Pesticide usage in Scotland: arable crops and potato stores 2020

Executive summary

This report presents information from a survey of pesticide use on stored potatoes harvested in Scotland in 2020. Data were collected from 81 growers, who collectively cultivated 33 per cent of the area of potatoes grown in Scotland. Pesticide use in potato stores was recorded for crops grown for seed production and for consumption (ware potatoes). Ratio raising was used to produce estimates of national pesticide usage from the sample data.

The overall estimated quantity of potatoes stored in 2020 was 987,615 tonnes (as of end of November). There has been a significant change in survey estimation methodology which must be taken into account when comparing storage data from this survey and previous surveys. When this methodological change is accounted for, the total tonnes stored in 2020 is 13 per cent higher than in the previous survey in 2018. Seed potato storage increased by 25 per cent to ca. 391,100 tonnes, influenced by slower domestic and non-EU seed sales. Ware potato storage increased by six per cent to ca. 596,400 tonnes when compared to the previous survey. This increase in storage is also possibly influenced by covid restrictions, which depressed consumer demand for ware potatoes during 2020.

Sixty per cent of seed and 86 per cent of ware potatoes sampled in 2020 were stored in refrigerated stores. The majority of the remaining stores were ambient ventilated stores. All the potatoes surveyed were stored in boxes.

The proportion of seed potatoes treated with a pesticide in 2020 was 39 per cent, this is within the range of estimated use in previous surveys (28 per cent treated in 2018 and 47 per cent treated in 2016 and 2014). However, the proportion of stored ware potatoes treated with a pesticide was six per cent, approximately half that of the 13 per cent in 2018 and 11 per cent in 2016.

As in 2018, the principal pesticide encountered on seed potatoes was the fungicide imazalil applied to an estimated 38 per cent of the stored crop for control of a range of tuber diseases. The only other pesticide encountered was the fungicide thiabendazole, applied to four per cent.

The principal pesticide used on ware potatoes in 2020 was the growth regulator ethylene applied to an estimated four per cent of the stored ware crop, compared with eight per cent in 2018 and one per cent in 2016. This is the first survey since the withdrawal of the growth regulator Chlorpropham which had a final use of date of 8^th October 2020. Chlorpropham had been the principal active substance in 2018 and 2016 (applied to 11 and 17 per cent respectively). The sprout suppressant spearmint oil was applied to an estimated two per cent of the stored ware potato crop in both 2020 and 2018. Less than 0.5 per cent of the stored crop was treated with a fungicide in 2020.