After a hot, dry summer, slugs might not be the first threat to crop establishment that comes to mind, but don’t be lulled into a false sense of security.

Even when parched conditions suppress populations, slug numbers can recover quickly once moisture provides the right environment.

See also: How to companion crop successfully in winter wheat

That is the advice of Hampshire Arable Systems agronomist Anna Dunford, who is prepared for the possibility of a wet autumn, and an early start to winter cereal drilling as growers seek to avoid the wet weather disruption of the past two seasons.

Anna advises farmers growing combinable crops and maize across Hampshire, the Isle of Wight and Surrey.

“There is a risk in thinking slug pressure is going to be much lower this year,” she says.

“After the very wet winter, followed by a dry spring, slug populations will have taken a hit. However, slugs will still be lurking below the soil surface, and a few heavy rain events will see them up and causing trouble again.”

Chemical control with slug pellets is a last resort action when following an IPM approach © Tim Scrivener

Anna’s primary concern is seed hollowing in the days post-drilling, which she saw a lot of last season. “If seed gets hollowed out there’s no going back, but slug grazing can be managed once the crop is up,” she says.

She notes that higher risk situations include crops following oilseed rape, cover crop mixes containing brassicas, or where establishing second wheats.

“Serious populations of slugs are incredibly hard to get on top of. For fields at high risk, based on previous cropping, soil type and cultivations, I make sure to have pellets in the shed and monitoring systems in place.”

Cultural measures

However, chemical control is a last resort in an integrated pest management (IPM) approach to slug control and there are cultural control measures that can be implemented before slug pellets are applied, she advises.

Whatever the method of cultivation, the aim should be to create a firm, well consolidated seed-bed.

“A cloddy, open seed-bed allows slugs to move around and graze more easily.

“Creating a good seed-bed will not only limit slug movement, but also conserve moisture meaning increased seed to soil contact for rapid germination and establishment to grow away from the slug danger zone,” says Anna.

Monitoring with slug traps is essential to assess the extent of the problem, too.

“We will be putting traps out pre-drilling and monitoring them constantly, so we can understand what the slug pressure looks like, and when the threshold is reached, we will apply pellets.”

She has a tried and tested approach to slug pelleting based around an initial application of Menorexx before switching to Sluxx HP.

“We tend to stick with these pellets because they do withstand the rain better,” says Anna.

Menorexx, with its mini-pellet formulation, is designed to deliver more baiting points per square metre during the early growth stages. 

In contrast, Sluxx HP, with its larger pellet size, offers greater durability, making it particularly suited to wetter conditions later in the autumn, she explains.

Both pellets contain 29.7g/kg ferric phosphate and at their maximum individual dose of 7kg/ha Menorexx delivers 94 baiting points per square metre and Sluxx HP delivers 59.

Manage the risk

For independent agronomist Tod Hunnisett, who advises farmers across the south of England, from Dorset to Kent, slug control in winter wheat is underpinned by being aware of risk situations, good seed-bed preparation and keeping a close eye on emerging crops.

“Slugs don’t like being moved about, especially in warm, dry weather. If you can desiccate the juveniles on the soil surface or break open the slug eggs, that goes a long way towards preventing a problem before it happens,” he says.

“If you’ve got winter wheat going in after winter oilseed rape, you can normally get a pretty good idea of what the slug situation is going to be by looking at the oilseed rape volunteers before your wheat goes in.

“If your field is completely clean of volunteers, you are going to be highly suspicious there’s a lot of slugs and so destroying the green material on top, whether by cultivation or by spraying off, will go a long way to helping manage the problem.”

When it comes to slug pellet dose rate, his preference is to apply the full recommended dose, or close to full dose. “I would rather go once with a reasonable rate and do the job,” says Tod.

Case study: Adam Hayward, East Yorkshire

Adam Hayward © Adam Hayward

Yorkshire farmer Adam Hayward has his slug control plans for the new season prepared well in advance.

Farming 300ha as E Dunning & Son at Bishop Burton in East Yorkshire, he grows cereals, spring beans and vining peas on free-draining soils over chalk.

Slugs are a recurring problem on the farm, so with harvest complete bar spring beans by mid-August, he has had time to plan his slug management strategy and order his slug pellets in readiness for expected problems in first wheats after oilseed rape.

“The slugs are deep down in the soil because it has been so dry for so long,” he says. “But it’s going to rain at some point and when it does, they are going to come up hungry and our newly-emerged crops are going to be easily available to them.”

Hitherto, his approach has been driven by soil moisture and weather conditions, with pellet applications supported by slug trapping and a range of IPM approaches, including variable seed rates and rolling.

“I run a few different variable seed rate maps, overlaid with a slug pressure map. Where I know where there’s going to be a tricky headland, I’ll up the seed rate knowing full well there’s going to be slug damage.

“If it’s coming damp, we will initially apply a low rate of pellets as a precaution and we will use a product that provides us with coverage for a long period of time,” he says.

“We will have discussed baiting points and how much weathering a pellet can take.”

A bad slug year will see pellet applications start at crop emergence, followed by several further applications up to the maximum permitted dose per crop.

Yet despite this robust approach, Adam has increasingly felt that he wasn’t getting on top of the farm’s slug problem. When the opportunity arose, Adam was keen to get involved with the Bofin Slimers project as a Slug Sleuth.

As the project enters its third and final year Adam and his fellow Slug Sleuths (see panel) will be putting to the test a model developed to predict field areas likely to harbour slugs.

“It’s a bit like using a variable rate map for nutrition application except in this case it’s variable rate for slug pellets, with applications made just to problem areas, not the whole field,” says Adam.

Provided by Certis Belchim in partnership with SCS Spreader and Sprayer Testing, the Calibration Wizard helps users switch between pellet types swiftly and accurately.