Less Toxic Insecticides

Less Toxic Insecticides

Less Toxic Insecticides

Clemson University Cooperative Extension Service
Prepared by Karen Russ, HGIC Information Specialist, Clemson University

While a good pest
management plan will start with preventative, cultural and other non-chemical
methods, these are sometimes not completely effective on their own. In this case
a pesticide may be considered. If pesticide use is deemed necessary for control
of the pest problem, it is good practice to use the least toxic pesticide that
will do the job effectively. Although all pesticides are by their nature toxic
in some way to some organisms, there are now a number of "less toxic" pesticide

Insecticides may be
considered less toxic for several reasons. Generally they should pose less risk
to human and environmental health than conventional insecticides. Many break
down rapidly and do not accumulate in the body or environment. Some are very
pest specific and do little or no damage to other organisms. Still others, such
as bait stations, minimize human exposure to the pesticide.

While "organic"
insecticides are often less damaging to the environment than conventional
insecticides, they are still pesticides. All pesticides should be evaluated
before selection for level of toxicity, effectiveness, environmental impacts and
costs. Some "organic" pesticides are as toxic, or even more toxic, than some
synthetic pesticides.

Soaps and Oils

Insecticidal soaps and
oils have a number of advantages for controlling insects. They are virtually
non-toxic to humans and other mammals, and are relatively safe to beneficial
insects in the landscape. They control a wide range of common soft-bodied pests
including aphids, mealybugs, thrips, whiteflies, mites, and scales. It is
difficult for pests to develop resistance to oils and soaps. Soaps and oils are
now readily available and relatively inexpensive.

Both soaps and oils can
cause damage to plants if applied when plants are water stressed, temperatures
are above 90 °F, or high humidity prevents rapid drying. Some plants are
sensitive to oil sprays. Read and follow the label.

Since soaps and oils
work on contact, an effective application must coat both the upper and lower
leaf surfaces as well as stems for best results. Repeated applications may be

Soaps: Insecticidal
soaps damage the protective coat of soft-bodied insects causing them to

Homemade soap recipes
are not recommended because they may be more likely to cause foliage burn.
Commercial insecticidal soaps are tested on plants and are less likely to cause
damage. Some common product names include Safer Insecticidal Soap and M-Pede.

Horticultural Oils:
Oil products smother soft bodied insects on contact. Oils are formulated as
either summer or dormant oils. Dormant oils are heavier oils used on dormant
plants to control overwintering insects (e.g., aphids, spider mites, and
scales). Dormant oils will damage plants if used during the growing season.
Summer oils are lighter and more refined and can be applied to both actively
growing and dormant plants. Do not apply summer oils when the temperature is
above 90 °F.

Some readily available
summer weight horticultural oils include Ortho Volck Oil Spray, Sunspray,
Control Solutions Ultra Fine Oil, and Green Light Horticultural Oil. Ferti-Lome
produces a Dormant Oil Spray.


Botanical insecticides
are naturally occurring toxins extracted from plants. There are several
advantages to using botanical rather than synthetic insecticides. Plant derived
insecticides breakdown quickly in the environment, resulting in little risk of
residues on food crops and less risk to beneficial insects. Some materials can
be used shortly before harvest. Most botanicals are rapid acting and most, but
not all botanicals are of low to moderate toxicity to mammals. Because most
botanical insecticides must be eaten by the insect pest, they are primarily
harmful to these pests and do little harm to beneficial insects.

There can also be
disadvantages to using these products. Rapid break down, while less risky to
health and environment, often creates a need for precise timing or more frequent
applications. Several botanical insecticides are quite toxic and should be
handled accordingly. Some botanical insecticides can be difficult to find in
local stores.

Neem: is a
relatively new and promising botanical insecticide made from extracts of Neem
tree seeds. It is used to control a wide variety of insects including
leafminers, whiteflies, thrips, caterpillars, aphids, mealybugs, spider mites,
scale crawlers, and beetles. Neem is most effective against actively growing
immature insects.

Azadirachtin, the
active ingredient in neem extracts, has a very low mammalian toxicity. It acts
as an insect feeding deterrent and growth regulator. Neem does not produce a
quick knockdown and kill, but stops insect feeding. The treated insect usually
cannot molt into its next life stage and dies without reproducing.

Many commercial neem
products exist, including Azatin XL, Neemix, SouthernAg Triple Action Neem Oil
and Safer BioNeem. These products are labeled for use on ornamentals, foliage
plants, trees, shrubs and food crops. Many neem products and formulations are
also effective as a fungicide against powdery

Limonene: (also
known as d-Limonene) is produced from citrus oils extracted from oranges and
other citrus fruit peels. It is used as a contact insecticide against ants,
roaches, palmetto bugs, fleas, silverfish and many other insects. Limonene has
low oral and dermal toxicity to mammals, birds and fish, although it can cause
skin irritation or sensitization in some people.

