Integrated Pest Management (IPM)
Why use an IMP approach to slug control?
An Integrated Pest Management (IPM) approach to slug control is more effective than relying solely on slug pellets and will help ensure maximum protection to the environment, in particular water, birds and small mammals. It is also an effective tool to boost crop productivity.
What does an IPM approach to slug control involve?
- Identification and analysis of the potential risk factors associated with slug damage
- Consideration of the most suitable cultural control techniques that can be used to help reduce slug habitats and overall pressure
- Trapping and understanding of thresholds to help ensure treatment decisions are justified
- Monitoring of crops while they are most vulnerable and assessing if further applications are required
- Record keeping and forward planning to improve IPM programmes for the next year.
1. Farm appraisal
Understand the risks associated with slug pressure and attack
Soil type - slug pressure is often higher in heavy soils with high clay or silt content as they can move around more freely.
Crop residues, organic matter and weeds - crop residues and weeds provide slugs with a source of food and shelter.
Agronomic conditions - lack of nutrients and poor drainage can all result in slow crop growth which increases the risk of slug attack.
Trapping and history of slug active areas on the farm - trapping should be carried out at this stage to assess the potential risk of slug pressure (refer to point 4 for more information).
Problem slug areas can also be pin-pointed using records and field history knowledge and can help make informed decisions on control techniques.
Cover crops - these can encourage slug populations, especially if they include brassica species.
2. Soil and Stubble Management
Create a slug-poor habitat to reduce pressure
Ploughing to bury surface trash considerably reduces slug populations and risk of damage to crops.
Minimum tillage also gives a considerable reduction in slug populations compared to direct drilling.
Rolling after drilling is a fundamental cultural control technique. It will create a firm, fine seedbed which will help reduce slug activity by making it harder for them them to move around. It also reduces the availability of safe resting places for slugs.
Stubble infested with weeds or with a lot of crop debris can provide a feed source for slugs and should be removed.
Plant crops to deny slugs access to seed
At appropriate dates, drill seeds into fine, consolidated seedbeds at 3cm depth to deny slugs any access to seed.
If seedbeds are cloddy, sow seeds deeper at 4-5cm depth as this will help to prevent slugs from reaching seed.
Trap slugs to assess thresholds
Trapping to assess slug threshold levels is key to understanding slug pressure and whether or not slug pellet applications are justified.
Trapping should be carried out during the farm appraisal, before cultivation, and while crops are most vulnerable to attack.
- Traps should consist of a cover, about 25cm across, such as a plant pot saucer
- Place two heaped spoonfuls of chicken layers’ mash or a cereal grain-based food under the trap (slug pellets should never be used)
- Place 9 traps in each field in a ‘W’ formation. For fields larger than 20 hectares, use 13 traps
- Leave traps overnight and examine early the following morning while the soil surface is still moist
- Count the number of slugs present and note any slime trails
- If slugs are found,refer to the next section,Thresholds, before making a decision on pelleting
- If no slugs are found,continue to trap until the crops have passed their vulnerable stage
Understand and refer to trapping thresholds
The following trapping thresholds indicate a possible risk of attack and justify slug pellet treatments.
6. Treat if required
Apply pellets responsibly
If trapping thresholds justify slug pellet treatment they must be applied responsibly:
- Apply pellets via broadcasting as this will kill slugs quicker than pellets that are drilled with seeds
- Apply pellets just after drilling or rolling if possible
- Ensure all applicator equipment is calibrated correctly and tested to the required standards for precise and safe applications
- Follow the Metaldehyde Stewardship Group (MSG) guidelines.
7. Record keeping
Keep records up to date
It is important to keep records of treatment, results seen in the field and machinery used, as these are legal requirements and are useful for future IPM planning.
- Trapping results
- Date of treatment by field
- Growth stage at time of treatment
- High risk field areas
- Field observations and slug pressure according to weather conditions
- Machinery used for application.
Know when crops are most vulnerable to slug damage
Once pellets have been applied, crops should be monitored regularly for slug damage, particularly when they are most vulnerable.
Oilseed rape crops should be monitored to the four true leaf stage
Winter cereal crops should be monitored to first tillering (GS21)
Potatoes have two critical control periods, at 50% to 75% canopy closure and at the early stages of tuber bulking
Trapping should be repeated as part of the monitoring process.
9. Evaluation and forward planning
Evaluate and plan ahead
It is critical to review IPM programmes from the previous year and use records to highlight areas for improvement for the next year.
Seek advice from advisers as they will be able to help you refine and implement a sustainable IPM programme for your farm.