There has been plenty of research carried out looking at slug behaviour in recent years, with one project at Harper Adams University microchipping molluscs to track their movements within field boundaries.
It was found that 80% of them stay within one metre of where they were originally caught, meaning populations are relatively stable in both space and time and could allow more targeted use of treatments.
Researchers are collaborating with precision farming and tech companies to enable automated detection and mapping of patches to facilitate this targeting.
There is also work aiming to produce robots that use a multispectral camera to find and treat slug hotspots with traditional pellets or biological controls, such as parasitic nematodes.
However, until these advances in slug control are realised, growers and advisers need to rely on the core IPM principles of slug control, says Certis Belchim’s Kate Downes.
This has led to the company developing the BASIS Classroom module, which outlines these principles and adds some practical advice in getting the most out of any slug pellets when treatment is required.
“Certis Belchim has been involved in the BASIS Class room from its early stages and it is a good way to arm those using slug pellets with the knowledge needed to achieve the best outcomes.
“Growers are now reliant on ferric phosphate pellets and although it does not come with the environmental concerns around metaldehyde, it still needs to be used in a targeted and responsible manner,” says Ms Downes.
Growers and agronomists will be familiar with the ideal conditions for slugs – poorly draining soils with open and cloddy seedbeds often created in these conditions, which increase the potential for crop damage.
Monitor Slugs require adequate soil moisture and mild temperatures of 5-20degC and they thrive under crop residue and other organic material on the surface of the soil.
Certis Belchim technical specialist Harry Raley says it is impossible to eradicate slugs, as studies have shown a large proportion of slug immigration comes from deep down the soil profile.
This means that prophylactically using pellets to crash populations is not effective, as numbers soon bounce back two or three weeks post-application, given the right conditions.
“That’s why it’s important to monitor populations with traps ahead of periods when the crop is vulnerable.
In OSR from just ahead of drilling up to four true leaves and in cereals to early tillering [growth stage 21].
“When numbers in traps exceed treatment thresholds at a vulnerable growth stage, a pellet treatment is required and will control the slugs when they can do the most damage,” he explains.
Knowing the differences between pellet products is key to good slug control, adds Mr Raley.
For example, premium pellet formulations such as Sluxx HP are made from wet extruded pasta so last much longer in wet conditions.
They are also less prone to breakage and spread more uniformly compared with dry pressed versions.
However, looking more closely at ingredients also teases out some differences, with ferric phosphate pellets requiring a chelating agent for effective absorption into the slug’s gut.
There are also different sized pellets on the market, with Men orexx being a ‘mini’ option – like former metaldehyde pellet Gusto – which offers a high number of baiting points per sq.m at a lower dose.
Mr Raley says this makes them ideal for early season use in oilseed rape when field conditions are less challenging, but adequate protection of seedlings is still required when the crop is at its most vulnerable.
Growers can then switch to standard sized pellets as the autumn progresses and conditions become more challenging, and the inherently larger pellet will last longer.
Ballistic properties “One thing growers must consider is there are differences in ballistic properties between premium and dry processed pellets and standard sized pellets and mini pellets.
“That’s why applicator set-up and calibration is so important when switching between products,” he adds.
Information on the capability of an applicator and ballistic properties of pellets are available from manufacturers and are essential pieces of information to check before using pellets.
If an applicator operator tries to spread outside these capabilities, slug control will be compromised.
While NSTS testing of slug pellet applicators is required every six years, Mr Raley says it is a good idea to have applicators calibrated, checked and tested much more regularly.
“Certis Belchim provides the Calibration Wizard online tool to help switch between products quickly and easily.
“You simply enter the applicator model and product, along with other information such as spread width and target rate.
It then gives you disc speed and aperture settings and an appropriate forward speed for accurate application,” says Mr Raley