Herbicide programme for forage brassica crops
Brassicas are especially susceptible to weed competition during early crop development when the seeds are small and do not contain a lot of energy. Having to compete with a lot of weeds in the early phases of growth, dramatically suppresses yield in the long term.
Chemical weed control is only one tool to get on top of weeds and the use of a glyphosate, such as Roundup® prior to planting, along with cultivations, can drastically reduce weed pressure early on.
Prior to seedbed preparation, spray with an appropriate dose of glyphosate and leave plenty of time for sprayed out pasture and weeds to take up and translocate the chemical right down to their roots before ploughing or cultivating. A single spray of glyphosate three to four days before deep ploughing to bury the turf will often suffice, but a double spray will provide better control of stubborn weeds. To achieve the best results when direct drilling, spray with a high rate of glyphosate four to six weeks before drilling, allowing the turf to break down. Apply another low dose of glyphosate within a week of sowing to achieve optimum results. An insecticide can be added to create a weed and pest-free area to drill into. Using this method is essential for achieving good results when direct drilling.
Effective chemical weed control is dependent upon using the correct chemical for the target weed along with accurate application rates and timings, water rate and using an appropriate application method.
If possible, always start with a pre-emergence herbicide. Some products can be applied pre-plant but most are best used post-plant and pre-emergent of the crop and any weeds. These herbicides usually require some moisture to lock onto the soil and form a barrier to stop any weeds from emerging. If weeds do manage to emerge, they are often damaged and suppressed by the chemical making them easier to kill with a follow-up spray post-emergence.
Using a pre-emergence herbicide allows the crop to get a head start on weeds and increases the crop’s chance of survival along with producing increased yield and quality. It is useful to know what weeds are expected so a choice can be made as to which herbicide products are best applied at that time.
A post-emergence herbicide following a pre-emergence spray should be made on a wait and see approach as often no action is needed, especially in short-life crops such as turnips. However, if a chemical is required, use one specific to the weed being targeted. Post-emergence is also the best time to tackle grass weeds.
To organise a spray programme to control weeds in your forage brassica crops, contact your local PGG Wrightson Technical Field Representative.
Registered pursuant to the ACVM Act 1997, Roundup® #P008725. Always read the registered label before use.
