Pesticide Usage Report: Outdoor Vegetable Crops 2023

SUMMARY

This is the twelfth survey of pesticide usage on outdoor vegetable crops in Northern Ireland, providing comparative data to that obtained in the previous surveys in 1991 (Jess et al., 1993), 1995 (Kidd et al., 1998), 1999 (Kearns et al., 2002), 2004 (Kearns et al., 2005), 2007 (Withers et al., 2009), 2011 (Withers et al., 2012), 2013 (Withers et al., 2014), 2015 (Lavery et al., 2016), 2017 (Kirbas et al., 2018), 2019 (Lavery et al., 2020) and 2021 (Kirbas et al., 2022)  Information on all aspects of pesticide usage was collected from 36 holdings throughout the province, representing 41% of the total population of outdoor vegetable crop growers in Northern Ireland (Table 1). Quantitative data have been adjusted to provide estimates of total pesticide usage. The area of outdoor vegetable crops grown in Northern Ireland in 2023 was an estimated 1,178 hectares; a 12% increase compared with 2021, though similar to the area recorded in 2017.  Carrots, parsnips and leafy and flowerhead brassicas continue to be the dominant outdoor vegetable crops grown in Northern Ireland, accounting for 65% of the area grown, 85% of the area treated with pesticides and 78% of the weight applied.

Totals of 63 products and 46 active substances were recorded in use in this survey. Although the area of outdoor vegetable crops grown in 2023 increased when compared with 2021, the pesticide-treated area decreased by 33% to 10,132 spray hectares, and the quantity of pesticide active substances decreased by 36% to 2,826 kilograms. The fungicide-treated area decreased by 45% and the quantity of fungicide active substances applied decreased by 52%. The area treated with herbicides decreased by 25% and the weight applied decreased by 29%. The insecticide-treated area decreased by 35% and the weight of insecticide active substances decreased by 15%.

The area of vegetable crops grown from treated seed (direct sown or propagated and transplanted) decreased by 20% since 2021, however, the weight of active substances used decreased by 84%, from 11 kilograms to two kilograms.  This was mainly due to the withdrawal of cymoxanil/fludioxonil/metalaxyl-m and tefluthrin as a seed dressing on these crops.

Fungicides, applied to 27% of the pesticide-treated area, accounted for 24% of the weight of pesticides applied. Herbicides accounted for 33% of the pesticide-treated area and 71% of the total quantity of pesticides used. Insecticides, applied to 30% of the pesticide-treated area, accounted for only 3% of the total quantity of pesticides used. Growth regulators and molluscicides both accounted for less than 1% of the pesticide treated area and the quantity applied.  Seed treatments applied to outdoor vegetable crop seeds grown in 2023 accounted for 9% of the pesticide-treated area, representing less than 1% of the quantity of active substances applied.

Carrots and parsnips accounted for 42% of the of the area treated with fungicides, and 49% of the quantity of fungicide active ingredients applied, with prothioconazole, fluopyram, azoxystobin/difenoconazole, difenoconazole/fluxapyroxad and metalaxyl-M being the active substances most used on these crops. Leafy and flowerhead brassica crops accounted for 52% of the area of vegetable crops treated with fungicides, and 39% of the total weight of fungicides applied.  The three fungicide active substances most commonly applied to brassicas were the curative triazole fungicides prothioconazole and difenoconazole, and the systemic translaminar fungicide azoxystrobin, primarily for general disease control.

The pre-emergent herbicide alconifen, and the isoxazolidinone residual herbicide clomazone, were the herbicide active substances most commonly applied to outdoor vegetable crops.  Overall, 54% of all herbicide applications were applied to carrot and parsnip crops, with 20% applied to brassica crops, representing 57% of the total weight of herbicides applied.

Carrots and parsnips accounted for 55% of the insecticide-treated area and 51% of the quantity of insecticide active substances applied.  Leafy and flowerhead brassicas accounted for 30% of the insecticide-treated area representing 32% of the weight of insecticides applied. Turnips and swedes accounted for 14% of the insecticide-treated area representing 17% of the weight of insecticides used.  The insecticide active substance most commonly used was lambda-cyhalothrin, being applied extensively for control of carrot fly (Chamaepsila rosae), aphids and general insect control. 

The only molluscicide active substance used was ferric phosphate.  Maleic hydrazide was the only growth regulator used, applied exclusively to parsnip crops.  There was no recorded use of biopesticides/biological controls in Northern Ireland vegetable crops in 2023.

Crops which were propagated from seed and/or grown under glass or polythene for the duration of their life cycle are recorded in the Edible Protected Crops in Northern Ireland 2023 report (Kirbas et al., 2024). These crops have previously been included in the totals for outdoor vegetable crops. The proportion of total treated area of vegetable crops attributed to propagation (edible protected) is estimated at <1%.

A number of new active substances and formulated mixtures, which were not recorded in the previous report, have been used during this survey period. These include the fungicide formulation difenoconazole/fluxapyroxad, and the insecticide active substances acetamiprid and esfenvalerate.

Conversely, a number of active substances and formulated mixtures which were used in 2021 have not been recorded during this survey. These include the fungicide actives isopyrazam and metconazole, the herbicide actives bromoxynil, clopyralid, cycloxydim, dimethenamid-P/metazachlor and ethofumesate, the insecticide actives chlorantraniliprole, garlic extract, indoxacarb and pirimicarb, and the seed treatment actives cymoxanil/fludioxonil/metalaxyl-m and tefluthrin.