Uppsala swarmed by aphids after summer population boom

Uppsala residents are finding themselves in the midst of an unprecedented aphid swarm, a phenomenon researchers attribute to a particularly favorable summer for insect reproduction. The sheer volume of aphids has made daily life uncomfortable, with many describing the experience of cycling or walking outdoors as akin to moving through a cloud of insects.

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We cycled into a cloud, you would have had to close your eyes.

Mats Jonsell, a researcher at the Swedish University of Agricultural Sciences (SLU), explained that aphids' survival strategy relies on sheer numbers. "When they have a good summer, many generations survive," he noted. While large aphid populations are common in late summer and early autumn, the current situation in Uppsala is described as an "explosive increase."

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It's incredibly much. In some places when you're out cycling, you have to keep your mouth shut, and preferably your eyes too... glasses are a help.

"It's incredibly much. In some places when you're out cycling, you have to keep your mouth shut, and preferably your eyes too... glasses are a help," Jonsell said. He identified the likely culprits as plum aphids, which feed on plum trees and related plants year-round, though their presence is not limited to these specific hosts.

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When they have a good summer, many generations survive.

The abundance of aphids this year could have implications for the following season. "There will be quite a lot at the beginning of next season unless things go terribly wrong for them during the winter," Jonsell warned. This suggests that the current aphid surge might lead to a similarly large population in the spring, depending on winter conditions.

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There will be quite a lot at the beginning of next season unless things go terribly wrong for them during the winter.