What Are Aphids?
Aphids are sap suckers. They are found throughout the world and have been around for millions of years. As a species they are enormously successful and consequently hated by farmers and gardeners alike. There are many types of aphid; in the UK and Europe they are often known as greenfly, blackfly or even white fly, and every gardeners heart sinks when he or she finds the tell tale signs of infestation on a healthy plant.
Greenfly in particular are invisible at a distance, but I have vivid memories of the first time I found a rose bush covered in them, it was only close up that I could see the green stem was actually a mass of tiny insects, all feeding on my lovely flowers!
Just as there are many types of aphid, there are many ways to keep your plants free of them. The aim of this hub is to explore a few, with an emphasis on avoiding unpleasant chemical sprays.
How to Tell if You Have an Aphid Problem
There are more than 4000 species of aphid, of which around 250 represent real problems for farmers and gardeners. Aphids feed on the sap of a plant by sucking and most species (not all) are monophagous; they feed on only one type of plant. Aphids typically pierce the stem of the plant to access the phloem, the part of the plants circulatory system which carries nutrients, and this is the aphids main source of food.
Aphids can be extremely small, less than a 1/10th of an inch, so a small infestation can be difficult to see, however these insects are so common that any plant which doesn't seem to grow well, has yellow leaves, curled leaves or generally stunted growth, is likely to have an aphid problem. The removal of sap reduces the plants food supply, aphid saliva is toxic to the plants and the insects often transmit plant viruses. While many insects have an 'up-side' in that they can be beneficial to plants in some way, aphids do not. They are a problem wherever they are found, hence gardeners with ailing plants are always looking for a good way to get rid of them.
My grandmother suggested this and I remember filling a garden spray with water and washing up liquid then rushing out to the rose bed. With only one rose badly infested this worked pretty well, though you do have to really soak the rose stem. Of course it's much easier now - you can by soap sprays from amazon, and they're all ready to go!
I've also tried this on hanging baskets which can be really devastated by black flies, and so far it works pretty well, but if you have room for some more flowers in your hanging baskets, there is something else you can try.
I adore nasturtiums and try to grow them every where, they have a wonderful taste and are really good in salads, but they also look fantastic in pots, flower beds and most especially when trailing over the side of hanging baskets. When I plant up a hanging basket I fill it as much as I can and then add a packet of nasturtium seeds. It looks good and the nasturtiums attract the black fly which then tend to leave the other plants alone. Since nasturtiums are annual plants this is not really a problem. They also attract predatory insects who help to keep the aphid population down.
Since many varieties of nasturtium are climbers, add some seeds at the base of your fruit trees and they'll help to keep them aphid free.
DIY Aphid Repellant
When I lived in England, we had a large walled garden and a fantastic gardener called Roger who became a good friend. He was a in his late seventies and full of useful information on how to keep the garden at it's best. Roger's method of aphid repellant was fairly typical. He gathered the nettles which grew at the edges and added some wormwood leaves, then soaked them together in a bucket of water. When he came back the following week, he sprayed the plants with the mixture. We had a small orchard at the bottom of the garden, we had some lovely fruit, and no aphid problem
At the front of the border he planted marigolds, and since we had no real insect problem, I can only assume that was another effective measure.
If All Else Fails
I don't like to use chemicals in the garden, I don't feel qualified, so I'm much happier to organize 'trap crops' like nasturtiums as this will, to some extent allow me to ignore the problem. However, when my roses are involved, I feel especially protective, but my experience is that, at least for small infestations, chemicals are really not required. If you have a high pressure hose, set that on your roses, a high pressure water jet will dislodge the insects, and pretty well everything drowns. Just be sure to do it regularly. One day there may be a 'one time only' solution to the aphid problem, but as far as I know, that day is yet to come.