is one of the leading food crops of the world, an important staple
food and cash crop of Pakistan. It contributes 15 percent to the
foreign exchange earnings. Its area under cultivation, production
and yield per hectare also indicates its importance. This crop is
very suitable, where other crops are not possible to grow or where
Kharif (summer) irrigation water supply is abundant. According to
Cheema et al. (1991) rice prefers 5.0-6.5 soil pH, and is moderately
tolerant to exchangeable sodium percentage (ESP) in the level of
20-40%. This crop may also tolerate up to 0.40-0.60 percent of white
alkali and 0.10-0.20 percent of black alkali in soil (WAPDA report,
1961). The rice is frequently grown on heavy clay soils that have
an impervious, subsoil layer (hard pan) that limits drainage, because
it requires a constant and plentiful supply of water. The rice production
can be used to reclaim saline soils, because flooding leaches salts
from the soils (Bhatti and Soomro, 1996).
The rice crop is subjected to more than forty diseases, which are
one of the factors, for low yields of rice in the world (including
Pakistan). The diseases may appear at any stage of the growth and
development of plant, attacking the seed sown, root system, foliage,
stalk, leaf sheath, inflorescence and even the developing grain.
The fungi, bacteria, nematode and virus cause different infectious
diseases. Non-infectious diseases may be caused because of low or
high temperature, decrease or increase in different nutritional
elements essential for the crop. Overall, Table present area, production
and yield per hectare of rice crop in Pakistan. The causes of fluctuations
in production may be many more, but the diseases could not be ignored,
neglected and or regretted, because they also cause variable loss
time by time to the crop. These all diseases are injurious in some
areas, in some years and on some plant parts. All parts of plant
are subject to disease and one or more diseases can occur on virtually
every plant and in every field. All draw attention because of symptoms
or signs and generate great concern because of their effects on
the quality and/or quantity of plants, straw or grain.
According to Kamal and Moghal (1968), Hafiz (1986), Nyvall (1979),
Bhatti and Soomro (1996) and Jiskani (1999), brown spot, blast,
stem rot, bunt, bacterial blight, false smut, ufra and khaira (zinc
deficiency) are sometimes considered important diseases at various
parts of rice growing areas of Pakistan. Therefore identification,
management practices and some other relevant knowledge of the most
important diseases of rice are being summarized, so that the growers
may protect their crop from these diseases, research workers may
decide their future strategies, extension workers may also to be
OR BROWN SPOTS (Helminthosporium oryzae)
Symptoms: This disease has been recorded all over Pakistan.
Initially small dots or circular eye shaped or oval spots appear
light in colour on leaves. These spots coalesce and result in linear
brown in colour. Later on withering and yellowing of leaves occur.
Seed setting also affected and causes sterility, shrivelling and
show rotting and poor germination.
Perpetuation: Diseased seeds, plant debris and
soils help the fungus to survive, while air and irrigation water
help to the fungus for transmitting from diseased to healthy plants.
Control: 1) Use of resistant varieties or disease
free seed in healthy soils, 2) Sanitation and crop rotation, 3)
Hot water seed treatment at 54 oC for 10 minutes or with seed dressing
fungicides, 4) Collection and destruction of stubble and spraying
with copper fungicides at right time and 5) Application of suitable
foliar fungicides may help to minimise further dissemination of
BUNT OF RICE (Tilletia barclayana)
Symptoms: This disease also called black or kernel smut
is generally distributed wherever rice is grown. Diseased grains
are filled with black powder, which can be detected by breaking
them. Only a few grains may be affected wholly or partially in an
ear. If not severely infected, seeds may germinate but seedlings
Perpetuation: The disease causing organism is soil borne.
1) Cultivation of resistant varieties, 2) Use of healthy seed, 3)
Sowing early maturing varieties, 4) Avoid high rates of nitrogen
fertilizer, 5) Avoid winnowing and threshing of diseased crop in
field, 6) Treat the seed with suitable chemicals easily available
in the market and 7) Collect and burn diseased ear heads.
