Populations of Ireland’s key tillage grassweeds are developing reduced sensitivity or full resistance to a number of widely used herbicides.

Ongoing work by Teagasc has identified populations of wild oats which require multiple times the recommended field rates of ACCase herbicides (Axial, Falcon, Stratus Ultra) to control them.

The populations were collected in tillage fields in Kilkenny, Wexford and Cork.

In one of the sampled populations, the wild oat plant survived eight times the recommended rate of the herbicide Stratus Ultra.

Brome

The results also showed increasing tolerance or early stage resistance in sterile brome populations collected in fields in the main southeast tillage counties.

Teagasc said this may be developing as a result of repeated application of herbicides at rates below the recommended levels.

The degree of resistance or reduced sensitivity across Ireland is unknown but if growers are finding weeds increasingly difficult to control with herbicides, they are urged to contact Teagasc, where samples can be tested for resistance.