slug pellets

I've had to use slug pellets this year, they'd helped themselves to my board beans and peas!

I used nematodes for vine weevils and slugs. But in an enclosed smallish back garden not on the allotment. They worked really well in the back garden.  You still get slugs but not as many. 

I'm not sure in the wide open spaces of an allotment they would work so well - it would be good to hear if anyone has any experience.  Also , as someone said up the thread (I think) it might upset the natural balance of predators on the plot.  I'm going to try putting in a small pond in to see if I can encourage a frog or toad...