Pesticide usage report: Edible protected crops 2017

SUMMARY 

This is the second survey examining pesticide usage practices on edible protected crops (excluding soft fruit) grown under permanent protection in Northern Ireland, providing comparative data to that obtained in the previous survey in 2015 (Lavery et al., 2016).  A previous report in 1991 included information on pesticide use on vegetable crops, strawberries and protected ornamental crops: Protected Crops (edible and ornamental), (Kidd et al., 1993).  For this survey, a number of different vegetable crops and tomatoes, which were propagated and/or grown under permanent cover of glass or polythene until harvested, were included.  Information relating to pesticide use on soft fruit crops is recorded in the pesticide usage report Soft Fruit Crops, 2016 (Lavery et al., 2017).

Protected crop cultivation is a very minor sector of agricultural production in Northern Ireland and includes a range of crops grown on relatively small areas which receive varying degrees of pesticide application.  These factors lead to greater statistical uncertainty associated with the estimates produced and, whilst these data give an indication of pesticide use in this sector, they are less statistically robust than the estimates from the other reports in this series and should be interpreted accordingly.  Also, unlike the previous survey in 2015, this report contains multiple-cropping areas, where successive crops are produced from the same basic area.  This may result in figures which differ from the basic farm level information contained in the farm census. 

Data were collected from eleven holdings, representing 63% of the total area of edible protected crops grown in Northern Ireland.  Holdings were selected from information contained in the Northern Ireland Agricultural Census, June 2017 (Anon., 2018) and Single Farm Payment returns, 2017.  Raising factors have been applied to estimate national pesticide usage from sampled data.  Data relating to individual crop types have not been published due to the small cultivation and sample areas and the possibility of identifying growers.

A total of twelve fungicide active substances including formulated fungicide mixtures were recorded in use on edible protected crops in Northern Ireland in 2017.  Fosetyl-aluminium/propamocarb hydrochloride and Mancozeb/Metalaxyl-M each represented 11% of the fungicide-treated area.  However, they accounted for 27% and 18% of the weight of fungicides applied, respectively, exclusively on brassica and lettuce crops for general disease and mildew control.  Other fungicides used were azoxystrobin, boscalid/pyraclostrobin, chlorothalonil, cyprodinil/fludioxonil, dimethomorph, fenhexamid, fluopicolide/propamocarb hydrochloride, mandipropamid and tolclofos-methyl (Tables 7 and 8).

In 2015, the dinitroaniline herbicide pendimethalin was the only herbicide applied,   accounting for an estimated 4% of the total pesticide-treated area and 1% of the total weight of pesticides applied.  There was no herbicide use recorded in 2017.

Chlorpyrifos, an organophosphorus insecticide and acaricide, was applied exclusively to brassica crops for control of cabbage root fly (Delia radicum).  The area treated with this active substance accounted for 5% of the insecticide-treated area but represented 98% of the total weight of insecticides applied.  This was due to the high rate of application as a drench treatment to brassicas during the propagation stage when the plants were still in module trays.  Indoxacarb, pymetrozine, spinosad and spirotetramat were applied exclusively to lettuce crops for control of aphids, caterpillars and thrips, accounting for 95% of the insecticide-treated area but only 2% of the weight of insecticides applied.

The soil fungus biopesticide, Gliocladium catenulatum, was applied as a drench to the compost in module trays containing brassica plant seeds exclusively for general disease control.  The predatory mite, Neoseiulus californicus, used exclusively on tomato plants for control of two-spotted spider mite (Tetranychus urticae), was also recorded but it should be noted that due to the nature of this control method, only the treated-area has been recorded and not a weight of application.  The bacterial fungicide Bacillus subtilis was the only other biopesticide used, exclusively on lettuce crops, for control of Botrytis cinerea.

Seed treatments, which accounted for 4% of the total pesticide-treated area and 3% of the weight of pesticides applied, were applied to all crops with tomatoes being the only exception.  Thiram and thiamethoxam both accounted for 31% the seed-treated area, though thiamethoxam represented 95% of the weight of seed treatments applied.  Lettuce seeds accounted for an estimated 93% of the area treated with thiamethoxam.

Azoxystrobin was the only fungicide applied to tomatoes, exclusively for general disease control.  An estimated 9% of tomato crops were treated with this active substance.  Seeds were germinated in rockwool and were sown from early spring to allow for summer and autumn cropping.  No seed treatments were applied to tomato seeds. 

Lettuce crops received an average of 1.7 fungicide, 4 insecticide, 2 biopesticide and 1 seed treatment application.  Lettuce crops accounted for the largest growing area of all edible protected crops though this was principally due to repeat cropping within the basic growing area.

Commercial edible protected cropping is a relatively specialist area of crop cultivation, extending the natural growing season to provide a continuous supply of crops for retailers.  Edible protected crops may also be imported from abroad to augment locally grown crops.

Edible protected crops can be grown on relatively small areas, particularly at propagation stage, but increased space is required to accommodate the crops as the plants mature.  Multi-cropping also allows successive crops to be produced from the same basic area.

Growing crops in permanent glasshouse structures or polythene tunnels enables the grower to closely monitor and maintain the conditions within the structure.  Biopesticides and pollinators can also be utilised to maximise effectiveness within the enclosed environment.   However, increased energy costs and the incidence of pests such as glasshouse whitefly (Trialeurodes vaporariorum) that reproduce rapidly under these conditions can prove problematic within a protected structure and lead to increased pesticide inputs.    

Crops which were grown outdoors for part of or all of their life cycle are recorded in the Outdoor Vegetable Crops in Northern Ireland 2017 report (Kirbas et al., 2018).