Papaya virus could affect your crops

by John Davis

Guam - During our tour of southern farms on Guam, we made stops at Duenas farm in Inarajan, the Salas farm in Umatac, the San Nicolas Aquaculture Farm Facility.  Our first stop was the University of Guam's College of Natural and Applied Sciences Experiment Station in Malojloj.  There we found many fruits and veggies, like Papaya, local lemon, wild berries. The most interesting part of our tour there was seeing the farms experiment plot. 

This plot ID being used to cross breed papaya, which folks at the Department of Agriculture say can be used as exports in the future.  Judging by the looks of the papaya, it didn't seem like they were susceptible to disease because they all looked so healthy.  However; the main reason they are being cross-bred isn't for a higher yield. 

These papayas are being cross-bred in hopes to eliminate a ring spot virus that attacks papaya trees.  Dr. George Whal, a plant pathologist scientist at the experiment station, explained by saying, "There's nothing you can spray on a virus to save a plant once it gets infected with the virus, so the best thing to have is something, some kind of resistance if you can find resistance."

Whal says a material to address the virus in Papaya has been found on Guam that aids in virus resistance and promotes fruit production.  Whal says although there resistance to the virus has been found, the color of the papaya fruit are affected.  Whoever has eaten a yellow papaya?  That's what Whal says their trying to change.

He said, "We're trying to make it, trying to change that one character and make it red.  So we've crossed it with a local favorite red papaya, dagu."

The papayas on the experiment farm now are the first of it's generation to be treated against the papaya virus.  This means that not all papayas will turn red when they are ready for harvest.  Whal says more change in the resistance of the virus and color of the papaya is expected in the 2nd generation. 

In the meantime, Whal adds, the papaya ring spot virus is more prevalent in northern farmlands and fortunately for southern farmers, the virus hasn't made its way down to southern farmlands where more damage can be done.  He says the best thing southern farmers can do is be aware of the virus' traits.

"Symptoms for the virus disease, if the plant has fruits when the tree is infected with the virus you're going to see ring spots on the fruit.  That's why it's called the papaya ring spot virus," he said. "If you don't know the symptoms of the virus you should call an extension agent and they can ID it for you."

I you'd like to know more about the Papaya Ring Spot Virus, call the UOG College of Natural and Applied Science at 735-2080.