Insecticides are often needed to control insects on plants--both houseplants and plants in the landscaping. Certain insecticides control certain pests. When choosing an insecticide, be sure it is formulated to control the specific pest on your plant. If you prefer to use natural insecticides, be sure that the chemical property kills the insect you are trying to control. Combine natural insecticides with manual bug removal, such as plucking bugs off the plant.
Microbial insecticides are chemicals that contain microorganisms. They have low toxicity to pets and humans. They are also called biological control agents or biological pathogens. They contain viruses, fungi, nematodes, bacteria or protozoa, or the toxins produced by these organisms. Microbial insecticides are applied as dusts, liquid drenches, sprays, concentrates or granules. The United States Environmental Protection Agency regulates all forms, except nematodes.
The are many benefits of microbial insecticides. The toxin is usually specific to a certain species of insect, so it doesn't affect the "good" insects. Good insects might be predators of other pests and do not destroy plants. The microbial insecticide is not deactivated or otherwise damaged by the residue of other insecticides, so it is often used in conjunction with other insecticides, if needed. It could even be sprayed on food crops just before harvest.
There are several botanical insecticides, including Rotenone and Sabadilla. According to Iowa State University, Rotenone comes from South American legumes. It controls leaf-feeding insects such as aphids and beetles because it acts as a stomach poison. It is toxic to mammals and extremely toxic to fish.
Sabadilla comes from the sabadilla lily--a South American tropical lily. It is sold as "Natural Guard" and "Red Dog." It kills on contact and is also a stomach poison. It controls caterpillars, thrips, leafhoppers, stink bugs and squash bugs. It breaks down fast once sun hits it and does not leave a residue. It is toxic to humans and honeybees.
Pyrethrin is a common natural insecticide. It comes from the chrysanthemum (not the cultivated mum). The active chemical is esters, which is found in the flower head of the plant. It works as a contact poison, paralyzing the insect. It takes about 90 seconds to paralyze insects. It can be purchased in dust form or as an emulsion. It is often combined with diatomaceous earth. According to UCLA, acute toxicity to humans, pets and other mammals is low.