Pests & Disease: How to control black aphids before you get an infestation!

Thanks all for your many questions regarding aphids and rust over the past two weeks – I will address these problems in the next two blogs.

‘What are all those black bugs on my onions, chives and garlic?’ you ask!

At this time of year, aphids are having their own party at the expense of our plants – more so if you live in humid areas!

The black spots or bugs you see on your onions, chives and garlic are black aphids which are merrily multiplying and sucking the life out of your plants. Some appear bigger than others – these are the ‘mothers’, which have wings. These aphids do not produce eggs but leave hungry young straight on to your plants. They are usually in a long line, as every couple of days more young are laid, and they can produce up to five every couple of days. The interesting thing is that all their babies are girls.

Where did my infestation come from?

The adults overwinter in the warmest spot they can find in your garden to protect themselves from the cold and the frosts so, if like me, you have no frosts or snow, your population or infestation is likely to be much, much higher than somewhere that gets these conditions.

They really like to overwinter in the thin skins of garlic or shallots and, for the life of me, I have never been able to see them! Yet as soon as the leaves start to sprout, the mother gets ready to lay her first lot of eggs on the small vulnerable leaves. From here, they pierce the young leaves and start to suck. Within these young leaves are sweet carbohydrates, which aphids desire the most. They are very slow at first while the temperatures are cool, but as soon as the sun comes out it is ‘yeeha!’ and all systems go…  Hence why you can sometimes feel you have an infestation overnight, while they have actually been there all the time but moving very slowly.

How do I control black aphids?

When my first leaves are up on my garlic and onions, I spray with Naturally Neem and then use EnSpray 99 oil in the following weeks. Naturally Neem is the best Neem product you can buy, as a lot of Neem products are not refined enough for edible application. Remember Neem must be sprayed in the cool of the day only.

How do I prevent black aphids?

Keeping your plants healthy from day one can really help keep away an infestation and I use regular spraying of Liquid Kelp which keeps the plants strong. Kelp strengthens the cell wall of the plants, making them less attractive to the aphids who are after the easy prey of weaker plants.

If you are buying chives, onions or leek plants at a garden nursery, I also recommend observing the leaves carefully and looking in between each leaf, as they can be hiding in there.

Beneficial insects can be your friends too – encourage ladybirds into your garden as they will eat aphids and take care of the problem for you! Check out my earlier blog here to find out how.

How do I manage an infestation of black aphids?

If you have a large infestation, my advice would be to pull the plants out carefully and submerge them in water to prevent any of them re-infesting elsewhere.

You can still eat the produce, it just may not be as juicy…

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Happy gardening