Pesticides derived from natural mineral or botanical sources are an alternative to chemical pesticides for organic gardeners. These substances may be organic, but they are still powerful, and in many cases poisonous. Always use care when handling any pesticides. Wear gloves and a respirator mask and eye protection when applying. Don't allow any of the pesticide to come in contact with your skin and keep all pesticides out of the reach of children and pets.
Neem is derived from a tree in India and is used to kill moths, caterpillars, thrips, leaf miners and other insect pests in the garden. Neem is not toxic to mammals and some neem products are used as a livestock and pet dip to treat fleas, ticks and other pests.
Nicotine, found in tobacco, is a poison that will kill many garden pests. You can purchase nicotine sprays for use in the garden. Some people make their own by steeping tobacco in hot water and straining the cooled solution into a sprayer. Nicotine can be harmful if ingested or absorbed through the skin.
Pyrethrum is made from an extract of chrysanthemum flowers. Pyrethrum is used to treat both flying and crawling insects and is available in liquid and powder form. Pyrethrum is slow-acting and nontoxic to most mammals.
Rontenone is made from the roots of plants in the Leguminocea family. Resin from the plant roots is ground into a powder that is used to kill harmful caterpillars and worms, aphids and beetles. Rotenone is extremely poisonous to fish, so avoid using it around ornamental ponds.
Sulfur powder kills many insect pests and can kill harmful plant fungi as well. Rock sulfur is ground into powder for use as an insecticide. The powder may be sprinkled from a shaker or broadcast with a spreader. Don't mix sulfur with other pesticides, as adverse chemical reactions can occur. Don't apply sulfur to plants on hot, sunny days, since the mixture of sulfur and sunlight can burn plants.