stupid dog and chewing gum (how to stop dog picking up & eating gum when out?)

Hope this is in the right bit!!!!!
Our notoroiuosly stupid 10 year old cross breed ( no really he is stupid) has, as I've mentioned already on here, started consuming chewing gum when he's out and about.
He is no longer vomiting it back up, but has been known to poo out lumps of it!!!!! For the first time yesterday OH caught him, onlead, grinding his teeth against the pavement in an attempt to eat a manky old bit of chewy!!!!! He was told off but then when he was off lead later on, he was doing it again.
I'm guessing it's not good for the daft mutt...any ideas why he may have started doing it or how we can stop him doing it off lead??????? Any help would be greatly appreciated.
This is the dog that has so many stories attached to him that he is no longer known just as 'Biff' but has earned the title 'the' before it....

Have you taught the command 'leave'? If not he is not too old to learn

With time and patience it is possible to teach a dog to 'leave' a particular substance even when off lead. He needs to associate finding the substance with a really super reward if he leaves it and comes back to you or lays/sits beside it Not pretending it is easy to train, but it is possible.

Otherwise, if he is ingesting potentially harmful things when off lead then the solution is to keep him on lead. Maybe not ideal, but safe

"Leave it" command is a must I'm suprised you've coped 10 years without it!

Carry something really tasty on walks; sausages cut up cheese etc as soon as dog looks at chewing gum give command "leave it" followed by tasty treat.

I do not believe your dog is thick they have more intelligence than a lot of humans! he has just learned how to play you!

No, The Biff is really thick.
Even the vet says my dog is really thick.
He always has been thick and always will be thick, it's quite appealing in a strange sort of way!!!!!!!!
The Biff knows the 'leave it' command and will 'leave it'....only to return to 'it' post yummy treat....thick but not as thick as we like to make him out to be!!!!!!!!!!!!
Thanks for the advice though. He also has a great recall...thanks to a love of his tummy...again will head back post yummy treat.....
I am sooooooo reluctant to keep him on the lead just because he eats any chewy he can find, but perhaps that's what we're going to have to do.......
What do you reckon to leaving bits of chewy on our patio with something disgusting in...pepper or the like.......?????? Just a thought, try to give him a negative association????? It's a relatively new behaviour (we think) so The Biff could be persuaded out of it perhaps???? What do you think?????

I know it sounds harsh saying The Biff is thick...but honestly if you met him....

nice but dim......

Yuk! The things our dogs pick up when out, but luckily mine both know the "leave" even thicko Georgie will drop anything instantly on the drop it command, but chewing gum they've never found!!! The other day Cassie picked up a black dead mouse and ran off with it, but as soon as I shouted leave, she tossed it in the air and left it. One day it was that horrible spikey long thin bone from a rabbits leg and if she hadn't known the drop it command I don't know what would have happened with that one. I think you might have a good idea there with the baiting of offending gum, it might put him off for the future? Good luck too

Thanks Helena!!! it's a good job we love them to bits isn't it??????!!!!!!