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If you are growing broad beans, then you know to be on the lookout for many pests and diseases, not the least of which is blackfly. Blackfly is problematic because it not only weakens your plants but it leaves them subsequently susceptible to infections. Thankfully, controlling blackfly on broad beans is not as hard as it might seem. 

What is Blackfly?

Blackflies are small aphids that attack your broad beans, suck the sap from them, and leave them weakened and compromised. The problem comes when the blackflies suck out more sap than they can eat and leave in its place a sugary substance called honeydew. This is effectively waste, but it is also food for ants. So, as blackflies give ants a source of food while also eating away at your plants. This can easily spread infections or diseases on the plants too. 


Removing the Ant Party

As blackfly attract ants in large groups, you can help protect your beans against this secondary invader by spreading a ring around the base of petroleum jelly. Place the ring about 50-80mm thick and this will prevent the ants from climbing around your plants. 

You want to do this first because the ants will work hard to defend their food source, and that means defending the blackfly. So if you eradicate the ants first, you can then eradicate the blackfly without any ants responding to their aid.

Prevention is Key

Pinching out young foliage from broad beans

Don’t over fertilise and pinch off new young growth

Prevention is the most important thing here, preparing good soil with compost in which to sow your beans. Adding extra ingredients can give your beans the nutrients they need to survive. Don’t over fertilise when you plant, as this can leave the broad bean weakened, more susceptible to the blackfly damage. As your plants grow, pinch off the young, green leaves and tips so that the plant focuses its energy into flowering. This will help prevent the blackfly too, as they often eat the younger parts of the plant. 

Plant companion plants

You can plant companion plants so that pests like blackfly leave your broad beans alone and head over to the other plants. Of course, here, you are offering the other plants as a sacrifice of sorts. 

Oregano herb
Oregano herb
  • Oregano is a very fragrant herb that will provide blackflies with better food than your beans, and attract beneficial insects too. 
  • Dill is another herb that can be grown in the company of your broad beans. It will not only lure away the blackfly but other aphids. 
  • Cosmos are beauty with wide flowers and feathery leaves, but what’s more exciting is how well cosmos attract blackfly, aphids, and beneficial insects so your broad beans can be left in peace.
  • Buckwheat, often grown for cereal, is a relative of rhubarb, attracts the blackfly, as well as butterflies and bees. 
  • Poached Egg, a plant called this because the blooms look like poached eggs, will self-seed with just one plant, so you can watch as its flowers attract beneficial insects and lure away the blackfly.
6 Pack of 9cm Mixed Herbs Plants Ready to Plant Out - 6 Varieties Per Pack
  • Top Quality 9cm Herb Plants Lincolnshire grown.
  • Seasonal Selection Of Top Quality Lincolnshire Grown Herbs
  • All These Herbs Are Perfect For The keen Gardener Or Cook
  • Perfect To Start Or Expand Your Herb Garden
  • Selection may vary with seasonal availability.

Getting Rid of Blackfly Infestations

Blackfly attaching broad beans

If you already have an infestation of blackfly, there are a few ways to get rid of them. First, you can remove them by hand. They have soft bodies, so you can easily squish them between your fingers. You can also spray your plants with a hose, which will wash the bugs away. You have to be careful with this, though, because the power of your water stream can damage young plants. 

Alternatively, you can make a mixture of warm water and liquid soap, then apply it to the plant with a spray bottle or a sponge. Similarly, insecticidal soap can be found at garden stores and sprayed on the plant too. 

We try to avoid using pesticides especially on plants you eat but if you have a bad infestation then we recommend use a pesticide that is safe to use on vegetables such as SBM Life Science Provanto Ultimate Fruit & Vegetable Bug Killer.

SBM Life Science 80585047 Provanto Ultimate Fruit & Vegetable Bug Killer RTU 1L
  • Kills most common insect pests on a comprehensive range of fruit and vegetable plants such as apples and pears.
  • Contact insecticide that can protect from pests for up to 2 weeks.
  • Ideal for Grow your own.
  • Kills and controls greenfly, blackfly, caterpillars, beetles, weevils, apple & pear suckers, capsids, sawfly, whitefly.

Natural methods include the use of neem oil. A small amount of neem oil, 2 ounces, mixed well with one gallon of water can be sprayed on your plants to get rid of the infestation. You can also use essential oils and water, like peppermint, rosemary, or thyme each of which can be sprayed over the plant. These should be reapplied after it has rained, or every week to make sure the infestation does not return.

Overall, prevention is the best way to keep your broad beans free from blackfly, but once you see an infestation you need to treat it immediately. The longer the pests affect your plant, the weaker it becomes. Make sure your plants are given the best possible start with companion plants that lure the bugs away naturally.

Last update on 2021-03-29 / Affiliate links / Images from Amazon Product Advertising API


Welcome to my site, my name is John and I have been lucky enough to work in horticultural nurseries for over 15 years in the UK. As the founder and editor as well as researcher, I have a City & Guilds Horticultural Qualifications which I proudly display on our About us page. I now work full time on this website where I review the very best gardening products and tools and write reliable gardening guides. Behind this site is an actual real person who has worked and has experience with the types of products we review as well as years of knowledge on the topics we cover from actual experience. You can reach out to me at john@pyracantha.co.uk

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