Rodenticides are always changing and millions of £ $ € get spent testing products each year. Ketchup on my broccoli worked a treat when I was in shorts.
Rodents have very poor eyesight and get by on smell and touch, their fur is very sensitive. Placed on a “rat run” they will have little choice of coming into contact with the foam whilst in search of food. They preen about 40% of the time they are awake and in certain circumstances can be more effective than bait.
Racumin Foam is another weapon in our armoury. It is used in difficult to reach places, behind plasterboard for example, where access is difficult. I mentioned it because it is new to the market. Sachets, grain, blocks, traps. Indoors or out. Pets, children and wildlife all need to be considered when attempting to remove a link in the food chain.
One of the best repellents is nicotine, so soaking fag butts in a bucket of water for a week, then spraying where you don’t want rodents is an option.