Homemade Aphid Spray Recipes

Tomato Leaf Spray: As a member of the nightshade family the leaves of tomato plants contain toxic compounds called alkaloids. Making a spray is simply a matter of chopping up a couple of handfuls of leaves to release the alkaloids, soak them overnight in water and strain into a spray bottle. This spray is toxic to aphids but safe for plants and humans, take care though if you're allergic to members of the nightshade family.
Garlic Oil Spray: For the garlic spray it's the Sulfur contained within that's the active ingredient we're after to kill the aphids. Finely chop or mince three or four cloves of garlic and soak in oil overnight. Strain out the garlic and add the oil to a pint of water. Add a healthy skoosh of dishwashing liquid to let the oil and water mix and dilute down further before use. Approx 2 tablespoons of the garlic solution per pint of water.

Choosing which of the above to use is down to you and what you'll use it for. The garlic spray is probably more potent and effective at killing aphids but it's also indiscriminate and will kill everything, including ladybirds and other beneficial insects. You also need to check that the plant you're spraying doesn't mind as it can yellow leaves and damage some plants. The tomato leaf spray shouldn't harm beneficial insects but some humans can be allergic.