Sprouts can damage ecosystem

Children and greenfly may have something else in common apart from being little pests – neither is keen on Brussels sprouts.

Brian Aldred

The difference is that while they are good for children, aphids (more commonly known as greenfly) that feed on Brussels sprouts grow to be smaller and in fewer numbers. Results from a study by Wageningen University in the Netherlands and Imperial College London show that the sprout-eating smaller aphids have a negative effect on the ecosystem as a whole.

They also found predators, such as wasps, feeding on the lesser aphids are likewise affected by the lack of nutrients. The impact on the ecosystem is extensive and could hinder important processes such as the natural predation and control of agricultural pests.

By comparing aphids living on sprouts and aphids living on wild cabbages they deduced that the sprouts were lower in nutritional quality as there were less aphids living on them and the ones that did were smaller in size. The group found that larger cabbage-eating aphids led to larger primary parasitoid wasps which attracted a bigger variety of further predators in the ecosystem.

Dr Frank Van Venn from Imperial College London explained: “The diversity and complexity of food webs have long been seen as good indicators of how well an ecosystem is functioning, and how stable it is, but until now we had very little idea of the processes that determine diversity and complexity. Our study has shown that changing just one element, in this case plant quality, leads to a cascade of effects that impact on predators across the food web.”

By Leila Sattary