Papaya trees are tropical plants that produce pear-shaped, melon-like fruit. They can be difficult to grow because they're sensitive to drought, cold temperatures, high winds and shade. In addition, they are very susceptible to disease, and can be damaged by chemicals used to treat diseases. Insufficient water, disease or attack by nematodes can all cause trees to wilt.
According to California Rare Fruit Growers, proper watering is the most decisive factor in successfully growing papayas. Plants will drop leaves, flowers and fruit if they don't receive enough water, and the fruit they do produce will be small and won't taste as sweet. Plants growing in loamy soil only need to be watered every three or four days, but if your papaya plant is growing in well-drained soil it needs watering every other day, or even daily if the weather's hot and dry. Reduce watering late in the fall and over the winter.
Apical necrosis is a viral infection that causes papaya leaves to curl downward and wilt. Leaf margins brown and young leaves are pale yellow. In addition, the leaves are smaller with shortened petioles. Apical necrosis begins in the top part of the plant and moves down the stem, eventually killing the entire plant. The organism responsible for transmitting this disease is unknown and there is no cure. Diseased plants should be isolated.
Phytophthora is a highly destructive fungal disease that causes root, stem and fruit rot as well as rapid wilting and death. Water-soaked areas appear on the stem and, if they encircle it, the entire top part of the plant will wilt and die. Water-soaked spots also appear on the fruit along with a white fungal growth. The fruit shrivels and drops to the ground where the fungus proceeds to infect the roots. This fungus is spread by wind and rain. Although fungicide sprays are available to treat this disease, they must be used in conjunction with good cultural practices. Ensure plants are growing in good-draining soil. Rotate crops. Remove and destroy fallen fruit. Avoid damaging papaya stems. Control African snails because they spread this disease.
Root-knot nematodes are microscopic worms that cause galls to form on papaya roots when they attack them. The galls interfere with the plant's ability to take in water and nutrients and cause wilting, stunting, yellowing, reduced crop yield and death. Although root-knot nematodes can be found in many types of soil, papayas are more apt to suffer severe infections when growing in sandy soil. Before planting papaya, prepare the soil by turning it over several times so the nematodes are exposed on the surface where they will die in the sun. Removing plant debris after harvesting and practicing crop rotation will also help reduce the nematode population. Some crops resistant to root-knot nematodes include cassava, taro and the Heatmaster variety of tomato.