Botanical Insecticides

 

Botanical insecticides are naturally occurring insect toxins extracted from plants. Several such chemicals have been formulated for insect management in the home garden. They act quickly, causing immediate paralysis, death, or cessation of feeding. Many botanical insecticides, but not all, are less toxic than synthetic pesticides to mammals and plants. Botanical insecticides also tend to break down rapidly in environment.

Botanical insecticides do have drawbacks. Because of their rapid degradation, botanical insecticides must be applied frequently and precisely. Many are broad-spectrum insecticides and will harm beneficial insects. Several botanical insecticides also are harmful to fish or other wildlife. Botanical insecticides are often more expensive to purchase than synthetic pesticides.

 

Commercial preparations of some botanical insecticides include a synergist such as PBO (piperonyl butoxide) or MGK 264 (N-octyl bicycloheptene dicarboximide) to increase the insecticide’s effectiveness. Both of these compounds have low mammalian toxicity butare not accepted by some organic certification programs. Without the addition of a synergist, the activity of some active ingredients (for example, pyrethrin) is too low for practical use. Applicators may be poisoned by careless handling or misuse of botanical insecticides. Always follow the label directions and wear recommended protective clothing.

Pyrethrins

Pyrethrins are common botanical insecticides derived from the dried flower heads of the daisy Chrysanthemum cinerariaefolium, which is grown in Kenya and Ecuador. Pyrethrins (six related insecticidal compounds that occur naturally in the crude flower dust) are contact poisons that knock down insects immediately. The addition of PBO greatly increases insect mortality. Pyrethrins act as stomach poisons and are labelled to control ants, aphids, roaches, fleas, and ticks. Apply pyrethrins frequently. They degrade rapidly, leaving little or no residual activity. Avoid mixing a pyre-thrin compound with soap solutions as soap

Pyrethroids, such as resmethrin and permethrin

are synthetic compounds that are closely related to natural pyrethrins. Pyrethroids tend to be more toxic to insects and to persist in the environment longer than pyrethrins. Because of their effectiveness, pyrethroids are applied at lower rates than other synthetic insecticides.

Rotenone

Another common botanical insecticide isrotenone, which is obtained from the roots of South American legumes. It acts as a stomach poison and can effectively control leaf-feeding insects such as beetles and aphids. A synergist, such as PBO or MGK-264, may be included to increase the effectiveness of rotenone. Roten-one is moderately toxic to mammals but is extremely toxic to fish. It is used as a fish poison in water management programs. Rotenone degrades rapidly in air and sunlight.

Sabadilla

Sabadilla is derived from the seeds of the sabadilla lily, a tropical lily found in South America. Sold under the trade names of “RedDog” and “Natural Guard,” sabadilla is a contact and stomach poison that can control caterpillars, leafhoppers, thrips, stink bugs, and squash bugs. It is labelled to control vegetable pests

Because sabadilla breaks down rapidly insunlight, no residue is left after application. Synergists also are added to sabadilla to increase insect mortality. Sabadilla is toxic tohumans and is extremely toxic to honeybees. Avoid applying sabadilla when bees are present.

Neem

Neem is a relatively new botanical insecticide in the United States even though it has been used in India for centuries. The neem active ingredient azadirachtin is extracted from neem tree seeds; it has both insecticidal and fungi-cidal activity. Neem acts as an insect repellent, feeding deterrent, and growth regulator. It is most effective when used early in the insect pest’s life cycle. Apply neem as soon as eggs hatch, when immature stages are present.