Maize crop diseases A Lecture by Mr Allah Dad Khan

2. CORN CROP DISEASES
A PRESENTATION TO IPM COURSE/FFS
PARTICIPANTS
BY
MR. ALLAH DAD KHAN
PROVINCIAL COORDINATOR IPM KPK FOR MINFAL
PAKISTAN

4. SEED AND SEEDLING DISEASES
SYMPTOMS:



Disease damage may appear similar to some
environmental stress, but general and specific
symptoms can help with diagnosis.
 General effects: reduced emergence, slow
growth and stunting in a random or circular
pattern, wilting, chlorosis/yellowing, post-
emergence damping-off.
 Specific symptoms of seed and root infections
include: rotted seed and seedlings before or
after emergence; red/yellow discoloration of
leaves; complete or partially rotted roots with
firm or soft, brown-reddish- to gray lesions or
decay; discolored and soft coeleoptile; death of
leaf tips; wilting; and sunken,discolored lesions
on mesocotyl.
 Leaf spots and streaks can also occur, resulting
from anthracnose and Stewarts wilt infections

5. SEED AND SEEDLING DISEASES
PATHOGEN INVOLVED:· DISEASE MANAGEMENT:PLANT
 Some common genera of `fungal'
pathogens that cause one or more of
the symptoms noted above are
Stenocarpella (Diplodia), Pythium,
Rhizoctonia, Fusarium, Colletotrichum,
and Penicillium.
 Two bacterial pathogens that can
affect corn seedlings are Erwinia
[=Pantoea] (Stewart's Wilt) and
Pseudomonas (holcus spot).
 The source of these pathogens is soil,
infested residue remaining from
previous years crops, or infested seed.
 Nematodes can also damage corn
seedlings, especially in sandy soils.
 into soil greater than 50-55°F.
 Use seed treated with
fungicides. However, these
chemicals are most effective
for about 2 weeks after
planting depending on soil
water content and
temperature.
 The primary fungicidal seed
treatments used are of two
main groups

6. FUSARIUM STALK ROT
SYMPTOMS
 Similar to Diplodia and
Gibberella stalk rots
 Inner stalk will have a light
pink discoloration, but no
black specks (fungal fruiting
bodies) will be present in or
on the stalk
 Ears may be small and lower
nodes may be shredded or
break
 Eventually, the stalks may die
and lodge

7. FUSARIUM STALK ROT
PATHOGENS INVOLVED DISEASE MANAGEMENT
 Fusarium moniliforme, F.
proliferatum, and F.
subglutinans (a fungus)
 These fungi are found
wherever corn is grown
 Overwinters in crop residue
 Use hybrids that are
resistant to other stalk rot
diseases.
 Minimize all crop stresses
 Control insects
 Use proper plant population

8. BACTERIAL STALK ROT
SYMPTOMS
 Symptoms are similar to those
of Pythium stalk rot
 One or more of lowest
internodes will turn tan to
brown and become water
soaked, soft, or slimy and
there may be a foul odor
 Upper leaves wilt and a soft
rot can occur at the base of
the whorl, and this may
spread rapidly down the plant
and cause lodging

9. BACTERIAL STALK ROT
PATHOGEN INVOLVED DISEASE MANAGEMENT
 Erwinia chrysanthemi pv.
zeae (bacterium)
 Wide host range, including
monocots as well as dicots
 Infection sites are stomata,
hydathodes, or the wounds of
leaves or stalks
 Overwinters in stalk residue
on the soil surface line
 May be transmitted by larvae
of the maize borer
 Incorporate soil debris with
fall plowing
 Avoid flooding and
excessive overhead
irrigation

10. ANTHRACNOSE STALK ROT
SYMPTOMS
 Symptoms usually most apparent
just before crop maturity
 Uniform or blotchy, shiny, black
color on the outer stalk
 Inner stalk may also be black
and systemically infected, or may
not have any discoloration
 Several internodes of the plant
may be rotted and easily crushed
with finger pressure
 The plant above or below the ear
may die and lodging may result.

11. ANTHRACNOSE STALK ROT
PATHOGEN INVOLVED DISEASE MANAGEMENT
 Colletotrichum graminicola
(a fungus)
 It is the same that causes
the Anthracnose leaf blight
disease
 The only common stalk rot
pathogen that can cause a
leaf blight disease
 Overwinters in corn residue
 Use disease resistance
hybrids
 Maintain balanced fertility
 Reduce plant stress
 Control the corn borer

12. CHARCOAL ROT
SYMPTOMS
 Symptoms may first appear
similar to Fusarium,
Diplodia, & Gibberella stalk
rot
 A key sign of charcoal rot is
gray or black discoloration
in the inside the rind due to
the presence of many tiny,
black sclerotia (can be
seen with hand lens)
 Plant may die and lodge

13. CHARCOAL ROT
PATHOGEN INVOLVED DISEASE MANAGEMENT
 Macrophomina phaseolina
(a fungus)
 Has a very wide host range
that include sorghum and
soybean.
 Infects soybeans more
often than corn in the
Midwestern U.S.
 The pathogen overwinters
on host crop residue
 Use hybrids resistant to
Diplodia and Gibberella
stalk rot.
 Minimize early senescence
of stalk tissue
 Reduce moisture stress

15. DOWNY MILDEW OF MAIZE

17. SOUTHERN CORN LEAF BLIGHT
SYMPTOMS:
 Common lesions are
elongated, tan lesions
between veins on leaves
 Different isolates of this
pathogen will cause lesions of
different sizes
 Race O causes long, tan,
lesions that have brown
borders on leaves.
 Lesions will develop
differently on various inbreds
and hybrids

18. SOUTHERN CORN LEAF BLIGHT
PATHOGEN INVOLVED: DISEASE MANAGEMENT:
 Cochliobolus heterostrophus
(=Bipolaris maydis) (a fungus)
 Overwinters in corn residue
 Especially prevalent in areas with
a warm, humid climate
 Three races known of this
pathogen: race O, race T, and race
C
 Race T and race C are known to
be specifically virulent to corn with
cytoplasm male-sterile T and
cytoplasm male-sterile C,
respectively. Since the switch from
cytoplasm male sterile T to normal
cytoplasm corn, race T is not
considered to be a threat.
 Use of resistant hybrids
 Crop rotation
 Tillage may be helpful