Sorghum crop diseases A Lecture by Mr Allah Dad Khan
1.
2. SORGHUM CROP DISEASES
A PRESENTATION TO IPM COURSE/FFS
PARTICIPANTS
BY
MR. ALLAH DAD KHAN
PROVINCIAL COORDINATOR IPM KPK FOR MINFAL
PAKISTAN
3.
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
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