Elizabeth McCorquodale looks at natural slug traps and tests out what worked in the Gardener Vs Slug war.
There is no doubt that slugs are a gardener’s worst springtime enemy. Later in the year the lush growth of a mature garden can usually cope with whatever the local slimy thugs throw at it, but in spring, or around very susceptible plants when a single sluggy mouthful can chop a seedling in half, or a hosta can be reduced to filigree almost before emerging, slugs must be controlled! If you go out with a torch, a stick and a bucket, you can get rid of dozens – even hundreds – of the slimy devils, but while you have to find the time to do it every night in order to keep on top of things, slug traps can be working away for you with only a modicum of maintenance.
Some time ago I ran tests on slug barriers and was quite happy using ground up eggshells and the accumulation of a winter’s worth of ash from my wood-burner as barriers around precious or delicate plants, but in the wet summer I needed extra control, so I set to work testing some proper slug traps. I have used traps over many years and have, over that time, weeded out those that are just not worth the expense or trouble, and have been left with four I know to be effective. Then it occurred to me that instead of dithering between these four, why didn’t I just sort out, once and for all, which really did work best.
There are numerous slug traps on the market, but the most successful all have three things in common: they are baited, they are covered, and they are dark and damp. As all this makes perfect sense, and I have no desire to reinvent the wheel, I stuck with these design principles and figured that the crux of the matter probably lay in the bait.
Consequently, I conducted tests with four different baits – beer, milk, a sugar/yeast mixture, and slug pellets based on organic iron phosphate.
I must add here that I am no great advocate of slug pellets; I am sceptical about industry-funded tests claiming something lethal to pesky slugs and snails is somehow not poisonous to any other garden wildlife. (Really? Not to any other soil-dwelling insects, to harmless slugs, to earthworms, to other insects in any stage of their life cycle…?) However, with the proviso that the pellets would be contained within a dark chamber, with the slugs hanging around that chamber as they breathe their last, I was willing to make an exception for the sake of science if it was effective and any potential harm might be mitigated. The theory is simple: slugs (and snails, sometimes) will be attracted to the bait and the nice dark atmosphere of the trap, and upon eating the bait they will die, either from falling in and drowning in the liquids, or in the case of the pellets, from the effects of the poison.
In the knowledge I would never buy expensive beer to feed slugs on anything like a regular basis, I chose a cheap brand of stout from my local supermarket. The milk I used was skimmed, as that is all I have in the house, and the sugar/yeast mixture was made up using a sachet of dried yeast and a tablespoon of sugar dissolved in a pint of warm water. The pellets were, as stated, organic ‘harmless to wildlife’ iron phosphate slug pellets.
Each trap was made using an ice cream container sunk into the ground, but with the lip sitting proud of the surrounding soil by a couple of centimetres to stop beetles accidentally trundling into the trap. In the container was a reservoir to hold the bait, and over the top was a cover, which served three purposes: to stop the bait becoming diluted; to exclude any curious visitors such as dogs or hedgehogs; and to provide a nice, damp and inviting environment for my intended dinner guests.
I sited the traps in four spots around my garden and rotated them every second day so each trap appeared in each of the four locations over the eight-day experiment. I checked the traps every day and emptied them of corpses each time I moved them. I didn’t top up the bait because all of these traps would be expensive to maintain if you were to top all of them up more than once a week over the growing season.
All the traps worked, and they all worked best in the same place – an area already well populated with slugs. After eight days the results were as follows:
- beer trap – 44 slugs
- milk trap – 29 (this trap became more effective as the week went on)
- yeast/sugar trap – 36; and the pellets trap – 39
The number of corpses in the trap didn’t seem to make any difference to the efficiency of the trap… slugs clearly aren’t put off by the dead bodies of their comrades.
So, the bottom line is that slugs are partial to all sorts of bait. In future I will be quite happy to chop and change between different ones in the knowledge that my slug population is quite happy to partake in a free lunch, whatever is on the menu. However, given the cost of slug pellets, as well as my continuing scepticism regarding overall safety, I think that I will stick to beer, milk, and sugar/yeast in future.