They are useful in controlling a wide range of pests. Another botanical insecticide is d-limonene . This citrus peel extract kills insects on contact. As of now, it is only available in the form of flea control sprays and shampoos. Inorganics Inorganic insecticides include boric acid and the desiccating dusts silica gel and diatomaceous earth.
Boric acid is derived from boron, a naturally occurring mineral.
It acts as a stomach poison and causes insects to die from starvation. Boric acid is available in powder, paste, aerosol, tablet, and liquid forms for use against cockroaches, ants, and other insects. Professional pest control professionals can use boric acid products to control wood-infesting beetles and to spot treat wood to protect it from termites. Silica gel is an inert, nonabrasive material that is very effective in absorbing moisture. It absorbs the waxy coating on the insect's body and causes death by dehydration.