Following several seasons of poor crop establishment, oilseed rape has fallen out of favour with a lot of growers, especially in areas where cabbage stem flea beetle populations pose a significant threat. Despite this, oilseed rape still has a valuable role to play in many rotations, but for it to remain a viable crop growers must do everything to ensure their crops get off to the very best possible start.
Our essential oilseed rape establishment guide provides the latest advice to make oilseed rape work and provide a better understanding of how to improve the efficacy of autumn herbicides.
ADAMA can also provide you with a range of oilseed rape herbicides which offers growers the flexibility to apply pre-emergence or post-emergence treatments.
Despite being a profitable and effective break crop, and one which enables cereal growers to introduce alternative black-grass herbicides into their rotation, the long-term future of oilseed rape in the UK is coming under scrutiny, with the UK’s annual acreage falling year on year.
With the loss of neonicotinoid seed treatments and changes to general licensing for bird control, reducing slug and pigeon damage has been increasingly more challenging to achieve and crop losses have risen as a result. Data carried out by The Andersons Centre suggest that a quarter of winter oilseed rape was written off post-autumn 2019.
Percent Oilseed Rape Written Off in England (2014-20)*
*Source: The Andersons Centre
With an increase in crop lost, the ability to establish a vigorous and viable crop, and to protect the young crop from competing weeds is more critical than ever. Thankfully, ADAMA’s portfolio of pre and post emergence herbicides means there is one less issue for growers to worry about this autumn.
There is an increasing problem of herbicide resistance, with several grass weeds and broad-leaved weeds already displaying resilience to a number of key herbicide active ingredients.
With the successful establishment of oilseed rape crops proving increasingly difficult to achieve it can be tempting to withhold pre-emergence herbicide applications until the crop has established.
Fortunately, while a combined programme of pre- and post-emergence herbicide treatments will give the best levels of weed control, the pre-emergence element isn’t necessarily fundamental to the crop’s viability: a well-timed post-emergence treatment (using a suitable herbicide applied at the optimum growth stage) will enable growers to wait until the crop has fully emerged before committing to the expenditure of a herbicide treatment.
Before settling on a specific herbicide protocol, it is important to understand both the advantages and disadvantages of pre- and post-emergence strategies and to develop a spray programme accordingly.
Metazachlor is one of the key building blocks for weed control in OSR and is highly cost-effective. With a wide spectrum of activity against grassweeds and a range of broadleaved weeds, it can be used as either a pre- and/or early post-emergence option and is a useful starting point for controlling black-grass typically delivering a 10% uplift in black-grass efficacy to a weed control programme when followed up with other grassweed active herbicides.
Using metazachlor at the pre-emergence stage provides the ‘insurance’ of getting an herbicide on early if conditions subsequently turn wet. Applying at pre-emergence also removes weeds early in the crop’s lifecycle thereby allowing the oilseed rape to establish without competition. The benefit of metazachlor in weed control programmes was found to be increased for early drilled crops in a trial investigating the performance of herbicides at early August drilled OSR compared to early September drilled OSR
However, growers must be aware of the Metazachlor Matters stewardship scheme and should abide by its recommendations for the safe usage of metazachlor to protect surface water and preserve the ongoing availability of metazachlor (and quinmerac) based herbicides.
Where oilseed rape has been sown early, there may be a tendency towards favouring post-emergence weed control: simply because there may not be time during the busy harvest, cultivation and drilling season for a pre-emergence treatment to be applied. Unfortunately, this strategy poses an increased risk for water quality as post-emergence treatments are often applied when drains are running in October and November.
To reduce this risk, growers should consider an earlier application of an effective herbicide such as Crawler (600 g/kg carbetamide) which can be applied from pre-emergence of the crop all the way through to stem elongation or the end of February. Using Crawler at pre-emergence is an effective way of kick-starting black-grass control as it targets the roots of young, shallow-rooted weeds and weakens their resolve to subsequent chemistries.
A residual herbicide for the control of a wide range of grassweeds including black-grass. It is also effective against some broadleaved weeds in winter oilseed rape and winter beans.
Crawler gives growers the option to apply an early (including pre-emergence) herbicide to kick-start black-grass control: it targets the roots of young, shallow-rooted plants and weakens their resistance to subsequent chemistries. There is no known resistance to Crawler, even within black-grass populations.
Active ingredient: 600 g/kg carbetamide
A residual herbicide for use in winter and spring oilseed rape which can be used to form the foundation for the control of a wide range of broadleaved weeds and annual grasses. In addition to oilseed rape, Sultan 50 SC can also be used in vegetable crops, fruit trees, ornamentals, nursery stock, forestry and woodland.
Active ingredient: 500 g/l metazachlor
A residual herbicide for the control of broad-leaved weeds in winter and spring oilseed rape. It can also be used in winter and spring field beans, combining peas, vining peas and potatoes.
Active ingredient: 360g/L clomazone
Recommended for the post-emergence control of a wide range of broad-leaved weeds in winter wheat, winter barley, winter rye and winter triticale.
Fox may be used under EAMU 20142318 for control of Geranium species in OSR. Application is ‘at the grower’s own risk’.
Active ingredient: 480 g/l bifenox
Get the latest crop management advice and seasonal updates this autumn
Hear expert advice from the ADAMA team and wider agricultural community