Tillage farmers are facing a serious problem this year with the discovery that the new chemicals they have been using have become resistant to septoria.
Septoria can cause up to 50 per cent loss of yields in cereal crops and the strobilurin chemicals, only introduced two years ago, cannot control the disease, the National Tillage Conference in Carlow heard yesterday.
Cereal growers who lost 10 per cent of their yields last year because of the wet weather were told of high septoria resistance to the chemicals in Cork and along the east coast.
Dr Jimmy Burke of Teagasc, the agriculture and food development authority, said strobilurin chemicals were first introduced here in 2000. Teagasc carried out more than 1,000 tests on their ability to control the disease in 2001 and found them to be suitable.
"However, things changed in 2002 when we had what could be termed 16 septoria events which would aid the spread of the pathogen, which is four times more than normal and this was probably as a result of the weather," he said.
Because of the bad weather last year, the number of satisfactory spraying days were greatly reduced and accurate spray timing seriously affected overall efficacy. As a result, he said, researchers had identified resistance levels in the crop and had identified the gene involved in this process.
He told the conference that farmers would have to stay strictly to the guidelines Teagasc had developed for the coming harvest, "otherwise the problem might not be contained".
Dr Burke said Ireland, with one of the highest use of cereal fungicides in the world, now had a "unique problem". Only one case of septoria resistance had been identified in Britain and one in France from the use of the chemicals.
Teagasc recommends that farmers use older triazole compounds to control the disease in their first and third sprays, while the new strobilurin chemical be used only when the crop begins to ripen, along with existing established sprays.