Rice blast (Pyricularia oryzae)
Symptoms: Some times this disease refers as Pyrricularia
blight or rotten neck, generally distributed where ever rice is
grown. Small spots appear on leaves, nodes, panicles and grains
and some times on leaf sheaths. The spots begin as small, water-soaked,
whitish, greyish or bluish dots. These spots rapidly increase and
become grey in centre. Brown to black spots also develops on inflorescence
and glumes. In later stages, diseased heads appear blasted and whitish
in colour. Grain development is affected and the panicles droop.
Perpetuation: The disease perpetuates through diseased
plant debris lying in the field, seed and wild grasses.
Control: 1) Burn and destroy diseased plant debris
and stubble, 2) Early planting, 3) Cultivation of resistant varieties,
4) Use of healthy seed, 5) Dusting the seed with any one of the
organic mercurial seed dressing fungicides, 6) Spray the crop with
organo-mercurials, 7) Avoid excessive depth application of irrigation
water, 8) Avoid excessive plant population and 9) Control grasses
and other weeds.
BAKANAE DISEASE (Fusarium moniliforme)
Symptoms: This disease is also called
white stalk, generally distributed where ever rice is grown. Infected
seedlings are thin, chlorotic, may die before or after transplanting.
In the field, infected plants have few tillers and leaves die in
short time. Live plants have empty panicles. Some infected plants
may be stunted instead of elongated, while the abnormal elongation
of these (infected) plants in seed bed or field is most common symptom
of this disease.
Perpetuation: The disease causing fungus is seed
and soil borne, through which it can survive for a long period.
Control: 1) Cultivation of resistant varieties
and 2) Seed treatment.
UFRA OF RICE (Ditylenchus angustus)
Symptoms: The disease has been reported from Bangladesh,
Egypt, India and South Asia. The leaves become yellow and wither,
seedlings die. Brown spots appear on leaves and leaf sheaths. Stems
may also bear spots. These spots become darker brown along with
upper inter-nodes of the stem. Ears may not emerge or may show swellings
and become twisted and distorted. Grains are not formed usually.
Perpetuation: Diseased plant debris carrying disease
Control: 1) Burn the stubble, 2) Grow early maturing
varieties, 3) Use healthy seed and 4) Plough the field thoroughly
after harvest so as to expose the soil to sun-heat.
Bacterial blight (Xanthomonas oryzae)
Symptoms: Water soaked stripes appear along the
margin of leaf blades, which later on enlarge and turn yellow. These
lesions may cover the entire blade, may extend to the lower end
of leaf sheath. Similar symptoms may occur on glumes of green grains.
Perpetuation: Survive in rhizophere of weed hosts,
infected straw and root stubble. Disseminate by wind and water.
Control: Cultivation of resistant varieties is
alone easy and safe way to prevent the crop against diseases including
this disease also.
Stem Rot (sclerotium oryzae)
Symptoms: Two to three months old plants begin to wither
and ultimately dry up; the sheaths soon turn somewhat dark and start
rotting. Black dots (fruiting bodies of sclerotia) occur at the
base of dried leaves and leaf sheaths. Stem begins to rot and become
soft, plant falls down.
Perpetuation: Infested soil helps the organism
for its survival.
Control: 1) Use of resistant varieties, 2) Burning
of diseased rice stubble, 3) Crop rotation and 4) Antagonistic organisms.
1. Bhatti, I. M. and A. H. Soomro. 1996. Agricultural inputs
and field crop production in Sindh. Agricultural Research Sindh,
2. Cheema, S. S., B. K. Dhaliwal and T. S. Sahota. 1991. Theory
and digest of agronomy. Kalyani Pub., New Delhi.
3. Hafiz, A. 1986. Plant diseases. PARC, Islamabad.
4. Jiskani, M. M. 1999. A brief outline “THE FUNGI”
(Cultivation of mushrooms).
5. Kamal, M and S. M. Moghal. 1968. Studies on plant diseases of
South West Pakistan. Agricultural Research Institute, Tandojam.
6. Nyvall, R. F. 1979. Field crop diseases handbook. AVI Pub. Co.
7. WAPDA Report, 1961.