How to control papaya diseases and pests-Papaya crop suffers from a number of fungal and viral diseases which are -
Fungal Diseases-1. Damping off (Pythium sp., Phytophthora sp, Rhizoctonia solani):
Symptoms: The disease is common in nursery beds. Affected seedlings are topple down on the ground. The disease is more severe in rainy season.
Control Measures:
1. Root Rot (Phytophthora palmivora and in nursery by Rhizoctonia solani and Fusarium sp.)-
Symptoms:The seedlings are affected in the nursery bed.
Control Measures:i. Remove and burn affected plants.
ii. Use resistant varieties like Ceylon, Singapore, Hybrid-1 etc.
iii. Drench the soil with 1% Bordeaux mixture. iv. Sterilize the nursery bed by burning dry leaves.
2. Collar Rot (Pythium aphanidermatum):Symptom: Water soaked patches are found on the stem which gradually enlarge and girdle the base of the stem. The affected area turns black and rots; later cracks are seen. It is more severe in rainy season.
Control Measures: i. Provide good drainage.
ii. Uprooting and burning of the infected plants as soon as seen in the field.
iii. Spraying of 1% Bordeaux mixture once may check the further spread of the disease.
3. Fruit rot (Phytophthora palmivora, Rhizopus stolonifer):
Symptoms:The fruits are invaded by Phytophthora palmivora causing firm rot, then the injured fruits are attacked by Rhizopus stolonifer and causes soft water rot. Excess soil moisture and soil temperature 20-30O C are favorable condition for diseases development.
Control Measures:i. Provide good drainage.
ii. Apply virgin soil in the pit before planting.
iii. Spray Bordeaux mixture (1%).
iv. Dip the fruits in hot water at 48-50OC for 5 minutes.
4. Black spot (Cercospora papayae):
Symptom:The affected leaves shows spots which are greyish-white, circular to irregular in shape. The leaves become yellow and later they die.
Control Measure:Removal of severely affected plants is the only control measure.
Viral Diseases-
1 .Papaya Ringspot virus: The occurrence of this disease has been reported from the USA, Hawaii, West Indies, Cuba, Brazil and Indica.
Symptom:The affected plants are stunted in growth, show yellow mottling and distortion of leaves, bending down of petiole and followed by death of the plant. Diseased plant yields little or no crop.
Spread:The disease is spread by several species of aphids, such as Myzus persicae, Aphis gossypii, Aphis malvae, Aphis medicaginis.
Control Measures:
i. Roughing of infected plant is most effective method to check secondary spread of the disease. ii. Protecting seedlings with a plastic bag after transplanting is also effective.
iii. Intercropping with a high stem barrier crop.
iv. Spraying of insecticide to check the population of aphid is found to be good enough to check the further spread of the disease.
v. High density planting (2222 plants/ha) is sometimes followed.
vi. Bi-weekly spraying with 1.5% mineral oil
2. Papaya leaf curl:
Symptoms:
The virus disease is characterized by severe curling, crinkling, enation and distortion of leaves accompanied by reduction of leaf size.
Spread:The disease is not sap transmissible. It is transmitted by white fly (Bemisia tabaci)
Control Measures:As the spread of disease is slow roughing of affected plants may give good result.
3. Papaya Mosaic virus (PMV):It is very wide in occurrence.
Symptoms-The affected plants becomes stunted, leaves become yellow petiole shows bending downward, occasional shoe-string symptom may also appear. In severe cases plants may fail to flower and plants may die in later stages.
Spread: It is reported to be transmitted through sap, graft and several species of aphids .
Control measures-
1. Roughing of infected plant and subsequent burning is effective.
Insects-pests:
1. Red spider mite (Tetranichus sp.)-
Nature of damage:Mites attack papaya leaves and fruits affected leaves become yellowish and the fruits become rough and brownish in colour.
Control Measures:i. Spray Sulphure or Lime Sulphur @ 0.05% and repeat it at an interval of 10-12 days.
2. Fruit files (Bactrocera cucurbitae)-
Nature of damage: It damages ripe fruits of papaya. Maggots feed in the fruit pulp causing rotting.
Control Measures:i. Collect all fallen infested fruits and destroy.
ii. Do not retain birds damaged fruits on the plant as they attract fruit flies for oviposition
3. Aphids (Aphis gossypii, Myzus persicae)-
Nature of damage: Nymphs and adult aphids suck sap from leaves and while doing so, they transmit mosaic virus diseases. The affected plants die gradually.
Control Measures:Destroy virus affected plants.
4. Stem borer (Dasyses rugosellus)-
Nature of damage: Its caterpillars bore into the stem and feed internally.
Control Measures:Destroy the stem if it is late stage if infestation.
5. Grey weevil (Myllocerus viridans)-
Nature of damage: This weevil has been found feeding skeletonizing leaves in south India. Sometimes, grubs feed on roots, causing death of young plants.
Control Measures:It is advised to use safer insecticide to control this pest.
6. Nematodes-
Nature of damage Papaya crop suffers by infestation of root knot nematode and reniform nematode. The affected plants become stunted growth, leaves show yellowish colour, later they dry.
Control Measures:Apply neem based products like Neemagon, Bioneem, Neemraj and many more for controlling this pest.
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