Pesticide usage in Scotland: arable crops and potato stores 2016

2016 Potato storage and pesticide usage

Seed Potatoes

• An estimated 415,023 tonnes of seed potatoes were stored in Scotland in 2016. This represents a four per cent increase from the estimated 398,780 tonnes stored in 2014
• 61 per cent of seed potatoes were stored in refrigerated stores, 37 per cent in ambient ventilated stores and two per cent in unventilated stores ( Figure 5)
• More than 99 per cent of seed potatoes were stored in boxes; the remainder (ca. 3 tonnes) were held in bulk stores
• Overall, 47 per cent of seed potatoes received a pesticide treatment in store
• The percentage of seed potatoes receiving an in-store pesticide treatment was 34, 69 and 45 per cent in refrigerated stores, ambient ventilated stores and unventilated stores respectively
• Two fungicidal formulations (imazalil and imazalil/thiabendazole) and one growth regulator (ethylene) were encountered in seed potato stores (summary below)
• Imazalil and imazalil/thiabendazole are applied as sprays to tubers. Ethylene is applied as a gas in the store
• Reasons for use were supplied for 77 per cent of the crop which was treated with fungicides (imazalil and imazalil/thiabendazole). The most commonly specified diseases targeted with these treatments were dry rot ( Fusarium spp.) and silver scurf ( Helminthosporium solani ) ( Figure 6)
• No reasons were supplied for use of ethylene. Ethylene has a growth regulatory function in seed potatoes. 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 ⁽⁷⁾

Figure 5 Seed potato storage by type - 2016

Figure 6 Reasons for use of fungicides on stored seed potatoes (where specified) - 2016

Ware Potatoes

• An estimated 725,263 tonnes of ware potatoes were stored in Scotland in 2016. This is a three per cent decrease compared to the estimated 747,902 tonnes stored in 2014.
• 77 per cent of ware potatoes were stored in refrigerated stores, 21 per cent were stored in ambient ventilated stores and two per cent in unventilated stores ( Figure 7)
• All of the ware potatoes sampled were stored in boxes
• 11 per cent of ware potatoes received a pesticide treatment in store
• The percentage of ware potatoes receiving an in-store pesticide treatment was 8 and 20 per cent in refrigerated stores and ambient ventilated stores respectively. No treatments were recorded in unventilated stores
• Two fungicidal formulations (imazalil and imazalil/thiabendazole) and two growth regulators (chlorpropham and ethylene) were encountered in ware potato stores (summary below)
• Imazalil and imazalil/thiabendazole are applied as sprays to tubers. Ethylene is applied as a gas, and chlorpropham as a fog, to stores
• Reasons for use were supplied for 86 per cent of the crop which was treated with fungicides (imazalil and imazalil/thiabendazole). The only specified reason for use of these formulations was general disease control
• Chlorpropham is a growth regulator and all use was reported to be for tuber sprout suppression. No reasons were supplied for use of ethylene, which is also a growth regulator used to suppress sprouting in ware potatoes

Summary of estimated pesticide use on ware potatoes in store

(1) This formulation is not approved on ware potatoes. It was applied to seed crops which were later reclassified as ware.

Figure 7 Ware potato storage by type - 2016