Papaya is a major commercial crop throughout the tropical and subtropical world and exported widely to areas where production is not possible. However, Florida has a small commercial industry. Papaya trees in the home landscape are susceptible to many diseases including papaya black spot.
Black spot of a papaya is a fungal disease that is now found worldwide where papaya trees can be grown. Usually papaya with black spots is a minor problem but if the tree becomes heavily infected, the growth of the tree can be affected, hence fruit yields, so treating papaya black spot before the disease progresses is important.
Black spot of papaya is caused by the fungus Asperisporium caricae, previously referred to as Cercospora caricae. This disease is most severe during rainy periods.
How to Recognize Papaya Black Spot Symptoms?
Both the foliage and fruit of papaya may be infected with black spots. Initial symptoms appear as small water-soaked lesions on the upper side of leaves. As the disease progresses, small black spots (spores) can be seen on the underside of leaves. If leaves are severely infected, they turn brown and die. The disease is more intense on the lower leaves. The black spots also occur on fruit. The lesions are superficial and do not enter the flesh of the fruit. The damage to fruit is entirely cosmetic.
How to manage black spot of papaya?
Removal of leaves and fruits with symptoms of black spot disease from the tree reduces the initial inoculum. Similarly, infected old leaves hanging from trees should be removed carefully to reduce the number of spores that spread the disease. Removal of infected leaves will increase air circulation and improve spray penetration through the fruit column. Wind protection around plantings is important to minimize fruit abrasions which can create an entry for pathogens. Scouting the tree periodically is very important to decrease infestation level.
Application of protective or systemic fungicides, such as those containing copper, when the first symptoms appear is the best option to early manage black spot disease of papaya. Make sure that the undersides of the leaves are sprayed, as this is where the spores are produced. It is advisable to look for signs of disease on the new growth since the fungicides protect the new leaves and fruits; but old damage cannot be undone.
For more information about papaya, please read EDIS article.