Organic products like pyrethrum, derris, bordeaux are safer than inorganic ones. Soil sterilisation by steam or solarisation may also worth considering for vegetable and flower beds. Companion planting is great for keeping soils free from harmful microorganisms and discouraging insect pests. Encouraging natural predators like ladybirds which help control aphids are also increasingly popular among natural gardeners. Not to be forgotten is the importance of management of the garden.
Earthworms are terrific for plants and soil.
They also help to break down organic matter, turning it into humus which is an important soil conditioner. Encourage earthworms by regular mulching or spreading. If a plant proves difficult to grow, don't persist with it. It's not all that hard either. In the first place you need to look at how you do things in the garden.