Following is a brief description of some least toxic botanical and mineral pesticides as well as biological controls available for managing insect pests, including insecticidal soaps, pyrethrum/pyrethrins/pyrethroids, rotenone, ryania, sabadilla dust, nicotine sulfate, superior horticultural oil, ladybird beetles, lacewings, predatory mites, trichogramma wasps, and Bacillus thuringiensis (Bt).
Pyrethrum/Pyrethrins/Pyrethroids
These are broad-spectrum insecticides. Pyrethrum powders are made
directly from the flowers of a species of chrysanthemum, and pyrethrins
are the active compounds from the pyrethrum flower. Pyrethroids are
synthesized pyrethrins. These materials disrupt the nervous system of
insects and cause paralysis. They are fast-acting and often used for
their "knock-down" effects to quickly reduce large insect pest
populations. They are moderately toxic to humans and other mammals and
break down quickly from sunlight, moisture, and oxygen, leaving no
residues. They are often combined with rotenone and/or ryania to
provide more effective and longer lasting results.
Rotenone
Rotenone is derived from the roots of several leguminous plants and is a
broad-spectrum contact and stomach poison that affects insect nerve and
muscle cells, causing the insects to stop feeding and die anywhere from
a few hours to a few days after ingestion. It is most effective against
leaf-eating caterpillars and beetles, can be applied as a spray or dust,
and is available in a variety of strengths as well as in combination
with pyrethrin and ryania. If rotenone is eaten by humans or other
mammals it is broken down by the liver with no long term negative
effects. It can be dangerous if large amounts are inhaled.
Caution: Rotenone is extremely toxic to fish! Keep out of water; special care should be taken near areas which contain fish populations.
Ryania
Ryania is extracted from the stems of a woody South American plant and
is a stomach poison that causes insects to stop feeding soon after
ingestion. It is reported to be most effective when used in hot weather.
Ryania is moderately toxic but considered to be relatively harmless to
humans and other mammals.
Sabadilla Dust
Sabadilla is a broad spectrum insecticide that comes from the seeds of a
lily indigenous to Central and South America. It affects the nerve
cells of insects, causing paralysis and then death. It is primarily
used for adult insects that are hard to control with other botanical
insecticides. Although the dust is considered to be the least toxic of
all registered botanical insecticides, the active alkaloids in its pure,
extracted form are very toxic and can make a person sick if ingested or
absorbed through the skin and mucous membranes. Sabadilla is highly
toxic to honeybees and should only be used in the evening, after they
have returned to their hives. It degrades rapidly in sunlight and air,
leaving no harmful residues.
Nicotine Sulfate
Nicotine sulafate is a contact poison derived from tobacco and is one of
the most toxic botanical insecticides. It causes severe disruption and
failure of the human nervous system, is easily absorbed through the
eyes, skin, and mucous membranes, and is extremely fast-acting.
Nicotine Sulfate should only be used as a last resort. Best results
have been reported with diluted mixtures. It biodegrades rapidly with
little residual effect.
Superior Horticultural Oil
Also called dormant oil, this is a highly refined mineral oil that
kills insects and their eggs by suffocating them. It is applied in
late winter or very early spring to kill scales, aphids, and other
overwintering insects. It is also used in the fall to kill eggs.
Ladybird Beetles
Ladybug larvae and adults are predators of aphids, small worms, and
other soft-bodied insects. Release at the rate of 7,000 per 5,000
square feet in the evening or early morning when they are calm and slow
moving.
Lacewings
Lacewing larvae prey on aphids, immature scales, spider mite eggs and
most other soft-bodied insects or eggs. It is the best all purpose
biocontrol predator available. Release at the rate of 1,000 eggs per
200 square feet for aphid infestations and 1,000 eggs per 900 square
feet as a preventive treatment. Three successive releases at 5-7 day
intervals are recommended. For release into trees, small amounts can be
placed in paper cups and stapled to the leaves or branches. The larvae
feed on pests for 1-3 weeks until they become adults, which primarily
eat nectar and honeydew. Adults will lay eggs to ensure a continued
lacewing population.
Predatory Mites
Predatory mites are released to control the two-spotted spider mite and
other pestiferous mite species. Predatory mites are most effective if
they are released when no more than 10% of the infested plant's leaves
have spider mites. Heavy infestations should first be treated with
insecticidal soap followed by weekly releases of predators until under
control. Release at the rate of 200 per 100 square feet.
Trichogramma Wasps
Trichogramma wasps are tiny parasites (4 or 5 would fit on the head of a
pin!) that lay their eggs into the eggs of over 200 species of moths and
butterflies. The larvae then feed on the pest eggs. The best time to
release them is in cool evenings and early mornings. A sequence of 3
releases at two week intervals is recommended.
Bacillus thuringiensis (Bt)
Bt is a bacterium used to control the larvae of moths, butterflies,
mosquitos, and other insect pests. It is sprayed or dusted onto leaves
and when target insects eat it they stop feeding, become paralyzed, and
die. Different strains of Bt have been developed and each one is
effective only for the specific pest or group of pests for which it is
intended, including the larvae of spruce budworm, tent caterpillars,
mosquitos, and many others.
Source: IPM Access - An Integrated Pest Management Online Service
All materials copyright IPMPA unless otherwise noted. All rights reserved.
E-Mail: ipmpa@efn.org
URL: http://www.efn.org/~ipmpa
Voice: (503) 343-6969 [office] or (503) 345-2272 [message]