ByKen Sakamoto, Star-Bulletin
Protect your papayas from virus.
IF you have a cold, you try to stay away from people. It's only sensible because it's the way germs spread and nobody knows a cure for the cold. Protecting papayas
Papaya ringspot virus is, among papaya growers, much worse than the common cold because it can be a killer. It not only produces deformed and inedible fruit, but will eventually kill the plant. It spreads by aphids and by touch, first appearing on the leaves, with areas developing different shades of green and translucence. Young leaves may turn yellow and there will be tiny circular green spots on the fruit.
When you see those spots, cut the tree down, says Dale Sato, of the University of Hawaii's College of Tropical Agriculture and Human Resources.
Plants infected with the virus do not develop normally. The growth of the tree is stunted and the number of fruit and their quality are sharply reduced.
The virus is carried by aphids that feed on the leaves. And they work fast. It takes an aphid only 10 seconds to infect a seedling..
Because the virus also affects squash, watermelon, cucumber, cantaloupe and melon family members, don't plant any of these near your papaya trees. Aphids that spread the disease can travel only a short distance, but if they have fed on the leaves of a diseased plant they will infect a healthy plant if it's a close walk.
The disease also spreads by carrying the infection on your hands or garden tools, so keep these clean.
Sato explained this to one of his classes in horticulture at the Pearl City center last week. The classes, which are $5 each, are open to the public and cover a variety of gardening topics. For information, call 453-6050.
When one member of the class asked why Sato was having such trouble with his papaya trees in Kaneohe, he answered that the fungus grows more readily in wet areas, and that papayas are best suited to the drier neighborhoods. The virus can exist only in a living plant, and will die with the tree that has been cut down.
"It doesn't live in the soil, so you can replant a new tree in the same hole," he said.
When you find a good papaya, take the seeds and wash off the surrounding gelatinous membrane that will prevent the seeds from germinating.
"You can remove it by rubbing them on window screen," Sato said. An ordinary metal strainer will also work. Air dry the seeds in the shade. They will keep as long as a year in a refrigerator.
When you are ready to plant, choose an area in full sun and protected from the wind.
Good drainage is essential, so organic matter should be added to the planting hole, which should be 12 to 18 inches in diameter and 8 to 10 inches deep. Sato recommends processed chicken manure, which should be worked into the soil as much as two months before planting. At the same time, throw in a handful of 10-10-10 or 16-16-16 fertilizer.
"Then plant about 20 seeds in the hole. When they come up, remove all but three by cutting them off at ground level. Don't pull them up or you will damage the roots of the plants you intend to keep."
Another option is to buy seedlings at the garden shop. The odds are that one of the three will be a hermaphrodite tree, having flowers with both male and female parts. You can't tell, even if you buy seedlings at a garden shop, what you've got -- male, female or hermaphrodite -- until the plant flowers.
Female flowers are large with a firm center which is the ovary, and with five petals fused to each other at the base. They have no stamens, the wire-like stalks inside the blossom. Herma-phrodite flowers are tubular in shape and have both the solid ovary and the stamen within the flower. Male plants rarely flower.
In five or six months when the plants flower cut down the females and males, saving only the hermaphrodites. Because they are self-pollinating, you will have more and better fruit. Sato recommends Waimanalo, Sunset, Sunrise and Kapoho varieties.
Young trees should receive 4 ounces of fertilizer monthly before flowering. When fruit appears, apply 3/4 pound of a 14-14-14 fertilizer every two months.
It's normal for the plants' lower leaves to yellow when the tree fruits. Cut the leaves off with a sickle, and if there are signs of powdery mildew, don't leave them on the ground. Get rid of them.
"As the tree gets taller, it becomes difficult to harvest the fruit," Sato said, "and the fruit gets smaller. When it reaches about 16 feet, cut it off about 3 feet from the ground. Make a clean cut and cover the cut surface with a 5 gallon can or heavy foil to keep water out. Side shoots will develop. Select the best branch and remove the others."
Commercial growers harvest when there is a tinge of yellow at the blossom end, but Sato says home growers can wait until one-third of the fruit is yellow.
Sato emphasized that growing papayas is an easy process, and they are delicious with a squirt of lemon or lime. You can grow those, too.
Gardening Calendar in Do It Electric!
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