New-generation fungicides that were once effective in controlling the wheat disease Septoria tritici are now virtually useless, the Teagasc national tillage conference in Carlow was told yesterday.
Teagasc scientists discovered last year that resistance levels to the fungicides were now very high, ranging from 9 per cent to 84 per cent.
Dr Jimmy Burke, head of the Teagasc Crops Research Centre at Oak Park, Carlow, told farmers to ignore these new fungicides in their efforts to control the disease.
"We were the first to discover the levels of resistance here using DNA techniques and these new chemicals are no longer useful in controlling the disease Septoria in wheat crops," he said.
He said a combination of the failure of the new fungicides, called strobilurins, and bad sowing conditions, meant that Irish farmers had lost their position as the most successful grain growers in the world in 2000 and 2001, a ranking they had held for nearly 25 years.
Dr Eugene O'Sullivan of the research centre said Septoria, commonly known as "leaf blotch", was a serious disease of wheat with the potential to cause massive reductions in yields.
The new fungicides, which were in use here for the past 10 years but had been used extensively in the past five, secured wheat yields of over 10 tonnes per hectare for Irish growers, at least a half a tonne per hectare more than growers worldwide.
When introduced, the fungicides were regarded as "dream chemicals" for controlling Septoria, which has a high prevalence in Ireland because of our wet climatic conditions.
Dr Brendan Dunne, who also works at the research centre, said an alternative control procedure must be put in place this year.
He suggested that the older chemicals which farmers had been using before the strobilurins came into widespread use would have to be applied this year.
Dr Jim O'Mahoney, Teagasc's chief tillage adviser, said the new chemicals would still have a role to play in controlling diseases in barley and oats but not in the wheat crops.
He said that the 16,000 cereal farmers in the State had already planted an estimated 80,000 hectares of winter wheat and, given good weather and the use of the older chemicals, Ireland could regain its position at the top of the global yield tables.
A French expert on tillage prices, Dr Andrée Defois, from Strategy Grains in France, said grain prices should continue to improve. World prices, having bottomed out at the turn of the century, were projected to display a slow and moderate recovery over the medium term as supply adjusted to demand.