Pestcide usage report: Outdoor vegetable crops 2017

SUMMARY 

This is the ninth 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) and 2015 (Lavery et al., 2016).  Information on all aspects of pesticide usage was collected from 42 holdings throughout the province.  Quantitative data have been adjusted to provide estimates of total pesticide usage.  The area of outdoor vegetable crops grown in Northern Ireland in 2017 was an estimated 1,178 hectares; a 2% decrease compared with 2015.

Totals of 93 products and 64 active substances were recorded in use in this survey.  By comparison with 2015, the pesticide-treated area increased by 6%, to 12,173 spray hectares, while the quantity of pesticide (active substances) decreased by 5% to approximately 4,208 kilograms.  The fungicide-treated area decreased by 19% and the quantity of fungicide active substances applied decreased by 33%.  The area treated with herbicides increased by 10% and the weight applied increased by 8%.  The insecticide-treated area increased by 4% and the weight of insecticide active substances decreased by 23%.  The area treated with molluscicides increased almost 3-fold and the quantity applied increased 5-fold when compared with 2015. This is possibly due to an increased use of the active substance metaldehyde which is applied at a higher dose than previously reported actives applied at lower doses. Growth regulators were recorded in use for the first time since 2013 and accounted for less than 1% of the total area and total quantity applied.

The area of vegetable crops grown from treated seed (direct sown or propagated and transplanted) increased by 59% since 2015 and the weight of active substances used significantly increased by almost 5-fold. In 2015, seed treatments applied to propagated vegetables to be transplanted outdoors were recorded only in the edible protected survey. In this survey, any seed treated at propagation stage then transplanted outdoors is also included in the seed treatment totals.

Fungicides, applied to 19% of the pesticide-treated area, accounted for 17% of the weight of pesticides applied.  Herbicides accounted for 39% of the pesticide-treated area and 69% of the total quantity of pesticides used.  Insecticides, applied to 27% of the pesticide-treated area, accounted for 13% of the total quantity of pesticides used.  Growth regulators accounted for less than 1% of the pesticide treated area and quantity applied. Molluscicides accounted for 1% of both the total pesticide-treated area and the quantity of pesticides applied.  Seed treatments applied to outdoor vegetable crops grown in 2017 accounted for 13% of the pesticide-treated area representing less than 1% of the quantity of active ingredients applied. 

Carrots and parsnips collectively accounted for 61% of the quantity of fungicide active ingredients applied, representing 61% of the area treated with fungicides, with the active substance prothioconazole being most frequently used on carrots and active substance formulation azoxystrobin/difenoconazole being most frequently used on parsnips.  Brassica crops received 25% of the total weight of fungicides applied, representing 25% of the area of vegetable crops treated with fungicides.  The single most commonly used fungicide active substance applied to brassicas was the curative fungicide difenoconazole and active substance formulation azoxystrobin/difenoconazole, primarily for general fungal control.

Clomazone and linuron were the herbicide active ingredients most commonly applied to outdoor vegetable crops, particularly to turnips and swede and carrots and parsnips respectively. Overall, 52% of all herbicide applications were applied to carrot and parsnip crops, with 23% applied to turnips and swedes. 

Carrots and parsnips collectively accounted for 69% of the insecticide-treated area, representing 91% of the quantity of insecticide active substances applied mainly due to garlic extract being applied at high application rates for the control of nematodes.    Leafy and flowerhead brassicas accounted for 23% of the insecticide-treated area representing 8% of the weight of insecticides applied.  The pyrethroid insecticide lambda-cyhalothrin was the most frequently used insecticide accounting for 45% of all insecticide active substances applied to carrot crops, primarily for general insect control.

With exception of the use of garlic oil in carrots for the control of nematodes there were no records of biopesticides/biological control in NI vegetable crops in 2017. 

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 2017 report (Lavery et al., 2018).  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 <0.20%.

A number of new active substances and formulated mixtures, which were not recorded in the previous report have been used during this survey period.  The fungicides chlorothalonil/cyproconazole, cyprodinil/isopyrazam, epoxiconazole/metconazole and isopyrazam, the herbicides bentazone, bromoxynil, clethodim, dimethenamid-P/metazachlor, ethametsulfuron-methyl (not currently approved for use in the UK), fluroxypyr/halauxifen-methyl, metsulfuron-methyl/tribenuron-methy, pyridate and S-metolachlor, insecticides acetamiprid, chlorantraniliprole and cyantraniliprole and the growth regulator trinexapac-ethyl were all recorded as used in 2017.  Conversely, a number of active substances and formulated mixtures which were used in 2015 have not been recorded during this survey period.  These include the fungicides azoxystrobin/chlorothalonil, copper oxychloride, cyproconazole/trifloxystrobin, fenhexamid, mancozeb, mandipropamid and sulphur, the herbicides chloridazon, ethofumesate ioxynil (withdrawn 2016), triflusulfuron-methyl and the insecticide oxamyl.