What is Papaya Anthracnose?
Papaya anthracnose is a serious fungal disease caused by the pathogen Colletotrichum gloeosporioides. The spores of this disease are spread in rainy, humid periods, by rain, splash back, plant to plant contact and unsanitized tools. Spore growth and spread is most common when temperatures are between 64-77 F. (18-25 C.). Spores infect the plant tissues then go dormant until around harvest time.
Anthracnose of Papaya Trees
Gardeners who live in Hawaii or other tropical to subtropical regions often grow tropical fruits, such as papaya. In fact, in Hawaii, papaya fruits are grown commercially as a major food and export crop, bringing in approximately $9.7 million each year. However, papaya anthracnose is a serious disease of papaya fruits that can lead to devastating crop losses each year. Your orchard may not be in the tropics, so you’re more likely to get anthracnose on papaya in certain types of weather. Environmental conditions favoring the fungus include very high temperatures plus high humidity. In these conditions, papaya anthracnose control is difficult. But humidity must be truly high to affect the papayas. The fungal spores causing anthracnose don’t usually germinate when your area has less than 97 percent relative humidity. They also need lots of rain. In fact, rain drops splashing on tree leaves is among the ways anthracnose of papaya trees spreads. The fungus doesn’t spread much at all when the weather is dry.
Identifying Anthracnose on Papaya
You can tell if you have papayas with anthracnose by keeping a close eye on the fruit as it ripens. Papaya fruit start out hard with smooth green skins. As they mature, however, the skin turns golden and the flesh softens. That’s when the anthracnose can appear. If your tree has developed the disease anthracnose, you may see small tan to gray spots on papaya fruit or foliage. As these spots grow, they become larger sunken lesions with a water-soaked appearance. These spots are the initial symptoms of anthracnose of papaya trees. You’ll see the centers of the spots blacken over time. As the fungus produces spores, the black spots turn pink and the fruit beneath gets extremely soft. The disease can be present on harvested fruit, but not appear until fruits are stored or shipped. In tropical or subtropical regions with high humidity and annual rains, papaya anthracnose can also cause crop loss of banana, mango, avocado, passion fruit and coffee.
Treating Papaya Anthracnose
Monitoring the ripe fruit for spots will help you identify anthracnose on papaya early. That means you can start treating papaya anthracnose early too. Once the disease is present, proper sanitation is essential. Early action means that you can probably avoid using chemicals when treating papaya anthracnose. Use cultural control measures like harvesting mature fruit promptly, instead of leaving it on the tree. You should also remove all dead leaves and fruit from the garden. Take special care to get all those fallen under and around the papaya tree. Cleaning up weeds or other garden debris can prevent the spread of papaya anthracnose from rain splash back and plant-to-plant contact. Also, always sanitize tools to prevent the spread of diseases. Before papaya flowers appear or just as they appear, preventative fungicides may help control papaya anthracnose. Use a fungicide containing Copper hydroxide, Mancozeb, Azoxystrobin or Bacillus. Spray the orchard with the fungicide every two to four weeks. You can also try growing resistant varieties such as Kapoho, Kamiya, Sunrise or Sunset to prevent the disease.
