BANANA is cultivated on about 40,000 hectares of which 30,000 hectares are in Sindh alone. It was introduced in 1913 with seven varieties brought from Mumbai in 1913; 15 from Poona, Kolkata and Sri Lanka in 1919; 23 in 1937 and one in 1972 were brought and tested for successful cultivation. Similarly, another variety Willium Hybrid was introduced from Australia in 1969 but it could not be accepted by local growers for commercial cultivation. However, because of its good height, it is grown in patches mainly alongside the bunds as wind-breaker.

The banana is a high yielding fruit crop of Pakistan. Ripe banana fruits are sugary and unripe fruits or plantains, are cooked and provide starchy food with important nutritional value. The fruit is useful in improving anemia, blood pressure, constipation, depression, hangovers, heartburn, morning sickness, ulcers, nervous system and other ailments.

The crop provides employment to thousands of farm workers, urban and rural contractors, transporters, commission agents, wholesalers, and retailers throughout the country.

There are approximately 300 species but only 20 varieties are commercially cultivated in the world. In Pakistan and especially in Sindh, the cavendish variety, locally known as basrai gives the most outstanding results by holding about 98 per cent of plantation.

The banana crop is known to be much more vulnerable to diseases than to insect pests. There are various diseases which attack the crop and cause huge losses every year. A major disease is called Panama, as it first originated from that area. It now is known as Fusarium wilt - a highly destructive and the most notorious of all plant diseases which affects the vascular system of banana. The causal organism is a soil-borne fungus, Fusarium oxysporum f. sp. cubense which colonises and occludes the xylem of susceptible cultivars to cause a terminal wilt.

The disease was first reported in Australia in 1876. By 1950, few banana-producing regions remained free of the disease. Panama disease is now found in all banana-producing regions except Islands in the South Pacific, the Mediterranean, Melanesia, and Somalia.

Panama disease impacts the production of a wide range of banana cultivars. In the Ulua Valley of Honduras alone, 30,000 hectares were lost between 1940 and 1960. Damage occurred more rapidly in areas such as Suriname, where an entire operation of 4,000 hectares was out of production within eight years, and the Quepos area in Costa Rica, where it took 12 years for 6,000 hectares to be destroyed. The loss was in millions of dollar.

The disease infestation may also be observed in patches in Pakistani areas of Badin, Hyderabad, Hala, Sanghar, Nawashah and other banana growing districts of Sindh, especially from April to August.

Infection: The infection is caused by fungus which enters through roots and move to xylem vessels where it grows and sporulates abundantly. Transport of spores upward in transpirational stream facilitates invasion of the entire vascular system by fungus growth thus wilting the plant.

Sympton: Any aged plant is susceptible with initial symptoms appearing as a chlorosis of the oldest leaves which extends rapidly from the margin towards the midrib (figure). These leaves hang withered around the pseudo stem and infection spreads to leaves except the top which hangs down. The heartleaf also withers after three to four weeks.

The plant exhibits longitudinal splitting with bulging and elongation of pseudo stem. When the rhizome is cut open, the discoloration of vascular bundles can be seen and the cut stem smells like rotten fish. The pseudo stem may develop a crack at the base and will remain standing for several weeks until it decays. Pseudo stem and corm-cut crosswise is of brown to purple colour with a reddish tinge extended throughout the pseudo stem and the fruit stalk. No symptom observes on fruits.

Control measures: Chemical control measures are either not effective or are of limited use against the disease and soil. Once infested with the pathogen it can not be planted with susceptible cultivars up to 10 years or more. Several studies have indicated that the pathogen was found to be soil borne and its entry to host plant was through roots.

Studies on biological and cultural control of this disease have begun recently. Arbuscular mycorrhizal fungi have been shown to reduce the disease severity in short-term green house studies, but results from long-term field studies have not been reported. Soil amendments, endophytic fungi and rhizosphere bacteria are currently being examined in Australia and South Africa. Achieving success with these or other approaches is a daunting task due to high susceptibility of cultivars for which protection is desired and the perennial nature of the pathosystem. Genetic resistance offers the greatest opportunity for managing this disease in infested soils. To date, pre-existing cultivars have been identified that perform well in different regions and against different populations of the pathogen. Resistant hybrids have also been produced in the breeding programmes, but these generally lack the flavour or post-harvest attributes that are found in cultivars. However, as experience increases with this recalcitrant crop, acceptable, resistant hybrids will surely be produced.

However the disease incidence can be reduced if the following management options are properly followed:

• Regular visit of banana fields may help in sorting out diseased suckers and plants for eradication.

• Plant tolerant banana cultivars should be used.

• Plant/ replant only with the disease-free planting materials.

• Implement sanitation practices on tools, moving equipment and infected materials to prevent spread of the disease.

• Remove diseased mat including healthy plants found within a 5m radius and treat the soil with formaldehyde solution if possible.

• Minimise cultivation to prevent the spread of disease in the already existing crop.

• Drainage practices should be strictly followed because stagnant water causes Panama disease.

• In disease-affected locations, weathering pits for a week or more and burning the soil with dry leaves is recommended.

• The studies indicated that the use of organic manures in banana cultivation could give a better stand of the crop against disease, probably due to improved soil structure with more aeration.

• Balanced use of fertilizers, especially potash (SOP) and micronutrients may also be helpful in minimizing the disease effects. However a new research clearly indicates that the high potassium level tends to reduce root infection while high ammonium nitrate levels increase it.

• The work conducted in South Africa show that methyl bromide significantly reduces the disease incidence but is effective for only three years due to re-colonisation of the fumigated areas by the pathogen.

• From experiments carried out on different chemicals to control Panama wilt in India, it was found that the corm injections with two per cent solution of carbendazim at 3ml/corm during the 5th, 7th and 9th month after planting could help in controlling the disease, but results have been erratic or unrepeatable. Drenching the soil with 0.2 per cent carbendazim is also effective.

• Heat treatment of soil was used recently to control the spread of pathogen in the Philippines, but this method is to likely suffer the fate described for methyl bromide-treated soil.

• Field sanitation, especially removal of grass weeds is necessary as they become critical alternate hosts.

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