Guide to Organic Pesticides

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Photo by iStock/BackyardProduction
With the right organic pesticides, you can stop tomato hornworms like this dead in their tracks.

The philosophy behind organic gardening is hardly new to
MOTHER EARTH NEWS readers, who’ve known about the benefits for years.
However, interest has grown markedly in the mainstream.
Many are finally joining the organic movement in order to
rebel against additives in food, chemicals in the soil and
water, pollutants in the air, and the dangerous pesticides
regularly sprayed. The balance of nature has been
precariously disturbed as the number of good and necessary
bugs has been diminished, and to make matters worse, many
of the harmful insects have developed resistance to common
pesticides. But there’s good news…

Today’s scientists are discovering more and more plants
that produce natural bactericides, fungicides, and
insecticides. In fact, many nontoxic household products are
considered effective in the war against gardening pests.
Below are the acceptable organic controls that gardeners
find most effective today.

Household Detergents

You can mix these
insecticides right in your kitchen.

1) USDA recommendation: Mix one teaspoon of liquid
dishwashing detergent with one cup of vegetable oil. Shake
vigorously to emulsify and add to a quart of tap water. Use
at 10-day intervals as an all-purpose spray for white
flies, spider mites, aphids, and various insects on
carrots, celery, cucumbers, eggplants, peppers, and others.
We’ve used it on evergreens and other ornamentals. Note:
Test on a single plant first, because it may cause tip
burn. This is a contact insecticide, so spray mix directly
on the pest.

2) Liquid detergent-alcohol spray: Mix one teaspoon of liquid dishwashing detergent plus one
cup of rubbing alcohol in one quart of water. Test on a few
leaves first to make sure no harm is done to sensitive
plants. Spray top and bottom sides of leaves; or if plant
is small and potted, invert it in a large pan of solution
(holding soil ball securely) and gently swish back and
forth. Repeat in seven days.

3) Liquid detergent—hot pepper spray: Steep three tablespoons of dry, crushed hot pepper in 1/2
cup hot water (covered) for half an hour. Strain out the
particles of peppers, and then mix solution with the liquid
detergent formula mentioned above. Good for a number of
insects on both indoor and outdoor plants. Note: Apply to
plants outdoors. Do not use on windy days. Avoid breathing
fumes, which can be irritating to nose and eyes. You can
substitute hot Tabasco sauce or Louisiana hot sauce for hot
pepper.

Pyrethrin

This natural insecticide derived from the
pyrethrum plant (Chrysanthemum cinerariaefolium). Along
with pyrethroid, its synthetic substitute, it is highly
effective against a wide range of insects. Each should be
used according to manufacturer’s directions.

Lime Sulfur

This old-timer, still used by both organic and
nonorganic gardeners, is applied during the dormant period.
Kills most species of mites as well as mite eggs and those
of many other insects. Lime sulfur also has fungicidal
value and can be used on fruit trees as well as
ornamentals. Note: Lime sulfur applied to plants near the
house will stain the paint. Apply cautiously near
buildings.

Sabadilla

Made from seeds of a South American lily. Used
for squash bugs and stink bugs. Irritating to eyes and
lungs if care is not taken. Use according to manufacturer’s
directions.

Garlic and Onions

Grind up raw onions or garlic into a
puree. Soak in warm water overnight and strain. Liquid can
be sprayed on roses, fruit trees, and flowers. Kills aphids
and apple borers. Scrape off any loose bark on the trunk
and swab liquid on. Many gardeners mix onion water and wood
ashes and paste mixture on tree trunks.

Ryania

Made from ground stems and roots of a South
American shrub. Controls European corn borer and other
worms. See directions on container.

Tomato Leaves, Crushed

To avoid chemical sprays, try using
crushed tomato leaves for leaf-spot diseases. Tomato leaves
contain solanine, a chemical that has an inhibiting effect
on black spot fungus. Grind two cups of leaves to a puree.
Add five pints of water and one ounce of cornstarch. Keep
refrigerated.

Tobacco Water

Cigar and cigarette butts will kill worms in
the soil of houseplants. Mix a solution of tobacco and
water so that it is the color of brown tea; pour on the
soil. Don’t let anyone drink it by mistake! The solution
kills fungus gnats, symphylids, centipedes, root lice, and
other underground pests—and it could kill you.

If you have aphids or other insects in your terrarium or
dish garden, ask a friend who smokes to blow cigarette
smoke into the glass and then seal the top. The smoke
knocks plant lice for a loop.

Snuff

For tiny flies or worms in the soil of house plants,
try sprinkling snuff on the surface. Note: Do not use
homemade tobacco remedies on tomatoes, peppers, eggplants,
and other members of the Solanum family. It could spread
tobacco virus to these plants. 

Hot Pepper

To discourage cats, dogs, many insect pests,
and snails from munching, dust powdered hot pepper or a
spray of hot pepper sauce on plants.

Oil and Sulfur Sprays

Petroleum oils (of organic
derivation) have been used successfully for killing insects
for over 200 years. Apply only on “hard” or woody plants.
There are two types:

1) Dormant oil should be used only when plants are
dormant—in winter or early spring.

2) Summer oil should be used during the growing season and
restricted to woody plants. Some oil sprays can be applied
in either summer or winter.

Miscible oil sprays kill insects and eggs such as
over-wintering leaf rollers and aphid and mite eggs. They
also kill scale insects and adult mites. Dilute with water
according to manufacturer’s directions. The oils cause
little or no harm to most beneficial insects, and
resistance to sprays does not build up with oils.

Talcum Powder

Effective against flea
beetles and corn ear worm. Lightly dust leave surfaces
after every rain.

Soaps as Insecticides

Soapsuds are ideal
for killing aphids. Many home gardeners prefer vegetable-
or plant-based soaps as effective aphicides.

Rhubarb Leaves

Boil one pound of chopped
leaves in one quart of water for 30 minutes. Strain and use
as a spray against aphids and other pests.

Garlic and Red-Pepper Spray

Grind up a large bulb of garlic (or a large onion). Add one
tablespoon of ground cayenne pepper and one quart of water.
Steep for one hour. Strain liquid into a sprayer or
watering can and refrigerate remainder in a tightly covered
jar. It will be potent for several weeks, and is effective
on all kinds of chewing and sucking insects.

Spearmint Spray

Put into a blender one
cup of chopped spearmint leaves, one cup of green onion
tops, and 1/2 cup of chopped hot-red pepper. Add 1/2 cup of
water to assist in blending. Pour solution into a gallon of
water. Add 1/2 cup of liquid detergent (preferably
lemon-scented). Dilute by adding 1/2 cup of mixture to a
quart of plain tap water.

If the plant is small, dunk it in this solution, otherwise
strain it and spray on. Effective on all chewing insects.

Editor’s Note: Adapted from The Green Thumb Garden
Handbook, published by Lyons & Burford.