Papaya Ringspot: How to Spot It and Keep Your Trees Producing

For a Filipino farmer, the danger is speed. The fact sheet says that once the virus is in a planting, it can reach all trees within three to seven months. Growing papaya near cucurbit vegetables can also keep the virus close to your trees. Our vegetables in the Philippines guide lists them.

How to Identify Papaya Ringspot

Look at the top leaves of the tree first. They turn mottled with a pattern of bright yellow and green, called mosaic, and may twist and stay small. Older leaf stalks carry dark green streaks. The fruit shows the best sign: dark ring shaped spots, from which the disease takes its name. Ring marks on the fruit are the clearest clue. Other causes of yellow leaves do not mark the fruit that way.

• The leaves get a mottled mosaic of bright yellow and green.
• Leaves are twisted or distorted, and the tree grows poorly.
• Dark green streaks appear on the leaf stalks of older leaves.
• Rings and spots mark the fruit, and the flavor changes.
• Fruit set is low, and trees infected young may never make fruit you can sell.

How Papaya Ringspot Hurts Your Crop

A tree that catches the virus early may never produce fruit that you can sell. Ringspots on the fruit also make the papaya less acceptable to buyers. The Pacific Pests and Pathogens fact sheet adds that moving papaya growing to a clean area only buys time. The disease eventually catches up.

A study in Bay, Laguna looked at the insects in papaya fields. It confirmed that only aphids were vectors of the virus. Aphid numbers were low in June and peaked in August. Farmers might time planting to avoid the high aphid months.

How to Control Papaya Ringspot

1. Buy seedlings only from nurseries you trust, and look at every seedling for mosaic before planting. The virus moves in infected nursery stock.
2. Plant when aphids are fewer. In the Laguna study, aphids peaked in August and stayed low in June.
3. Walk the orchard often. Remove sick trees as soon as the first signs appear, and remove volunteer papaya seedlings that came up by themselves.
4. Take out badly hit blocks, since an infected block is a source of virus and aphids for the rest.
5. Wash pruning tools between trees, and keep papaya away from cucumber, melon and squash fields, which host the virus too.
6. Ask your agriculturist about resistant or tolerant varieties. Breeding and gene modified resistance have been used, and mild strain protection has also been tried in other countries.

Why No Spray Cures It

Spraying insecticide is not a good control for this disease. The fact sheet explains that aphids pick up the virus and pass it on to healthy trees. They do it before an insecticide can kill them. So money spent on sprays rarely saves the trees.

Keep It Out Next Season

• Raise seedlings under fine net or buy from a nursery you trust, and check each seedling for mosaic before planting.
• Plant new papaya far from old papaya and from squash, melon and other cucurbits, and time planting for months when aphids are fewer.
• Pull sick trees and stray papaya seedlings at once, and end badly hit blocks. They feed the virus and aphids to the rest.
• Plant two or more rows of corn or another tall crop around the papaya block so passing aphids probe there first and lose the virus.
• Wash knives between trees, keep weeds down, and grow tolerant or resistant varieties where you can get them.

Natural Enemies and Biological Help

• Ladybird beetles, hoverflies and small wasps keep aphid numbers down, but no natural enemy is fast enough to stop the virus.

Not Sure What You Are Seeing?

Take a clear photo of the spots or the damage up close, then the whole plant, then ask Anee, the smart farm technician in anee.io, in Tagalog or English. Anee tells you what it most likely is and what to do at the age of your crop. You can also put your scouting days on the cropping calendar, so the team knows when to walk the field.

Questions Farmers Ask About Papaya Ringspot