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Close up shot of slug in lettuce crop
grey field slug

Slug Force

We've been developing and refining our ferric phosphate pellets for over 10 years, and in that time we've learnt an awful lot about slugs. That's why Certis Slug Force is the place for integrated slug management.

The UK climate is particularly favourable for the breeding and multiplication of slugs.

There are 46 species in the UK but there are three key arable and potato pests:  

•    Grey Field slug (Deroceras reticulatum)
•    Round back slugs (Arion spp.)
•    Keeled slugs (Milax / Tandonia spp.)

Slugs within any population have variable lifecycles. Typically anywhere between 2 and 4 cycles per year. Slugs from the same batch of eggs may also grow at very different rates, some remaining very small whilst others reaching full size very quickly. It is believed that this is a survival strategy based on food supply and environmental conditions. Grey field slugs have a maximum life span of 9-12 months and are the most important slug pest in OSR and cereals.

a grey field slug
Grey field slug (Deroceras reticulatum)
Keeled slug (Milax/Tandonia budapestensis)
Garden slug (arion hortensis)

Key crop impact

Cereals - Slugs will cause seed hollowing and an individual slug can kill up to 50 seeds in the first week following drilling. Smaller slugs are more damaging and will actively feed in the top 2 cm of soil. Additional damage on shoots and leaves can occur and cereals are vulnerable until GS21.

OSR - This crop is very susceptible to damage. As the seedling develops the growing point is exposed above ground and is therefore at risk of damage. The crop is most at risk until the four leaf stage so early protection is critical.

Potatoes - The critical period for damage is early tuber bulking when slugs will enter the tuber and cause significant cavities. Be aware there are varietal differences in susceptibility to slug damage. On susceptible crops ensure a suitable durable pellet is applied during the risk period and critically  before canopy closure to ensure some forward protection is offered.


Slugs are most active at night and will feed until full, rest until the food is digested before commencing further feeding. As night length increases during the autumn and early winter then the number of feeding cycles increases.

Slugs are most active when 

  • Average night time temperature is above 5⁰C
  • Soil surface conditions are moist. Moisture levels in the top 5cm of soil is critical to slug activity

What risk factors are important?

Moisture and temperature are the two most influential factors. Cool, wet conditions are favoured by slugs in order to thrive. Hence mild and wet spring/autumn conditions provide ideal conditions. Even in a dry season slugs can quickly repopulate and thrive at the first arrival of rain. 

Crop type - previous cropping and cover crops can all have an effect on slug populations

Soil type and drainage with water retaining soils like clays and silts, and poorly draining soils providing higher moisture levels.

Cultivation method has an effect with direct drilling, delayed drilling dates, little soil disturbance (no till) all providing good conditions for slug populations. 

Crop residues, organic matter and weeds will provide cover and protection for slugs.

Nearby hedges, wasteland and ditches are refuge areas for slugs to migrate from into cropped areas.

Understanding slug pressure on an individual farm basis is essential and taking an integrated approach to slug control will prove to be the most efficacious, far more reliable than just using slug pellets alone.

There are several critical considerations for any successful integrated slug management programme.


slug feeding on early oil seed rape

Impact of Crop Rotation

Slug damage is much greater following leafy crops such as OSR. The leafy structure creates moist soil conditions and can leave significant crop residues on the surface post-harvest, creating an ideal habitat for slugs in terms of food and shelter.

Do avoid planting very susceptible crops (salads and leafy vegetables) after OSR.

Late drilled cereals can be at greater risk as it often takes longer for the crop to grow out of the susceptible growth stage.


Production of firm seedbeds makes it more difficult for slugs to move, and will also help crops grow quickly, minimising the critical period of risk.

Small grey field slugs are responsible for much of the seed hollowing in cereals and they typically feed in the top 2 cm of soil. If the seed bed is cloddy and loose, growers are advised to drill cereal seed deeper than normal to reduce seed hollowing.

Some growers are now adopting the practice of rolling newly drilled crops at night hoping to kill slugs on the surface.

