Q & A
Please see a list of commonly asked questions below. You just need to click on a question to reveal the answer.
Metaldehyde is a selective molluscicide used to control slugs in a wide range of crops. It is applied as an edible bait containing a small amount of active substance and it has been used for slug control for over 50 years, having first been observed in the 1930’s when metaldehyde was used in camping stoves as a fuel.
Slug control has been identified as a key priority among farmers growing cereals, oilseed rape, potatoes and vegetable crops. A variety of reports underline the potential devastation that slugs could cause to UK agriculture if they are not controlled effectively.
- For oilseed rape, around 59% of the total area is affected by slugs. Without pesticides, the calculated annual tonnage lost is 54,354 tonnes, costing the industry something like £18 million a year1
- For wheat, about 22% of the total area is affected by slugs. Without pesticides, the calculated annual tonnage lost is 153,280 tonnes, costing the industry an estimated £25.5 million per year1
- Slugs affect approximately 37% of the UK potato area with estimated losses of 422,000 tonnes per annum equating to a cost of £54 million to UK growers should no viable treatment be available.2
- Slugs can attack and cause damage to vegetable crops at varying stages of their development. Attack in the early stages can result in plant loss by direct feeding on seedlings. At later stages, feeding can lead to cosmetic problems such as holes and grazing damage.3
1 AHDB (2014) Implications of not controlling slugs in oilseed rape and wheat in the UK. Available online at: http://www.ahdb.org.uk/projects/documents/AHDBResearchReview-Slugs.pdf [accessed 6 January 2017]
2 Twining,S.; Clarke,J,; Cook,S,; Ellis,S,; Gladders,P,; Ritchie,F,; and Wynn,S. (2009). Pesticide availability for potatoes following revision of Directive 91/414/EEC: Impact assessments and identification of research priorities Research Review 415, Potato Council.
3 AHDB (2009) Slug control in field vegetables. Available online at: http://www.ahdb.org.uk/slugcontrol/[accessed 6 January 2017]
It has been found in very small quantities in some reservoirs and rivers known as raw surface water. In a few cases the levels have breached the Drinking Water Regulations of 0.1 part per billion (ppb) i.e. 1 in 10,000,000,000.
Very small quantities of metaldehyde were first detected in raw surface water in 2007 following the introduction of new analytical techniques which had increased sensitivity.
Research by the Metaldehyde Stewardship Group (MSG) highlighted that diffuse field losses, via field drainage and surface runoff, are more significant than previously understood in terms of the possible routes by which metaldehyde is reaching raw surface water.
No. Although the concentrations being detected are occasionally above the standard for drinking water, the standard for individual pesticides is not set on a health basis. Water companies are focused on maintaining a very high quality of drinking water in the UK to ensure that water is safe to drink and to meet the national and European standards.
The Health Protection Agency (now part of Public Health England) has confirmed that there is no risk to health from the concentrations that have been detected in drinking water supplies. Using toxicological studies it is possible to determine a maximum ‘Acceptable Daily Intake’ and this indicates that to be exposed to this amount of metaldehyde, the average size person would have to drink more than 1,000 litres of water each and every day of their life.4
4 Water UK (2013) Briefing paper on metaldehyde. Available online at: http://www.water.org.uk/sites/default/files/documents/Policy-Briefings/[accessed 6 January 2017]
Current raw water treatment processes are less effective for metaldehyde than for other pesticides. The water industry is working on treatment methodology – the work is ongoing.
A stewardship group, made up of all the main pellet manufacturers was formed in 2008. Since then, the group has worked continually with water companies and industry bodies such as Agricultural Industries Confederation (AIC), Association of Independent Crop Consultants (AICC), Crop Protection Association (CPA), National Farmers Union (NFU) and the Voluntary Initiative (VI) to develop and implement stewardship approaches.
The regulatory risk assessment process is now more rigorous than ever. There is no evidence of harm to populations of birds and small mammals from the approved uses of metaldehyde. Nevertheless, according to the current precautionary approach, the possibility of effects could not be completely excluded. Therefore, strengthened regulations now require a higher level of protection and as a result of this, enhanced stewardship has been introduced by the Metaldehyde Stewardship Group (MSG) in conjunction with the Chemical Regulations Division (CRD).
The product labels remain unchanged. However, enhanced guidelines have been issued and should apply to all metaldehyde applications.
- No metaldehyde slug pellets to be allowed to fall within a minimum of 10 metres of any field boundary or watercourse
- Use minimum active per ha to avoid drainage and run-off losses
- Maximum application rate 210g metaldehyde a.s/ha* For additional protection of water, suppliers/BASIS advisors may recommend rates reduced to 160g a.s/ha or less*
- Maximum total dose from 1st August to 31st December: 210g metaldehyde a.s/ha* For additional protection of water, suppliers/BASIS advisers may recommend rates reduced to 160g a.s/ha or less*
- Maximum total dose rate: 700g metaldehyde a.s/ha/calendar year*
- Do not apply when heavy rain is forecast
- If drains are flowing do not apply metaldehyde based slug pellets
*from any combination of metaldehyde products. 700g is also the statutory limit.
a.s.: active substance (or active ingredient)
The guideline has changed to help increase protection of birds and small mammals that tend to feed and breed in hedgerows. Ensuring that no pellets are allowed to fall within a minimum of 10 metres of any field boundary or watercourse will help reduce the possible risks that have been identified.
Metaldehyde products may not be re-registered.
The pesticide usage data over the period 1990-2015 shows that the total area of land treated with metaldehyde is variable and has remained very similar, on average, over the period 2000-2014. However, over the same period 2008-2014, there has been a significant decrease in the total amount of metaldehyde applied per hectare.5
5FERA (2016) No.8
Trapping should be used to make sure that there are active slug populations and pellets should only be applied when levels reach the thresholds.
Integrated Pest Management (IPM) entails taking a holistic approach to slug control and avoids a reliance upon slug pellets alone. Techniques include crop establishment and seedbed condition, assessing slug numbers and activity prior to treatment, considerations of field history, crop type and alternatives to chemical control measures.
See the Integrated Pest Management (IPM) section of the website.
As with all pesticides, metaldehyde products in the UK are subject to periodic re-evaluation. And this is on-going, and coming towards a conclusion, for all UK metaldehyde products.
Under the increasingly stringent pesticide regulatory requirements [Regulation (EC)1107/2009 and, in this case, the EFSA Guidance for risk assessment of birds and mammals (EFSA Journal, 2009:7(12):1438)], the hurdles around demonstrating adequate protection to birds and small mammals are higher.
No, not yet. But, we’re continuing to work with the regulators for a positive outcome. The enhanced stewardship requirements for this season are part of that process.
From the edge of non-cropped land (i.e land taken permanently out of agricultural production, that encompasses the compliance strip adjacent to hedgerows and watercourses established under the Single Payment Scheme).
Cropped land includes managed buffer strips (e.g grass strips, wild flower margins and conservation headlands).
From the top of the bank.