I remember when I was a tourist on Kaua’i, I was a bit concerned about these big signs posted on both highways into Lihue. I’d never heard of a banana virus before, and quarantines are usually serious affairs.
Then after driving past them all the time, you forget about them and don’t even notice them. After one trip back to the mainland, they again stood out for me and I took the picture above, southbound on Hwy. 56, as you approach Hanamaulu. That’s Ha’upu Mountain in the background, several miles away on the other side of town.
But what is the banana virus? It really is a virus that infects banana plants and keeps them from producing fruit. It is spread by aphids that feed on an infected plant and then infect any other banana plant they feed on. It is commonly called the banana bunchy-top virus because it causes all the leaves to grow stunted together at the top of the stalk, instead of spreading out palm-like. Here are two fact-sheets with much more detail about the virus, a PDF from the College of Tropical Agriculture and Human Resources at the University of Hawai’i, and another PDF from the International Network for the Improvement of Banana and Plantain.
Aphids don’t fly very far, so it spreads mostly by people moving infected plants, which is the reason for the signs. After escaping the virus for a long time, it showed up on Kaua’i in 1997. I don’t know if the quarantine is meant to protect the local banana producers, keep the virus from spreading from one part of the island to another, or just to slow it down. Sadly, I’ve seen banana plants in the back of a pickup truck drive right past the sign—like I said, the locals probably weren’t even aware of it anymore. And I doubt anyone enforces the quarantine.
Source: bananas.bioversityinternational.org (PDF)
I do know the virus is all over the Wailua Homesteads area, inland of the Sleeping Giant. When I lived there, our banans were infected, and a friend who lives there says his area is infested. Normally bananas grow by themselves with little care, but that leads to people forgetting to inspect their banana patch, and then it becomes a reservoir for the virus. When you notice the disease, you have to chop down the plant, dig up the roots, and take it all to the dump in black plastic bags. And you probably have to do this for all the plants around it too, when they start to show the disease.
After I planted the bananas at our second house, I was careful to spray for aphids every month and trim off the old drooping leaves that tend to attract the aphids, and this really seemed to keep the plants healthy.