A research project looking at rhizoctonia in oilseed rape highlights the potential of an SDHI seed treatment and opportunities to breed for resistance to the disease.
Rhizoctonia solani is a common soil borne crop pathogen which can cause OSR establishment losses of 17-65 per cent, according to a recently published AHDB fact sheet on the disease.
Thiram-based treatments have provided some control, however, sale of products based on this active ingredient is no longer permitted and products must be used up by January 30, 2020.
Problems associated with growing oilseed rape such as loss of neonicotinoid seed dressings, cabbage stem flea beetle and oilseed rape yields remaining static are well documented. Against this background Syngenta, University of Nottingham and AHDB decided to focus on the effect of R solani on the crop with the launch of the ICAROS project (Integrating control strategies against soil-borne R solani in oilseed rape).
R solani hits yield most under very low cumulative rainfall as good soil porosity favours spread of the pathogen, said University of Nottingham researcher Dr Rumiana Ray.
Differences were found between OSR variety performance under moderately R solani infected soils, said Dr Ray. “Campus yields best, Skye, Anastasia and Saveo next and most affected are Mantara and Sensia.”
A seed treatment under development by Syngenta which contains sedaxane – an SDHI fungicide, fludioxonil and metalaxyl-M was also tested.
Dr Ray said: “It [the seed treatment] protects crop establishment and increases vigour and green area index by reducing the pathogen in the soil. There was less damage due to CSFB in treated plots. Irrespective of seed rate, seed treatment increases developmental uniformity under high disease pressure. The yield response is up to 2t/ha depending on sowing rate.”
Fellow University of Nottingham researcher Dr Dasuni Jayaweera said the reduction in CSFB damage in treated plots is unexplained. “We have not looked at the relationship, we just observed - there was about 20 per cent less damage.”
While Syngenta plans to register the seed treatment by the third quarter of next year, there is one regulatory hurdle to overcome in that one of the AI’s, metalaxyl-M is currently up for renewal, with a vote by EU member states due in January 2020.