Aphids - also known as greenfly, blackfly and whitefly - are tiny little insects that colonise the underside of leaves. They suck sap out of the plant leading to yellowing, wilting, low yields and even death. They can also transfer plant viruses.
Small, young plants with tender leaves are the most attractive to aphids so make sure you start all small plants off indoors and only transfer them outside when they are big enough. You can also try a slow release fertiliser - this will feed the plant while making sure it doesn’t grow a huge crop of new leaves, which would attract aphids.
Fortunately they do have some natural predators - and one of the best ways to prevent aphids from colonising is to encourage these predators. Try planting calendula or morning glory next to aphid-prone plants - these attract insects like the hoverfly. Hoverflies don’t prey directly on aphids, but their larvae do - hoverflies lay their eggs right on top of aphid colonies.
One thing to be mindful of when using this technique is that once the population of aphids drops below a certain level, predators will move elsewhere - but there’s a solution for this as well. If you don’t mind having nettles in your flowerbed, that is! Nettles attract nettle aphids (don’t worry, they only prey on nettles - not your prize roses), which will provide a constant supply of aphids for your hoverfly larvae.
Another easy way to help avoid aphids moving in is to make sure you clear out all the rubbish and dead leaves from your beds before winter, as this is where they lay their eggs. Keeping air circulating is important as well, because stale air provides ideal conditions for aphid eggs to keep warm and alive over the winter.
Sometimes, no matter how hard you work to prevent aphids nothing seems to stop them. You could use chemical sprays to get rid of them, but this is no good if you’re growing edible plants or if you have pets. Another downside to this technique is that chemical sprays can be dangerous to ladybird larvae - ladybirds are predators of aphids. There are quite a few tried and true non-chemical methods to get rid of them, so try one of these if the chemical route doesn’t appeal.
The spray bottle can still be your friend - dilute some washing up liquid very weakly (about a teaspoon in 2 litres of water) and spray once a week, paying most attention to the underside of the leaves. Aphids can only breathe through their skin, and the soap will clog them up so they suffocate.
You could also try some natural remedies; garlic is toxic to pests because it contains sulphur. If your greenhouse is under attack, you could try a garlic smoke generator to deal with the infestation - this is also good for the plants themselves, as it helps them to build up anti-bacterial agents.
Natural chemicals can also include Pyrethrin, which is found in our Protector Natural Insect Killer for Plants, derived from the African Chrysanthemum, non-residual so environmentally friendly. It is A ready to use aqueous solution for the control of aphids, blackflies, greenflies, caterpillars and whiteflies on garden flowers, fruit and vegetables. It can be used outdoors, in greenhouses and on pot plants throughout the season. Repeat treatments of every 3-7 days will be required to achieve effective aphid control.
Another technique to use against aphids is a physical one - you can knock them right off the leaves with a strong jet of water from a hosepipe. This needs to be done every few days for best results. It might not be the best idea if your plant won’t withstand such brute force, however. Aphids are attracted to yellow, so you could try some yellow flypaper or yellow double sided tape instead.
If you keep a close eye on your garden particularly in early spring, and follow the above advice then you should be able to prevent an aphid infestation. And even if not, you will be able to get rid of them quickly and prevent a lot of the damage they cause. Then you can be free to enjoy the beauty of your garden for the rest of the year.