Green Insecticides

Going Green Using Diatomaceous Earth How-To Tips: An Easy Guide Book Using A Safer Alternative, Natural Silica Mineral Insecticide: For Homes, … & Environment– A Healthier Life For All from Tui Rose
Diatomaceous Earth is a food grade insecticide that originates from ancient fossilized algae provided by Mother Nature. Safe as a natural insecticide for homes, gardens and pets.

Soap like Savona is a fatty acid, non toxic insecticide that is a safer alternative to chemical pesticides.
Savona is made from potassium salts
It is effective against mealybugs, whitefly and aphids. 1 bottle will cover 500 sq.m, simply dilute with water for application. link

Green Pesticides for Insect Pest Management by S. Ignacimuthu (Editor) and S. Jayaraj (Editor) is not cheap at £56.05 but is aimed at a professional market.