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Disease Management
- Sugarcane crop is affected by numerous diseases. A
conservative estimate puts the loss in cane yield to
about 15 to 20 per cent. Maximum damage is caused by
sett transmissible diseases.
- The red rot is the most serious disease of sugarcane.
Other important diseases are smut, wilt, ratoon stunting
disease (RSD), grassy shoot disease (GSD), and leaf
spot disease which occur sporadically, mostly during
winter period and are of minor nature.
- The red rot and wilt in severe form can cause total
loss of yield.
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Grassy Shoot Disease
(GSD)
- GSD is a mycoplasmal disease. The disease is found
in most sugarcane growing areas of the country.
Symptom
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- Profuse tillering is a typical symptom.
- Narrow chlorotic leaves giving a grass like
appearance
- Very few tillers form canes which are thin
and produce white shoots from the side buds.
- The primary transmission is though diseased
setts
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Management
- Heat therapy is the best way to eliminate GSD.
- use of healthy seeds is important.
- The diseased clumps should be rogued out.
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Leaf Spot: Helminthosporium
sacchari Butler
- Infection occurs under humid condition. The fungus
penetrates the host tissue either through stomata or
directly through the cuticle.
- Usually, a crop of 6 - 7 months is more susceptible
to the disease. High soil fertility and higher fertilizer
application (N) also favour the spread.
- Cloudy weather, high humidity with drizzle coupled
with low night temperatures greatly enhance disease
development.
Symptoms
- The lesions first appear as small water soaked spots,
darker than the surrounding tissues. The spot becomes
more elongated, resembling the shape of an 'eye' and
turns straw coloured within a few days
- Finally the central portion becomes reddish brown
surrounded by straw coloured tissues.
- Reddish brown streaks of "runners" develop extending
from the lesions towards the leaf tip along the veins.
- The spots and streaks coalesce to form large patches
and cause drying of leaves.
Management
- Avoiding water logging, burning trash, avoiding excess N application.
- Restriction of irrigation in leaf spot affected fields.
- Copper oxychloride spray at 2 g / litre once a month during the disease initiation period.
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Mosaic
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- This is a viral disease.
- The affected cane leaves show dark green patches alternating with light green patches.
- Mild strains of mosaic do not cause yield loss while severe strains result in considerable loss of yield.
- The mosaic is transmitted through infected setts. Aphid vectors are known to transmit the disease to healthy crop.
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Management
- Use of healthy setts from disease free crops.
Top Pineapple
Disease: Ceratocystis paradoxa (de Seynes) Morean)
- It is essentially a disease of the seed pieces. The fungus enters the seed piece through cut ends and destroys the central soft portion and then damages the buds, thus causing germination failure.
- The diseased stalk when cut open smells like mature pineapple. The pineapple odour is due to production of ethyl acetate by the fungus.
Symptoms
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Typical disease symptoms are detected in setts after
2 –3 weeks of planting. The pathogen enters mainly
through cut ends and proliferates rapidly.
- The affected tissues first develop a reddish colour
which turns to brownish black in the later stages.
- The presence of the fungus inside the sett prevents
their rooting. In most cases setts decay before bud
sprouts.
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Management
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- The best way to control the disease is through
sett treatment with a fungicide, Carbendazim
at 1g / litre for 5 – 10 minutes before
planting .
- Use of long setts with 3 – 4 buds is
helpful as the central buds get protection.
Maintaining good field hygiene is important.
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Ratoon Stunting Disease
(RSD) : Clavibacer xyli David
Symptoms
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- Diseased stools are stunted in growth, thin stalked
with short internodes and have pale yellowish foliage.
- The stem tapers rapidly towards the top. When split
open longitudinally, pinhead like orange coloured
dots of bacteria can be noticed on the nodal region.
- Progressive yield decline takes place due to the disease.
The disease is more pronounced in ratoon. Primary
spread of the disease is through infected setts.
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Management
- Use of disease free setts for planting.
- Hot water treatment at 50 degree C for 2 hours may be done to eliminate sett borne infection of RSD.
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Red Rot : Colletotrichum falcatum
- The most dreaded disease of sugarcane which has caused
the elimination of several important sugarcane varieties.
- In peninsular India, the disease was mostly restricted to
Andhra Pradesh and coastal areas of Tamil Nadu.
- The disease was responsible for the failure of many important
commercial varieties like C0 997, Co 1148, and CoC 671.
