The blackfly have moved in
“Pinch out the tops of your broad bean plants” they tell us “that will stop the blackfly taking hold.”
Well, not this year, maybe because the wet winter followed by a hot June caused a lot of lush and sappy growth, so attractive to blackfly and other aphids. Not only the broad beans have been affected, also French beans and nasturtiums. It could have been worse, my broad beans were autumn planted so the pods were well developed before the main onslaught, but the nasturtiums have been so badly affected they have had to be binned.
What is to be done? Like lots of gardeners I’m reluctant to use pesticides, especially on food crops, so I Googled for advice. The most commonly used non-chemical remedy is to spray them with soapy water. Insecticidal soaps are available to buy but many people make up their own using a teaspoon of washing up liquid diluted in 3 litres of water. The aphids are unable to breath under a coating of soap and subsequently suffocate. The addition of a drop or two of neem oil or garlic juice can also act as a deterrent. However, unless one is very careful to spray late in the day when other insects are not about, this spray can present a risk to beneficial insects, pollinators and indeed the predators of blackfly, like ladybirds, lacewings and hoverflies - the very creatures we want to encourage to keep the blackfly in check.
There is an argument that blackfly are an essential part of the ecology of the garden providing food not only for other insects but also birds and that we should leave it to Nature to sort out the balance, but meanwhile our beans are being mutilated.
The next piece of advice is wash them off with a hosepipe. But there is a hosepipe ban! The final advice has a big yuck factor - squash them to death with your fingers!
So what did I do? Well, the beans were ready to pick, so I did, then threw them in a bucket of water. It was easy to wash off the aphids in the water and the beans emerged clean and unscathed. In fact, I could have used grey water from the washing up bowl (that would definitely have killed off the blackfly) before I threw the water on some thirsty plants in the border.
As the summer progresses I can hope the predators will keep numbers in check and the beans are able to out pace the blackfly.
One other piece of advice I found is that the aphids overwinter as eggs on shrubs such as common spindle (Euonymus europaeus), Viburnum and Philadelphus. Useful to know if you love growing beans and are planting a new garden, but my veg patch is between two well established Viburnums, so I’m going to have to rely on that bucket of water next year and beyond.