Pesticides Made with Essential Oils
Pesticides made with
essential oils are derived from plants that are known to have insecticidal
properties. It is important to remember that just because a pesticide
is derived from a plant does not mean that it is safe for humans and other
mammals or that it cannot kill a wide variety of other life. Many pesticides
made with essential oils are formulated with synergists. These have no
insecticidal effect of their own, but serve to enhance the insecticidal
effect of the botanicals. Carefully read the labels on all products before
use to make sure that they do not also contain toxic pesticides. Some
botanical pesticides can be quite toxic to humans and should not be used.
Neem oil, garlic oil, and sabadilla are some least-toxic botanical pesticides
listed below. Others that can also be used as a last resort are citrus
oils, mint oil, pine oil, pepper extracts, tree oils and herbal extracts.
Neem oil, extracted
from the tropical neem tree, azadirachta indica, contains insecticidal
properties that are composed of a complex mixture of biologically active
compounds. It has a strong, unpleasant odor. Its various active ingredients
act as repellents, feeding inhibitors, egg-laying deterrents, growth retardants,
sterilants and direct toxins. Neem has both contact and systemic action
in plants. The active ingredients biodegrade rapidly in sunlight and within
a few weeks in the soil. Neem oil has very low toxicity to mammals. In
India, neem products have been used in toothpaste, pharmaceuticals, and
as a grain protectant for centuries without apparent harm to humans.
Garlic oil
exhibits antibacterial, antifungal, amebicidal and insecticidal qualities.
Although garlic oils kill pest insects and some pathogens, it also kills
beneficial insects and microbes. Thus, it is not recommend as an all-purpose
spray for outdoor use.
Sabadilla alkaloids,
from the dried ripe seeds of a member of the lily family, Schoenoxaulon
officinate, are often used as a broad spectrum low-persistence insecticide.
Discovered by Native American peoples in northern South and Central America
centuries ago, it was used in wounds against vermin, and came to be used
also by the Spanish invaders as a louse powder. The powdered seeds have
been known to require aging to become fully active, but potency can be
increased by heat treatment and extraction of the alkaloids into a solvent,
like kerosene. The alkaloids are photoreactive or unstable in the presence
of light. Reported acute toxicity of the crude dust to mammals is low,
with an oral rat LD50=500 mg/kg, but the purified sabadilla alkaloids
are known to be toxic to bees. Sabadilla dust is very irritating to the
upper respiratory tract, causing sneezing, and is irritating to the skin.
Poisoning symptoms include: retching, muscle spasms, and especially, slowed
heart beat and decreased blood pressure, not unlike that seen with the
drug digitalis. The symptoms are slow to disappear. A researcher noted
in 1901 that repeated small doses showed possible cumulative effects.
Bio-Integral
Resource Center. 1987. "Update: Neem - A New Era in Pest Control Products?"
The IPM Practitioner 9(10). U.S. EPA. 1999. Recognition and Management
of Pesticide Poisonings. EPA 735-R-98-003. Office of Prevention, Pesticides,
and Toxic Substances. Washington, DC.
