Posted: 20/06/2016 at 18:58
The smell of onions and garlic deters aphids hence the advice to plant them with roses to confuse the pests. I grow ornamental alliums near my roses but the best treatment for aphids are birds and hoverflies and ladybirds which hoover them up by the thousand so I put out bird feeders near my roses to attract the birds to feed the aphids to their chicks and other flowers to attract the hoverflies.
Slugs and snails can, apparently, be put off eating our treasures if they are sprayed with an infusion of garlic in water. I have never tried it as I don't want a garlic smelling garden and, besides, it doesn't work in wet weather which washes it off.
I just use wildlife friendly slug pellets around the most susceptible plants and leave the rest to get to get on with it. When I find a slug in my treasures I lob it into the road to be splatted by traffic.