- The disease which was prevalent in Coastal Tamil Nadu has
now spread to other areas of the state.
- Recently the disease has assumed serious proportions in Tamil
Nadu because of growing of highly susceptible varieties like
CoC 671, CoC 90063 and CoC 92061.
Symptoms
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- The first external symptom appears mostly on the third
or fourth leaf which shows yellowing and drying
from margin to midrib.
- At advanced stage of the disease, the entire top
including the crown dries and dies.
- The natural colour of the stalk is lost and the
rind becomes dark.
- Reddish lesions are also noticed on the rind.
- There is considerable shrinkage of the stalk.
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- Under high humid condition, pinkish powdery mass of
spores of the pathogen is seen on the nodal region.
- The most characteristic symptoms of the disease
are observed when the affected stalks are cut open
longitudinally.
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- The internal tissue shows reddish discoloured patches or lesions interspersed with white horizontal patches.
- As the disease progresses the internal tissues become dark in colour and dry up, resulting in longitudinal pith cavities.
- At the final stage, grayish cottony growth of the fungus is seen on these cavities.
Management
- The most important approach to contain the disease is
to grow red rot tolerant varieties in red rot endemic areas.
- Since primary spread of the disease is through infected setts,
indiscriminate movement of seed material from one region to
another should be prevented, may be through legislation. Commercial
varieties which are resistant may break down and become susceptible
due to emergence of highly virulent pathotypes of red rot
pathogen. Thus there is constant need for obtaining resistant
varieties.
- The most satisfactory, dependable, long lasting and economical
means of fighting red rot is the use of resistant varieties.
Therefore, very great importance is attached to develop varieties
resistant/ tolerant to red rot. Varieties Co 8021, Co 86010
and CoG 93076, Co 85019, Co 86249, Co 87263, Co 87025, CoSi
95071, CoSi 96071, CoG 95076, are tolerant to red rot.
- The disease can be effectively managed by following certain
phytosanitary practices in combination with resistant varieties.
- The crop residues- stubbles, dry leaves, dead and dry canes
should be burnt after harvesting the crop to reduce the inoculum
of the pathogen.
- Monoculture of sugarcane leads to a build up of inoculum in
the sugarcane debris. To eliminate this, crop rotation, particularly
with paddy is important and desirable because under anaerobic
condition the fungi do not survive in soil and are destroyed.
- As infected setts are the primary source of infection, it
is most important to use healthy seeds from a red rot free
crop. Setts must be obtained from nurseries which have been
given heat treatment.
- The pathogen can spread from one region to another; from field
to field and from clump to clump through irrigation water.
Therefore, flow of irrigation water from the red rot affected
fields to healthy areas should be avoided.
- Delayed irrigation or alternate row irrigation reduces the
red rot disease incidence level to 48 per cent while normal
irrigation elevates the incidence to 74 per cent.
- As the incidence of red rot increases in successive ratoons,
ratooning should be discouraged in red rot infected fields.
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Smut:Ustilago scitaminea Sydow
- Smut is prevalent in all the states, but more in the tropical states of Andhra Pradesh, Maharashtra, Karnataka and Tamil Nadu.
- The loss caused to the sugarcane in terms of yield and quality depends on factors such as primary or secondary infection; plant or ratoon crop that is affected and early or late infection.
Symptoms
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- The characteristic symptom is the production
of long whip like structure from the terminal
bud of the stalk, which is black in colour covered
by a thin silvery membrane.
- This silvery membrane ruptures releasing millions
of reproductive spores of smut fungus which
are present in the form of powdery mass. The
affected stalks are usually stunted.
- The disease is more in ratoons and more pronounced
in dry weather.
- The losses due to smut have been reported to
range from 30 to 40 per cent in plant crops
and even upto 70 per cent in ratoons.
- Sucrose content in infected cane is reduced
to a range of 3 to 7%.
- The primary spread of the disease is through
infected setts and the secondary spread is through
wind borne teliospore.
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Management
- Roguing of disease affected clumps: whips must be located in time, before the silvery membrane breaks, covered with paper or cloth bags and then removed. The whips must be burned or buried in the soil.
- Resistant varieties (viz. Co 6806, Co 449, Co 527) (Cosi 86071, Cosi 96071, Cosi 98071) ( Co 86249, CoG 94077, CoG 95076) should be cultivated in smut prone areas.
- No seed material should be drawn for further planting from the affected fields.
