Blackfly are one of Britain’s most common and widespread aphid. They mainly colonise broad beans, but can also be found on French beans and runner beans too. So you know what to look out for in your vegetable garden, here’s a pest and disease guide to blackfly and removing them from broad beans.
What is blackfly?
Aphis fabae is the Latin name for black bean aphid, but many people call them blackfly. It’s the winged females that tend to swamp the soft young growth of bean plants. Although they can look quite shocking, there are easy ways to deal with these colonies.
Blackfly will colonise poppies, dahlias and nasturtiums as well as bean plants. They’re likely to be spotted en masse from May to June and then sporadically throughout the summer. The proper formation of broad bean pods can be poor if the plants become heavily infected.
How to control blackfly
The ideal situation is to create an environment where aphid eaters are present to deal with them. Some predators of aphids are ladybirds and ground beetles. Earwigs will also munch on them too.
If you can bear to do it, aphid colonies can be squashed between a finger and thumb.
Some people advocate picking off the soft shoot stem containing most of the blackfly at the top of the plant.
There are some organic sprays available containing natural pyrethrum and plant oils that can be used. Those containing plant oil are less likely to negatively affect adult ladybirds.
Try to avoid using pesticides as these can also kill off the blackfly’s natural predators. However, if you do decide to use them, follow the instructions to use very carefully. Also, do not spray on plants in flower as the sprays can harm and/or kill bees and other pollinating insects.
Companion planting
To stay one step ahead, there are a couple of companion plants that can prevent aphids from feasting on your vegetable garden.
Alliums like onions, garlic, leeks, and chives have a strong fragrance that repels aphids.
Then, planting marigolds can drive a variety of pests away including cabbage moths and cabbage white butterflies, once again because of the strong scent.
With this pest and disease guide to blackfly, you’re one step closer to having pest free plants. With a few methods of control, there are many ways to deter aphids from the area to keep your broad beans clear of blackfly. If you need specialist advice, you can get in touch with your local garden centre.
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David Domoney is a Chartered Horticulturalist, Broadcaster, and Author. David has worked with a number of the UK’s leading garden retailers as a plant buyer and strategic consultant. With more than 30 years experience, in horticulture, David is as passionate about plants now as he was when he bought his first plant at a village fete.
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