Cats can be a nuisance when they enter a garden and use an area as their toilet. Cats are creatures of habit and will regularly use the same area for toileting; burying the waste in soil or gravel areas. If this is a vegetable patch it can be rather unpleasant and unhealthy to come across the waste when working in the vegetable garden or when harvesting vegetables.
Cats can also be transport for fleas and leave these behind where they regularly rest. When the cat/s are not there the fleas will find other sources of blood to feed on; perhaps you or your pets.
Such cat habits can be hard to break. But cats can be re-educated to find a more suitable place for their toilet and to rest. Cats use smell to locate their toileting and resting areas. If you already have a problem, then the first step is to remove the existing waste and water the surrounding soil to wash the smell away. Then apply NO Cats & Dogs animal repellent to the soil or resting area (note NO Cats & Dogs will leave a white residue). The smell of the spray is repellent to cats; whose sense of smell is many times better than ours; we are unable to detect the smell.
Initially, the cats may try and ignore the smell or even try to cover it with their own scent or burying the treated soil, but over time they will be inclined to find another location to toilet or rest.