Ever since a family friend suggested growing Broad Beans over winter on the allotment and using them as a green manure, we’ve directly sown some seeds in late October / early November, which then get covered with fleece over winter. We also sow a backup batch in pots at home in late February, ready to be planted out in the spring.
Generally speaking, the second batch of beans gets caught with Black Bean Aphid (blackfly), whereas my first crop are fine. I don’t know if it was the unseasonably cold March, or the unusually hot summer, but 2018 was not a good year for Broad Beans.
I pulled out the vegetable books that sit on the bookcase until there’s a semi-disaster I need to research(!) and looked through the RHS website, discovering that Broad Beans can suffer from four main problems. And of course my plants had each of the four, which wasn’t good for the plant but at least means I can add some photos here to show what to look out for!
First up is the “blackfly” my later sowings usually get caught with – Black Bean Aphid which suck the sap from the plant. That leaves a sugary residue which ants then eat, but the ants also eat ladybird larva which means there’s less ladybirds to eat the aphids. We’ve previously tried spraying the plants with a mixture of washing up liquid and water, but 2018 seemed a particularly harsh year for aphid attacks.
This isn’t one I’ve noticed before, but maybe I was just looking at the aphids and missing the leaf damage, but Pea and Bean Weevil will munch notches around the outside of the leaves, giving them a serrated appearance.
I’ve seen rust on other plants in the garden, but I would say there’s no mistaking Broad Bean Rust! This is caused by fungus, and apparently isn’t as damaging as chocolate spot, but can make the leaves drop, and a leaf-less plant isn’t likely to be a healthy one!
Rust likes damp and high humidity, so leaving more space between plants is claimed to be a good way of reducing the risk of rust, but allowing more airflow around each plant. However my allotment is on an exposed north / northeast facing sloping site so I’m surprised these beans were so badly affected.
Unfortunately the fungus spores can actually survive over winter, so this could possibly be the result of a previous damp winter, rather than being solely the 2017-2018 growing season.
And last but not least, is Chocolate Spot which like Rust is caused by a fungus. Chocolate Spot however, is worse in cool damp conditions.
Like Rust, Chocolate Spot can overwinter in the soil if infected plant matter was left to rot – so no digging in the plants for green manure. Chocolate Spot can also lurk in the seeds from affected plants, so I’ve thrown out any saved seeds I had from previous years, just in case.
2019 will be a Broad Bean-free year, as I think it’d be stupid growing them again so soon, given the problems we had last year. Hopefully with digging in plenty of compost and manure during the year, plus growing other plants in those areas, we’ll be able to go back to Broad Bean growing in 2020 or 2021!
Just before I finish, I took this photo at a similar time to the others – however, I haven’t been able to identify this insect that I found on the bean leaf. Do any of you know what it is?