A ridiculous question about banana peels

August 26, 2008 9:36 AM

Are banana peels contagious?

Silly question, I know. My mother and I were arguing about whether it's safe to compost banana peels. She is worried that Panama disease -- the disease that is wiping out the Cavendish variety of bananas -- will be spread from the peels of the bananas to ... er, the plants surrounding the compost bin...

This sounds completely ridiculous to me. Is it? If so, please help me persuade her that it's safe to compost them.

posted by non-kneebiter to home & garden (10 comments total)

According to your profile, you're in Wisconsin. I'm pretty sure there aren't commercial banana growing operations in Wisconsin.
posted by Cool Papa Bell at 9:42 AM on August 26

This official Australian government publication lists the plants that can be affected by Panama disease. If your mom doesn't grow any of those plants, she's in the clear no matter what.
posted by Sidhedevil at 9:46 AM on August 26

Wikipedia says Panama disease is casued by Fusarium oxysporum, the same fungus that casues Fusarium wilt in, among other plants, tomatoes. I'd not heard this before, but it concerns me now, since we compost and grow tomatoes, which are looking rather wilty this year. Are there botanists out there who can weigh in on this?
posted by MrMoonPie at 10:40 AM on August 26

Maybe I should clarify my question a bit.
I'm not concerned about infecting banana plantations in my area.

My mom is making two assumptions in thinking that local plants could get the disease:

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.

I think these are the questions that I'm more interested in finding answers to.
posted by non-kneebiter at 10:57 AM on August 26

plantations in my area

Because of course they don't exist.
posted by non-kneebiter at 11:00 AM on August 26

This link says that plant matter infested with Fusarium should not be composted but rather destroyed to prevent soil from becoming tainted with the fungus. Plants that can be infected by Fuslilarium range from cotton to beans to peppers to common weeds.

Fusarium, once introduced into the soil, will stay there for years. Fusarium causes wilt in many nightshade crops--I just had to rip my tomatoes out because of it. I won't be composting the plants.

I'm bummed too, actually, because I didn't know about bananas being infected with Fusarium. My poor little wormies won't get their preferred snack anymore.
posted by Stewriffic at 11:16 AM on August 26

Hmm, yeah, they are pathogenic, but what about boiling them to disinfect then composting? I'm sure you could find a similar protocol for antifungal composting methods. If you care, that is.
posted by wuzandfuzz at 11:34 AM on August 26

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.

Biology is complex. Feel free to compost your banana peels in Wisconsin.
posted by emyd at 11:39 AM on August 26 [6 favorites]

Fusarium oxysporum is a vascular wilt, but it could infect the fruit over time. I guess that, in theory, your banana peel could harbor mycelium/spores of the fusarium. So, if the fruit was infected, if the pathogen or its spores survived post-harvest treatment and composting heat....then they could end up in your backyard soil.

If your banana peel does lace your backyard with the pathogen, then what might happen? In order to get disease, you’ll need the fusarium, the susceptible host plant, the right germinating conditions (proper moisture/temp), and the pathogen would need access to the plant roots (fusarium infects through the roots).

Do you have the host plant part of this equation?

Panama disease is caused by a specific form of Fusarium oxysporum (forma specialis cubense). This form infects bananas and also some other hosts – see the link above.

Tomato fusarium wilt is a different form of Fusarium oxysporum. Cucumber fusarium wilt is a different form. Etc. Basically, Fusarium oxysporum has different asexually reproduced forms that cause disease on different hosts/host groups.

Agrios has a good entry on fusarium wilt in the pathogen bible Plant Pathology if you really want to read up on fusarium & forma specialis.

Oh and I’ve also seen research indicating that plants can acquire resistance to their form of fusarium if they are inoculated with a different form of fusarium (one to which they are not susceptible). Nonhost forms may cause weaker plant symptoms - turning on defense mechanisms. (Don't know if this is still current info though. Reader beware.)
posted by fiore at 11:52 AM on August 26 [1 favorite]

From Temperature effect on Fusarium oxysporum f.sp. melonis survival during horticultural waste composting: "The composting process is an excellent alternative for the management of plant wastes after harvesting, as this procedure is able to suppress infective capacity of several harmful phytopathogens such as F. oxysporum f.sp. melonis."

I can't address your follow-up clarification questions; but generally speaking, hot composting (at temperature from 130 to 150 F for four to six weeks with several turnings) kills most plant pathogens. This requires a well-managed hot compost pile, which is a little more work than a pile of plant material and kitchen waste. So I think the answer lies more in how you manage your compost pile than what you put in it.
posted by peeedro at 12:07 PM on August 26