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Slugs capable of rapid return to full force

Despite periods of prolonged and persistent dry weather over the last two seasons, experts advise that slug populations have not suffered significant losses.

Despite periods of prolonged and persistent dry weather over the last two seasons, experts advise that slug populations have not suffered significant losses.

Rainfall in early May and now warm day and night time temperatures will combine to increase slug activity, with populations likely to be eager to feed and breed, capable of quickly resuming to high-pressure levels.

“Growers this season are likely to find that the majority of slug populations will have endured, despite low levels in 2011 and 2010 and dry conditions over the last few seasons,” explains Dr Gordon Port from Newcastle University.

“Slugs are remarkably sensitive to a dry soil surface, but also very tolerant to a wide range of conditions. They retreat down into the soil as far as two metres deep, depending on the soil cracks and structure.

“Studies undertaken at Newcastle University have found that slugs survive and will come up from deep in the soil structure, even if they have been down for many months,” notes Dr Port.

“Although some will have succumbed after the prolonged drought, they are more resilient than you think. Going through a period of de-growth they utilise their body reserves to survive, shrinking in size to take on an almost juvenile slug appearance,” he explains.

Dr Port notes that across most of the UK in the last few weeks there has been a lot of rainfall, or at least enough to wet the soil surface, meaning egg lay will have occurred and now with temperatures having really picked up over the last few days they will be on the move.

“And they will be eager to feed. We will likely see them becoming active again very quickly,” he highlights.

For growers dealing with the problem in potatoes, there is a need for control at every opportunity, believes Dr Port.  

Close monitoring of numbers and keeping an eye on the local forecast and weather conditions should inform decisions as to whether an application is warranted. “If overnight temperatures at the soil surface are below 5oC, activity is unlikely, but the recent weather presents a threat of rising slug numbers.”

According to Dr Tudor Dawkins, Certis’ technical manager, if slugs do make the anticipated come-back, there is a clear need to protect crops once they reach the critical stage of tuber formation.

He adds that much better control of slug populations will be achieved when the target is active, with sufficient moisture and warm soil temperatures.  

And where treatment is warranted, Dr Dawkins advises that a solution such as Sluxx (ferric phosphate) with no harvest interval restriction and with a strong environmental profile is a key advantage. “This allows treatments of headlands, up to the field edge – an area of significant value – and will also preserve all important tuber yield and quality,” he explains.

He notes that Cambridge University Farm trials have very successfully illustrated the advantages of Sluxx compared with other industry established pellets based on other active ingredients.  

“Sluxx came out on top, performing extremely against the other trialed treatments, with significant results in terms of affected yield and affected tubers with tuber damage following a programme of Sluxx delivering the lowest levels of damage when compared against all other treatments.

“The trials results have proven it’s an efficacious and reliable pellet which represents  a commercially viable alternative.

“With slug pressure increasing and the possibility of a high slug pressure this autumn it is critically important that growers plan all their molluscicide programmes carefully,” he urges.