Ant infestations rising because of warm winters, says pest control group

Homeowners and gardeners have been advised to prepare for a rise in ant populations if warmer winters become a common occurrence in Ireland.

The number of callouts for pest controllers responding to ant infestations in business and homes rose by 35 per cent in January and February of this year when compared to the same period last year, according to the Rentokil pest control group. The highest number of callouts were in Dublin followed by Cork, Kerry and Kildare during what was one of the mildest Irish winters on record.

Dr John Coll from Maynooth University says higher winter temperatures could lead to growth in insect populations and that the rise in pest control callouts could be attributed to the unusually warm conditions in recent months, adding that a rise in insect numbers had already been noted among deer tick populations in North America.

The short life cycles of insects and their high reproductive capacity and mobility could also lead to a “particularly large and rapid effects on species population dynamics”, he said.

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“Warmer temperatures generally lead to more rapid development and survival in insects in mid to high latitude locations such as Ireland, hence insect populations here are among those expected to benefit most from climate change through more rapid development and increased survival,” said Dr Coll. He added that warmer temperatures could also push the onset of insect life cycles for species who use temperatures as a cue to match the timing of their biological life events.

‘Disruptions’

These natural “phenological patterns” are being increasingly disrupted by climate warming yet the consequences of these disruptions remain “poorly understood”, he said.

“With mid-late century projections of climate change showing milder winters than present for Ireland, and if this apparent ant population response is sustained, Ireland’s gardeners and homeowners may increasingly have to consider how they adapt alongside these opportunistic little foragers in the relatively near future”.

Dr Tomás Murray from the National Biodiversity Data Centre questioned Rentokil’s claims that winter infestations are on the rise and underlined that Ireland does not carry out any “systematic recording of ants” and as a result would have no baseline for measuring changes in numbers.

Ireland experienced one of its mildest ever winters this year while Dublin had its mildest winter since records began more than 160 years ago. The Phoenix Park weather station recorded a mean temperature for the months of December, January and February of 7.1 degrees, 1.9 degrees above the winter average. It was also the mildest winter in recorded history at the Valentia Observatory in Co Kerry going back to 1893.

Irish winters are set to be wetter but with fewer storms in the coming years while the country is facing a temperature rise of at least 3 degrees this century, the National Biodiversity Conference heard last month. Initial forecasting out to mid-century shows Irish summer temperatures will increase by up to 2.5 degrees, with the East coast being most affected, though more heatwaves will affect the entire country.