Meeting the Major Slug Control Challenge - Agrii - Connecting Agri-science with farming

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September 4, 2012

Meeting the Major Slug Control Challenge

Following record-breaking spring and summer rainfall, this autumn is set to be one the most challenging for slug control in many years, warns Agrii crop protection technical manager, Chris Bean. All the more so given the tightrope the industry treads in maintaining access to metaldehyde by keeping it out of ground water.

 “Generally low slug levels in recent years, have made effective metaldehyde management to industry-wide Metaldehyde Stewardship Group (MSG) guidelines relatively easy for most,” he suggests. “But this autumn promises to be a totally different ball game, with plenty of moisture and vegetation allowing early populations to recover sharply.

“This means everyone will need to take a thoroughly integrated approach to slug control, using all the non-chemical weapons in their armoury alongside especially careful pellet planning and application.”

Such an approach is vital since slug pellet label changes means that no more than 700g of metaldehyde can now be legally used in calendar year.  In addition, MSG stipulates a maximum of 210g between August 1 to December 31 as well as no spreading within five metres of any watercourse.

“Only effectively being able to use 7kg/ha of a 3% active pellet in the main season of arable crop use is a serious step back from previous practice,” Chris Bean stresses. “It makes alternative and well-integrated methods of slug control particularly important.

“Just like black-grass, slug control is very much a numbers game. The more you limit populations with other methods the less you need to control with slug pellets.

“Simple steps like effective elimination of rape or cereal volunteers with glyphosate pre-planting can be invaluable in reducing food sources. Equally, well-consolidated seedbeds will markedly reduce the ability of slugs to move through the soil to find seed or newly emerged plants. And, in addition to being a great boon for BYDV control, treating cereal seed with Deter will prevent post-drilling grain hollowing.”

As the basis for careful pellet planning, Chris Bean considers it important to get a good idea of slug numbers in individual fields ahead of drilling. To do so he suggests test baiting in key areas with a chicken layers mash or other attractive (non-chemical containing) pellet, checking regularly for slug feeding.

“Where populations are high I’d apply a low concentration metaldehyde pellet like Tremolo or Allure Metamax around five days before drilling,” he says. “Both are 1.5% pellets so, at 5kg/ha, you can apply plenty of baiting points but only use 75g of your seasonal metaldehyde stewardship allowance. Alternatively, of course, you can use ferric phosphate-based Sluxx which falls outside the MSG rules.

“Drilling is both the best time to control slugs and to ensure crop survival with the most effective pellets, preferably after drilling and rolling to maximise slug access.

“Hybrid metaldehyde pellets like Lynx H or Pesta may well be sufficient for earlier drilled rapes. Much superior to the old mini pellets, they offer improved longevity in the wet. However, they don’t have quite the structural integrity of pasta-based products. Typically an old fashioned mini pellet will persist around 2 to 3 days, a hybrid around 15 days and a pasta one around 18 to 21 days.

“Hybrid pellets are fine at cereals drilling, but its worth bearing in mind that pasta-based products like TDS Major, TDS Amba, Steadfast and Gusto have a longer life under wet conditions and offer valuable improvements in feeding and kill.

“Importantly too, both modern hybrid and pasta pellets are much better able to withstand the tendency of application machinery to cause a particular environmental contamination risk in the form of dust than traditional formulations.”
Whatever products are chosen, Chris Bean insists users must be aware that, with 3% metaldehyde pellets, a 5kg/ha dose uses 150g of the stewardship allowance. This and the specific risks to water courses need to be carefully taken into account in planning any top-up applications.

As metaldehyde applications should be avoided whenever drains are running, he advises employing the ferric phosphate product Sluxx or methiocarb (such as Draza Forte, Karan or Cobra) which also falls outside MSG rules if the need is desperate and conditions or application limits rule out metaldehyde. He does, however, warn that methiocarb carries its own environmental health warnings.  

Alongside watercourses of any type he also urges everyone to bear in mind the inaccuracies of spinning disc type applicators and to consider a separate ferric phosphate headland applications.