Pesticide usage report: Edible protected crops 2019

SUMMARY

This is the third 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 surveys in 2015 (Lavery et al., 2016) and 2017 (Lavery et al., 2018).  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, 2018 (Kirbas et al., 2019).

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.  In keeping with the 2017 report, 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 nine holdings, representing 56% of the total area of edible protected crops grown in Northern Ireland (Table 1).  Holdings were selected from information contained in the Northern Ireland Agricultural Census, June 2018 (Anon., 2019) and Basic Payment Scheme returns, 2019.  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 fourteen fungicide active substances including formulated fungicide mixtures were recorded in use on edible protected crops in Northern Ireland in 2019.  Cyprodinil/fludioxonil represented 16% of the fungicide-treated area and Boscalid/pyraclostrobin represented a further 14% with both accounting for 5% of the weight of fungicides applied.  However, Fosetyl-aluminium/propamocarb hydrochloride, which accounted for 14% of the fungicide-treated area, represented 65% of the weight of fungicides applied, primarily on brassica crops during propagation stage for general disease control.  Dimethomorph, which represented 16% of the fungicide-treated area, accounted for 4% of the weight of fungicides applied (Tables 7 and 8).

In contrast with 2017, when there was no herbicide use recorded, there were five herbicide active substances applied, accounting for an estimated 6% of the total pesticide-treated area and 7% of the total weight of pesticides applied.  The residual benzamide herbicide propyzamide accounted for 85% of the herbicide-treated area and 73% of the weight of herbicides applied, exclusively on lettuce crops for general weed control (Tables 7, 8 and 14).

The oxadiazine insecticide indoxacarb accounted for 31% of the area treated with insecticides, representing 3% of the weight of insecticides applied.  Both spirotetramat and spinosad represented 24% of the insecticide-treated area and 8% of the weight of insecticides applied.  Chlorpyrifos, an organophosphorus insecticide and acaricide, was applied exclusively to ‘other crops’ for general insect control and, although representing less than 1% of the insecticide-treated area, accounted for 73% of the weight of insecticides applied.  This was due to the high application rate as a drench treatment during the propagation stage when the plants were still in module trays (Tables 7, 8 and 16). 

The bacterial fungicides Bacillus subtilis and Gliocladium catenulatum, which accounted for 42% and 54% of the biopesticide treated-area and 36% and 64% of the weight applied, respectively, were applied primarily to lettuce crops for the exclusive control of Botrytis cinerea.  The only other biopesticide recorded in 2019 was the chalcidoid parasitic wasp, Encarsia Formosa, which was used exclusively on tomato crops for control of glasshouse whitefly (Trialeurodes vaporariorum), representing 4% of the biopesticide-treated area.  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.  (Tables 7, 8 and 17).

Seed treatments, which accounted for 4% of the total pesticide-treated area and <1% of the weight of pesticides applied, were applied primarily to leafy and flowerhead brassica crops, with iprodione being the only active substance applied to these crops representing 76% of the seed-treated area and 73% of the weigh applied.  The only other seed treatment active substances applied in 2019 were thiram and metalaxyl-M, which were applied to celery and parsley, onion and leek and ‘other crops’ seeds.  

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.  Lettuce crops received 75% of all fungicides applied representing 26% of the weight applied.  Conversely, leafy and flowerhead brassica crops, which received 20% of all fungicides applied, accounted for 71% of the weight applied.  Lettuce crops received an average of 2.7 fungicide, 1 herbicide, 1.6 insecticide, 2 biopesticide and 1 molluscicide application (Tables 6 and 14). 

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 2019 report (Lavery et al., 2020).