Pesticide usage crops: Outdoor vegetable crops 2015

Summary

This is the eighth 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) and 2013 (Withers et al., 2014). Information on all aspects of pesticide usage was collected from 44 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 2015 was an estimated 1,203 hectares; a 14% decrease compared with 2013.

Totals of 97 products and 72 active substances were recorded in use in this survey. By comparison with 2013, the pesticide-treated area decreased by 17%, to 11,432 spray hectares, while the quantity of pesticide (active substances) decreased by 26% to approximately 4,429 kilograms. Both the fungicide-treated area and the quantity of fungicide active substances applied decreased by 11%. The area treated with herbicides and desiccants decreased by 25% and the weight applied decreased by 28%. The insecticide-treated area decreased by 10% and the weight of insecticide active substances decreased by 33%. The area treated with molluscicides decreased by 28%. However, the quantity applied increased by 63% when compared with 2013 but decreased by 37% when compared with 2011. This is possibly due to the high application rates of these products. The area of vegetable crops grown from treated seed (direct sown or propagated and transplanted) decreased by 9% since 2013 while the weight of active substances used significantly decreased by 51%.

In 2015, Northern Ireland had a very wet autumn/winter and many growers could not get onto the ground to spray throughout this period. This led to a wider problem with rots such as Xanthamonas and leaf spots on Brassicas. During the same period, root vegetables such as carrots and parsnips were unable to be harvested in some cases as growers could not access nor use machinery on the fields.

Fungicides, applied to 25% of the pesticide-treated area, accounted for 24% of the weight of pesticides applied. Herbicides and desiccants accounted for 38% of the pesticide-treated area and 60% of the total quantity of pesticides used. Insecticides,

applied to 28% of the pesticide-treated area, accounted for 16% of the total quantity of pesticides used. 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 2015 accounted for 9% of the pesticide-treated area representing less than 1% of the quantity of active ingredients applied.

Carrots and parsnips collectively accounted for 62% of the quantity of fungicide active ingredients applied, representing 58% of the area treated with fungicides, with the active substance formulation azoxystrobin / difenoconazole being most frequently used on these vegetable crops. Brassica crops received 16% of the total weight of fungicides applied, representing 18% of the area of vegetable crops treated with fungicides. The single most commonly used fungicide active substance applied to brassicas was the triazole protectant and curative fungicide difenoconazole, primarily for general fungal control.

Linuron was the herbicide/desiccant active ingredient most commonly applied to outdoor vegetable crops, particularly carrots and parsnips. Overall, 41% of all herbicide/desiccant applications were applied to carrot and parsnip crops, with a further 20% applied to turnips and swedes.

Carrots and parsnips collectively accounted for 58% of the insecticide-treated area, representing 43% of the quantity of insecticide active substances applied. Turnips and swedes, which accounted for only 3% of the insecticide-treated area, represented 40% of the quantity applied, mainly due to garlic extract being applied at high application rates for insect deterrence. Leafy and flowerhead brassicas accounted for 27% of the insecticide-treated area representing 12% of the weight of insecticides applied. The carbamate insecticide pirimicarb accounted for 33% of all insecticide active substances applied to brassica crops, primarily to control aphids. Pyrethroids were, by far, the most frequently used of all insecticide active substances, with lambda-cyhalothrin being the most frequently used insecticide.

With exception of the use of garlic oil in brassica crops for the control of root flies there were no records of biopesticides/biological control in NI vegetable crops in 2015. 

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 2015 report (Lavery et al., 2016). 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) would be an estimated <0.25%.

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 azoxystrobin/chlorothalonil, cyproconazole / trifloxystrobin, fenhexamid and sulphur, the herbicide chlorpropham, the insecticide spinosad and the molluscicide metaldehyde were all recorded as used in 2015. Conversely, a number of active substances and formulated mixtures which were used in 2013 have not been recorded during this survey period. These include the fungicides dimethomorph (as an individual active substance) and iprodione (as a fungicide spray), the herbicides bentazone and MCPB, the insecticides diflubenzuron and dimethoate and the seed treatment imidacloprid.