Get ready for the fight against potato blight
The pressure of potato blight will be high this year with growers being advised to make the most of their fungicide armoury.
Scotland’s Rural College potato consultant Ruairidh Bain says the big lesson from last year is to use fungicides if a similar wet season hits the UK again.
“One of the big differences last season compared with previous ones is just the sheer number of high risk days, meaning there was a good reason to get the curative fungicide on,” he explains.
“Vigilance, planning and timeliness will also be critical in maximising the effects of these fungicides and keeping on top of the blight,” he says.
Disease pressure will be high across the country. Mr Bain notes crops that haven’t been harvested or that have been discarded will be one of many contributors to this.
“Generally the wastage in 2012 was quite high and unless those tubers have been mashed up or rotted away, then they are a potential source of inoculum for the 2013 crop,” he says.
However, Mr Bain does warn growers to avoid automatically assuming the coming season will replicate the one just gone.
“The thing about blight is we don’t really know too far in advance what the season will be like as so much depends on the weather,” he says.
“There is obviously a lot of inoculum going to be about, but whether or not it causes the problems it did last year remains to be seen,” Mr Bain adds.
“The thing about blight is we don’t really know too far in advance what the season will be like as so much depends on the weather.”
Ruairidh Bain, Scotland’s Rural College
Following two relatively low pressure years, last season provided growers with a wakeup call to the problems potato blight can cause to the national crop.
Costing UK agriculture £20m in fungicide use just to keep the disease in check, last year saw growers out in the fields far more regularly, applying fungicides.
Mr Bain says last season was one of the worst on record through a combination of factors which ultimately could come back to haunt growers this season.
“What we got was an early epidemic, so the inoculum was available early in relation to crop growth, which wasn’t helped with a lot of crop emerging relatively late,” he says.
Keep your spuds protected
- Start early – Blue 13_A2 is one of the first strains to appear in the crop. It is active at low temperatures and is prevalent in blight populations throughout the growing season. Assume this is the genotype you are tackling.
- Tight timings – Spray programmes should build well-timed applications around a realistic threat-based blight control strategy.
- Robust rates – Stick to full label rates and maintain throughout the season.
- Vigilance – Stay alert for signs of blight and control sources of infection, such as outgrade piles and volunteers
“This got us off to a bad start and then we were chasing it from then on.
“The same blight pressure later on in the season wouldn’t have been as damaging because the crops are slightly better protected and it is easier to keep on top of the protection,” he adds.
One worry at the end of 2011 going in to 2012 was the new strain of potato blight that appeared to have reduced sensitivity to a popular fungicide active (fluazinam).
The strain “green 33” was previously found in the Netherlands before being found in volunteers in Norfolk.
Senior plant pathologist for the James Hutton Institute, David Cooke, notes this risk appears to have subsided through good management, but warns growers still need to be vigilant.
“It didn’t spread last year and I think growers used the active fluazinam lightly, not putting too much selection pressure on it.” he says.
Mr Cooke notes it looks set to be a late planting season and advises growers to be aware of new sources of inoculum, particularly if soils continue to be so wet throughout the spring.
He also highlights that growers should be flexible in their assessment of blight following recent research by the Potato Council.
Traditionally, the risk of potato blight infection has been based on the calculation of Smith Periods – a system that uses hourly temperature and relative humidity recordings.
“We’ve seen evidence showing the pathogen is actually active outside the threshold which Smith Periods define, so it’s trying to make people aware that Smith Periods are a good guide for blight activity generally, but you should use your initiative as well,” he says.
Mr Cooke says it’s about keeping the threat of blight in peoples’ minds, and being vigilant of unusual outbreaks and patterns.
The early part of the season is all about being aware that there may be inoculum about and of getting a protective fungicide on early, he adds.
New blight strain prompts fungicide concerns
