About 7.5 million euro-worth of forest has been destroyed by the fires of the last week.
A total of 985 hectares worth about 5 million euro and managed by Coillte has been wiped out, with Donegal and the Galway-Mayo area worst hit. Private forests worth about 2.5m euro have also been lost to fire.
Environmentalists have written to Agriculture Minister Simon Coveney accusing farmers of using fire to clear scrubland in order to claim compensation through the Single Farm Payment.
John O'Sullivan, Coillte's regional director, said the vast majority of fires spread from scrubland into woodland. "The primary cause of forest fires is the burning of gorse on adjoining lands," he said.
"Forest fires put the lives of the people who have to fight them at risk, as well as causing major damage to property, wildlife and habitats.
"These forest fires are mainly as a result of careless and dangerous burning of vegetation in close proximity to forests."
Mr O'Sullivan said evidence has been found of arson and anti-social behaviour causing some fires. The regions worst affected were Donegal with 550 hectares burnt and Galway-Mayo where 250 hectares were destroyed. Elsewhere, Monaghan had 80 hectares destroyed, Sligo 40, Cavan 25, Roscommon 20 and Cork/Waterford 20.
Coillte, which owns around 445,000 hectares of land, about 7% of the land cover of Ireland, said four times the annual average of forestry has been destroyed by fire this year compared with normal levels. Mr O'Sullivan said the fires were unprecedented and said there is zero tolerance on fires in woodland and Coillte-owned property.
Tony Lowes, spokesman for Friends of the Irish Environment which represents 19 groups, said farmers were using rules governing the single farm payments as an excuse to clear land using fire.
The Irish Farmers' Association declined to comment.