Mixed and mild weather has been forecast for Friday and Saturday, with Sunday turning warm and bright.
It is more likely for blackgrass and Italian ryegrass samples to be resistant to one or more herbicides than not, writes Vijaya Bhaskar of Teagasc.
Rat's tail fescue can become dominant where ploughing is not practiced due to limited effective chemical options, writes Vijaya Bhaskar of Teagasc Oak Park.
Some weeds have developed resistance to herbicides. Teagasc is collecting weed seed samples from farmers to test for resistance for free.