Key aims of cultivation

  • Distribute and mix in straw and crop debris
  • Reduce clods
  • Reduce cavities

Impact on slugs

  • Direct mechanical damage which can significantly reduce populations in the worked soil
  • Exposure to desiccation
  • Exposure to natural slug predators





Monitor Slug Activity

When using slug pellets it is important to apply the slug pellet early to minimise damage.

Application needs to be timed to coincide with favourable weather conditions, producing a moist surface soil layer and when slug numbers are confirmed.

Growers are advised to utilize slug traps to monitor populations (details on slug trapping can be found in the section Tools).

The Sluxx HP pellet contains ferric phosphate. It has a different effect on slugs when compared to metaldehyde. Growers will see that slug pellets have been eaten but will not see many dead slugs on the surface.

When slugs eat a Sluxx HP pellet they quickly stop feeding and retreat underground to try and recover. They do not recover and will die underground.

Growers are advised to monitor crop damage as an indicator of slug activity along with remaining numbers of slug pellets. In high pressure situations it may be necessary to apply more than one application. Sluxx HP has a label which allows up to 4 applications per crop.



It is important to calibrate the applicator when changing brand and type of pellet.  

Download our callibration guide for SluxxHP here.

Each brand may have different characteristics in terms of size and ballistic properties, which lead to potential variations and discrepancies if not callibrated when changing between pellet.

Further information and applicator testing can be found at


Sluxx HP is the culmination of 10 years field experience and continuous product development. Growers and Agronomists have confidence in its performance and have made it the bestselling ferric phosphate pellet in the UK market.

The Sluxx HP formulation has a number of significant benefits which differentiates it from other pellets in the market, therefore it carries the Ferric Field Technology quality mark.   

What does this mean for you?

Slugs are random feeders. They literally stumble across their food source during their periods of activity. There is no evidence to suggest that they are attracted at a distance to a food source. Once the slug encounters potential food it uses chemical sensors to establish if it is appropriate and will then test the food before feeding.

Attractants added to slug pellets have no real benefit, but the inherent palatability of the pellet is critical to ensure the slug consumes a lethal dose. SluxxHP is made using processed durum wheat flour which makes it very palatable to slugs. 

As you can see from the photographs below Sluxx HP pellets have a very uniform size and minimal dust content. This ensures good spread-ability up to 24m and gives a consistent number of baiting points. 

Left: SluxxHP high quality uniform pellets. Right: Alternative ferric phosphate pellet


Sluxx HP has a patented formulation which includes a food industry preservative to prevent moudling and ensure the active ingredients remains available and active even during wet weather conditions. This is important as it enables the pellet to be more effective when slugs are most active.

Sluxx HP Ferric Phosphate vs. alternative pellet


Not all ferric phosphate pellets are the same

Product performance under dry and wet conditions

A very simple experiment clearly shows this

  • Grow susceptible plants in a tray.
  • Apply slug pellets. Keep dry or irrigate with 5mm of rain twice per day
  • After 4 days introduce a known quantity of grey field slugs
  • Assess plant damage 3-10 days after slugs have been introduced.

% Plants Attacked

  • Both of the products tested offer similar levels of protection under dry conditions.
  • However under wet conditions, when slugs are most active, the Sluxx HP formulation shows significantly better levels of protection versus a leading ferric alternative.

Baiting points

Sluxx HP offers an excellent number of baiting points when compared to an alternative leading ferric phosphate pellet. This ensures that the slug will quickly come across the pellet during feeding activity and help protect the crop.

Slug Trapping

Slug monitoring  is essential to understand what is happening at field level and slug traps can be used to monitor activity.

Guide to using slug traps:

  • Ideally moist soil surface and mild weather (5C-25C)
  • Trap covers ideally a plastic cover approx. 25 cm across. Remember to weigh down traps
  • Use a grain based bait. E.g. layers mash (not slug pelelts)
  • 9 – 13 traps per field in ‘W’ pattern and known hot spots
  • Leave overnight and examine early morning 
  • Continue to trap until crops have passed vulnerable stage

For wheat: a catch of 4 or more slugs per trap indicates a possible risk, where soil and weather conditions favour slug activity

For winter oilseed rape: weather conditions during the short period between harvesting cereals (especially wheat) and drilling may not suit trapping.

