THE ANNUAL Potatoes In Practice day held at Gourdie on the western outskirts of Dundee is now a major event, writes Ewan Pate, farming editor.

For some years it has been hailed as the largest outdoor potato exhibition in the UK, but this year it looked the part with larger marquees, more exhibitors and more visitors from across the country and overseas.

Much of the success must come from cross-industry support. The event is jointly run by Scottish Crop Research Institute, British Potato Council, SAC and CSC Crop Protection.

There is now new confidence in arable farming, with cereal prices greatly improved. Those who also grow potatoes are slightly more nervous and for good reason.

Although yesterday the sun shone across the site, which is part of SCRI, there was a spectre at the feast—potato late blight is undoubtedly present in many crops and the effect is as yet unknown.

East Lothian farmers who are already lifting potatoes reported that they are seeing some blighted tubers but the biggest problems are in wetter hollows where water has been lying and where the crop has completely rotted out.

To add to the problems of controlling blight in such a difficult year, SCRI plant pathologist Dr David Cooke released information on changes in the blight pathogen, phytopthora infestans.

He has been involved in a team looking at the increasing incidence of the A2 type which can sexually reproduce with the much more prevalent A1 type to produce spores which can be soil borne and survive for several years, creating a reservoir of infection and making control of the disease even more difficult.

“We are in the middle of a three-year project but it seems we have a blight which is harder to control and more aggressive,” he said.

SAC head of crop services Stuart Wale said, “There are problems with these new strains which seem to originate from the continent. They are more variable and more difficult to control. It looks like it means starting to spray earlier and possibly fitting in two extra sprays.

“With the new strains leaving resting spores in the soil it creates problems but the good news is that wide rotations of five years, or preferably more, should keep the risk low.

“I have been preaching the advantages of wider rotations for ware growers for some time. There might be a short term gain in growing in close rotation but it is outweighed by disease problems and the need for more chemical use.”

Chemicals themselves may be a problem. David Nelson, of potato packers Branston Ltd, said 60% of the chemicals approved for use on potatoes in 1993 are no longer on the approved lists.

There are also pressures from retailers and other agencies such as SEPA to grow potatoes with less risk to the environment, including safeguarding water quality and preventing soil erosion. There are also questions raised about the crop’s carbon footprint.

“In general vegetables compare favourably with meat and produce low CO2 emissions. But the industry does use refrigerants which are greenhouse gases and 1.25% of fertilisers are lost as nitrous oxides which are 310 times as harmful as CO2,” he said.

The challenges of accelerating changes in climate and diseases is one which Professor Peter Gregory, chief executive of SCRI, is only too well aware.

“Blight pathogens are an example. Much of it fits into a climate change scenario which we have to understand in terms of increasing rainfall and higher temperatures, said Professor Gregory.

“We have to be able to look ahead and much of the work funded by SEERAD helps us to develop genetic markers so that we can quickly identify change and then tweak research in the right direction.

The information we amass is important to potato breeders, for example, who are working hard to breed in disease resistance.”

Some of the new varieties will be targeted for export markets. A group of Egyptian growers and potato specialists were at Gourdie yesterday on a visit organised by fertiliser company Yara and potato specialists Greenvale.

Tarek Osama, of Yara Egypt, said, “We are big consumers of potatoes with much of the domestic supplies coming from the old production areas in the delta.

“But the real expansion is in the new growing areas on sandy soils near Cairo where over the last 10 years the area has increased from nothing to 50,000 hectares.

“These are grown for seven or eight processors including Fritolay and Farmfrites. One of my colleagues here is responsible for growing 400 hectares and the whole area is irrigated using centre pivots, micro sprinklers or drip irrigation.”

Hopefully the interest they were showing in the variety plots will lead to new orders for seed potatoes.