Diseases of maize, millet and sorghum
Symptoms, perpetuation and control
By M. Mithal Jiskani
Aug 20 - 26 , 2001
Maize is most important cereal crop of the world in
terms of its total global production. It ranks second to wheat and
equal to rice. Globally, 67 per cent of maize is used for livestock
feed, 25 per cent for human consumption and industrial purposes, while
5 per cent is used for seed purpose to sow next crop.
Millet and sorghum are most important cereal crops
of the Desert and Mountain (Thar-Cholistan and Kohistan) areas of the
world including Pakistan. Millet is the principle cereal crop in the
infertile, semi arid zones. Its acreage is dependant on the amount and
time of the rain fall, as it is mostly confined in rained areas.
Sorghum is heat and drought resistant cereal crop and remain dormant
during moisture stress conditions and resumes growth under favourable
These crops are subjected to a number of diseases,
which are responsible for reducing their overall production to a great
extent. The plants in all stages of growth and in all natural
environments are subject to various mechanical, physiologic and
biological stresses, that interfere with their normal growth and
development. Weather, toxicants, pollutants, insects, viruses, fungi,
nematodes, bacteria and weeds are primary hazards to the production of
crops. The actual number of maize, millet and sorghum diseases is
unknown, but some of the most common and important diseases are
discussed according to Kamal and Moghal (1968), Hafiz (1986), Nyvall
(1979) and Jiskani (1999).
Diseases of maize (Makki)
Maize is very efficient water user. It needs large
quantities of irrigation water for high yield, because drought
conditions lead to lower yields and lower quality grains. Maize
requires 6-8 irrigations. First irrigation 3-4 weeks after sowing,
remaining may be given at 10-15 days interval. The grain formation is
critical growth stage. It is not important grain crop in Sindh, but is
grown mostly as fodder crop and very rare as for grain. More than 70
different diseases of maize are reported in the world, which hit the
crop and cause considerable damage. Seedling rots reduces stand. Many
fungi produce root rot, stalk spotting and early dying due to stalk
and root rots. Helminthosporium leaf spots are characterised by small
spots with light border or very large light grey spots. Common corn
smut, discussed below, is one of the most important than all others.
SMUT (Ustilago maydis)
Symptoms: White to greyish-white galls (soft
tumors) develop on any part of the plant. These galls are light
coloured in early stages, become blackish on maturity and filled with
black powder (spores of disease causing fungus). Large sized galls
involving the entire head.
Perpetuation: The disease causing fungi
perpetuates through diseased plant debris lying in the field.
Control: (1) Do not sow diseased seed, (2)
Follow 2-3 years crop rotation and (3) Do not expose the manure heaps
near the field.
Diseases of millet (Bajra)
The area under millet crop is highly variable,
because it is dependent on the amount and time of the rainfall. It is
mostly confined to the desert and mountain (Thar-Cholistan and
Kohistan) area. 3-4 irrigations (30-35, 50-60 and 70-80 days after
sowing) are sufficient for better yield. Near about 40 diseases are
reported on millet but following are most important because of their
considerable losses to over all production.
Green ear or downy mildew (Sclerospora
Symptoms: It can be characterised at ear
formation stage, when the leaves become distorted, twisted, crinkled
and lose their green colour, become white and later turn brown. The
ears are transformed in to green leafy structures with enlarged
glumes, turning wholly_or partially into loose heads. The affected
portions are sterile and they do not produce grains.
Perpetuation: Diseased plant residues help the
fungus to survive and oospores present in soil cause primary
Control: (l) Use of resistant varieties, (2)
Collection and burning of diseased plants or plant parts, as soon as
they appear, (3) Destroy and burn carefully all the diseased plant
debris, (4) Use of 2-3 year crop rotation and (5) Avoid cultivation in
low lying and drained lands.
Grain smut (Tolyposporium penicillariae)
Symptoms: Infected grains from the smut sori,
are thickened, slightly elongated, covered by tough and blakish green
membrane filled with fungal spores. These are present singly or in
groups, usually a one side of the ear or towards its base, scattered
or collected together in patches on the ear.
Perpetuation: Infection is usually through
air-borne sporidia released from germinating chlamydospores in soil.
Control: (1) Cultivate resistant varieties, (2)
Early collection and burning of diseased ears on appearance and (3)
Follow 2-3 years crop rotation.
Diseases of sorghum (Jowar)
The major area of sorghum in Pakistan lies in
Punjab, but the yield per hectare is higher in Sindh. The sorghum
plants are drought resistant, but 3-4 irrigations (30-35, 50-60 and
70-80 days after sowing) are compulsory for better yield. In case of
sorghum, about 50 diseases are recorded world over but following are
Grain smut (Sphacelotheca sorghi)
Symptoms: This disease also known as covered or
kernel smut. The grains are transformed into white greyish sacs (smut
sori), are slightly pointed to oval and filled with black powder (chlamydospores).
Most of the grains are found infected.
Perpetuation: Perpetuate through contaminated
Control: (1) Use healthy seed, (2) Sow seed by
broadcasting and water the field immediately thereafter, (3) Treat the
seed with any one of the organic mercurial or copper seed dressing
fungicides and (4) To collect and burn diseased heads.
Long smut (Tolyposporium ehrenbergii)
Symptoms: Individual grains are transformed
into large sized smut sori, which are full of solid spores. The
diseased grains (smut sori) are found scattered on head. These grains
turn into cylindrical and elongated sacs. Mostly upper portions of ear
head have higher number of infected grains.
Perpetuation: The disease causing fungus is
seed, soil and air-borne.
Control: (1) Use healthy seed, (2) Seed
treatment with organic mercurial, (3) Collect and destroy diseased
grains, (4) 2-3 years crop rotation and (5) Cultivate disease
resistant or tolerant varieties.
Red leaf blight or anthracnose (Colletotrichum
Symptoms: Initially small ovate to irregular
red spots appear on leaves. Later on, these increase in number and
size to cover larger area of leaf. The infected leaves become reddish
brown, show necrosis and become dry. Premature ripening and
shrivelling of grains also occur.
Perpetuatlon: Plant debris and seeds may serve
Control: (1) Use of healthy seeds, (2)
Destruction of plant debris and (3) Soak the seed in ordinary water
for 4 hours and then dip in 55.5°C hot water for one hour.
Red leaf spot (Phyllosticta sorghina)
Symptoms: Small red spots on leaves, stems and
grains. These increase in number and size and join up leaves dry 2
Perpetuation: Seed-borne or through diseased
Control: Same as recommended for red leaf
The author is Assistant Professor (Plant
Pathology), Sindh Agriculture University, Tandojam.