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    Pepper, Cure Thyself! Hotter Chilis Aren't Better Against Blight
    By Stephanie Pulford | February 4th 2009 10:27 AM | 7 comments | Print | E-mail | Track Comments
    About Stephanie

    As engineering grad student at UCDavis, I am interested in the common ground between biology and machinery. Incidentally, my column's title refers...

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    It seems that a new study is always uncovering new health benefits of hot peppers. Garnering a high-profile endorsement  from Hillary Clinton as well as doctors and scientists, peppers' heat producing chemical capsaicin has been linked to benefits ranging from anti-inflammatory properties to cancer killing.  Though capsaicin is beneficial to humans, packing heat isn't a cure-all for the peppers themselves.  A recent study busted the myth that hotter peppers are more resistant to Phytopthora blight.

    Phytophthora blight, also known as root rot, is caused by a fungal infection.  Though most parasites have the good sense to drain their host slowly, the Phytophthora capsisi has been known to slay plants within five days of infection.  A bit of witch hazel and a few days' drying can save a houseplant from fungus, but farmers can easily lose vast fields to phytophthora in wet conditions.

     Soumaila Sanogo  In addition to endangering the world's peppers,  the blight has also caused serious losses in tomatoes, eggplant, cucumber, squash, and melons.  No universally resistant strains have been developed.  

    When farmers started reporting that their hottest peppers were least affected by blight, it implied more than a good year for habaneros.  If capsaicin could stave off blight, it implied the potential to create blight-resistant hybrids of all susceptible crops. 
    This makes sense, intuitively.  If capsaicin can kill bacteria, cancer cells and any germs Hillary Clinton encountered on the campaign trail, fungus should hardly be a challenge. According to the authors, the statistics didn't support the story.  The Phytophthora parasite has no particular preference for low heat or no-heat variety, in the capsaicin-rich pepper fruits as well as the unprotected roots.  Researchers will have to look for different chemical or morphological traits to engineer flood-hardy crops.

    Blight killer or no, capsaicin is fascinating stuff.  Though it is most commonly associated with the sensation of heat, it has been shown to activate the same sensing pathway as a scorpion sting.  In addition to its culinary value, it is the active ingredient Zostrix osteoarthritis ointment and pepper spray.  Though it is an irritant to mammals, it has no effect on birds.  Coincidentally, pepper seeds become nonviable after mammalian digestion, but bird digestion leaves the seeds unharmed.  Because capsaicin is most concentrated in the pith around pepper seeds, it is thought to have evolved as a deterrant to mammals so that seeds could instead be safely spread by birds.  

    The chili pepper is fast catching up on the pop-science food trifecta (coffee, chocolate, and alcohol).  It occupies a spot in both Johnny Bowden's The 150 Healthiest Foods On Earth and Oprah.com's "10 Superfoods".  Unfortunately, it won't be making anyone's list of top natural fungicides.  But go ahead surround your tomato plants with cayennes  anyway-studies suggest that capsaicin inhibits the toxic E coli, and experience confirms that the results will be delicious.  


    Tahboub, Mohammed B., Sanogo, Soumaila, Bosland, Paul W., Murray, Leigh Heat Level in Chile Pepper in Relation to Root and Fruit Infection by Phytophthora capsici. HortScience 2008 43: 1846-1851

    Mori A, Lehmann S, O'Kelly J, Kumagai T, Desmond JC, Pervan M, McBride WH, Kizaki M, Koeffler HP.Capsaicin, a component of red peppers, inhibits the growth of androgen-independent, p53 mutant prostate cancer cells. Cancer Res. 2006 Mar 15;66(6):3222-9.

    Nzegwu, HC, Levin, RJ. Luminal capsaicin inhibits fluid secretion induced by enterotoxin E. coli STa, but not by carbachol, in vivo in rat small and large intestine. Exp Physiol 1996 81: 313-315


    Becky Jungbauer
    I wonder if marigolds have capsaicin...maybe it's an old wives' tale that a border of marigolds keeps the pests out of a garden; perhaps you could use super hot peppers.
    Stephanie Pulford
    I've heard the marigold border thing, too.  I have a sad chewed-up plot in UCDavis' pest-ravaged organic community garden, so I figured the theory was worth looking up.  Looks like the internet hasn't made up its mind. This site claims that marigolds protect against nematodes but not insects, and this one says (uncited) that marigolds help against beetles.  Then there's a book that says they end up attracting more pests than they repel.  Kind of disappointing-- my garden has a "New Jersey" theme, and the marigold is NJ's state flower.  It would have been perfect.
    Becky Jungbauer
    Interesting...Mom said they kept out the rabbits and deer because they taste bad, so when they'd come nibbling around the garden they wouldn't get past the marigold border. (Now the deer stand on their hind legs and eat off the apple and pear trees in the orchard - I'm not kidding. We'll have to grow tree-sized marigolds.)
    Stephanie Pulford
    If they keep out rabbits, I should totally give them a try.  We have mammoth-sized rabbits here.
    I'm pretty sure this won't actually be helpful in any way, but when I was reading the marigold stuff some sites suggested nets of human hair to keep deer out.  You know, if you just happen to have a net made of human hair laying around.  Ugh.
    Keeping a Gerke on hand is a foolproof method for keeping varmints from your greens.
    You mean Gerkes are real?  I thought they were part of some Princeton mythology!
    Becky Jungbauer
    That would keep me out, that's for sure...hmm, do you know any hair salon workers? I see the potential for a big business - cost cutters and home depot garden center join forces and revolutionize garden pest control.