Black clouds of mosquitoes are infesting the marshes of the Dee Estuary.
The infestation was brought to the attention of this newspaper by Ness resident Rick Bachelor, who said: “We are for the last few evenings being invaded by plagues of mosquitoes.
“They are so dense they appear as black clouds over the canopy of trees, we estimate millions.
“Over the years the marsh was sprayed to try and keep the infestation under control but looking at this it is now out of control.
“Of course if one is bitten and a serious reaction sets in, which it can, I will be the first to say my warning was ignored.”
Prof Clarkson has been studying the mosquitoes from the marshes, which have been found up to 3km inland, for seven years.
He points out studies have previously been carried out on the number of mosquitoes in Neston, initially with a variety of traps being used to capture adult insects.
Results of the identification of over 3,000 adult mosquitoes found in gardens, homes and schools were published in the European Mosquito Bulletin.
A total of 3,213 mosquitoes were caught, 2,787 in traps and 426 by residents, two thirds of which were salt marsh mosquitoes.
These were found in every month of the year except January, with September being the peak.
Reports of people being bitten were received by the local authorities each year with the survey suggesting the salt marsh mozzie was responsible for virtually all the complaints.
Attempts have been made by the local authorities to control the mosquitoes by spraying some pools on the estuary, but it is recognised the extensive area involved is greater than can be reasonably sprayed.
More recently, attempts have been made to alter the environment on the marsh at Parkgate and Little Neston by digging the drainage channels and deepening the pools.
These schemes are being developed and monitored by staff from Neston Town Council, the borough council, the Royal Society for the Protection of Birds (RSPB) and by Prof Clarkson at Leahurst.
This group meets regularly to exchange information and discuss future plans.
Neston Town Council said earlier this year that working with the borough council and the RSPB it had completed phase two of its battle to reduce the development of mosquito larvae in the Riverside area.
Phase two involved the merging of a number of small ponds which had previously been identified as mosquito hotspots by Prof Clarkson and Colin Wells from the RSPB.
Prof Clarkson has installed a trap in Mr Bachelor’s garden and explained the factors which have given rise to the plague to him.
“I have answered many individual complaints by home visits and setting a mosquito trap in gardens to identify the species involved but there is no doubt that it is the marsh mosquito, ochlerotatus detritus, which only breeds in salt water pools,” he said.
A report he has written, available on the internet, provides background information to help Neston residents, ‘of which I am one’, to understand how difficult it is to control the mosquitoes when conditions favour their development.
“It is no consolation to all of us being bitten but my studies enabled me to forecast the present problem in August but, unfortunately, there was nothing we could do to prevent it occurring,” he explained.
“It is due to a particular set of circumstances with unusually high tides in August followed by heavy rain showers for some two weeks so that not only are the usual pools full of water but the areas of marsh between the pools have a shallow covering of water and since last week have been full of pupae.
“In effect, the whole marsh is a breeding site. I have found immature stages almost anywhere and everywhere I put my dipper except in the deep pools, either the natural pools or the ones constructed in recent years, which contain no mosquito larvae.
“There are high tides this week (September 9-12) which may wash out the remaining pupae but could set off another batch of larvae from the eggs in the mud if the weather in September is warm.
“It would be impossible to spray this vast area and unless we could produce a huge deep lake instead of a marsh, digging pools will not succeed either.
“I have no answer, I’m afraid except repellents containing 50% DEET and thick clothing!”
Prof Clarkson suggested: “It really needs a lot of finance to study the mosquitoes by modern genetic techniques in order to have any chance of a long-term solution and not be simply the hobby of a retired vet!”
Little Neston and Burton ward borough councillor Kay Loch (Con) added: “There certainly has been an explosion over the last few days in Ness – I can’t go into our garden as they bite through clothing!”
Background information can be seen at www.zoonosis.ac.uk/media/zoonosis/documents/Mosquito_group.pdf .