Do the new ferrous phosphate organic slug pellets work as well as the old metaldehyde slug pellets? This question was posed by a reader who felt the new slug pellets were ineffective.
Banning Metaldehyde Slug Pellets
The government moved to ban metaldehyde pellets that have been a gardener’s staple for as long as I have been alive. The ban was overturned on technical grounds but it remains a possibility.
There is supposed to be a danger that the poisoned slugs and snails would be eaten by wild life and poison the wild life in turn. Although the risk is there in theory there is little evidence for it in reality.
The main reason behind a ban was farmers using metaldehyde based slug pellets near water courses causing pollution problems. Remember, gardeners use a handful but farmers use hundreds of kilos.
Ferrous Phosphate Slug Pellets
The alternative slug pellet are thosed based on ferrous phosphate. Ferrous phosphate pellets are organically approved and, in the UK & EU, further treated with a bittering agent to dissuade pets from eating them.
There’s no evidence of risk to wild animals or pets from pellets or corpses except for some vet reports in the USA about dogs eating large quantities of pellets falling ill.
Eventually uneaten pellets degrade and become nutrients for the plants. Incidentally, I think they last longer in showery weather than the metaldehyde pellets.
When a slug or snail eats a metaldehyde pellet they produce a lot of slime which they leave behind them as they slither off and die. It’s very easy to see how many have been killed.
With ferrous phosphate slug pellets the action is different. The slug loses the desire to eat and goes off to wherever it hides in the day and dies out of sight. It’s not at all obvious to the gardener that they’ve been effective.
The Slug Pellets Disappear
If you scatter them as directed, i.e. thinly, and they’ve vanished over a night or two it means they’ve been eaten by the slugs & snails. Re-apply and you’ll get their surviving pals. The pellets actually attract the slugs so don’t over-apply as it can be counter-productive.
To sum up; I think ferrous phosphate slug pellets are probably slightly more effective than metaldehyde slug pellets. They are also arguably safer and definitely greener. On the negative side, they are slightly more expensive but there’s not a lot in it.