‘No flies on us’, goes the saying.....

Well, many of us experienced plenty this week during what can only be described as a greenfly invasion.

Taking advantage of the recent warm weather we set out on a stroll and within a few steps I had accumulated seven greenfly crawling up various strands of hair - we were swatting them off our sleeves, our legs and judging by the few social media posts I spotted, we weren’t the only ones....

There was talk of a ‘plague’ of the pesky insects in East Bierley - they certainly appeared to be in swarms - there was a photo of a parked car covered in them and one driver talked of driving through what appeared to be a ‘cloud’ of greenfly.

Once attached, you end up carrying them indoors leading to some very unwanted visitors creeping up your curtains and walls before you shoo them back out again.

Greenfly became the subject of discussion when the heat was on in May last year after similar invasions so what is the situation? Time to ask the experts....

Dr Steve Compton, Reader in Entomology at the University of Leeds, explains it is all about the weather...

“We had a mild winter and we have had some really hot periods.

“The biology of greenfly it’s about building up their populations quickly. These things can breed really quickly.”

Although greenfly aren’t harmful to people, they can harm plantlife.

“They can damage and weaken plants and they carry viruses - that is more of an agricultural issue,” explains Dr Compton.

He identified thousands in his own garden and says their presence this year is ‘exceptional.’

But there is hope - within the next couple of months the arrival of their natural enemy will help to keep things under control.

Professor Simon Leather, Professor of Entomology - Crop & Environment Sciences at Harper Adams University, Newport, explains ladybirds eat aphids (greenfly) - and that could lead to another invasion.....

He explains a good aphid year provides plenty of food for ladybirds.

“So next year the ladybirds will be having a bumper year as there are lots of them to eat - next year there will be a ladybird population outburst,” predicts Professor Leather.

“That is what happened in 1979/80 - the ladybirds ran out of food because so many from the previous year and they were biting people on the beaches at Cromer - there was a ladybird invasion.”

Professor Leather’s fascination with insects stems from being ‘knee high to a grasshopper.’ “I got interested in aphids when I was an under graduate at Leeds University,” he explains.

According to Professor Leather there are around 6,000 aphid species in the world - only 250 of those are pests - some live in the bark of trees and others live underground with ants.

“I find the whole thing fascinating - when looking at an aphid, daughters are there inside daughters - there are three generations in one.”

Professor Leather believes the recent greenfly invasion we experienced recently could be related to the sycamore tree.

“I am almost certain it will be the sycamore aphid - we had our big flight a week or so ago - it’s just as spring progresses the aphids have come through matured, got their wings and as sycamore trees get more into leaf they disperse into other trees,” explains Professor Leather.

He says in Autumn he noticed a lot of aphids were laying lots of eggs in Shropshire.

“They had favourable conditions last year and it is reflected this spring,” says Professor Leather, adding that we are now seeing the results of that.

“Aphids are really responsive to weather, if we have a bad winter - cold - then their population suffers a little bit. If they have nice warm spring you get a rapid growth.”

Spending more time outdoors in warmer weather we become more aware of the insects inhabiting our surroundings.

“It is a combination of things happening and sycamore aphids had a good spring this year,” concludes Professor Leather.

But we shouldn’t be too harsh about them - according to Professor Leather aphids provide food for other insects so they have a part to play.

Bee-keeping expert, Bill Cadmore, training officer with Bradford Beekeepers Association, acknowledges ‘a population explosion in the last week or so’ of aphids.

Says Bill: “The burst of warm spring weather is the cause - resulting in lots of soft young plant growth which the aphids love to suck the sap from.

“Aphids are able to reproduce really quickly because the female can produce live young ‘clones’ without mating - and can do so at a fantastic rate - called parthenogensis.

“Unfortunately, the dry second half of summer last year resulted in fewer ladybirds being born and, therefore, overwintering so the natural predator population is low.”

Bill explains wasps are the other major predator. “But wasp populations are very low at this time of year.”

  • Gardeners take note - for those particularly pestered by greenfly on their plants, Bill has this tip:- “We treat our plants with weak solution of ordinary washing up liquid applied with a spray rather than use insecticides - using a hand sprayer you can spray the aphids directly and so avoid killing other insects.”