Aphids are plaguing gardeners this spring due to the warm weather, with higher numbers of the rose-killing bugs expected to thrive in the UK as a result of climate breakdown.
The sap-sucking insects have topped the ranking of gardener queries to the Royal Horticultural Society, with many of its 600,000 members having complained of dozens of aphids on their acers, roses and honeysuckle plants.
They thrive in warm, dry weather, exacerbated by climate breakdown. Additionally, they can be killed off by frost, and the change in weather patterns is making frost less regular.
Hayley Jones, the principal entomologist at the RHS, said: “Climate change and more pronounced warm spells in many parts of the country could be a boon for some of the 500 species of aphid found in the UK, but there are other factors at play, including predator populations, the effect of climate change on general plant health and temperature swings and extremes.”
Aphids are also spreading to plants they never used to feed on in the UK. The RHS is calling on gardeners to support research into an aphid that has only recently affected buddleia, causing distinctive distortion to the leaves. It is asking the public to submit information on theRHS websiteto help map its spread.
There are more than 500 species of aphid found in UK gardens, and they are commonly known as blackfly, greenfly and plant lice. They can be red, yellow, black, green, brown or pink insects and feed by sucking sap from plants. They can significantly harm their host plants, causing death in some circumstances, but also cause distorted growth, sooty mould and can transmit plant viruses.
Aphids, despite causing annoyance to many gardeners, are an important part of the garden food chain, and are fed on by birds, earwigs, ladybirds and other larger insects. However, when their population booms and there are not enough predators, they can get out of control and cause visible damage to plants.
This is happening this spring, the RHS says, which recommends manual removal while predator numbers catch up. The charity is also finding environmentally friendly ways to manage aphids as does not recommend using harmful pesticides.
One RHS trial involves growing poached egg plant (Limnanthes douglasii) alongside cabbages to determine if this encourages predatory hoverfly larvae, and installing earwig shelters in the RHS Garden Wisley orchard.
The results are expected next year and, if successful, the RHS will encourage widespread use of these methods.
Jones added: “Aphid biology means they are well-placed to make the most of a warm spring; aphids are a bit like Russian dolls, being born pregnant with the next generation so their populations can bloom rapidly.
“Understanding how they can be managed through simple planting choices or encouragement of natural predators will help minimise damage and potential plant losses while maintaining a healthy garden ecosystem.”