My broad beans are flowering and beginning to form small bean pods lower down on the plants. I spent a few minutes yesterday pinching out the tops. Pinching out broad bean tops helps to avoid an infestation of black bean aphid, it also encourages the plants to direct their energy into forming nice big pods of beans rather than putting on more top growth. It’s easy to do, just pinch the very tops off with your thumb and forefinger once the lower pods are approx 3in long. If you see clusters of black dot like creatures, often with a sticky substance covering them, this is black bean aphid. Pinch the tops off as normal to try to bring the problem under control.
If you’re a wildlife nerd like me, you might be interested in another way of knowing if your broad beans have black bean aphid infestation – keep an eye out for black ants on the plants. When feeding, black bean aphid secrete a sticky, sugary substance called honeydew. Ants ‘farm’ the aphids, milking the honeydew produced by the aphids as well as moving them to the fresh new growth. Apparently the sweetest honeydew is produced by aphids eating the youngest, freshest leaves – that’s probably why broad bean tops tend to get infested so easily.
Once you have pinched off your broad bean tops don’t throw them on the compost heap, try eating them instead. They can be cooked like spinach or add to a stir fry – just make sure they’re not infested with black bean aphid first!