OILSEED RAPE growers in Scotland and the north of England can expect a severe light leaf spot epidemic next spring.
According to the latest PASSWORD forecast, 68% and 58% of unsprayed crops in those regions respectively are likely to suffer with more than a quarter of plants affected by the disease, says Neal Evans of Rothamsted Research.
Last season the comparative figures were 45% and 34%.
“Further south, even though we have not had the warmest or direst of summers, the model predicts that risk has reduced slightly compared to the forecast for last season,” said Dr Evans.
“This reflects the low levels of light leaf spot in 2003/2004 crops.”
Much depends on rainfall in the coming months, with the risk increasing in wet years, as splashes transfer infective spores from plant to plant, he explained.
“We will be monitoring rainfall and fine-tuning the predictions as the autumn progresses.”
Even in East Anglia, where the forecast is only 9%, nearly one in 10 unprotected crops could lose 0.5t/ha (4cwt/acre) to light leaf spot, warned DuPont‘s Andy Selley.
For crop specific forecasts from the project, funded by HGCA, DEFRA, DuPont, Perry Foundation, ProCam and Syngenta, visit http://www3.res.bbsrc.ac.uk/leafspot