Securing effective autumn weed control in newly established cereal crops is crucially important if optimal yileds are to be secured.
Growers must target grass and broad leaf weeds in equal measure.
According to Teagasc, pre-emergence herbicides have been shown to be more effective in controlling many problem grass weeds, such as bromes, blackgrass and annual meadow grass.
There are plenty of options, so it’s a case of picking a mix that will control the main weeds in each field.
It is unlikely that the same mix will cover all weeds in all fields, so knowledge of the predominant weeds is vital for pre-emergence herbicides to work efficiently.
If in doubt, Teagasc advisors will offer insights regarding what weeds the different herbicides give best control over.
It’s a case then of individual growers developing a spray programmes that best meets their specific needs.
Products such as pendimethalin (contained in various products), prosulfocarb (Defy/Roxy), and flufenacet (Firebird/Navigate) give best results when applied early, especially where annual meadow grass is a problem. Chlorotoluron (Tower) can be used as an early post-emergent spray.
Diflufenican (Stride/Diflanil, etc.) can be used to improve the control of charlock, chickweed and speedwells.
Meanwhile, Firebird Met will help to control groundsel, as well as many other broadleaf and grass weeds.
Teagasc has reported that new blackgrass infestations have been identified in Irish crops. Many of these fields will have break crops. But but some will be drilled with wheat or barley.
Avadex Factor (tri-allate) will improve control of blackgrass and Italian ryegrass as part of a strategy with flufenacet.
Autumn weed control
Zypar will improve control of fumitory, poppy and volunteer beans. Many of the active ingredients will appear in mixes, so growers should choose products that will control as many weeds as possible.
Targeting the most problematic weeds first is the most effective strategy to follow: the less important ones can be tidied up later.
Farmers must commit to using different herbicide strategies each year, if they want to prevent weed resistance becoming an issue on their farms.
The results of recent grower surveys indicate that grass-weed challenges are on the rise in Ireland.
Specifically, there are increasing cases of blackgrass and Italian ryegrass resistance to herbicides now being identified in Ireland.
Moreover, the apparent speed at which resistance is developing in both these species, pose a significant threat to crop production
Non-inversion tillage particularly when coupled with earlier sowing increases the grass-weed threat.
As a consequence, there is a need to develop effective cultural/non-chemical weed control tactics to protect existing effective herbicides.