems and
crowns
s Stems turn brown, then soft and mushy then
disintegrate.
s Black fruiting bodies (Sclerotia) on stem
145. Sclerotinia crown rot (fungus)
Conditions favoring development
s Infection occurs in fall
s Plants die in cool, wet spring
s Favored by late summer early fall planting
s Planting into clovers
146. Sclerotinia crown rot (fungus)
Control Methods
s Spring planting date
s Deep plowing to bury sclerotia
s No resistance
155. Verticillium wilt (fungus)
Symptom/Sign
s Scattered infected stems
s Early symptoms include V-shaped chlorosis
at leaflet tips
s Not all stems on the same plant infected
initially
s Internal root tissue is often brown, but it is
not a dependable diagnostic feature.
158. Verticillium wilt (fungus)
Conditions favoring development
s Introduced on seed usually
s Could be disseminated in manure
s Insects can can serve as vectors
s Can spread within the field during cutting
159. Verticillium wilt (fungus)
Control Methods
s Plant clean seed free of debris
s Plant resistant varieties
s Disinfestation of cutter bars and equipment
160. Most Common Symptoms of
Nematode Injury
Field Symptoms
s Stunting and sometimes yellowing of plants in
patches of varying size
s Not definitive, need to look at roots
Plant Symptoms and Signs
s Galls, cysts, lesions or dead areas on roots
161. FUNGICIDE CLASSIFICATION
s PROTECTANT
– Forms a protective barrier on the plant surface that
prevents spore germination eg. Dithane, Bravo, thiram
s SYSTEMIC
– Moves in the plant from point of application across the
leaf or into new growth. Can move from roots to
above ground parts. Prevents spores from germinating
or kills them soon after germination. Eg. Tilt, Baytan,
Raxil, Quadris, Ridomil.
s ERADICATIVE (Curative)- kills fungus already
present. Some systemic fungicides have some curative
activity
162. TREATMENT THRESHOLDS FOR
FUNGICIDE APPLICATION
s Thresholds are available for making spray
decisions for wheat in the mid-Atlantic
region.
s Use stage of development and amount of
disease present to determine need for an
application.
