Pesticide usage - arable crops and potato stores 2018: survey results

2018 Potato storage and pesticide usage

Seed potatoes

• An estimated 408,870 tonnes of seed potatoes were stored in Scotland in 2018, compared with an estimated 415,023 tonnes stored in 2016
• 67 per cent of seed potatoes were stored in refrigerated stores, 33 per cent in ambient ventilated stores and less than one per cent in unventilated stores (Figure 5)
• All seed potatoes sampled in 2018 were stored in boxes
• Overall, 28 per cent of seed potatoes received a pesticide treatment in store
• The percentage of seed potatoes receiving an in-store pesticide treatment was 33 per cent in refrigerated stores and 18 per cent in ambient ventilated stores.  No treatments were recorded on unventilated stores (Table 1)
• Two fungicides (imazalil and thiabendazole) and one growth regulator (ethylene) were encountered in seed potatoes (summary below)
• Imazalil and thiabendazole are applied as sprays to tubers.  Ethylene is applied as a gas in the store
• Reasons for use were supplied for 62 per cent of the crop which was treated with fungicides.  27 per cent for dry rot, gangrene and skin spot, and 20 per cent for silver scurf
• The only specified reason for ethylene use was sprout suppression.  It is used, in conjunction with modified temperatures, to increase the number of sprouts and stems, resulting in increased tuber numbers

Summary of estimated pesticide use on seed potatoes in store:

(1) Ethylene is not approved as a pesticide for use in seed potato stores under PPP regulations.  However, it is approved as a commodity substance for plant growth regulation in post-harvest crops under COPR⁽⁶⁾

Figure 5: Seed potato storage by type – 2018

Ware potatoes

• An estimated 697,021 tonnes of ware potatoes were stored in Scotland in 2016.  This is a four per cent decrease compared with the estimated 725,263 tonnes stored in 2016
• 80 per cent of ware potatoes were stored in refrigerated stores, 18 per cent were stored in ambient ventilated stores and two per cent in unventilated stores (Figure 6)
• All ware potatoes sampled were stored in boxes
• 13 per cent of ware potatoes received a pesticide treatment in store
• The percentage of ware potatoes receiving an in-store pesticide treatment was 13 and 14 per cent in refrigerated stores and ambient ventilated stores respectively.  No treatments were recorded on unventilated stores (Table 1)
• One fungicide (thiabendazole) and three growth regulators (chlorpropham, ethylene & spearmint oil) were encountered in ware potato stores (summary below)
• Thiabendazole is applied as a spray to tubers. Ethylene is applied as a gas, and both chlorpropham and spearmint oil are applied as a fog to stores
• No reasons were supplied for the use of fungicides on ware potatoes
• The only specified reason for use of growth regulators was sprout suppression

Summary of estimated pesticide use on ware potatoes in store:

Figure 6: Ware potato storage by type – 2018