Sugarcane is not only cash crop for the growers, but it is main source of white crystal sugar. It also provides grower with a very good substitute of sugar as ‘gur’ and ‘khandsari’ (brown sugar). Sugarcane tops serve as fodder for cattle, baggage and leaf trashes as fuel, stubble and roots as organic manure and crop residues as mulch and compost (Bhatti and Soomro, 1996 and Khoso, 1992). It may also be kept in mind that sugarcane leaves are used as substrate for the artificial cultivation of edible mushrooms.

There are many constrain, including the heavy losses, caused by a number of diseases to the sugarcane crop in Pakistan. More than 50 diseases are reported in sugarcane, fungi, bacteria, viruses and nematodes cause the most destructive diseases. The losses (due to the diseases) vary from place to place, depending upon the crop variety and 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 cane.

WHIP SMUT (Ustilago scitaminea) Syd.

Symptoms: The affected canes produce long, black whip-like and coiled or curved shoots, which are covered with a thin silvery membrane, containing masses of chlamydospores of the fungus. The smutted shoots may arise from the top of the cane or from lateral buds. Later on that membrane ruptures and releases a multitude of spores, which contaminate soil and the standing crop. In certain cases, the infected plants remain stunted in growth with increased tillering of little value. The diseased plants are unfit for use.

Perpetuation: The disease is carried over from year to year by ratooning or planting sets taken from smutted shoots of cane. Soil borne infection may also takes place, while wind disseminates disease.

1) Sets from smutted canes should not be used for planting.

2) Seed-sets should be disinfected either in 0.1% mercuric chloride or formaline solution for 5 minutes followed by 2 hours covering under a moist cloth. The other effective chemicals available in market may also be used.

3) Hot water treatment of sets at 52OC for 18 minutes can help eliminate the internal infection.

4) Smutted plants should be rouged out and burnt before the bursting of the spores.

5) Ratooning of the diseases crop should be discoursed.

6) Suitable rotations with non-host crops should be practised.

7) Planting should be done in healthy soil.

8) Dry sowing of the crop should be carried out, where disease is prevalent.

9) Autumn planting of sugarcane should be avoided.

10) Use of resistant varieties should be encouraged.

Stem canker (Cytospora sacchari) Butl.

Symptoms: The disease causes wilting of canes. The affected canes show drying of leaves from top to bottom. The cane stems are shrivelled with considerable reduction in quantity and quality of juice. Small black dot-like bodies of disease causing fungus may develop on bud sheaths and hollow portions of canes. Sometimes only a few internodes are affected, but whole stool or only a few canes in a stool may also be affected.

Perpetuation: The fungus remains in diseased canes or plant debris, which remain lying in the fields after the harvest of crop. Ratoon crop also helps the disease causing fungus to survive.

Leaf spot (Helminthosporium spp.)

Symptoms: The disease may be characterised itself on leaves as small lesions, which gradually enlarge along mid rib and assure dark red to brown colour. In severe infection, the leaves become dry affecting photosynthesis.

Perpetuation: The disease perpetuates through the fungus present in the affected leaves lying in the field and spreads fresh crop of conidia falling on leaves of adjacent plants.

Control: Collection and burning of leaves or phyto-sanitary precautions in suppressing the sources of inoculum reduces the incidence of disease.

SUGARCANE MOSAIC VIRUS (SCMV, Potyvirus group)

Symptoms: Mottling of young crown leaves showing a definite pattern of alternating dark and light green coloured patches of varying size and run parallel to the midrib of leaf.

Transmission: Transmitted through mosaic infected sets and an aphid.

Alternate hosts: Maize and sorghum.

Control: Planting virus free sets and avoid ratooning of diseased crop.

Minor Diseases

The other minor diseases of sugarcane reported from Pakistan are: chlorotic streak virus, ratoon stunting, yellow spot, red stripe, rust and genetic variegation of leaf and sheath.

Reference:

1. Ahmad, I. 1988. Fungal Diseases of Sugarcane. In “Plant Disease Diagnosis Manual, Vol.2”. CDRI, NARC, PARC. Islamabad.

2. Bhatti, I. M. and A. H. Soomro. 1996. Agricultural inputs and field crop production in Sindh. Agricultural Research Sindh, Hyderabad.

3. Bhatti, I. M. and M. M. Jiskani. 1996. Modern Agricultural Guide. Agricultural Research Sindh, Hyderabad.

4. Hafiz, A. 1986. Plant Diseases. PARC, Islamabad.

5. Jiskani, M. M. 1999. A brief outline “THE FUNGI” (Cultivation of mushrooms).

6. Kamal, M. and S. M. Moghal. 1968. Studies on plant disease of south West Pakistan. ARI, Tandojam.

7. Khoso, A. W. 1992. Crops of Sindh. 5th Edition.

December,2004