Diseases and Management

 Banana is much more vulnerable to disease than to the insect pests. The diseases often occur in epidemic proportions and bring about catastrophic losses. Among the diseases, the banana wilt ranks first. In addition to fungal diseases, the bunchy top virus has created a situation of a dismal future for the banana industry.

Anthracnose:

• Severe during June-September when temperatures are high accompanied by rain. Attack plants at any growth stage.
• Both green and ripe fruits are attacked; however, ripe fruits are more susceptible to the disease.

Anthracnose symptom

Symptoms:

• Infection of green fruits, flowers and distal end of hands show circular black, sunken spots surrounded by yellow halos later convening the entire fruit resulting in premature ripening.
• Ripe fruits develop symptoms from the tip as minute, circular dark brown sunken spots invading the entire tip which becomes black.
• A pinkish fungus sporulation is produced in the black, sunken areas of fruit.

Control:

• Spraying Chlorothalonil 2 g/I at 15 days interval is effective in minimising later infections. 
•   Careful harvesting, clean packing, refrigeration at 10⁰C after harvest, fruit dip in aqueous solution of Benomyl at 1000 ppm or aureofungin 100 ppm help in reducing blemishes.

Sigatoka Disease

• Sigatoka is the name of the valley where the disease first attracted attention. A monogrpah has reviewed information of leaf spot disease. It is a fungal disease.
• Causes severe economic losses. Spreads very fast during rainy season. Attacks mostly leave.

Symptoms:

• ·         Spots are concentrated towards the leaf edges.

• ·      Streaks enlarge and form small spindle or eye shaped spots with greyish centre and dark brown or black borders and chlorotic halo around them.

Sigatoka symptom

• ·       Disease first appears as pale yellow or greenish yellow streaks running parallel to leaf veins on both the leaf surfaces.

• Leaves present a scorched appearance, petioles collapse and leaves hang down from pseudostem. If severe, bunch maturity is affected.
• Early diseased plant produces poor fruits.

Control

• Removal of infected leaves and burning.
• Proper drainage, spacing, weed management are very effective.
•  Spraying of Thiophanate methyl 1 g/l, or 1per cent Bordeaux mixture + 2% linseed oil, or Captan 2 g/l are some practices that can manage the disease.

Panama Disease or Banana Wilt

Banana wilt is a soil-borne fungal disease and gets entry in the plant body through roots and wounds caused by nematodes. It is most serious in poorly drained soil. Disease spreads through infected suckers.

Symptoms

Panama Disease symptom

• Initial symptoms appear in older leaves as characteristic yellowing which ultimately wither, break at petiole and hang down along the pseudostem.
• Young leaves may not dry immediately but are erect and also get affected later. If severe, entire foliage wilt within 2-3 days
• Splitting of pseudostem , discoloured vascular region in rhizome are also seen.
• Individual strands appear yellow, in addition red or brown dots and streaks are also seen.
• Longitudinal splitting of pseudostem, emittance of rotten fish smell when cut, stunting of plants, wilting and death of suckers are other symptoms of the disease.

Control

• Use of disease-free planting material and resistant cultivar are recommended. The diseased plants should be uprooted and burnt.
• Highly infected soil should not be replanted with banana at least for 3-4 years.
• Other measures include use of quicklime near the base of the plant and soaking with water.
• Application of lime to infested pits, dipping suckers in carbendazim 1 gl/I before planting followed by bimonthly drenching starting 6 months after planting are effective management practices

Bunchy Top- Viral disease

Symptoms

Bunchy Top symptom

• Symptoms appear at stage of growth associated with occurrence of prominent dark green streaks on petioles and along leaf veins.
• In badly diseased plants leaves bunch together, margins of lamina become wavy and slightly roll upwards.
• In case of secondary infections, irregular, dark green streaks occur along the secondary veins from series of dark green dots to a continuous dark green line.
• Severe stunting, non-elongation of leaf stalks, more erect leaves, non-production of bunches are other external symptoms.
• The virus spreads through infected suckers and by banana aphid Pentalonia nigronervosa.

Control

• Adoption of strict quarantine measures. The diseased plants along with rhizomes should be destroyed as soon as they are detected.
• Planting materials should not be collected from places affected by this disease.
• The aphid should be controlled to check spread of the disease by spraying with an effective insecticide (Metasystox 0.1 to 0.5%, Dimecron or Parathion).
• Regular inspection, roguing of diseased plants, and planting virus-free corms have reduced bunchy top disease in Australia.