Wet summer weather has led to at least five major farm blazes in the Westcountry, caused by spontaneous combustion worth a total of £130,000.
Difficulties harvesting hay and straw during 2012 – the wettest summer in 100 years – saw farmers across the region struggling to avoid baling and stacking hay, straw or other crops when still damp, thanks to the increased risk of heat build-up and fire due to natural fermentation.
Insurance firm Cornish Mutual is warning its farming members to be careful how they stack. Two blazes this year in North Devon and Somerset followed three similar fires at farms in Cornwall and Somerset during an equally difficult 2011.
The incidents were among an estimated £543,000 worth of claims involving farm fires handled by Cornish Mutual between July 2011 and June 2012, compared to £145,000 in claims during the same period in 2010/2011.
Farmer Dudley Easterbrook was one of those affected when 110 tonnes of hay, worth more than £16,000, were destroyed in a barn fire caused by spontaneous combustion at his farm near Menheniot, in South East Cornwall.
He worked long into the night with firemen to battle the flames and pull burning hay from the barn and succeeded in stopping the building itself going up in flames.
He said: "We've been fighting the weather over the last two years when trying to bring in hay.
"I didn't think the hay was too damp when we baled and stored it and I added a hay preservative too.
We regularly monitored the hay and my daughter came in one evening and told me the hay was really steaming. I went right out and by then it was already smoking and in flames."
Spontaneous combustion can happen if crops are not dry enough when stored in bulk and put away too soon. Fermentation due to naturally occurring bacteria which leads to a build-up of heat which cannot dissipate in the centre of a haystack. Over a period of time this raises the temperature inside to the point at which a fire starts.
Philip Wilson, of Cornish Mutual, said: "Spontaneous combustion is something farmers always need to be alert to, but the last two summers in particular have been extremely challenging, with long periods of bad weather punctuated by short windows of opportunity to bale and store hay and straw. Ideally, farmers will cut the crop, lay it on the field and turn it before baling it, but if the crop isn't dry enough when it's baled and stored and the moisture content is too high, it could ignite through spontaneous combustion and go up in flames."