Broad Beans and Brown Spot

Posted by Yvonne Nikolaison on August 21, 2010 at 2:55am

I got carried away a few months ago and planted some broad beans, they germinated and flowered and are still flowering but no signs of beans as yet.  I noticed today that some of them have brown spot on their leaves.  Oh yes I live in Dunedin.

 

So my question is, will the brown spot affect the production of the beans or am I better to pull them out and plant again now?

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Replies

  • Yvonne Nikolaison August 22, 2010 at 2:18am
    Thank you everyone for your replies, it has given me foood for thought. I did read it in the NZ gardener but then forgot where I had read it, (currently reading too many medical journals)
  • Sean Kemball August 22, 2010 at 1:46am
    The brown spot appears to be fungal - Botrytis fabae from the pics I can find. This gets worse in wet weather, which might explain it in an early crop (mine are close-planted too). It is likely to spread so might be worth spraying. Not sure if digging the plants in once they are finished (which I would normally do) will be a good idea.

    Organic spray options (from http://www.gardenzone.info/articles/indexnew.php?article=32) look to be bicarb, sulphur, potassium permanganate, seaweed. None of those are specifically for B. fabae, but seem to be general Botrytis treatments. Might be worth a try...
  • Angie Gibbons August 21, 2010 at 11:11pm
    I have bees still in my garden and no broad beans! I left brocolli to flower and have Borage for the bees, but they dont seem to want anything to do with the Broad beans or is it only bumble bees that pollinate?

    Someone said you can hand pollinate, but sounds a bit much work for a broadbean.

    Angie
    • Sean Kemball > Angie Gibbons August 22, 2010 at 1:09am
      I've only seen bumble bees on mine, but a quick skim through Acta Hort. indicates bees and other insects are also possible pollinators.

      Rebsie Fairholm (who knows a lot about pea and bean genetics) has an interesting article about them:
      http://daughterofthesoil.blogspot.com/2006/05/everything-you-wanted...

      Also, from another blog comment I came across while googling:
      "The pollination of broad bean ... was studied by Free (1966) who concluded that insect pollination greatly increased production of broad beans but had little effect on production of field beans.
      Darwin (1889*) showed that 17 broad bean plants covered with a net to exclude pollinators produced only 40 seeds, whereas 17 exposed plants produced 135 seeds.

      Holden and Bond observed that the pollen (of a broad bean) is in contact with the stigma 24 hours before the flower opens, therefore ...are capable of selfing (self-pollinating) "

      So, sounds like more is better for pollinators. Maybe spraying them with sugar water is actually a good option?

      Haven't found anything on the brown spot yet...
  • Sean Kemball August 21, 2010 at 1:05pm
    I planted some early beans too, and pulled the first pods off today. They have brown spot (not all of them) but otherwise look fine. They seem to be cropping fine considering the weather lately.
  • Richard Watson August 21, 2010 at 11:53am
    Ive notice that Broad beans do develop those spots as they age and so i think its just a natural part of there make up.

    As for no beans,its probably because its a bit early for the bumblebees to be about yet....Maybe??
  • Kali August 21, 2010 at 9:57am
    HI Yvonne, mine usually get some brown spot but I don't really take much notice because usually even if the leaves and pods have some the beans inside are still fine. I never spray things though, other more meticulous gardeners might have other ideas. The bean pods usually don't form until temperatures rise and bees get out to do their work. There was a comment about this problem in the NZ gardener email this week do you get that?
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