- Hot water treatment at 50 degree C for 2 hours in combination of fungicide Bayleton at 1g / litre will completely eliminate sett borne infection.
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Wilt: Cephalosporium
sacchari Butler or/and Fusarium moniliformae
Sheldon.
- The disease spreads through infected setts. The fungi gain entry mainly through injuries.
- Biotic stresses like nematode, root borer, termite, scales, mealy bugs etc., and a biotic stresses like drought, water logging, etc., predispose the plants for wilt infection.
Symptoms
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- Typical wilt symptoms appear during the monsoon and post monsoon periods.
- The affected plant appears wilted and conspicuously stunted. The crown leaves turn yellow, lose turgor and eventually wither.
- On splitting open the canes at early stage of infection, diffused reddish brown patches are seen. Later canes become light and hollow and shrink.
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- The disease reduces germination, causes drying up of shoots and subsequently results in wilting of the stalks.
Management
- Effective method of control is not yet available to eliminate wilt pathogen. Following wilt management techniques are recommended:
- Use of wilt-free seed material for planting
- Crop rotation with crops like paddy
- Cultivating wilt resistant varieties (like Co 8338 in Gujarat)
- Avoiding ratoons
- Burning trash and crop residues
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Nematode Management
- Realisation of nematode as being an important pest in sugarcane was only in the last two decades. It is now estimated that there is approximately 15 per cent total loss in sugarcane by nematodes. Five genera of nematodes are widely distributed and are of economic importance in sugarcane ecosystem.
Lesion nematode: Pratylenchus spp
- The lesion nematode has been observed to be the predominant
nematode causing economic losses to sugarcane. It is widely
distributed in sugarcane ecosystem.
- Usually paling of leaves, first in the form of streaks, later
complete yellowing-chlorosis, occuring in patches spread out
all over the fields can be noticed in deficient soils.
- Chlorosis in severe cases, accompanied by drying up of the
margins and leaf tips is more common in young crop and ratoons.
- Stunting of the crop and reduction in number and size of internodes
are also observed.
- Pratylenchus spp have been found to be associated with disease
complex of sugarcane.
- Losses ranging from 15-16 per cent have been estimated due
to this nematode alone and 75-90 per cent when the nematode
is associated with the wilt fungi.
Lance nematode: Hoplolaimus spp
- Hoplolaimus spp normally occur only in low
populations and the economic importance of this nematode
is generally not realised. However, high population
of this can cause yield loss of about 11 to 13 per cent.
- The symptoms of attack include stunting of the crop and loss in both fresh and dry weight of the tops. The roots formed are very sparse and stubby leading to their gradual decay.
Root-knot nematode: Meloidogyne spp
- In India, root-knot nematode was first reported from Tamil Nadu in Nellikuppam (South Arcot District) where chlorosis and drying of cane was noticed .
- Symptoms caused by root-knot nematodes in sugarcane are discernible, both above and below the ground.
- The disease is characterised by chlorosis of leaves. The leaves are rolled and appear short of moisture. The younger leaves show chlorotic symptoms and this is more accentuated in ratoon crops.
- The plants are stunted and present an unhealthy appearance even from a distance.
Stunt-stylet nematode:Tylenchorhynchus spp
- The loss caused by this nematode is only minimum and generally above ground symptoms are not expressed. The feeding by the nematode causes some damage to the root cells. As a result the roots become stubby and sparse .
Spiral nematode Helicotylenchus spp
- Spiral nematodes are also ectoparasites not causing discernible symptoms. Severe stunting and chlorosis of the crop has been observed in fields with heavy infestation. The infested roots show discolouration of cortical cells and brown lesions.
Integrated Nematode Management
- Deep ploughing in summer and solarisation. This helps in complete drying of small roots and desiccates the soil and the nematode.
- Crop rotation: Sugarcane followed by rice helps in nematode population reduction.Growing of antagonistic crops like Tagetes( Marigold), sunnhemp prior to sugarcane reduces the nematode population and damage. Intercropping of daincha in sugarcane significantly reduces the nematode population.
- Organic amendments: Application of 35 tonnes of pressmud or 25 tonnes of well decomposed farm yard manure or 1.5 tonnes of neem cake before planting helps in the multiplication of antogonistic fungi suppressing nematode population.
- Chemicals: Carbofuran 3G @ 35 kg / ha mixed with sand and applied when the crop is three month old reduces the nematode population in sugarcane.
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