To many gardeners and growers, the first appearance of aphids (greenfly and blackfly) on their garden plants and vegetables, signals the time to start protecting those plants from a potentially escalating and plant-damaging infestation.

And invariably, some gardeners reach for a bottle of proprietary bug-killing insecticide and try to eradicate the aphids. 

It might seem a bit odd though but killing the aphids when they first appear on a plant with an insecticide is really not the best thing to do for the health and wellbeing of a garden, particularly one which aims to help wildlife species that are steadily declining within home gardens such as the songbirds, hedgehogs and pollinators.

Not only are the chemical insecticides toxic to the aphids, but they’re usually broad-spectrum bug-killers that can also kill a wide range of beneficial creatures. This includes the invertebrates that predate and parasitise aphids (the natural enemies), and also the pollinating insects that visit the plants such as bees, bumblebees, butterflies and hoverflies. 

Unfortunately, it’s not always clear which are the broad-spectrum bug-killing products that harm the beneficial species, since this negative aspect of them would unlikely be mentioned on their labels. So for wildlife-friendly gardening, it’ll always be the best option to use a non-toxic product that deters and repels plant pests rather than one that kills them. These environmentally safer products will always display ‘non-toxic’ and ‘environmentally friendly’ on their labels and are becoming more-readily available from retailers.

The other important thing to realise, is that when aphids first appear in a garden during Spring, they’re a vital foundation stage of the natural food chains that have to develop within a garden, the food chains that sustain a rich and healthy biodiversity.

This is because aphids are in the group of creatures that are called the ‘Primary Consumers’ which are the herbivores and omnivores that feed on the plants (the ‘Producers’) that are at the bottom of the food chain.

Species that are further up the food chain will then feed on the Primary Consumers and will have coordinated their life cycles around the appearance and availability of the ‘Primary Consumers’ which will be their vital food source.

This means that when aphids first start to colonise the garden plants, the ladybirds, hoverflies, lacewings and parasitic wasps will all be attracted to the infestation to feed and lay their own eggs, which will then increase their numbers to a point where the aphids are naturally under control.

By killing the aphids with a pesticide, not only will the beneficial creatures already on the plant be killed, but there will be no food source for attracting any more of them. 

This in turn will deprive creatures who are even further up the food chain from finding their food, such as spiders and insectivorous birds.

So, for the establishment of a wildlife-friendly garden and the essential food chains that need to exist within it, the aphids are indeed very important, and should either be left alone, or managed in a safe and non-toxic manner, which could even include reducing their numbers with a fine spray of water from a garden hose. A method that would not harm the beneficial creatures.