SCOTLAND'S farmers are bracing themselves for the worst harvest in 30 years as wet weather threatens to devastate key crops

and the prospect looms of higher prices for shoppers.

The wettest June on record has led to waterlogged fields and, coupled with warm conditions, it has meant more than twice the number of potato blight outbreaks reported in the past few weeks than for the whole of 2011.

There have been 20 alerts in the east and the Borders, with many over the past week, and the Scottish Agricultural College (SAC) has already launched an investigation.

Other crops – including spring and winter barley, and wheat – are also struggling, and the normally resilient oilseed rape has been flattened in swathes by heavy rain in some places.

Poor harvests could have a far wider effect on other industries such as distilling and cereal production, and flux in the marketplace could again hit supermarket prices.

Separately, at a mass rally in Lanark yesterday, 300 dairy farmers agreed to co-ordinated action over 2p-a-litre cuts in milk prices, amid claims many farmers are being forced out of business.

Meanwhile, Dr Fiona Burnett, an expert at the SAC, warned of devastation in the potato farming industry, adding: "The farmers need dry weather to spray the crops against blight with fungicides, and they should do that about every seven days.

"But they have not been able to get out. There were only five dry days in six weeks. The farmers said it has not been as bad as this since the 1980s.

"Everyone knows the devastation blight can cause. The main crop of spring barley is really struggling, winter barley also."

Last year Scottish farmers produced £129 million worth of wheat, £285.9m of barley, £209.6m of potatoes and £53m of oilseed rape.

Dairy farmers have had to keep cows inside, and silage supply may also be a problem, adding pressure to farmers' profit margins.

Allan Bowie, NFU Scotland vice- president, said ground that is difficult to manage has cost some potatoes this year already, but so far there have been no cases of blight on his Fife farm.

The potato farmer warned the UK's wet weather would be expected to affect prices, but the extent would not be known until after September's harvest.

Mr Bowie added: "Ground conditions are a big problem now. It

is sodden. We've already lost potatoes, although we've not had blight. It is a very serious disease. With this weather, you would look to spray about once a week to cover the new growth from now on, if it is dry enough to get out.

"The crop will certainly be cut back because of late planting – which was also because of the weather – but on the UK basis, they are also getting bad weather down south and there will be an effect [on prices]."

Blight reports have come from Perthshire, Dundee, Fife, Lothians and the Scottish Borders.

A spokesman for the Potato Council, part of the Agriculture and Horticulture Development Board, a levy body funded by farmers and growers, said warmth and humidity increase the risk of blight, but it was actively monitoring the situation and taking action to protect crops.

Blight is caused by the fungus-like organism Phytophthora infestans, which spreads rapidly in the foliage of potatoes, causing collapse and decay.

Alasdair Fletcher, editor of the Scottish Farmer magazine, said: "If there is a poor harvest, for potatoes probably more than any other commodity, prices go through the roof. It is certainly not looking good."