Papaya Ringspot Disease – A Threat to Papaya Trees
Papaya ringspot disease is a highly destructive ailment caused by the Papaya ringspot virus – type P (PRSV-P). It poses a significant threat to papaya trees and is widespread in regions where papayas are cultivated.
Susceptible Host Plants
PRSV-P primarily affects plants in the Caricaceae (Papaya), Cucurbitaceae (e.g. cucumber, squash), and Chenopodiaceae families. Among these, papaya is the most vulnerable to the disease.
Mode of Spread
Aphids, small sap-sucking insects, play a crucial role in transmitting the papaya ringspot virus from one plant to another. When an aphid feeds on an infected plant, it becomes contaminated with the virus within seconds. As it moves on to feed on the next plant, the virus is transmitted.
The disease does not persist in soil or dead plant material. Instead, the movement of infected plants becomes the primary pathway for spreading the virus over long distances. Additionally, the virus can also spread mechanically when the same garden tools are used on both infected and healthy trees.
Symptoms of papaya ringspot disease may vary in intensity, but a distinctive diagnostic feature is the presence of dark green rings, often slightly sunken, on the fruit. The number of rings can differ, but they become less visible as the fruit matures and yellows.
Infected fruits may exhibit uneven bumps, especially those that develop after the tree becomes infected. Key symptoms on leaves include intense yellow mottling or mosaic patterns, followed by severe blistering, distortion, and vein clearing, particularly in young leaves.
Dark green streaks and occasional rings can also appear on leaf stalks and stems. As the disease progresses, the leaf canopy becomes smaller due to the development of smaller leaves and stunted growth. Fruit quality, including flavor, is negatively affected, resulting in lower yields and brix levels compared to healthy plants.
Prevention and management are crucial since there is currently no cure for papaya ringspot disease once a tree is infected. The following strategies can be employed:
To control the aphids that spread the disease, insecticides can be used. Recommended insecticides include KINGCODE ELITE, PENTAGON, LEXUS, SINOPHATE, PRESENTO, EMERALD, LOYALTY, EPITOME ELITE, and DEFENDER. These should be applied as foliar sprays, with INTEGRA incorporated to enhance their effectiveness.
Several non-chemical approaches can be employed, such as using disease-free planting materials, removing infected plants promptly, planting resistant/tolerant cultivars, maintaining field hygiene, rotating with non-host plants, and sterilizing tools and equipment before and after use. Spraying crops with OPTIMIZER can also boost their immunity and act as a stress manager.
Timely control of aphid vectors is critical to effectively manage the papaya ringspot disease. By implementing these preventive measures, farmers can protect their papaya trees from this destructive ailment.