Pesticide usage report: Outdoor vegetable crops 2021

SUMMARY

This is the eleventh 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) and 2019 (Lavery et al., 2020).  Information on all aspects of pesticide usage was collected from 37 holdings throughout the province, representing 40% 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 2021 was an estimated 1,049 hectares; a 4% decrease compared with 2019.

Totals of 64 products and 50 active substances were recorded in use in this survey. By comparison with 2019, the pesticide-treated area increased by 18%, to 15,100 spray hectares and the quantity of pesticide (active substances) decreased by 30% to 4,423 kilograms. The fungicide-treated area increased by 62% and the quantity of fungicide active substances applied increased by 41%. The area treated with herbicides decreased by 10% and the weight applied decreased by 33%. The insecticide-treated area increased by 43%, though the weight of insecticide active substances decreased by 89%, primarily due to the withdrawal of oxamyl, pymetrozine and thiacloprid since 2019. The only molluscicide active substance used in 2021 was ferric phosphate. Maleic hydrazide was the only growth regulator used in 2021, applied exclusively to 2 hectares of parsnip crops.

The area of vegetable crops grown from treated seed (direct sown or propagated and transplanted) decreased by 24% since 2019 and the weight of active substances used decreased by 13%, from 13 kilograms to 11 kilograms, mainly due to the withdrawal from use of thiram which was used extensively as a seed treatment in 2019.

Fungicides, applied to 33% of the pesticide-treated area, accounted for 33% of the weight of pesticides applied. Herbicides accounted for 30% of the pesticide-treated area and 64% of the total quantity of pesticides used. Insecticides, applied to 29% of the pesticide-treated area, accounted for only 2% of the total quantity of pesticides used. Growth regulators accounted for less than 1% of the pesticide treated area and the quantity applied. Molluscicides accounted for less than 1% of both the total pesticide-treated area and the quantity of pesticides applied. Seed treatments applied to outdoor vegetable crops grown in 2021 accounted for 7% of the pesticide-treated area, representing less than 0.1% of the quantity of active ingredients applied.

Carrots and parsnips collectively accounted for 85% of the quantity of fungicide active ingredients applied, representing 90% of the area treated with fungicides, with the active substance prothioconazole being most frequently used. Brassica crops received 10% of the total weight of fungicides applied, representing 7% of the area of vegetable crops treated with fungicides. The two most commonly used fungicide active substances applied to brassicas were the curative triazole fungicides prothioconazole and broad-spectrum fungicide mixture azoxystrobin/difenoconazole, primarily for general disease control.

Alconifen, clomazone, metribuzin and pendimethalin were the herbicide active ingredients most commonly applied to outdoor vegetable crops, particularly to carrot and parsnip crops. Overall, 81% of all herbicide applications were applied to carrot and parsnip crops.

Carrots and parsnips collectively accounted for 83% of both the insecticide-treated area and the quantity of insecticide active substances applied, mainly due to the pyrethroid insecticide lambda-cyhalothrin being applied extensively to carrots and parsnip crops for control of carrot fly.  Turnip and swede accounted for 10% of the insecticide-treated area representing 2% of the weight of insecticides used. Leafy and flowerhead brassicas accounted for 6% of the insecticide-treated area representing 14% of the weight of insecticides applied. With exception of the use of garlic in carrots for general insect control there were no records of biopesticides/biological controls in NI vegetable crops in 2021.

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 2021 report (Kirbas et al., 2022). 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 SDHI fungicide fluopyram, used as a nematicide in carrot and parsnip crops and the herbicide actives clopyralid, ethofumesate, isoxaben and s-metolachlor.

Conversely, a number of active substances and formulated mixtures which were used in 2019 have not been recorded during this survey period. These include the fungicide actives mancozeb/metalaxyl-m and the herbicide actives diflufenican, imazamox/pendimethalin, desmedipham/ethofumesate/phenmedipham, lenacil, phenmedipham, and propaquizafop. There are also a number of actives for which approvals have since expired from the 2019 survey period which were not recorded in this survey period. These include the fungicide actives chlorothalonil/metalaxyl-m and fenpropimorph; the insecticide actives oxamyl, pymetrozine and thiacloprid; the herbicide actives chloridazon, chlorpropham and diquat and the seed treatment active thiram.