Pesticide Usage in Scotland: Rodenticides on Arable Farms

Supplementary data

In addition to the collection of rodenticide usage data, farmers were also asked a series of supplementary questions relating to aspects of their farm operation, their use of non-chemical rodent control, rodenticide stewardship and their compliance with best practice in rodenticide use.

In contrast to the rodenticide usage data presented in the previous sections of this report, this information is not raised to provide national estimates and is presented as responses from the sample surveyed.

Non-chemical rodent control

Farmers were asked about non-chemical methods employed for rodent control. A range of measures were conducted, with some farmers employing more than one method (Figure 10).

On holdings on which rodenticides were not used (n=99), 46 per cent of the farmers reported using one or more non-chemical controls. The most commonly encountered methods were use of cats and traps (65 and 27 per cent of all methods reported respectively). Shooting and dogs were also used to control rodents.

On holdings using rodenticides (n=199), 46 per cent reported that they used additional non-chemical methods of rodent control. Again, the most common methods used were cats and traps (47 and 31 per cent of all methods reported respectively) with lower use of dogs or shooting.

Most of the traps reported across both farms using and not using rodenticide were concussive (spring or 'snap' traps) (85 per cent of those who specified trap type) but cage trap and glue traps were also used (19 and five per cent of trap users respectively).

The number of farmers reporting that they employed non-chemical rodent control was lower in 2022 than in 2020 but similar to 2018 on holdings where rodenticides were used (46, 52 and 46 per cent respectively). For holdings where no rodenticides were used the numbers reporting the use of non-chemical rodent control was slightly lower in 2022 than in 2020 and 2018 (46, 51 and 60 per cent respectively).

Compliance with rodenticide best practice

All farmers and PCPs who were responsible for rodenticide baiting on the surveyed farms were asked about their training history and their compliance with the principles of best practice of rodenticide use^[7] (Table 3).

These data are expressed as percentage of respondents giving a positive answer to each question. Responses were provided by 69 farmers, representing 97 per cent of those farmers who conducted their own rodenticide baiting and 23 PCPs, representing 92 per cent of the contractors encountered during the survey. Where statistically significant differences in the response between farmers and PCPs were found these are noted.

All PCPs and 43 per cent of farmers had attended a training course on rodenticide use. The uptake of training was significantly different between farmers and PCPs (p-value<0.001).

All PCPs and 97 per cent of farmers stated that they recorded the quantity and location of baits. All PCPs and 99 per cent of farmers stated that these baits were protected from non-target animals. Bait was reported to be regularly inspected by all PCPs and farmers. One hundred per cent of PCPs and 80 per cent of farmers removed bait after targeted baiting periods. There was a significant difference between farmers and PCPs removing bait (p-value 0.032). Levels of permanent baiting are lower than those recorded in 2020 and 2018, when 64 per cent and 65 per cent of PCPs respectively, and 65 per cent and 75 per cent of farmers respectively removed bait after targeted baiting periods. The CRRU UK Rodenticide Stewardship regime published updated permanent baiting guidance in July 2019^[10] following changes to make the rules around permanent baiting more prescriptive.

Ninety-one per cent of PCPs and 99 per cent of farmers stated that they searched for and removed rodent carcasses, with no evidence of a significant difference (p-value 0.15). Many respondents stated that they rarely saw carcasses. However, those farmers who did encounter carcasses employed a range of disposal methods; primarily burying and landfill, but also incineration (refer to table 3 for details).

Thirty-six per cent of PCPs and six per cent of farmers used non-toxic indicator baits to monitor rodent activity on farm. This use of indicator baits was significantly different between farmers and PCPs (p-value <0.001).

The pattern of responses to these questions, both by farmers and PCPs, are very similar to those provided in the 2020 and 2018 arable crop surveys. The level of training and use of non-toxic indicator baits were the only questions where there was a significant difference between farmer and PCP response.

Farmers were asked if they had ever encountered or suspected resistance to rodenticides. Of the 69 farmers who responded to this question five (seven per cent) answered confirmed that they had. Three of the five farmers responded to their concerns by changing the bait formulation used.

Farm operation data

Farmers were asked a series of questions relating to aspects of farm operation which might affect rodenticide use pattern (Table 4). Responses were provided by all 298 farms sampled.

The majority of respondents (95 per cent) were a member of a quality assurance scheme, similar to the 96 per cent recorded in 2020. A range of assurance schemes were encountered; the most common were Quality Meat Scotland (QMS) and Scottish Quality Crops (SQC). Both of these schemes specify that effective rodent control measures must be in place, although the use of anticoagulant rodenticides is not mandatory. Membership of both QMS and SQC also permits purchase and use of rodenticide products authorised under stewardship conditions. More farms that practised rodenticide baiting were members of a quality assurance scheme (98 per cent) than farms that did not use rodenticides (87 per cent) and this difference was significant (p-value <0.001).

