COMMON DISEASE AND PESTS OF PAPAYA AND THEIR CONTROL
1. Phytophtora blight – caused by Phytophtora palmivora. Common symptoms are found on stems and fruits. Small, water-soaked, discolored spots may occur anywhere on the stem, around the fruit or leaf scars, especially during fruit production. These infected areas enlarge and often completely encircle stems of young trees. Green fruits are resistant to infection but can be invaded through the wound or through the peduncle from the stem cankers. Infected mature fruits that hand on the tree shrivel as disease progresses, turn dark brown, become mummified and fall to the ground. Mummified fruits become reservoir for fungus and source of infection.
Control – remove rotting fruits from the tree as these serve as reservoir of spores from fungal mass which is carried by rain or wind to healthy parts of plants. These spores may infect non-injured leaf tissue, stems or fruit. Good drainage conditions reduce infection and use of protectant spray such as copper sulfate or Dithane M-45 fungicides limit extent of injury.
2. Anthracnose – Affects both plants in the field and the fruits at harvested. First symptom is usually a small, round, water-soaked area on ripening portion of the fruit. As fruit ripens, these spots enlarge rapidly, forming circular, slightly sunken lesions; these enlarge up to 2 inches in diameter as fruit matures. Fungus frequently produces large, light orange or pink masses of spores in the center of the lesions. Sometimes spores are produced in concentric rings similar to a bull’s eye. In addition to producing this surface damage, the fungus also advances into the fruit.
Occasionally, green portions of the papaya become affected with anthracnose. Disease first appears as a small, water-soaked lesion. Soon after fungus penetrates the fruit, latex comes out in sticky mound of horns. These lesions enlarge to ½ inch in diameter as fruit remains green and eventually plant dies. Infected petioles may act as source of inoculum for infection of fruit.
Control – Control of this disease can be achieved only by means of a thorough spray program. In rainy areas with high temperatures, spray Dithane M-45 at 7 to 10 days intervals. Copper-based fungicides also provide good control.
3. Papaya mosaic – Initially, leaves develop rugged appearance. Undersides of leaves show thin, irregular, dark-green lines etching the borders of cleared area along veins. Younger leaves of crown are generally stunted and severely chlorotic with veins banding; transparent oily areas are scattered over leaf or along leaf veins. In mature leaves, chlorotic patters is light color between veins accompanied by numerous small rinds ranging from transparent yellow to tan yellow. In several affected areas, defoliation progresses upward until only a small tuft of leaves remains at the crown. Stems of infected plants show pinpoint-sized, water-soaked spots may develop into linear or concentric ring patterns, w/c become larger and more intense in color. This is generally transmitted by green peach aphid, Myzuz persicae.
Control – The only satisfactory way of controlling mosaic is by destroying source of the virus. A strick roguing program should also be followed:
- Spray all infected trees with insecticide to kill aphid carriers.
- Cut all infected trees and remove them from growing trees and other cucurbit plants.
- Avoid nearby cultivars of cucurbit plants.
- Control aphids with pesticides since they are disease-carriers.
1. Mites – They colonized on different parts of plants and feed on plant, causing premature leaf drop, reduce tree vigor and produce external blemishes on fruit. They puncture plant tissues with their needle-like mouthparts and feed on tissue juices. Some mutiply rapidly throughout the year and cause widespread damage in a very short time.
Control – Control mites by sulfur dustings. Spray Malathion at rates recommended by manufacturers.
2. Fruit fly – These infest papaya when fruits are allowed to ripen on the tree beyond recommended picking stage. Fruits harvested in the mature green stage are not infested due to the milky substance they exude when fruit is punctured.
Control – Sanitation is important. Destroy all dropped and pre-mature ripe fruits and suspected of being infested to prevent larvae from developing into adults flies.
MEDICINAL VALUES OF PAPAYA
Bruised papaya leaves are used as poultice in treating rheumatism. In nervous pains, leaves can be dipped in hot water or warmed over a fire and applied. As purgative, one tablespoon of the fresh fruit juice mixed with honey and 3 to 4 tbsp. of boiling water is taken one draught by an adult; two hours later, it is followed by a dose of castor oil. This treatment is repeated for 2 days, if necessary, for children aged 7 to 10 years old. The children under 3 years, half the dose is given.