I’m fed up with talking about the weather, but I can console myself with the fact we have grabbed every opportunity so far and progress is not too bad.Little change in phoma predictions but LLS risk higher
THE first signs of phoma infections are appearing in oilseed rape crops slightly later than usual this autumn across the country as a whole.
However, backward crops, particularly in the East, will be more at risk from the disease. And bad weather during harvest in the North means the predicted onset of phoma into crops is earlier this year, says Dr Neal Evans, plant pathologist at Rothamsted Research.
“As you come further south into Lincolnshire and Nottinghamshire growers will be seeing 10 per cent phoma leaf spotting now in their crops, which follows a similar pattern to last year,” he says.
Despite very dry weather in East Anglia in recent weeks, there is little change in the predicted onset of the disease compared with last year’s estimates. “It certainly has been dry in this region but the forecast takes into account maximum temperatures from July 15 to September 26, in addition to rainfall during that period,” says Dr Evans. “We did get some rain in July in the East before it turned dry and this has to be taken into account.”
Preliminary predictions for light leaf spot show increased levels in crops compared with forecasts for 2008/09 in the North, East Midlands and West (see story below), however crops in the South West may get less disease than last season.
Light leaf spot
“Inoculum has been building up generally over the past few seasons because of wet weather, and there is more light leaf spot out there as a result,” says Dr Evans, adding that snow last February may also have been a factor, acting as a thermal blanket for the disease. “There’s a slightly increased risk in the South and East but the main concern is again in the North.
“Light leaf spot is a strange disease in that it’s very crop specific and you can get high infestation on one farm and no sign of it in the next. It’s very affected by, and dependent upon, rain and with the increasing pattern of localised downpours that we seem to be getting, it can be a very specific problem.”
Dr Evans reminds growers crops should be sprayed for light leaf spot when 25 per cent of plants are affected.
Latest forecasts
The latest phoma and light leaf spot forecasts for 2009/10 are available online at http://www3.res.bbsrc.ac.uk
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