Pre-emergence herbicides have been shown to be more effective in controlling many problem grass weeds such as bromes, blackgrass and annual meadow grass, according to Teagasc.
There are plenty of options, so growers can pick a mix that will control the main weeds in each field.
It is unlikely that the same mix will cover all the weeds in fields, so specific knowledge of the predominant weeds is vital for pre-emergence herbicides to work efficiently.
If in doubt, farmers should ask their local advisor for details of what herbicides are best suited to the weeds they need to control and use this as the base of a programme.
Pre-emergence herbicides
Products such as pendimethalin (found in various products), prosulfocarb (Defy/Roxy), flufenacet (Firebird/Navigate, etc.) give best results when applied early, especially where annual meadow grass is a problem.
Meanwhile chlorotoluron (Tower) can be used at early post-emergence.
Growers should add in diflufenican (Stride/Diflanil, etc.) to improve the control of charlock, chickweed and speedwells.
Firebird Met will help to control groundsel as well as many other broadleaf and grass weeds.
There have been a number of new reports of blackgrass appearing on different farms this year.
While many of these fields will be sown in break crops as part of an integrated pest management (IPM) approach, some will probably be drilled with wheat or barley, even though this is not recommended.
Avadex Factor (tri-allate) will improve the control of blackgrass and Italian ryegrass.
It is not recommended in these situations to use it alone and it will possibly require a follow-up treatment of flufenacet or, in wheat, Pacific Plus or Monolit – provided that it is not resistant.
But growers should be aware that the cost of controlling blackgrass in wheat or barley with all of these herbicides will be extremely expensive.
Zypar will improve the control of fumitory, poppy and volunteer beans. Many of the active ingredients will appear in mixes, so farmers should choose products that will control as many weeds as possible.
It is a case of targeting the most problematic weeds first; the less important ones can be tidied up later.