Traditionally growers often reach for contact acting post emergent herbicides for spring cereals. However, weed control can often be improved whilst reducing the total spent on sprays by considering the use of pre-emergence residuals.
A clean start is essential for a successful crop. Competition from weeds can result in establishment issues, lodging and reduced yields. The temptation is to apply herbicides in a tank mixture with the first fungicide to save time, making only one pass with the sprayer. However, the timing is often too late to provide adequate control because the weeds may have advanced beyond a susceptible growth stage. It is crucial to apply pre-emergent herbicides as an approach to ensure they are in place to control the weeds as soon as they germinate.
Following crop restrictions
For many livestock farmers, an essential part of the rotation is to follow a barley crop with stubble turnips or other ‘roots’ for grazing. The following crop restrictions associated with the use of a wide range of herbicides are often overlooked.
Many pre and post-emergence products applied to the cereal crop can affect the following root crop, with the symptoms varying from a general lack of vigour, right through to complete crop failure. It is worth remembering when planning ahead, there are some residual herbicides available which can be applied pre-emergence, that provide cost-effective, broad-spectrum weed control and which have no following crop restrictions.
"A clean start is essential for a successful crop. Competition from weeds can result in establishment issues, lodging and reduced yields."
If growers are considering the use of pre-emergence herbicides, they could also consider purchasing the products along with the seed, so everything is ready early for spring drilling when the time comes.
Risks of herbicide resistance
We must also be mindful of the increasing risk of herbicide resistance developing. Already, a small number of species of common weeds are reported to be showing a level of resistance to certain herbicides that have been very widely used over many years. Populations of herbicide-resistant broad-leaved weeds are not common, but the frequency of new reports is increasing. For example, resistance in common chickweed to the ALS group of herbicides has been reported from more than 10 counties across the UK.
To reduce the risk of selecting for resistant strains, avoid the use of herbicides with a single mode of action from the same chemical group. A mixture of active ingredients with diff erent modes of action will greatly reduce the chances of resistance developing.
If a pre-emergence, residual herbicide cannot be applied, there are still effective post-emergence, contact-acting options. Product choice must be guided by weed spectrum and timing is decided by weed size, crop growth stage and whether or not other chemistry is to be included in a tank mix.
It can be difficult to make early decisions on herbicide inputs that will be applied months down the line, but by considering options beforehand and planning ahead, you will benefit.
Spring Seeds 2023
The Spring Seeds 2023 guide includes information and advice on the latest spring cereals seed varieties, as well as informative articles on key topic areas for the coming season.
