The problems with weed control in-game cover crops usually arise because the combination of several different crop species in the mixture, it can make it difficult to find herbicides that are safe to all the components. Weed pressure is also increased when cover crops are sown on the same piece of land for a number of years.
How to reduce the weed burden
By planning sufficiently far ahead it is often possible to greatly reduce the weed burden by establishing a ‘stale seed bed’. The ground is cultivated as usual and a seedbed is created, but the game cover crop is not sown yet. Instead, the conditions created are ideal for weed seeds to germinate. Once the area has greened over with weeds, a quick pass with a low dose of glyphosate gives extremely good results.
If the components of the mixture enable residual pre-emergence herbicides to be used, the application must be made as quickly as possible after drilling (within 48 hours). Broadcast or shallow-drilled crops should not be treated pre-emergence with residual herbicides.
The most commonly used pre-emergence herbicides are pendimethalin (e.g. Stomp Aqua), propyzamide (e.g. Kerb Flo) and metazachlor (e.g. Sultan). If a residual pre-emergence herbicide cannot be used, or the application window is missed, there may be post-emergence options available. The product label must be consulted before application for full details of timing and sowing depth.
Herbicide choice is dictated by the components of the game cover mixture and by the weed species to be controlled. For the control of some grass weeds, products such as Laser and Fusilade Max can be applied to certain crop species. The vast majority of the herbicides used on game cover crops are applied under the terms of an Extension of Authorisation for Minor Use (EAMU) and the requirements of the EAMU must be followed along with information on the product label.
For more information about products, rates and timing, please speak to your local Wynnstay agronomist or ring Dr Simon Pope, Crop Protection Manager on 01939 210555.