It may be worthwhile to trap in standing cereals up to 10 days before harvest, particularly if you plan to broadcast seeds into standing cereals or stubble (e.g. Autocast). In the 7-10 days before cereal harvest, or in stubble.
A catch of 4 or more slugs per trap in standing cereals, or 1 or more slugs/trap in cereal stubble indicates possible risk.

Potatoes and Field Vegetables: a count of 1 slug per trap indicates risk to the crop

Slug trap (using lettuce as bait) reveals high population well above threshold levels

Slug Watch

Download our SlugWatch app to help monitor the slug pressure in your area.

Live slug pressure information by postcode at the touch of a button. 

Our app provides the opportunity to view location-specific live slug activity data, along with weather data from over 10,000 weather stations to help anticipate slug activity and plan pellet applications. Provides growers and agronomists with another tool to aid in making informed decisions on applying slug pellets. 

Input your own trapping data to help create a bespoke slug activity forecast and refine the dataset. 

Available to download for Android and IOS.

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screenshot of slug watch homepage app
screenshot of slug watch app forecast


Come and see us at Croptec 2019. 

Visit the Certis Slug Hub - join us for discussions in how to build an efffective integrated approach to slug control and tips on application & calibration support. 

Featuring contribution from slug experts, Dr Gordon Port and Professor Keith Walters. 

Sessions will run at: 11.00-11.15am, 1.00-1.15pm and 2.50- 3.05pm each day.  

Learn more

Talk to your advisor or distributor.

Read and watch more ferric phosphate related news below.

Contact our technical experts on 0845 373 0305 or send us this quick form.

Sluxx HP


Granular bait formulation containing 29.7 g/kg (2.97% w/w) ferric phosphate for the control of slugs in all edible and non-edible crops. High efficacy against all relevant slug species.

See more…

Find out more about Sluxx HP

Slug Facts with Dr Gordon Port

Hear all the facts you need to know about slug behaviour from Dr Gordon Port. Including most common species in UK crops and their feeding habits

What makes a good slug pellet?

Dr Gordon Port explains the characteristics that make a good quality and effective slug pellet, based on years of in-depth slug research and understanding of slug behaviour

What makes Sluxx HP different?

Neil Beadle explains what makes Sluxx HP such an effective, high quality slug pellet

Slug Tracking Trial

Certis UK regional technical specialist Geoffrey Bastard along with Professor Keith Walters of Harper Adams University explain how we investigated the behaviour of slugs once they have ingested ferric phosphate pellets

In the first autumn without insecticide seed treatment Deter, growers should place added emphasis on seed-bed quality.

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Last year dry, hot weather persisted throughout the summer, suppressing slug levels in winter crops. This August was quite a contrast, with warmer wetter conditions dampening soil and potentially increasing...

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The UK climate provides a perfect environment for slugs to thrive and most arable farmers have an annual battle with the pest. Certis arable product manager Neil Beadle offers some useful advice on how to win...

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With chemical tools for managing slugs in arable crops being lost, there is more emphasis on cultural controls for reducing risk. We speak to a Yorkshire farmer who is combining good crop husbandry and...

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Certis Slug Watch APP

Download our SlugWatch app to measure slug pressure in your area.

The app provides the opportunity to view location-specific slug activity data, along with information on weather conditions, helping you to make informed decisions on slug monitoring and applying slug pellets.

Available to download for Android and IOS


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Metaldehyde Use

'Get Pelletwise’ is the campaign of the Metaldehyde Stewardship Group (MSG).

The group’s aim is to promote and encourage best practice with metaldehyde slug pellets, amongst agricultural users.

Pelletwise stewardship program logo

Integrated Slug Control Guide

More information from the AHDB, a comprehensive guide on integrated slug control.

Updated December 2018 following the ban on Metaldehyde use from June 2020.