How to deal with aphids
Tim Rumball looks at products to tackle these pests when they get out of control
IWOULDN’T want to deny other wildlife a good meal – a wide range of creatures from insects to garden birds eat aphids – but aphid infestations can sometimes reach plague proportions on plants. And when they do in my garden, they’re toast!
There are many different types of aphid, some plant-specific, others greedy for any succulent green leaf or shoot they can suck sap from. They cause leaf distortion, stunt growth, attract moulds and spread diseases.
Avoid infestation first
But before we reach for the spray gun it’s wise to ask why they proliferate on some plants and not on others, and deal with any problems. Most sprays are contact insecticides, and systemic ones are not as powerful as they used to be. If you don’t tackle the root cause, once the spray wears off more aphids may attack.
Stressed plants are most vulnerable. Dry conditions are a common cause, so in prolonged dry periods water plants to keep them making strong new growth. Healthy plants can more easily ‘grow away’ from aphid damage so don’t neglect an occasional feed, and keep soil in good condition incorporating compost or applying mulches in spring and autumn where appropriate.
Ants ‘farm’ aphids on plants to eat the honeydew they produce, so destroy ant nests in or near flower and veg beds with regular soil cultivation or using products like Ant Stop Bait Station, which holds the active ingredient in a covered container rather than spreading it on the soil.
On strong-stemmed plants like artichokes, and shrubs and trees, apply a ring of sticky-stuff such as Agralan Insect Barrier Glue around the trunk to stop ants climbing. Good ventilation also helps to keep attacks to a minimum, so don’t crowd plants and prune back dense older foliage on things like lupins or runner beans to improve airflow. Except in certain cases such as agapanthus, don’t let container plants indoors or out get potbound – move them on and give them fresh compost.
Organic product options
In spite of all this, aphids will still attack – they have to eat, after all. The odd one or two should get picked off by predators, but as soon as numbers grow, reach for the spray gun. Squishing aphids with your fingers risks damaging the plant and rarely gets all the offenders. So your first stop should be organic contact aphid killers such as Ecofective Bug Control, Neudorff Bug Free Bug and
Larvae Killeror Doff Greenfly and Blackfly Bug Killer. The spray needs to make physical contact with the aphids to be effective, so hunt them down by turning over leaves (they like to hide underneath) and inspecting shoot tips. Spray every one you see, but don’t spray where you don’t see them – it only works on contact, so you’ll be wasting it.
Other options
There’s a product called Grazers that is not an aphid killer but a deterrent. When sprayed on leaves it dissuades pests from eating the plant. Some gardeners swear by it, but I have yet to try it. Organic sprays are safer to use on veg crops, and are less likely to harm other garden insects when used on ornamentals. Washing-up water is often heralded as an effective aphid spray, but
I’ve never found it reliable. If you want to make your own organic spray, buy a small tub of soft soap from a chemist and dissolve one teaspoonful in half a litre of warm water.
Something stronger
For serious infestations you may need something stronger. There are few
systemic (stays in the plant and continues to kill bugs that feed on it) chemical options nowadays, but Roseclear Ultra is very effective on roses, killing aphids and protecting against further attack for up to 21 days. It also tackles black spot and powdery mildew.
Bug Clear Ultra is a broadspectrum insecticide killing aphids, caterpillars and red spider mites, among other things, and protecting for up to 21 days.
This one is certified for use on a limited range of veg crops and fruit, as well as ornamentals. Some aphids have developed immunity to the active ingredient in these sprays.
In years gone by gardeners would have been encouraged to give a preventative spray of one of these systemics before there was sign of any pests, but in these more environmentally enlightened times the advice is to only spray if necessary and then only if you can’t control pests any other way.
Both these products are available as a concentrate or in a ready-to-use spray gun. As with any insect killer or garden spray, always read the instructions on the label and only use as directed.