Pesticide usage report: Edible protected crops 2021

SUMMARY

This is the fourth 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 2017 (Lavery et al., 2018) and 2019 (Lavery et al., 2020).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, 2020 (Kirbas et al., 2021).

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 2019 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 seven holdings, representing 33% 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 2020 (Anon., 2021) and Basic Payment Scheme returns, 2021. 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 2021. Dimethomorph represented 15% of the fungicide-treated area and 1% of the weight of fungicides applied. Cyprodinil/fludioxonil represented a further 14% with both accounting for 3% of the weight of fungicides applied. However, fosetyl-aluminium/propamocarb hydrochloride, which accounted for 13% of the fungicide-treated area, represented 55% of the weight of fungicides applied, primarily on brassica crops during propagation stage for the control of downy mildew. Propamocarb hydrochloride accounted for only 25 of the fungicide-treated area but 31% of the weight of fungicides applied. (Tables 7 and 8).

There was only one herbicide active substance applied in 2021, exclusively applied to lettuce crops, which accounted for an estimated 5% of the total pesticide-treated area and 3% of the total weight of pesticides applied. (Tables 7, 8 and 13).

A total of five insecticide active ingredients were recorded in 2021. The oxadiazine insecticide indoxacarb accounted for 24% of the area treated with insecticides, representing 11% of the weight of insecticides applied. Both spirotetramat and spinosad represented 60% of the insecticide-treated area and 80% of the weight of insecticides applied. The diamide insecticide cyantraniliprole, applied exclusively to brassica crops, accounted for 3% of the insecticide-treated area and 7% of the weight of insecticides applied. (Tables 7, 8 and 12).

A total of two microbial pesticides were recorded in 2021, Bacillus subtilis and Gliocladium catenulatum, applied primarily to lettuce crops for the control of Botrytis cinerea accounted for 71% of the biopesticide treated area and 21% of the weight of biopesticides applied. Bacillus subtilis  accounted for 19% of the biopesticide-treated area of brassica crops and 10% of the weight of biopesticides applied. .  (Tables 7, 8 and 11-15).

Seed treatments accounted for 4% of the total pesticide-treated area and <1% of the weight of pesticides applied. The seed treatment active substances applied in 2021 were fludioxonil and metalaxyl-M,  were primarily applied to leafy and flowerhead brassica crops, representing 95% of the seed-treated area and 86% of the weight applied. Lettuce was the only crop not to receive a seed treatment.

Lettuce crops accounted for the largest growing area of all edible protected crops, although this was principally due to repeat cropping within the basic growing area. Lettuce crops received 66% of all fungicides applied representing 14% of the weight applied. Conversely, leafy and flowerhead brassica crops, which received 32% of all fungicides applied, accounted for 84% of the weight applied. Lettuce crops received an average of 2.8 fungicide, 1.0 herbicide, 1.6 insecticide, 1.5 biopesticide and 1 molluscicide application (Tables 6 and 13).

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 2021 report (Kirbas et al., 2022).