Oilseed rape disease shifts northwards

Lodging due to stem canker could halve yields in untreated oilseed rape crops in much of southern England by 2050.

But Scottish growers look set to benefit from more favourable growing conditions.

Those were the predictions of the impact of climate change on the crop outlined by Rothamsted Research scientists Neal Evans and Jon West.

As part of a team they had used Met Office data to examine the likely effects of changing weather patterns to 2020 and 2050 on the phoma disease, which leads to cankers.

The study combined models on the crop’s growth and phoma forecasting with another predicting UK temperatures and rainfall under both high and low carbon emission scenarios.

“At the moment phoma’s most severe in the south and east, but it’s going to shift north,” said Dr Evans.

“Growers in N Yorkshire often see phoma spotting, but it’s not generally warm enough for the spots to lead to severe cankers. In future they’ll have to spray for it.”

Clearly, many already did treat their crops with fungicide, but mainly against light leaf spot, for which the optimum timings could be different, Dr West pointed out.

“So there will be implications both for spray timings and variety choice.”

Conversely, the severity of light leaf spot, which was favoured by cool conditions, was likely to decline in the north.

Another prediction was that increasing carbon dioxide levels in the atmosphere would boost Scottish yields.

The DEFRA-funded forecasts had important greenhouse gas ramifications in guiding growers on future disease control practices, added Dr West.

“Good crop protection is much better for the environment.

“In oilseed rape nitrogen is the main contributor to greenhouse gases. So it makes sense to maximise yield rather than allow diseases to run riot and waste nitrogen. The better the yield the more the carbon footprint per tonne goes down.”