UK: Potato crops under threat as blight pressure soars

Potato growers are facing soaring blight pressure in their crops following a massive increase in the number of Smith Periods, combined with difficulties in applying vital protectant fungicide sprays as a result of the wet weather.

Adverse weather conditions, including prolonged periods of heavy rain, have continued to interrupt blight spraying activities in all regions.

Potato Council blight specialist Gary Collins says there were 5,587 cumulative Smith Period events to July 11, 2012, compared with 1,034 by the same date last year.

He says: “It is clear that, not only is there high pressure, but the high pressure season has been driven by the last two to three weeks. The number of suspected blight samples sent in by blight scouts and monitors has more than doubled in a week, rising from around 40 to more than 100.”

Early sampling

Results from early sampling of blight infections from Cornwall show strains 13_A2 and 6_A1 to be present.

Independent potato agronomist John Sarup, of Spud Agronomy, who advises growers in the north of England, says he is seeing a lot of blight in potato crops as growers battle to maintain optimum spray intervals in the wet weather.

Some growers have fitted sprayers with wider tyres in a bid to enable machines to travel in saturated field conditions and in doing so have sacrificed potato rows, he says.

In Cheshire and Lancashire, growers struggling to keep on top of blight outbreaks are following behind the sprayer with a knapsack and spraying off blighted areas of crop with diquat.

In Yorkshire, however, weather conditions have improved this week and growers are starting to get blight programmes back on track.

"2007 is remembered as an extremely wet season but having such a long period of Smith Periods as we’ve seen this season is pretty unusual,” says Mr Sarup.

This season’s wet weather has hampered growth and led to earlier tuber initiation, which means blight programmes must include fungicides with foliar and tuber blight activity, advises Dr Dominic Lamb of Gowan.

Extended plantings

He says: “It has not been an easy season for potato growers, with extended plantings plus a dry March which hampered emergence and a very wet April, May and June which hampered growth.

"This has meant crops have been struggling and in Scotland crops are still not meeting across the rows. This has lead to much earlier tuber initiation and means the blight programme must include fungicides which have proven foliar and tuber blight control.”