For The Truth About Garden Remedies: What Works, What Doesn't and Why (Timber Press, softcover, 212 pages, $14.95), University of Minnesota horticulturist Jeff Gillman tested homespun garden remedies.
Here’s a summary of what worked.
Garlic as a pest repellent: Repels whiteflies, aphids and beetles. Gillman offers a few recipes, but this is one of the simpler ones. Peel the cloves of a garlic bulb and chop in a blender along with two cups (500 mL) of water, blending thoroughly. Strain the mixture, then dilute with about four litres of water for spraying.
Beer for slug control: Use a container about 15 centimetres deep, dug into the ground so its top is even with the soil surface; fill with beer to within 2.5 centimetres of the rim so slugs have to extend to reach it, which causes them to fall in and drown.
Dishwashing liquid for insect control: This works, but plants can be damaged. Avoid using antibacterial or super-strength products in particular. Or, as Gillman suggests, rely instead on commercial insecticidal soaps, which are both safe and effective.