Slugs: Do you know how to control them?

Slugs can cause major problems on tillage farms, according to Markus Bieri. However, speaking at the Irish Tillage and Land Use spring workshop, he said damage can be limited when monitored and treatment is timed correctly.

Slugs are independent animals. They don’t crowd together and they tend to be evenly distributed throughout fields, as they live on their own.

They are nocturnal; they leave the soil cracks after sunset and come out in search of food. After sunrise, they will stay in an area that provides them with moisture and a food source.

How to find out if you have a slug problem?

An easy way of detecting slugs is to look for slug feeding traces and activity. However, in order to find out how bad the slug problem is, you need to set up some slug traps.

As slugs are independent creatures, these traps should be set up across a field at several different points.

A good trap, according to Bieri, would be a teaspoon of pigeon mash placed under a saucer from a potted plant. As slugs come out at night and go back to the soil at sunrise, these traps should be checked before sunrise.

If two slugs are found in the traps of an oilseed rape crop, treatment is needed. This number increases to four slugs per trap in a crop of wheat.

Derosceras reticulatum which attacks oilseed rape. Image source: Lonza

When to apply slug pellets?

Timing of slug pellet application is crucial. Plants are most vulnerable when they are sprouting, as this is when the tissue is soft and very easy to eat.

Damage done at the fresh sprout stage can be very severe and can’t be corrected. This is when the plant needs to be protected most and when slug pellets should be applied.

However – in the case of potatoes – the time to apply slug pellets is when the first tubers start growing.

The most-efficient method of application is on the soil surface. It is also better to apply pellets in one application, as this provides more bait points. If slug pellet application is split, then there are less bait points for the slugs to meet.

Weather effects

The good news is that slugs don’t like the cold weather. So, the snow of late will keep them below the surface. They also like moist conditions. This doesn’t mean it has to be warm. A cold wind with no precipitation can cause very dry conditions.

Where slug numbers are high in the autumn and there is a mild winter then there is a high risk of high slug numbers in the spring time.