Teagasc tillage specialists are advising that pre-emergent herbicides can provide a better opportunity to get on top of difficult weeds, such as blackgrass and sterile brome.
Speaking on a recent edition of the ‘Tillage Edge’ podcast, Teagasc’s Shay Phelan confirmed that the better ground conditions and the longer working days are additional factors that favour the use of pre-emergent herbicides.
He said: “Compared to later in October and November, conditions are better now to allow for the effective application of a herbicide.
“So pre-emergent products work from both an efficacy and convenience points of view.”
Pre-emergent herbicides and winter barley
Speaking specifically on the role of pre-emergent herbicides within a winter barley scenario, Teagasc’s Ciaran Collins suggested that products of this type should be focused on the control of annual meadow grass.
He explained: “Very early post-emergence applications of the same products can also work well in this context.
“This is especially the case with a competitive crop. The key is to avoid the peri-emergence stage, when the shoot is just visible above the ground. The crop is most sensitive at that stage. This advice covers all the relevant products that are available to growers.”
Sterile brome has been confirmed as a difficult weed to control, particularly within winter barley crops that have been put in as part of a min till operation.
Collins commented: “There is no 100% effective control option for this weed within winter barley crops. As a rule of thumb, fields that have bad infestations of winter barley within them should not be targeted for winter barley production at all.
“In cases where there are small infestations of brome, these must be tackled using a pre-emergent herbicide.
“Applying a recommended herbicide at both the pre-emergent and very early post-emergent stages should also be considered.
“This approach will help. But it’s rare that growers will get 100% control if they are dealing with bad brome infestations.”
Winter wheat
Shay Phelan pointed out that there is more flexibility available to growers when it comes to putting pre-emergent herbicides on to winter wheat crops, relative to winter barley.
He commented: “Again it’s important to avoid the peri-emergent stage.
“While, the overall application rates may be the same for both crops, the likelihood is that a single spray at the pre-emergence stage will be sufficient for wheat. In contrast, a split application will be required on winter barley crops.
“Using herbicides with differing modes of action in pre and post-emergent scenarios will, for the most part, give growers more flexibility when it comes to dealing with weeds,” he concluded.