After two years of wetter than average weather slug numbers have slowly built up to a level where considerable damage was caused in some of last autumn’s sowings.

Slug trap
Slug trap

First step

The first step is assessing the slug risk by trapping when weather is mild and soil moist.  Traps consist of a tea tray sized cover with suitable bait such as layers mash underneath.  Do not use pellets when baiting as the high concentration of pellets may cause poisoning to wildlife or pets.  Leave traps overnight and check the next day.
The table below are thresholds at which potential slug damage is likely to occur in various crops.

Crop Threshold (slugs/trap)
Cereals 4
Oilseed rape (Trap in presceding crop) 4
Oilseed rape (Trap in stubble) 1
Potatoes, vegetables and suger beet 1

There are a number of risk factors which increase the potential for slug damage.

  • Damp mild weather.
  • Heavy clay that retain moisture well and tend to be more open and cloddy allowing slugs to easily attack seeds and seedlings.  
  • The previous crop being dense and leafy such as oilseed rape or cover crops.  
  • In fields where organic Manure is applied or straw incorporated back into the soil.
  • Reduced cultivation establishment as fewer slugs are destroyed.
  • Course open and poorly consolidated seedbeds.
  • Autumn sowing when populations tend are high and weather favourable for slugs.
  • Slow growing conditions which lengthen the vulnerable establishment period.

Control strategy

Good seedbed preparation is crucial in controlling slugs.  Start by removing weeds and green cover as potential hosts and feed source for slugs.  The aim should be to have a fine firm seedbed which restricts slug movement making it difficult for them to find seed and seedlings.  Good seed soil contact enables seed to germinate and grow quickly through the high risk establishment period. 

If conditions are expected to be wet at drilling an approved insecticide dressing will provide protection if weather conditions are unsuitable for applying slug pellets.  

If trapping thresholds are met and one or more risk factors are applicable then it is advisable to apply slug pellets.  Slug pellets contain one of three active ingredients, methiocarb, ferric phosphate and metaldehyde.  Slug kill from methiocarb and ferric phosphate pellets is not easily visible as slugs ingest and move out of sight to die.  Slugs feeding on metaldehyde secrete excessive mucus and tend to be found close to the baiting point.      
Regardless of active choose a product that will satisfy your needs.

Durability when spreading, persistence for the desired period and number of baiting points should be considered along with price.  

Metaldehyde Stewardship guidelines

Due to metaldehyde detection in water a Metaldehyde Stewardship Group has been established to prevent pollution through responsible use.  Further to label restrictions a number of recommendations have been made to protect drinking water and maintain metaldehyde as an approved active ingredient.  For up to date advice and recommendations on best practice when applying metaldehyde, please visit the Get Pelletwise website

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