Although all the farms surveyed grew arable crops, some were also mixed farms and 49 per cent of those surveyed kept livestock on their holding, lower than the 55 per cent observed in 2020. Only three per cent of farms had a pig unit and just two per cent had a poultry unit. These intensive livestock production sectors tend to be greater users of rodenticides due to storage of large volumes of feed and concern about feed spoilage and rodent related disease.

Lastly, 40 per cent of holdings surveyed had an on-farm grain store, and a significantly greater number of farms using rodenticides had a grain store (48 per cent) than farms that did not use rodenticides (23 per cent) (p<0.001).

In 2022, as in 2020 and 2018, statistically significant differences between those farmers using and not using rodenticides were found in relation to quality assurance membership uptake and presence of a grain store. However, unlike the previous two surveys, in 2022 there was also strong evidence that a significantly greater number of farms using rodenticides also kept livestock (p-value <0.001). There was weak evidence that a greater number kept pigs (p-value 0.059), but this was based on a very small sample size.

Rodenticide approval and stewardship

EU and UK Regulatory risk assessments have concluded that the use of first and second generation anticoagulant rodenticides outdoors present a higher level of risk to non-target animals (such as predatory birds and mammals) than would normally be considered acceptable. As a result, outdoor use of these rodenticides would not usually be approved. However, the UK Government recognises that, despite these risks, outdoor use of anticoagulant rodenticides is necessary for rodent control.

In order to be able to re-authorise these rodenticides for use outdoors, the Government must be assured that the risks will be properly managed to minimise unacceptable effects to non-target species. This has been addressed by an industry led stewardship scheme, managed by the Campaign for Responsible Rodenticide Use (CRRU)^[7], which was launched in 2015.

With the launch of the stewardship scheme providing environmental risk mitigation measures for rodenticide use, HSE from 2016, re-approved anticoagulant rodenticide product authorisations. As part of this re-authorisation the approval conditions for some products were amended, notably in relation to the outdoor use (around buildings only) of active substances that were previously restricted to use inside buildings (brodifacoum, flocoumafen and difethialone). Since the introduction of the scheme CRRU has continued to consider ways to strengthen the regime. The CRRU Code of Best Practice was revised in September 2021 to take into account further changes in permitted practical uses of professional rodenticides. For example, in the updated code, rodenticide use for permanent, pulsed or burrow baiting, or in covered and protected bait stations, is now only legal if the product label permits these 'non-standard' scenarios specifically. The updated code also includes new information about two active substances returning to the UK market, cholecalciferol and hydrogen cyanide, including their roles in rodenticide resistance management. When first published in 2015, the code's legal status was guidance. Since then, the Biocidal Products Regulation governing rodenticide authorisations has determined that "biocidal products shall be used in compliance with the terms and conditions of authorisation". These are summarised on product labels, thereby placing a legal obligation on pest controllers, farmers and gamekeepers. The 2021 Code of Best Practice also contains new details for using a risk hierarchy to plan effective rodent control at minimum risk to people, non-target animals and the environment. Pre-control environmental risk assessments are also recommended. Further changes due to take effect by the end of 2024 will end the authorised use of all SGAR compounds for open area baiting (i.e. away from buildings)⁹.

Changes to the Code of Best Practice may influence rodenticide usage patterns. As discussed earlier, it is possible that decreased rodenticide usage and increased adoption of non-chemical control reported in most surveys from 2016 onwards may have been influenced by the introduction of the stewardship scheme and increased adherence to best practice. The slight increase in rodenticide usage and similar levels of non-chemical control reported during 2020 may be an anomaly related to other factors such as the influence of COVID-19 pandemic restrictions.

Farmers were asked a series of questions to investigate knowledge and participation in the rodenticide stewardship scheme (Table 5). Not all of those surveyed provided this data; responses were provided by 69 farmers, representing 97 per cent of those farmers who conducted their own rodenticide baiting. All percentages given in the following two paragraphs are based on these 69 respondents.

Eighty per cent of farmers were aware of the rodenticide stewardship scheme's existence in 2022. Forty three per cent of the farmers responding had attended a training course and 30 per cent stated that they intended to complete training in future. Only 28 per cent had attended a stewardship compliant training course which provided certification acceptable for point of sale purchase of professional rodenticide products. In 2020, 87 per cent of farmers were aware of the scheme, 28 per cent had completed stewardship compliant rodenticide use training and nine per cent intended to complete training in the future. The proportion of farmers that were stewardship trained has not increased in this survey, although considerably more now say they intend to undertake training. The static proportion who are stewardship trained may reflect the fact that it is not considered a priority due to the ability to obtain and use rodenticides under QA scheme membership.

Farmers were also asked how they last purchased rodenticides. Of those answering, the majority (78 per cent) obtained rodenticides by demonstrating membership of a stewardship compliant quality assurance scheme (72 per cent in 2020), 20 per cent produced a stewardship compliant training certificate, compared 26 per cent in 2020. Three per cent of farmers reported either buying amateur products, or in the case of one farmer, still using product purchased pre-stewardship. (there were no farms using these latter two methods in 2020).