Pesticide products
containing limonene are used for flea and tick control on pets, insecticide
sprays, outdoor dog and cat repellents, mosquito larvicides, and insect
repellents. Many products containing limonene are labeled as safe for use in
areas near food. Limonene is the active ingredient in Ortho Home Defense Indoor
Insect Killer, Concern Citrus Home Pest Control, and in products made by Orange
Guard. Safer Fire Ant Killer and Citrex Fire Ant Killer also contain

Capsaicin: is the
material that makes chili peppers hot. It can be used on ornamentals outdoors
and indoors for control of aphids, spider mites, thrips, whitefly, lace bugs,
leafhoppers, and other pests. It is important to note that capsaicin containing
products are primarily used to repel insects, rather than to kill existing

To date there is
limited research showing the effectiveness of capsaicin products as
insecticides, although they appear to be effective at repelling certain animal
pests such as rabbits, deer and squirrels.

Products containing
capsaicin include Hot Pepper Wax Insect Repellent and Bonide Hot Pepper

Pyrethrum: is made
from the finely powdered flowers of a species of daisy. The word pyrethrum is the name for the
crude flower dust itself, and the term pyrethrins refers to the insecticidal
compounds that are extracted from pyrethrum. Pyrethroids are not botanical
insecticides, but synthetic pesticides that are very similar in structure to the

Pyrethrum is a contact
insecticide and must be applied directly to the insect to be effective.
Pyrethrum rapidly paralyzes pests, but may not kill them. Pyrethrum and
pyrethrins are often formulated with another insecticide to ensure that
paralyzed insects do not recover and once again become pests.

Because the pyrethrum
mammalian toxicity is very low, it can be applied to food crops close to
harvest. Pyrethrum has high contact toxicity for common beneficial insects.

Pyrethrum and
pyrethrins are marketed under a wide variety of trade names, including Concern
Multi-Purpose Insect Killer and Natural Guard Natural Insect Spray.

Garlic: is marketed
in several products intended to repel insects, much as capsaicin does. Products
are labeled to repel a wide variety of pests on ornamental plants, but garlic
may also repel beneficial insects. To date there is little research showing
effectiveness of garlic insecticides.

Products containing
garlic or garlic oil include Garlic Barrier and Mosquito Barrier.

Rotenone: is one of
the most toxic of the commonly-used botanical insecticides. Rotenone acts as a
nervous system poison. It is highly toxic to fish and other aquatic life and is
commonly used as a fish poison. Rotenone can be toxic to mammals through
inhalation and may cause skin irritation. Rotenone will also kill many
beneficial insects and should only be used to control severe insect
infestations. In most cases, other, safer pesticides should be used in
preference to rotenone.

Sabadilla and
Ryania: are older botanical
insecticides that are rarely available. No sabadilla or ryania products could be
found that are currently registered for use in South Carolina.

Nicotine: derived
from tobacco, is one of the most toxic botanicals. It is a fast-acting nerve
toxin and is highly toxic to mammals. It is easily absorbed through the eyes,
skin, and mucous membranes. Because of its high toxicity it is no longer
registered for use as a pesticide. Home brewed nicotine preparations can also be
quite toxic. Less harmful products will produce equal results.


A variety of pesticides
based on essential oils or components of essential oils have come on the market
in the last few years. Essential oils are volatile, highly concentrated
substances extracted from plant parts. In 1996 the EPA established that certain
ingredients that pose minimum risk to users no longer require EPA approval to be
marketed as insecticides. A number of these ingredients are essential oils,
including the oils of cedar, cinnamon, citronella, citrus, clove, eugenol (a
component of clove oil), garlic, mints, rosemary, and several others. As
insecticides, these work most commonly as contact killing agents only, so
re-treatment may be needed. Most essential oils used as pesticides work by
disrupting an insect neurotransmitter that is not present in people, pets, or
other vertebrates.

Eugenol: is a
component of clove oil. It is a fast acting contact insecticide that is
effective on a wide variety of household pests such as cockroaches, ants, dust
mites, flies, wasps, spiders, crickets, and fleas. It is also used on some
ornamental plant pests such as armyworms, thrips, aphids and mites.

Eugenol has little or
no residual activity, although the scent of cloves will linger. Products based
on eugenol are considered minimum risk pesticides with very low risk of damage
to the environment or user.

Products that contain
eugenol include Bioganic Brand’s Flying Insect Killer and Bioganic Lawn and
Garden Spray.


