A chemical used by farmers to kill rushes and weeds such as docks has been detected in two rivers in North Kerry.
The Environmental Protection Agency has detected small amounts of MCPA in both the Feale and Smeala rivers; even this amount can break EU directives for water quality.
August and September is a busy period for spraying after the silage has been cut.
Chemicals such as MCPA can enter water courses in a number of ways including leaking from storage areas, run off from fields after rain and not maintaining a correct buffer zone.
Teagasc advisor in Tralee, Denis Brassil, is urging farmers to take care when spraying: