The garden used to be overrun with aphids, sometimes to the extent that it was hard to find some plants under the seething mass of bugs (eww!).
One thing I learnt at my permaculture course was that umbrelliferous plants (plants with umbrella-shaped collections of tiny flowers) attract beneficial wasps into the garden. The wasps then inject their eggs into aphids, which hatch and eat the aphids from the inside out.
This all sounded good in theory, but I was doubtful. Nonetheless, I tried a different tack this year, and let many more plants to go seed. This included parsley, dill and fennel (all umbrelliferous plants). Much to my surprise, it worked! Narry an aphid to be seen anywhere since.
(We’ve also had good success with companion planting, such as garlic chives next to our climbing rose.)
Good scores for natural pest control…