Microbial insecticides
contain microorganisms (viruses, bacteria, fungi, protozoa, or nematodes) or
their by-products. Microbial insecticides are especially valuable because their
toxicity to nontarget animals and humans is extremely low.

Insecticidal products
comprised of a single species of microorganism may be active against a wide
variety of insects or group of related insects (such as caterpillars) or they
may be effective against only one or a few species. Most are very specific.
Since there is such a narrow range of insects killed, they spare the beneficial
insects almost entirely.

Bacillus Thuringiensis:
products are the most widely used microbial insecticides in
the United States. They are commonly known as Bt. Different subspecies of Bt are effective against different groups
of insects or their larvae.

You will achieve the
best results with Bt products by
following a few guidelines.

  • Make sure the Bt product you have chosen lists the
    specific insect you want to control.
  • Make sure the insect is at a stage where it
    is susceptible to control by Bt.
    In general, Bt products are
    effective against young larval stages but will not kill adults.
  • Spray the parts of the plant on which
    insects are feeding thoroughly, including the underside of leaves. Bt products must be eaten in order to be
  • Treat with Bt in late afternoon or evening, or on a
    cloudy day as Bt breaks down in
  • Be aware that Bt does not kill immediately, but that
    poisoned insects will stop feeding almost immediately.

var. kurstaki
(Btk) products are toxic only to larvae of
butterflies and moths. They are used to control many common leaf-feeding
caterpillars, including caterpillar pests on vegetables, bagworms and tent
caterpillars on trees and shrubs, and European corn borer larvae.

Some caterpillars are
not effectively controlled by Bt,
especially those that live in the soil or bore into plant tissues without
consuming a significant amount of the Bt
applied to plant surfaces.

Bacillus thuringiensis
var. kurstaki
products include Dipel, Javelin, Thuricide, Safer Caterpillar Killer, and
several others.

var. israelensis
formulations kill mosquito, black fly, and fungus gnat larvae.
Bti is most effective for
mosquito or black fly control when it is used on a community-wide basis. For
most homeowners, eliminating standing water sources is more effective than
applying Bti or other
insecticides. Floating products sold as dunks or pellets can eliminate mosquito
larvae in ornamental ponds and other areas that cannot be drained.

Bti products that
are available commercially include Mosquito Dunks, Vectobac, Teknar, and

var. tenebrionis
(Btt) products are toxic to
certain beetles. They are commonly used to control Colorado potato beetle and
elm leaf beetle adults and larvae, but are not pathogenic or toxic to some other
key beetle pests. Bonide Colorado Potato
Beetle Beater, and Novodor are products containing Btt.

Milky Spore:
products contain the bacteria Bacillus popillae and Bacillus lentimorbus. Milky spore is
applied to turf and watered into the soil below to control the larval (grub)
stage of the Japanese beetle and, less effectively, some other beetle grubs. If
a substantial grub population is present at the time of application, milky spore
can survive beneath undisturbed sod for a period of 15 to 20 years.
Consequently, lawn applications of milky spore bacteria might not have to be
repeated each year.

Spinosad: is an
insect toxin derived from a soil-dwelling bacterium. It kills primarily by ingestion and is
used against fire ants, caterpillars, thrips, whitefies, aphids, leaf miners,
scales and plant bugs. It is also used against borers of fruit trees. When
applied at recommended rates, this product poses less risk than most
insecticides to mammals, birds, fish, and beneficial insects. It is, however,
toxic to bees, and should not be applied to plants in flower. Affected pests
stop feeding within minutes, but may remain on the plant for up to two

Ferti-lome Borer,
Bagworm, Leafminer & Tent Caterpillar Spray contains spinosad. Fire ant
baits formulated with spinosad include Conserve Fire Ant Bait,
Justice, Payback Spinosad Fire Ant Bait and Eliminator Fire Ant Killer

: is a fungus that attacks and kills a variety of
immature and adult insects. Insects affected by various formulations include
whiteflies, aphids, mites, caterpillars, leaf hoppers, grasshoppers, Colorado
potato beetles, Mexican bean beetles, Japanese beetles, boll weevils, cutworms,
sod webworms, bark beetles, chinch bugs, fire ants, European corn borers, and
codling moths. Beneficial insects, such as lady beetles, are also susceptible.

Products containing
Beauvaria work best when applied
at the onset of an infestation. It typically takes three to seven days after
application for the spores to germinate, penetrate, and grow throughout the
insect, thus killing them. Thorough spray coverage is essential because fungal
spores must contact the insect for infection to occur.

Commercial products
contain spores that germinate after application. New formulations do not require
high humidity in order to provide effective control. Commercial products
containing Beauvaria include
Naturalis H&G and Botanigard.

