The Broadbeans Have Spots!

Chocolate spot is a broadbean thing that typically happens at this time of year. Like rust is a celery thing, or black spot an apple thing – all crops have a thing they do when life’s not completely to their liking. And in my case it’s sprung forth in the wet, humid conditions created by the weather and my over crowded crop. My broadys are jam packed this year. Usually 20cm apart, this year they’re closer to 5. The over sow was an insurance moment, unsure as I was of the older, unlabelled seed in my stock. Turns out the seed was still viable and intentions of thinning later (if required) never came to pass.

Like most evil spots in the garden, chocolate spot is a fungus. It begins as a harmless looking reddish/ brown spot, that will, if conditions carry on, expand and turn chocolate brown then black. Leaves and flowers shrivel, and if the stem gets streaky you’re heading for plant collapse.

A Rescue Gets Underway

Alternating wet and dry periods show up as concentric circles as the fungus does a stop go, stop go dance. Should the weather dry out, the fungus can loose it’s impetus. Dry? Unlikely at my place for a good few months yet, so I’m ruthlessly cutting out infected bits, even if it means pulling a whole plant. It’s worth it to save the rest. Airborne fungi like this spread like mad.

Needless to say, I’m also (finally) thinning my crop. Infected foliage hits the bonfire as I go, burning up the raspberry and rose prunings and providing me with a lovely pile of potash which I’ll sprinkle around the remaining plants. Potash is highly mobile and the next rain (we won’t wait long!) will flush it through. Is it too late for such amendments? Probably, but in a rescue one pulls out all the stops.

The real blow is the impact on flowering which means, of course, an impact on fruiting. Luckily I have loads of flowers and thus far a whole row unscathed.

Beans impacted by the fungus will be slightly discoloured. They’re perfectly safe to eat, but no good for seed as the disease can carry over.

Thoughts on Prevention

• Spacing is the first thing – too close (my hand shoots up!) means air can’t flow and humidity rises
• Acidic, poorly drained soils favour fungal growth – pay heed in your preparations
• Add potash when you prepare the bed
• Autumn/ winter sown beans are the most susceptible – perhaps spring sowing suits your place if it’s a persistent problem
• The spores can survive a good few years in the soil, so crop rotation is once again, your friend
• I wonder if an excess of nitrogen contributes. It’s such a common theme, and would make sense in a legume who doesn’t need it to begin with

Is there a Cure?

Cure in this case, being the bottom of the cliff. But worth a look see if it means saving a crop!

• If you’re happy to use copper – you could go this route were you to catch the fungus at the small circle stage.
• I’ve been spraying the foliage and soil with EM as I’ve been cutting out/ removing infected bits. I’ll give the plants and soil a weekly EM from now on if the weather lets me.
• I wonder if good old milk sprays would work? They make such a difference with mildew on zucchini and black spot on tomatoes. More likely a success in prevention mode rather than a cure though.