Papaya Ringspot

Do your cucumbers, melons, squash, and watermelons have spots? Do your pumpkins have warts? It may be papaya ringspot.

Pumpkins infected with papaya ringspot virus (Mary Ann Hansen, VPISU, Bugwood.org) CC BY 3.0

Papaya ringspot wiped out 94% of the papaya crops grown on Oahu in the early 1960s. As a result, papaya production was moved, under quarantine, to the Big Island of Hawaii. As is often the case in these situations, the virus found its way there, again devastating the papaya industry and homegrown papaya trees. More moves and quarantines occurred, but it wasn’t until resistant varieties were developed that papayas could be grown successfully. That might have been the end of the story, but it’s not.

Papaya ringspot virus symptoms on fruit (APS) Public Domain

The papaya ringspot virus (PRSV) mutated, traveled, and expanded its diet to include several common garden plants. These include members of the squash family, tree spinach (Chenopodium amaranticolor, aka C. giganteum), peas, castor beans, and quinoa (C. quinoa). Currently found in the U.S., Europe, India, the Middle East, and South America, it is safe to say that papaya ringspot falls under the plant pandemic category.

Papaya ringspot symptoms

Like many other viral plant diseases, papaya ringspot looks like infected cucumbers and melons have developed measles. A mosaic of scattered dark green or intense yellow spots appears on the fruit surface. Blisters may also occur. Leaves of infected plants are chlorotic and distorted and may develop shoestringing. Stems and petioles may have oily streaks. This disease looks a lot like watermelon mosaic. In both cases, remove infected plants and toss them in the trash.

Papaya ringspot virus leaf symptoms (Scot Nelson) Public Domain

Papaya ringspot lifecycle

This virus congregates around the mouths of aphids, never actually entering the pest. As the carrier aphid feeds on sap, the virus moves from the aphid’s face to the plant’s veins. Wouldn’t that make an interesting video? The papaya ringspot virus can also travel on seeds and seedlings.

Papaya ringspot prevention

There is no cure for papaya ringspot, and it is highly contagious. Quarantining new plants and investing in certified pest- and disease-free seeds and seedlings are the best ways to prevent the papaya ringspot virus from attacking your garden.