Beneficial Nematodes:
Nematodes are microscopic, worm-like parasites. While some
species of nematodes are pests of turf grass and other plants, others are
beneficial, being parasites of harmful insects. Since beneficial nematodes can
not develop in vertebrate animals, they are very safe for use in pest control.

Beneficial nematodes
can be used to control a variety of plant pests, including larvae of black vine
weevil, clearwing borers, cutworms, sod webworms, mole crickets and white grubs.
It is important to select the proper nematode species when trying to control a
particular pest.

Nematodes can be
difficult to use for most home gardeners. They must be shipped, stored and used
under specific temperature and moisture conditions, and generally must be used
very soon after shipping. For this reason, they are best ordered from suppliers
immediately after a pest problem is observed.

A number of nematode
products are available by mail order. Be sure the product you are ordering is
specified for the pest you have and that you are able to provide proper
environmental conditions for the nematodes. In general, nematodes require moist
conditions, high humidity, and temperatures between 55 and 90 °F with little
direct sunlight.


Diatomaceous Earth:
is a nontoxic powder composed of fossilized, one-celled
organisms called diatoms. It is used to control slugs, millipedes, sow bugs,
cockroaches, ants and soft-bodied insects like aphids. It has low mammalian
toxicity. Use the "natural grade," not the type used as a filtering agent in
swimming pools.

Prolonged exposure to
diatomaceous earth will irritate lungs and other tissues of people or pets.
Because it also kills honeybees, avoid applying the product to crops in

Commercial products
include Concern Diatomaceous Earth and Natural Guard Diatomaceous Earth.

Kaolin Clay:
products act as a barrier that irritates insects and disguises
the host plant by coating it with a ghostly white film. Insects are apparently
unable to recognize plants treated with kaolin. It is most commonly used against
a wide variety of pests on apple and pear trees. Also, kaolin can be used to
control Japanese beetles, tarnished plant bugs, thrips, leafhoppers, cucumber
beetles and Colorado potato beetles on vegetable crops. Kaolin must be applied as a preventative to be
effective and can not control a pest that is already established.

Kaolin clay can be
applied up to the day of harvest and is non-toxic. Kaolin is sold as Surround
Crop Protectant

Sodium Fluoaluminate:
is a mineral that forms sharp, glass-like particles that
puncture insect gut cells if ingested. Since it only affects insects that have
eaten treated leaves, it does not adversely affect beneficial predators and
parasites. It is effectively used against leaf feeding caterpillars, sawflies
and beetles. Sodium fluoaluminate is sold as Kryocide.

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. Most boric acid products are available as ready-to-use products.
Boric acid is sold under a number of brand names, including Roach Prufe, Terro
Ant Killer II and Borid.

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.
Silica gel products are often used by professional pest control operators to
control cockroaches, silverfish, and other pests.

Sulfur: is probably
the oldest known pesticide in current use. It can be used as a dust, wettable
powder, paste or liquid, and is primarily for disease control. However, mites,
psyllids and thrips are also controlled by sulfur. Sulfur is nontoxic to
mammals, but may irritate skin or especially eyes.

Sulfur is also used as
a fungicide to control powdery mildew, rusts, brown rot and leaf spots on
fruits, vegetables and ornamentals.

Sulfur has the
potential to damage plants in hot, dry weather. It is also incompatible with
other pesticides. Do not use sulfur within 20 to 30 days of applying
spray oils to plants as it reacts with the oils and is more likely to cause
damage to foliage. Do not apply sulfur when temperatures are above 80


Insect growth
regulators (IGRs) are juvenile insect hormone analogs. They interfere with egg
development and molting of various insect life stages. Because of their mode of
action, they are very safe for vertebrate animals. IGRs are among the safest
pesticides for application in homes. They are primarily used in homes for flea
control. More information is available in HGIC 2502, Flea

Two commonly available
IGRs are methoprene (Precor) and pyriproxyfen (Nylar).


Bait Stations:
deliver an insecticide through a sealed plastic or metal
chamber that insects enter. This gives bait stations the advantage of decreasing
both the amount of insecticide used and the likelihood of exposure to it. Bait
stations are particularly suitable for use in situations where the safety of
children is a concern, or in areas where food is prepared or stored.

Numerous brands of bait
stations are commonly available to control cockroaches and ants.


Always: read the pesticide label and follow its directions exactly.
You may only use the
pesticide on sites or crops listed on the label. Be sure to observe all special
precautions that are listed on the label. Wear protective clothing or equipment
as listed on the label when mixing or applying pesticides. Mix pesticides at the
rate recommended for the target site as listed on the label. Never use more than
the label says. Follow all label directions for safe pesticide storage and
disposal. Always remember to read and heed the six most important words on the

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