4 myths about broken slug balls for better control

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The withdrawal of metaldehyde means that producers will soon have nothing but ferric phosphate pellets to rely on to tackle this devastating pest.

However, there are a number of myths about the use of ferric phosphate, which can hamper farmers’ efforts to stop crops from decimating pests.

Myth 1: Attractant additives improve control

The slug pellet is purely a vehicle for introducing the active ingredient into the slug, the bait having to be sufficiently palatable to ensure that each animal eats enough to deliver a lethal dose.

See also: How To Grow Potatoes Using Minimal Tillage

This saw that almost all major manufacturers offer a premium wet processed metaldehyde granule made from durum wheat flour (basically pasta!)

These premium granules also had the added benefit of durability in wet conditions and uniformity in both size and spread.

For a long time, only Certis offered a ferric phosphate pastille based on pastes of a similar ilk in Sluxx HP.

However, now that the metaldehyde has been phased out, other players have entered the high end of the iron market, including Gusto Iron from Adama and Ironmax Pro from De Sangosse.

There are a few differences between these premium granules, in terms of additives believed to improve control.

Attractants that are believed to contain a substance that attracts slugs to the pellet are one such additive, but Newcastle University slug expert Gordon Port has debunked the theory surrounding attractants.

“We haven’t seen any evidence of any commercial granulate acting as an attractant and by that I mean the pest can sniff them from a distance and then move towards them.

“These are random feeders and if they hit a pellet, the quality of the feed is more important. If it is good, they will continue to eat to get an adequate dose. Some lower quality pellets will see them turn away, ”he explains.

© Jon Rowley / SWNS

Myth 2: A higher load of ferric phosphate is more deadly

Some ferric phosphate pellets contain a higher load of active ingredients, which are said to be more lethal.

However, as an active substance, ferric phosphate is relatively harmless to slugs because it is not easily absorbed in the intestine.

This phenomenon is overcome by adding a chelating agent, which is an essential ingredient in ensuring that enough ferric phosphate is absorbed into the slug’s system.

Most lozenges contain an EDTA chelating agent. However, Sluxx HP and related brands of Certis contain EDDS, which works similarly, but is less easily leached from the pellets under humid conditions.

The company claims this has been proven in independent trials conducted by i2L Research in Newcastle, with EDDS-based lozenges giving a much longer period of effectiveness after application than EDTA alternatives.

Certis tech expert Harry Raley says you can put any of the premium ferric phosphate pellets on the soil surface and they’ll be good enough to structurally last in wet conditions, but the agent chelating agent escapes all the time.

“With the naked eye you can still see the bait on the surface, but because the chelating agent has been lost, the ferric phosphate that remains in the pellet will be ineffective when consumed by the slug.

“Sluxx HP has the build quality to last on the soil surface, but also the chemistry to ensure that its effectiveness lasts as long as its integrity,” he explains.

Myth 3: Pre-drill or “nose-down” applications are justified

Some labels of ferric phosphate products – such as the metaldehyde labels before these – allow the granules to be applied before crop emergence, but after seedbed preparation is complete.

The main goal of this practice is to reduce the number of slugs in the soil profile before the crop is established.

Some growers also apply granules in the furrow with the seeds to prevent seed digging, which many believed was reduced by using a Deter (clothianidin) seed treatment.

Regarding the first tactic, Dr Port says it is a waste of time to apply before drilling, as recently published work by himself and others at Newcastle University has discovered.

They tracked plots with restricted and open access to slugs over a 32-month period, allowing a comparison between the extent of migration from adjacent areas and the soil profile under the plots.

It was found that for the gray field slug, Deroceras reticulatum, which is the most important species in grain and rapeseed crops, much of the immigration came from below.

“Within two weeks of initiating a treatment, the slug count bounces back to where they were before, so the best time to release slug pellets is also close to when you would expect damage – at moment or soon after drilling, ”says Dr. Port.

For “on-the-fly” applications, Dr Port says that the evidence he has seen in his own experiments – published in the journal Behavior of Deroceras reticulatum in response to on-the-fly, drilled and soil-contaminated molluscicide pellets – suggests that the pellets are less effective when placed with seeds.

This is because when most species are active, they move on the surface of the soil before diving to find grain, so the contact between the bait and the slug is higher when the granules are applied on the fly. during drilling or shortly thereafter.

Misconception # 4: Heavier, denser granules spread better

© Tim Scrivener

There has always been a huge range of slug control granules available in all shapes, sizes and densities, from light and brittle dry-processed types to heavier and denser premium pasta granules.

Some formulations are classified as “mini” granules, such as the popular metaldehyde bait Gusto (which is now rebranded by Adama as the Gusto Iron ferric phosphate product) and Certis Menorexx, which is a compact version of Sluxx HP.

The spreading capacity of the different granules varies, the dry processed products generally being less homogeneous in size and density, so they spread less well.

Conversely, a more uniform spread is obtained when using a wet processed pasta product.

It has been claimed that a larger, heavier, wet-processed granule will spread more consistently over greater distances than smaller granules with a similar bulk density.

However, this was found to be false during testing by SCS Spreader and Sprayer Testing.

The Staffordshire-based application specialist has shown that with a properly configured and calibrated Ag Fanjet Duo Stocks, the Menorexx mini pellet will propagate as precisely 24m as a standard size pellet.

Despite the premium quality pasta-based pellets in both small and large sizes spreading equally well up to 24m, SCS’s Charlotte Foxall warns that there are limits to how far you can throw a light object, especially when environmental factors like wind come into play.

She says as sprayers get larger growers are looking to reach 36m or even 40m, but accuracy can be compromised.

“A few disc applicators will extend over a width of more than 24 m, the Stocks AG Twin PLUS going to 30 m and the Duo PLUS to 36 m.

“However, most of our customers applying 36m granules tend to opt for a pneumatic drop and diffusion applicator – like those used to spread Avadex (tri-allate) granules – installed on the boom,” adds. she does.

Regardless of which pellet is used, Foxall says knowing the ballistic properties of each pellet and how to set up and calibrate the machine for each is essential for an accurate application.

Most pellet and applicator manufacturers will be able to provide the relevant information for in-season setup, with manufacturer Certis even offering a mobile-friendly calibration assistant online tool that gives the correct settings in depending on machine, spreading width, product and application rate.

Companies like SCS offer tray testing and calibration of pellet applicators and this process is recommended annually before the main farm use period and when switching from one product to another with ballistic properties. different.

In Brief – The Myths About Shattered Ferric Phosphate Pellets

  • Attractant additives do not improve slug control
  • Chelating agent more important than the active load for slug mortality
  • Pre-drill or nose-down applications offer no advantage
  • Heavier, denser granules don’t necessarily spread better – applicator setup and calibration is critical


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