Papaya Anthracnose

Papaya anthracnose is caused by the fungus Colletotrichum gloeosporioides and is one of the most widespread and devastating disease of papaya, especially during storage. It is a major constraint to papaya production as well as to export of the fruit to bigger overseas markets.

Papaya anthracnose is caused by the fungus Colletotrichum gloeosporioides and is one of the most widespread and devastating disease of papaya, especially during storage.

It is a major constraint to papaya production as well as to export of the fruit to bigger overseas markets.

Anthracnose infections are usually initiated in the field at early stages of fruit development, but the pathogen remains quiescent until the fruit reaches the climacteric phase.

The fungus is spread by wind and rain while disease emergence is favoured by high temperature and humidity. The disease can have a serious impact on refrigerated fruit for export.

Disease Cycle

The Colletotrichum fungus overwinters majorly in plant debris and the produced spores depend upon water for spread and infection. They may also be spread by cultivating equipment or workers when the foliage is wet.

The fungus can penetrate the plant tissue directly and does not require natural openings e.g., stomata or wounds, and symptoms may appear within 5-7 days after infection has taken place.

Disease development is favoured by warm, humid, and rainy weather usually frequent intervals.

Signs & Symptoms

The fungus can infect immature green fruits attached to the plant and remain quiescent until the fruit begins to ripen, when symptoms of anthracnose or chocolate spot appear.

The first symptoms are small well defined dried pink spots on the surface of ripening fruit.

Later, these lesions enlarge, become rounded, sunken and brown to black in colour.

The lesions can be water-soaked or dried and hard. In the centre of the lesions, the fungus produces dark acervuli, frequently in a concentric pattern and orange to pink gelatinous mass of conidia can be observed. The whole lesion can be easily separated from the flesh of the fruit as a corkscrew, using a knife, leaving a well-defined hole in the fruit.

Post-harvest infection usually produces superficial lesions, seldom slightly sunken, irregular to rounded and well defined with characteristic reddish-brown colour. As the fruit ripens the lesions can either remain superficial or grow and become sunken. Sometimes these symptoms together with latex exudation on the centre of the lesion can be observed several days before harvest.

Infected leaves develop brownish to black spots which initially appear circular, but later coalesce into more irregular necrotic areas. Severe infections can lead to defoliation.

On the petioles, it occurs as elliptical lesions, with dark acervuli in a concentric pattern.

DISEASE CONTROL

Chemical control

The following fungicides are recommended for use in prevention and eradication of anthracnose disease in papaya.

  • ABSOLUTE 325 SC 10g/20l
  • RANSOM 600WP 15g/20l
  • DUCASSE 250 EW 20ml/20l
  • DOMAIN 250 EC 10ml/20l
  • BRADLEY 500SC 10ml/20l
  • EXPLORER 3SL 10ml/20l
  • MEGAPRODE LOCK 525WP 30g/20l
  • JUPITER 125SC 15ml/20l
  • RIMETA GOLD 300SC 40ml/20l
  • PROVIDENCE400WP 50g/20l
  • MILLIONAIRE 690WDG 40g/20l
  • GREENCOP 500WP 50g/20l

Non-chemical control method

  • Remove and destroy infected plants or plant parts and do not compost them.
  • Use resistant/tolerant varieties.
  • Plant certified, disease free/healthy planting materials.
  • Plant trees in well-drained soil.
  • Ensure rotations with non-host plants.
  • Ensure proper weed control
  • To prevent post-harvest losses avoid fruit wounding, i.e. through bruising, scratching, or puncturing the fruits.

Note;

  • Treating seeds with BIODISTINCTION XTRA helps to control seed coat infections.
  • Fungicides should be mixed with INTEGRA 3ml/20l when spraying, which improves the efficacy of the fungicide by acting as a sticker, spreader, wetter and penetrant.
  • Alternating different fungicides throughout a plant’s season prevents the fungus from developing resistance over any of the fungicides.
  • Timely control of the diseases is very critical as it prevents/reduces losses attributed to anthracnose infection.
  • Fungicides should be reapplied after 1-2weeks.
  • A proper nutrition boosts plant’s immunity.

Last updated on Thursday, March 16, 2023 at 9:38 pm

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