The effect of climate change on winter oilseed rape diseases

Both phoma stem canker and light leaf spot are diseases that currently affect the production of oilseed rape crops cultivated in the United Kingdom. Evans et al. (2010) researched the effect of climate change on future projections of these diseases and the yields of this crop. The researchers found that the canker thrives in hotter temperatures. They also noted that the light leaf spot disease generally prefers a cooler and wetter climate. Climate change, therefore, is expected to affect the yield of fungicide-treated oilseed rape crops differently based on the two diseases. The authors predict that there will be an increase of phoma stem canker severity on yields and a decrease in yield loss as a result of the light leaf spot disease. The authors validate these predictions and suggest further research to fully understand the effect of climate change on phoma stem canker and light spot disease that affect the oilseed rape crop.—Daniela Hernández­
Evans, N., Butterworth, M., Baierl, A., Semenov, M., West J., Barnes, A. Moran, D., Fitt, B., 2010. The impact of climate change on disease constraints on production of oilseed rape. Food Security 2, 143–156.

For their research, the authors created five different climate scenarios: baseline, 2020s low CO2 emissions, 2020s high emissions, 2050s low emissions, and 2050s high emissions. The scenarios were based on projections they gathered from sources such as the UKCIPO2, the HadCM3, and the IPCC. Using these scenarios, Evans et al. produced the following weather data for fourteen different areas in the United Kingdom and projected it for thirty years: daily minimum temperature, daily maximum temperature, daily rainfall, and daily solar radiation. The researchers then used these data as the parameters for three already established models; the first model projected the yield of oilseed rape treated with fungicide, the second looked at the severity of phoma stem canker on oilseed rape, and the third predicted the occurrence of light leaf spot on oilseed rape. The models were adjusted to reflect United Kingdom particularities and were then employed to investigate the effect of climate change on the two oilseed rape diseases.
The authors measured the damaging effects of the phoma canker disease on the crop by quantifying the yield loss of the oilseed rape. To find out how much was lost, they compared the total fungicide-treated crop yield to the untreated crop yield when infected by the disease. Evans et al. also investigated the impact of climate change on light leaf spot incidence. They used these projections to estimate yield loss caused by the disease. The results projected that there will be a significant increase in the severity of phoma stem canker disease infection throughout the UK. Conversely, it was shown that there will be a decrease in infection of the oilseed rape by light leaf spot. Overall, however, the researchers found that there will be a notable yield loss caused by the combination of the diseases on the yield of the crop. To fully understand the total scope of the yield loss, both diseases were taken into consideration, showing that the positive correlation between the decrease in light leaf spot occurrence and climate change will not offset the negative results of phoma stem canker without the use of fungicides.

However, the authors found that climate change will increase oilseed rape yield in fungicide crops; this trend is expected for all the climate scenarios. The greatest increase in crop yield is projected to result from the high CO2 scenario, and is thought to be especially true in eastern Scotland and northeastern England. Furthermore, Evans et al. also investigated the predicted economic costs involved, ceteris paribus, with the change in treated oilseed rape yield predicted as a result of climate change. The predicted decrease in yield caused by the phoma stem canker and light leaf spot diseases is expected to counter the predicted increase in the treated oilseed rape yield caused by the climate changes. Therefore, the UK is expected to face a low economic cost for the treated crop. Further research is warranted to have a more complete understanding of the costs involved and the effects these diseases will have on crop yields.

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