Irrigation and free living nematodes can play a role in increasing blackleg infection in potato crops, according to Professor Ian Toth of the James Hutton Institute. Ewan Pate reports.
At the AHDB potato conference Prof Toth highlighted results from a major AHDB and Scottish Government-funded project, which ran between 2014 and 2017, looking at all aspects of the spread of blackleg.
To examine the role of water, a series of trials were planted with high grade mini tubers as a means of ensuring uninfected seed. Irrigated and un-irrigated plots were then compared and it was discovered that the irrigated plots had significantly more infection. In one case infection levels reached 7% even though the water had come from a bore hole. Contaminated water seemed unlikely in this case.
“This could be taken to prove that the infection had been in the soil and the irrigation had made the problem worse by allowing the bacteria to spread in the soil. This has led us to ask if irrigation management could lead to reduction in blackleg in ware crops and we are now working with Mark Stalham of NIAB-CUF on this", said Prof Toth.
As regards free-living nematodes, Prof Toth said they were present in all soils but some acted more effectively than others as pathogen vectors.
“There can be ten times as many pectobacterium in the presence of free living nematodes and we need to do more work in this area,” he said. Scottish Government has funded a new blackleg project and the role of nematodes would be examined further.
James Thorburn of Farewells Farm on South Ronaldsay told the conference that he had now become only the second seed potato grower on Orkney. Formerly head of seed buying with Greenvale AP at Burrelton he had travelled the world looking at seed production in isolated regions. Countries such as Australia and the United States had big areas of land to choose from but even in Prince Edward Island in Canada where potatoes are grown one year in three he had found that growing seed on an and adjacent island with no potato production was showing seed health benefits.
“There were obvious advantages of growing in isolation. Our farm near St Margaret’s Hope is 58.9 degrees North, there is no large scale ware growing, low blight and virus and only one other seed grower.
To minimise the risk only PB1 and PB2 grade mini tubers are planted. In 2017, the first year of production, 4000 tubers were planted from three varieties and this year 55,000 tuber from eight varieties. The crop is harvested into trays or boxes and 200 tuber samples from each batch sent to SASA in Edinburgh for testing.
Potato consultant Stuart Wale said he was very interested in the project but advised Mr Thorburn to stick to PB1 and PB2 grades and not multiply stocks to a lower grade.
“I recall when there were quite a few growers in Orkney and blackleg was often an issue,” he said.