Teagasc has confirmed that the growing threat of clubroot could hamper the further expansion of Ireland’s oilseed rape (OSR) acreage.
The disease has become an issue on a number of farms this year, according to tillage specialist, Shay Phelan.
“Clubroot attacks all brassicas. Developing effective rotations is the best way to prevent the disease from becoming a problem in the first place,” Phelan explained.
“Adding to the challenge is the fact that a number of cover crop mixtures contain brassica species.”
Oilseed rape
It is estimated that 19,000ha were sown out in OSR last autumn, up from 15,000ha the previous year.
Significantly, the Agriculture and Horticulture Development Board (AHDB) in the UK is also highlighting the threat of clubroot in OSR crops of oilseed rape (OSR).
This follows the damage caused by the disease courtesy of a trial in carried out in southern Scotland.
Similar problems were also encountered during 2021 at a trial in the north east of England. No history of clubroot had previously been recorded at either site.
The bad news is that clubroot will persist in a field for 20 years or more.
Weeds such as charlock and hedge mustard or brassica cover crops growing in the field will act as a host and may prolong the disease even longer.
Prevention
Long rotations are the best preventative action. High pH soils and clubroot tolerant varieties can also help. But results can be inconsistent.
At present, there are no options for controlling clubroot with fungicides or biocontrols.
The key to management is to understand clubroot pressures, restrict its spread and make informed rotational/varietal decisions, according to the tillage specialist.
In particular, it is important to base decisions on the long-term profitability and sustainability of a field, not on a single season’s predicted margin.
Early detection of clubroot infection is extremely important. As patches of poor growth or establishment can have multiple causes, it is important to investigate them and establish the cause.
Mapping affected areas can help guide management decisions. An understanding of the field factors that favour the pathogen is also essential.
Clubroot can spread in several ways, including via soiled machinery and infected organic material.
There is now growing concern that the frequent use of clubroot-resistant varieties is likely to increase selection pressure on the pathogen population and may lead to the emergence of new virulent strains able to infect previously resistant crops.
