What hasn't been stated here yet is that you have to fill out a declaration form. It asks about shoes / boots etc, and also where you have been (farms, hiking etc.)
My experience is - declare everything you have a concern about and then explain it so - 'Yes I do have hiking boots but I have cleaned them so you could eat your lunch of them'.....
....I saw one young couple just infront of me who hadn't declared anything and when they were x rayed they had to go to one side and unpack ALL their cases - I think they had dirty shoes, and food and .......
......and that could lead to a BIG fine.
Anyway if your emigrating it's going to be your country so I think everyone would want to keep it free from imported pests and diseases or?????