Harpenden researchers studying the effect of climate change on aphids

APHIDS, the bane of many an urban gardener, are being put under the microscope, literally, in an effort to determine how climate changes impact on their populations.

The bad news is that global warming has resulted in the sap-sucking insects multiplying earlier. The good news is that Harpenden scientists are pinpointing when they are likely to be a problem and giving crop growers advance notice so they are prepared for population spurts.

Dr Richard Harrington, an expert on insects who is leading a project on aphids at Rothamsted Research, confirmed that for every degree Centigrade rise in winter temperature, migration of many of the country’s 500 aphid species comes forward by about two weeks.

The entomologist, deputy science director of Rothamsted’s Centre for Bioenergy and Climate Change, said: “Aphids have been flying earlier by approximately one day per year for the past 40 years and in larger numbers at just the time they pose the greatest threat to crops.”

Scientists at Rothamsted, one of the largest agricultural research institutes in Britain, have had a head-start in determining the impact of climate change as there has been continuous sampling of the insects at Harpenden since 1965.

Dr Harrington said: “The main objective is to understand what makes aphid populations decrease and increase to see where and when they are likely to become a problem. Others at Rothamsted are working on biological and chemical ways to combat them.”

He is coordinating data obtained from insect suction traps set up throughout Britain and in 16 European countries, enabling his team to study a wide range of insects including aphids.

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Dr Harrington, whose lifelong interest in the insect world was triggered after accidentally capturing a butterfly in a crab net when six years old, explained: “We send bulletins to the agricultural industry on which aphids are present in the suction traps, and what actions would be appropriate to control them.”


He added: “Unfortunately the recent cold snap has done little to knock back some of the pests as several species lay eggs that survive very low temperatures. However several aphid species which don’t produce eggs would have been badly hit and are expected to cause fewer problems early on.

“One drawback though is that the enemies of aphids such as ladybirds and parasitic wasps will then fare badly because they will have little to eat and as a result aphid populations may get away later in the year.”

Aphids are the UK’s and Europe’s most economically damaging agricultural pest.

Yet Dr Harrington is a staunch defender of the much-maligned insect, and said: “They are not all bad. Many species do no harm to crops or garden plants and are food for other insects and birds. We have created artificial environments for them, such as gardens and large areas of crops. Some have been smart enough to take advantage of that and we therefore regard them as pests.”

Apparently aphids’ alternative moniker, “greenflies” is a misnomer as they appear in many shades other than green – black, brown, yellow, red, orange and even purple.