An accidental touch of a branch brings a handful of little sticky dots. Looking at the branch, the surprise is that all the lower ones are covered with a shifting pointillism of dots moving together. Under a hand lens they become autonomous animals – aphids. There are thousands of them, moving independently as individuals, each with a sense of purpose and moment, determined and working together. Forming clusters around scar tissue on bark wounds, walking upwards towards the canopy of opening leaves, the aphids catch the sunlight and their amber bodies shine with the viscosity of drops of honey. In the morning sun they cast shadows, an imaginary material to which old fears and prejudices stick. When garden wildlife was divided into friend and foe of the gardener, the sap-sucking, leaf-distorting, flower-blighting, honeydew-pissing, disease-magnet aphids were definitely foe. Collective nouns such as swarm, horde, infestation, invasion, triggered a disgust response that got gardeners reaching for the insecticide. That may be less so now, but the curse of insecticides is still big business and responsible for reducing populations of aphid predators. In this garden, there have been woolly aphids, rose aphids, whitefly, blackfly, but these aphids seem new. This colony is moving through the branches of a 40-year-old Japanese maple, Acer palmatum ‘Dissectum atropurpureum’. These trees and their cultivated varieties reached here in the 19th century and it seems the aphid could be the Californian Maple aphid, Periphyllus californiensis. Despite its name, this species is native to east Asia and has been here since the last century. Attached to fallen leaves and winged seeds, female aphids overwinter to produce eggs through parthenogenesis to recolonise the tree in spring. In beams of sunlight through the tree, there is a rain of honeydew falling from the aphids. After a few days, black dots appear on nearby leaves of plants. These sooty moulds can be complex communities of black mycelia fungi feeding on the sugars the aphids produce. And the aphids are becoming alates – adults, darker with knobbly black bands, and some have wings. This fascinating and beautiful disruptive ecology of global trade, climate change and a human desire for embellishment, all happening in a back yard in Oswestry. • Under the Changing Skies: The Best of the Guardian’s Country Diary, 2018-2024 is published by Guardian Faber; order at guardianbookshop.com and get a 15% discount
Author: Paul Evans