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10 Aug 2020

Get even for optimum slug control this autumn

Get even for optimum slug control this autumn

by Arable Farming August 2020

With oilseed rape drilling less than a month away, slugs will soon be a foremost consideration for growers once again. Arable Farming gets some advice from three experts on how to ensure hassle-free, accurate molluscicide application this autumn.

Set up applicators correctly from the start

Applicator setup is the first obstacle that can trip operators up and is vital in achieving an even spread pattern, says Henry Potter of Stocks AG.

This means achieving optimum baiting points across the field and a greater likelihood of killing slugs.

Most applicators are fixed on ATVs and it is important to first check the mounting is secure, so it is both safe and unlikely to move and affect spread pattern.

The applicators disc also needs to be set at the correct height above the ground and tilt or pitch, which both have a significant impact on spread width/pattern.


Applicator manufacturers provide this basic information. As an example, Stocks Ag specifies that to spread ferric phosphate pellet Sluxx HP, its Fanjet Pro 65 should be set at 120cm from the ground with a one-degree tilt and bias set at 90.

Across the whole Fanjet range, and some other machines, tilt is adjusted on a tipping pin with two settings. Increasing elevation slightly widens spread width.

For applicators mounted on UTVs or tractors and self-propelled sprayers, similar rules apply. On ATVs and UTVs, when setting height and tilt, consider the weight of the applicator, the operator and product, both in the hopper and carried on the vehicle for later fills.

For example, a fully laden spreader may be level and spread evenly to 18 metres but as the hopper empties the reduced weight can pitch the applicator up, altering spread.

Most ATVs have coil spring suspension that can be adjusted for load, so refer to the manufacturers settings and tweak accordingly.

Get applicators calibrated

A job often neglected, applicator calibration is crucial in ensuring product reaches the right place in the right quantity.

Since 2016, under the Sustainable Use Directive, pellet applicators must be tested every six years and certified by a National Sprayer Testing Scheme accredited inspector.

However, as components wear and provide suboptimal application within the six-year time frame, it is seen as inadequate.

Certis technical specialist Harry Raley recommends a tray test and calibration is carried out annually.

This involves driving the vehicle and applicator(s) over 0.25sq.m trays at one-metre spacings across the spread width and counting pellets falling in them to assess evenness of spread.

Disc speed, tilt and left/right bias can then be tweaked to correct spread.

Stocks Ag advises operators to carry out regular checks to see if there are any issues with spread pattern during the season.

This requires using a quadrat or similar to count pellet numbers at points across the spread width but should not be seen as a suitable replacement for an annual professional tray test for ultimate accuracy.

Understand pellet ballistics

Slug pellet products have different ballistic properties which, along with weather

conditions, can have a dramatic impact on how they spread.

Cheaper, dry processed wheatbased pellets can vary greatly in size, may be prone to breakage and they may have a lower bulk density, making it more difficult to get an accurate spread pattern, and to widths greater than 18 metres.

Conversely, premium wet processed pasta-based pellets such as Sluxx HP and Ironmaxx have a higher bulk density and are said to be more even in size and less prone to breakage, so offer a more uniform spread to greater widths.

Rob Foxall, of SCS, says farmers often think their applicator is accurately spreading to 24m, but after a tray test find it is only reaching 16-18m and leaving strips with suboptimal baiting points.

This shows it is advantageous for molluscicide users to seek advice on the allistics of a product and ensure it is able to meet the farms spreading requirements.


Many pellet manufacturers have trialled their products to show how they behave through spreaders, checking what widths they can be spread to with an acceptable pattern, for example.

Getting this advice is particularly important when attempting to spread to widths of 32-36m, where the spread pattern of some pellets can fall away with the wrong applicator and setup.

Experts advise that when switching products, or from standard sized pellets to minis or vice versa, a calibration for application rate is carried out to cater for the different products flow through the applicator.

It is also advisable to carry out a full width tray test to ensure bout width is suitable for the pellets being applied.

Mini pellets offer growers the ability to achieve a high number of bait points with lower rates when pest pressure is lower, helping cut slug control costs but there is a concern they dont spread as far as standard sized pellets. However, work by SCS has shown a Stocks Ag Fanjet Duo setup, calibrated correctly, spreads Menorexx minis up to 24m as accurately and evenly as the standard sized Sluxx HP and a similar competitor product.

SCS says although some manufacturers have updated designs to allow a single disc machine to spread to 24m, trials show a twin applicator is a better option for spread pattern.

Carry out essential maintenance

On many arable farms, applicators have been sat idle since early spring and will need a once-over ahead of autumn plantings.

Ideally, they should have been completely cleaned after last use. Where they werent, the hopper may need to be removed to clean out any old product or residue.

On gravity-fed machines, such as the Stocks Ag Fanjet Pro, check actuator controlled plates which control product flow to the spinning disc are clear and working in their full range, open to shut.

On units with metering systems, such as the Fanjet Duo, remove the feed roller block, blow it out with an airline and make sure it turns freely with little effort using thumb and forefinger.

If the machine cant clear any settled or wedged product or residue stuck in the feed block when started up, it can burn out the drive motor.


Another pinch point is between the hopper base plate and the spinning disc itself.

Check this and blow out to clear any obstructions ahead of work.

Operators are advised against pressure washing any part of an applicator, as water can be forced into electrical components.

Once clean, check the disc and vanes and replace if there is any sign of pitting or wear. Although uncommon, some applicators have vanes sandwiched between two discs. Nuts and bolts holding the assembly together can loosen, along with the grub screw holding the disc tight to the drive shaft.

Any play may affect the spread pattern or dosage, so check and tighten all nuts, bolts and grub screws.

When clean and assembled, fire up the machine and check each control box function for faults.

A tachometer can be used to check disc rpm is performing as it should.

Note that this often does not match the manufacturer rating, voltage can drop, particularly along lengthy wiring from vehicle battery to applicator.

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