Monday, September 8, 2008

Should we stop composting banana skins because of Panama disease? Are they contagious?

This question was posed on another site. The two main concerns were:
1) That bananas from plants with the disease might be sold.
2) That the peels would have some vestiges of the disease that might be transmitted to other plants.


My response:
Mycologist checking in here: Fusarium oxysporum is a fungal species that is found practically everywhere on the planet. It is different varieties of F.o. that cause diseases in specific plants. I don't know if the Panama disease variety of F.o. actually grows up into the fruit itself (I am guessing only rarely, because it infects the roots and lower stem of the tree), BUT even if it is found in banana skins, I don't think there is any reason to worry about composting it. Because 1) people have already spread banana peels every conceivable place in the US and 2) the F.o. variety that causes Panama disease only affects certain plants - check out the link Meagan and Sidhedevil provided. 

Okay, so the answers to your questions:
1) bananas from plants with the disease are most certainly being sold - most banana plantations around the world have reported it.
2) I sort of answered above - it is possible that the peel has some fungus growing in it, but it is unlikely that it would be harmful to other plants in your area.

I hope that the growing interest in the banana epidemic will cause the public to become more educated about fungi in the environment in general. Fungi are omnipresent and incredibly important to ecosystems. Their interactions with plants run the gamut from parasite to mutualist, and depending on how you run the numbers, upwards of 80% of plants have a beneficial symbiosis with a fungus. But these interactions are held in a delicate balance by environmental conditions and competing species. The Panama disease Fusarium is a problem because our all our Cavendish bananas are a monoculture of genetically identical individuals. Other types of Fusarium (even other varieties of Fusarium oxysporum) are beneficial to other plant species.