Lead researcher and consultant, Scottishpotatoes.org, a partnership of SRUC, James Hutton Institute and SASA.

Who knows what a normal potato season looks like? But we can be sure it doesn’t look like 2021 and we have only just started.

A long hard winter was appreciated, reducing aphids to low numbers and hopefully getting on top of groundkeepers in fields where the frost could get to them. But the cold and dry weather continued into April.

With excellent soil conditions many growers planted crops into cold seed beds with the expectation of warmer weather just around the corner. But it just didn’t happen and the seed tubers just sat there.

Many began to question whether they would have been better in the shed, rather than planted in the field.

April turned into May and the weather remained cold, soils still barely above the usually recommended soil temperature for planting of 7°C. Then it got wet. Very wet. And all action ground to a halt for several weeks.

Meanwhile, the crop sat in cold, wet fields. Thankfully, conditions finally improved towards the end of the month and most have now completed their planting. A long hard slog for many.

What will be the outcome from this extended planting season? We have, in effect, two crops planted this year. The early crop, which took longer to emerge than any crop I have ever known and the later crop which will hopefully grow fast in an attempt to catch up.

The early planted crop will need attention. Herbicides have been delayed and crops could be damaged by residual and contact herbicides. Not ideal for a crop that's taken long to emerge.

The long slow emergence is also ideal for development of some diseases and crops need to be inspected to understand what’s happening. Look for rhizoctonia exhibiting itself as dark brown lesions on stems below ground, sometimes pruning through the stem completely and leading to gappy, uneven crops.

Another issue we are likely to see more of is free living nematodes (FLN) feeding damage, especially as Vydate granules (oxamyl) were withdrawn for use abruptly in December.

The slow emergence and moist conditions are ideal for these nematodes to feed on roots and stems. If you find light-brown coloured, often thickened, or distorted roots and stems it could well be FLN feeding damage.

Blackleg is also well known to be worse in waterlogged soils and we can expect to see more of this disease. Early planted seed crops could well see roguers kept busy.

Even in crops which have emerged largely unscathed from disease, we are seeing more variation in emergence than usual. This will make timing of all applications more difficult.

Perhaps most important for prepack growers, irrigation is even more difficult. There has been a lot of Maris Piper planted this year – this variety has many weaknesses, but most important is susceptibility to scab.

Irrigation to field capacity is needed to keep on top of common scab. Usually it is required for four weeks from tuber initiation, but in 2021 with crops emerging less evenly, it might be six weeks before the risk phase passes.

That might mean an extra three passes! More cost and simple hard graft. Growers relying on rainfall (ie luck!) for control, need to be even luckier than usual!

What are the prospects for the later planted crops? We hope these emerge quickly into warm conditions and sunny weather. But day-length will start shortening soon and some of the best days to photosynthesise will be past.

These crops are also likely to be emerging into an environment with aphids and blight ready to infect unprotected foliage.

Long-term trials in Aberdeen show the optimum date for planting sits around mid-April. There is a small reduction in yield potential entering May but it is not until the second half of the month that there is a noticeable decline. Unfortunately, June planted crops have even lower yields.

To an extent this can be offset, particularly in seed crops by burning down a little later. The effect on tuber numbers is unknown as yet. This is largely influenced by conditions during initiation.

Only a fool would forecast the outcome for the 2021 crop, but I’m expecting more problems and quality issues than usual and few bumper yields. For those who want to see a silver lining, a late season appears to have tightened the market!