Aphid Infested Plant

Millions of people around the UK, and around the world enjoy spending time tending to their gardens. In fact, many people would call gardening one of their main hobbies. However, with the fun and joy of gardening comes many problems and if you don’t stay on top of things, it won’t be long before your garden deteriorates.

Black fly on plants?

Blackfly is a species that will actively destroy your plants, but can you get rid of blackfly without damaging your plants?

Fortunately, there are many natural ways that you can remove blackflies without causing any harm to your plants. Furthermore, there are things gardeners can do to prevent an infestation in the first place.

Knowing how to control the blackfly population in your garden is imperative if you want it to remain healthy and happy. In this short guide, we will be detailing everything you need to know.

What Are Blackfly And Why Are They Such A Problem?

If you’re an experienced gardener, you will probably already know what a blackfly is and why it is so destructive. However, for those who are new to gardening, understanding what you are going into battle with can give you the upper hand.

Blackfly is a species of aphid, a small flying insect whose most common type is the black bean aphid. While they may be small and seemingly harmless, these creatures can have a devastating effect on plants. These flies are able to quickly infect a plant with a harmful virus, but that’s not all.

They will suck the sap, and literally the life out of plants, young ones in particular and leave a sweet substance behind known as honeydew which will eventually result in fungal growth.

Once this fungal growth begins, the sunlight to the plant is partially blocked which can stunt its growth and affect its well-being. Another common issue with the blackfly is that the females are able to reproduce without a male. This means that, over the course of a growing season, hundreds of new blackflies will be introduced to the population.

As this happens, the blackflies will be able to infect more and more plants with a virus and once this begins, it can be difficult to stop. The only way to stop the spread is to remove and destroy the infected plants. This may be devastating but any plants that are not yet infected will still stand a chance.

There are many plant species that can be affected by a blackfly infestation but the most commonly affected are:

  • Cucumber
  • Strawberry
  • Tomato
  • Tulip
  • Raspberry
  • Dahlia
  • Runner beans

How To Get Rid Of Blackfly Safely

If you have recently noticed more and more blackflies appearing in your garden, it is essential that you handle the problem sooner rather than later. The longer you leave it, the more problematic it will come and the more likely it will be that your plants become infected.

There are several ways that you can attend to this issue naturally, without causing any damage to the plants. As we have already mentioned, if you have plants that are too far gone, the only way to prevent others from being affected is by disposing of them. We would recommend burning them so that none of the viruses remains in your garden.


You can simply wash the blackfly away but this is something that you will need to keep on top of. It is a good idea to rinse them off your plants at least every couple of days until the infestation clears. However, you should also keep in mind that a relatively strong jet of water is needed so this may only be suitable for less delicate plants.

Essential Oils

While essential oils may come from plants, they can also help your plants when there is an outbreak of blackflies. Some of the best options include clove oil, thyme, rosemary and peppermint; these are all incredibly strong.

You should place between three and four drops into a spray bottle and finish off the solution with water. This can then be sprayed onto the affected plants and the blackfly, along with their eggs will be killed. Make sure that you get the whole of the plant including the undersides of the leaves.

Bird Water Bath

One of the best natural methods of removing blackfly is to encourage predators. Birds will make a meal of an infestation but they first need to be encouraged to your garden. Leaving out a bird feeder or a bird water bath (amazon link – opens in a new tab) will bring more attention and once they spot those blackfly, they’ll soon gobble the lot.

Squash Them

It may seem obvious, but one of the most effective ways to remove blackflies is to simply pick them off the plants and squash them between the thumb and forefinger. Of course, this will take a little longer than other methods and you’ll have to be patient, especially if there is a larger presence, but it can be incredibly effective.

Preventing Blackfly

If you want to get the best results for your garden, preventing blackflies in the first place is the best way. If you’re yet to experience an infestation, now is the time to start taking preventative measures. One of the best ways to do this is to distract any ants in your garden. Yes, you heard us correctly.

These insects typically feed off the honeydew left by the blackfly, however, if you can replace this with a sugary feed, the ants will be less likely to interact with the blackfly. Since the blackflies rely on the ants’ interaction to help them spread, they will be less likely to thrive.

Furthermore, it is important to aim for some diversity in your garden. The more varieties of plants that you grow, the more variety there will be when it comes to predators. Since blackflies and other aphids are very low down in the food chain, they will stand less chance of thriving.

Finally, you should try to avoid using too much nitrogen-rich fertiliser. While this may be good for your plants, it will cause them to produce more sap which is what the blackfly feeds on.


Blackflies are a species of aphid, a small, flying insect that loves to feed on the sap from your favourite garden plants. While they are a part of the UK’s wildlife, and won’t ever be completely eradicated, there are ways that you can control them and prevent them from damaging your plants.

However, it is important to choose methods that will not cause further damage to your plants, that is what we are trying to avoid in the first instance. Using essential oils, encouraging predators and simply squashing the bugs between your fingers are all viable methods. Furthermore, it is imperative that you take preventative action to avoid future infestations.

Garden Doctor Tips

Garden Doctor Trev

“Dilute a few drops of peppermint oil in a spray bottle and coat your plants!”

“Give your ants something sweet away from your plants so they are not tempted to farm the aphids!”

“Be careful if washing down your plants, some plants are extremely delicate and won’t cope too well!”

“Having a good variety of plants in your garden is a good way to keep down the number of aphids as it increases the number of predators too!”

Frequently Asked Questions

How do you get rid of black flies naturally?

Black flies are common pests that can be frustrating and difficult to kill. The best way is by using peppermint oil, which will repel the insects from your plants without any harsh chemicals or toxins. Dilute a few drops in water and spray liberally.

How do you get rid of black aphids?

You will see that many people recommend using neem oil or other horticultural oils. These are not necessarily good for the environment and in fact, neem oil is banned in the UK. We recommend using diluted natural peppermint essential oil. 

How do I keep blackfly off my runner beans?

The best way to keep blackflies off your runner beans is to dilute a few drops of peppermint essential oil and spray them over your beans. Remember to spray the underside of the leaves too!

About Me

Hi, I’m Trev and I’ve been growing things since I can remember. When I was younger, I grew up on a farm, so I have always been around plants and animals. After studying horticulture at university, I decided to start my own nursery which I have run now for 25 years. In my spare time, I run this website – which is a resource for people who want to learn more about their gardens.

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