The extent of the damage caused by slugs can only be assessed by walking crops – not by looking at them from the roadside.
This is the clear advice from Teagasc tillage specialist Ciaran Collins, who addressed the issue of slug damage on a recent issue of the Tillage Edge podcast.
“Slugs are nocturnal, they are going to work at night,” he explained.
“So, if farmers suspect a specific problem in a field, they should set up some slug traps. This is the easiest way of assessing the size of the pest challenge.”
Traps for slugs
A slug trap can be made from an upturned plant pot, saucer or even a piece of slate, the end of which is raised off the ground.
It can be baited with some layers mash or muesli.
“Each trap should cover an area of around 25cm². They should be laid out in a ‘w’ format across the field as would be the case when soil sampling,” Collins continued.
“The traps should be put out during the day and then checked the following morning before the sun gets down on them.
“The heat from the sun tends to put them back down underground as they are nocturnal.”
According to Collins, the threshold would be four on average. Beyond this, a treatment should be considered.
Treatment
“There are two main options available, where slug pellets are concerned,” Collins commented.
“One contains metaldehyde as the active ingredient, the other contains ferric phosphate.
“The establishment of buffer zones is very important, where the use of slug pellets is concerned. This is particularly so in the proximity to water courses or drains.
“We tend not to have slug damage on headlands, where the ground tends to be that little bit tighter. We definitely do not want slug pellets getting into water courses,” he added.
Research would suggest there is no difference between metaldehyde and ferric phosphate, when it comes to managing slug populations.
But as the Teagasc representative went on to point out, farmer perception is a different thing altogether.
“When the metaldehyde products are used, the slugs tend to die on the surface. So, the farmer is seeing a direct consequence of his actions.
“But when ferric phosphate is applied, the slugs tend to go underground.
“As a result some farmers might think that the product has not worked. But really they should be looking to see has the damage to the crop stopped.”