[shokkyy]

Last week I put a load of brassica and onion seedlings under fleece in my tunnel, and today I discovered something has  eaten their way through 3 trays of brassica seedlings and made a serious dent in the onion seedlings too. I could murder the little toads. I saw where they'd dug a hole up through the bed, kind of big for mice but much too small for anything like rabbits. Is this more likely to be voles or mice?

I've put a couple of traps on the bed, filled the hole and put a brick on top of it, so hopefully that'll stop any further damage, but they're very hard to discourage once they've found a good food source. I can easily sow new brassicas but it's getting a bit late for new onion seeds. Yes, they'll give a crop but they're not likely to be very big onions if I start them now.

[parsley]

Onions are harmful to rabbits and mice, will kill a rabbit because they can't vomit, not sure about voles though. Hope you get it sorted 

[arugula]

Voles are not dissimilar in size to mice, could be either.

[shokkyy]

They laughed at my traps, and last night ate an entire kohl rabi plant down to the ground. Not a seedling, a full sized plant. I can't find their new hole, or maybe they've just moved into the tunnel full time since the selection of food is so good.

[arugula]

You might have to put mouse poison down, you can place it in a small container in the tunnel and they will come and eat it. You could also flush them out with a hose, if you can see the hole they are using - just place a hose down the hole and leave it running for 10 -20 minutes... Neither pleasant from the point of view of a lover of widlife but they're eating your food. 

[parsley]

It's not just that they are eating your food, they carry some nasty germs too. Moving them on won't do it, they'll just come back. The best way to know what you are dealing with is by their poo. If they've eaten a whole kohl rabi could be a mouse family or even a small rat. Might be worth getting some expert advice?

[shokkyy]

No, I wouldn't be tempted to use poison because I have two dogs and I've seen a dog almost die, not from eating the poison but from eating the dead rat that ate the poison. Catching and displacing mice or voles does work, as long as you take them at least half a mile away, and I've got plenty of quiet locations round here that are nowhere near anybody's house. No sign of any droppings I can see, and no interest from my lurcher either, and there likely would be if it was rats.

I think voles  can eat their way through substantial amounts of vegetation, which is their main source of food, but they are a protected species. I know I have them in my garden because I have caught them in box traps before and the owls love to hunt them in my garden at night. So for now I think I'll just persevere with the box traps and relocate my seedlings until I've caught them. I do have an awful lot of mice and voles in my garden and in the past the box traps have worked pretty well for me.

[arugula]

No, I wouldn't be tempted to use poison because I have two dogs and I've seen a dog almost die, not from eating the poison but from eating the dead rat that ate the poison.

Surely the dogs don't go in the polytunnel and definitely not unsupervised? If the rodents are using a run from underground into your tunnel, then they're likely to go back down the hole to die. We have dog(s) and have never had a problem with this.

Moving them on won't do it, they'll just come back.

I don't think anyone suggested moving them on, flushing out as I suggested will kill them by drowning.

[parsley]

Oh no I knew what you meant but I've seen people try several times to move rodents somewhere else with no success. They'll always come back to a good food source (or others move in)