Organic Pest Control
Insecticides should be used only as a last
resort to prevent serious insect damage. There are many ways to
reduce or eliminate the need for insecticides in your gardens.
The best approach is to use a combination of techniques,
including:
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Building a healthy soil. We recommend
amending your soil with compost each year, and avoiding
synthetic fertilizers. And remember to mulch your gardens.
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Planting
companion plants.
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Attracting beneficial insects. Not all
insects are bad. Your garden and surroundings contain many
insects that are actually beneficial because they feed on
harmful insects. Therefore, a gardener should be able to
identify garden insects and determine whether they are
harmful or beneficial. Many organic gardening books
provide pictures of the most common beneficial and pest
insects (try the Color Handbook of Garden Insects
from Rodale Press), and information on how to encourage
populations of beneficial insects like ladybugs,
lacewings, Assassin Bugs, predaceous wasps, spiders, and
more. Remember that the application of insecticides -
either synthetic or organic - can destroy the natural
balance by eliminating beneficial insects as well.
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Practice proper crop rotation and
create a diversified planting.
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Plant trap crops. Trap crops are those
preferred by an insect, and located a bit away from your
growing beds. In many cases, weeds or wild flowers are
preferred by our insect friends.
Aphids
Make aphid traps by erecting yellow boards
and covering them with Tanglefoot (replace Tanglefoot weekly).
Make a water trap by painting several small, shallow pans bright
yellow and filling them with soapy water (refill them after each
rain). Anchor aluminum foil to the soil for 1 foot around
transplants to repel aphids (slope soil away from plants so rain
water and mud do not obscure the reflective surface. Repel
aphids by spraying a mixture of 2 tsp. hot pepper, 2 cloves
garlic, 1 tsp. liquid soap (DO NOT use anti-bacterial soap!) and
1 quart of water. Peppermint soap sprays are said to work well -
1 T to a gallon of water. Also try a garlic spray - soak 3
ounces of finely minced garlic cloves in 2 tsp. of mineral oil
for 24 hours. Stir well and strain into a glass jar for storage.
Combine 1-2 T of this concentrate with 1 pint of water. Spray
directly on the bugs. Make some rhubarb tea - shred several
leaves and boil for one hour. Let steep overnight, strain and
spray. We've found insecticidal soap (Safer's) works wonders -
just don't spray your plants too frequently, or you will damage
tender leaves (which curl and dry up). Plant marigolds to repel
aphids, and try planting nasturtiums or sunflowers as a trap
crop. Garlic planted near roses and rosemary is reputed to repel
aphids. Aphids can transmit plant virus diseases, so remove and
destroy diseased plants to avoid the spread of the virus to
healthy plants. Back to Top
Asparagus Beetles
Plant marigolds near asparagus to repel
beetles. Compost plant refuse in the fall to remove
overwintering sites. Hand pick and destroy eggs, larvae and
adults (in the morning before they become active). Cut foliage
off at the ground as soon as it begins to die back. Pyrethrum
and Rotenone sprays will work on severe infestations. Back to Top
Cabbage Loopers & Cabbageworms
Cover plants with cheesecloth or floating row
covers to prevent egg-laying. Hand pick the green worms. Spray
infested plants with Bacillus Thuringiensis when worms are still
small (Bt stops the caterpillar from feeding, but only works
after it is ingested). Remove alternate host weeds such as wild
mustard and shepherd's purse from the garden. Interplant a hot
pepper plant between every 2 cabbage plants. Mint, sage, and
rosemary are the traditional enemies of cabbage moths - so plant
them to deter the adult moths. Back to Top
Colorado Potato Beetle
Potato beetles prefer to feed on potato,
eggplant and tomato. Interplant non-host crops with preferred
host crops, and practice crop rotation. Hand pick the orange egg
masses, reddish-brown larvae, and yellow and black striped
adults and destroy. Place straw mulch around plants as a barrier
to beetle colonization of plants in the spring. Horseradish has
the reputation of being able to repel potato beetles. Back to Top
Corn Earworm (Tomato Fruitworm)
With no controls applied, earworms usually
damage only the tip of the ear. Cut off the damaged tips and the
remainder can be eaten. Plant and harvest corn as early in the
season as possible to avoid heavy infestations. Drop * teaspoon
of mineral oil on the silks of each corn ear after the silks
have wilted but before they begin to dry; this helps to repel
moths and egg-laying. Select tight-husked corn varieties for
planting; this inhibits worm movement into the ear. Beginning at
the flower stage, check upper tomato leaves once per week for
small, round, white fruitworm eggs. Spray plants with Bacillus
Thuringiensis (Bt) weekly as long as eggs are detected. Back to Top
Cucumber Beetles
Plant "non-bitter" cucumber varieties; the
bitter compound in cucumber attracts beetles. Cover young plants
with cheesecloth or floating row covers until just before bloom.
Interplant cucumbers with radishes; radish seems to repel
cucumber beetles. Tansy, marigolds and nasturtiums are also
repellent to beetles. Eliminate weeds in and around the garden;
some weeds are hosts for bacterial wilt disease that is spread
by cucumber beetles. Back to Top
Cutworms
Cutworms emerge to feed at night and often
bite through seedlings or small stems, causing the plants to
fall over. Because grass and many weeds are preferred hosts,
remove grass and weeds in the garden, and prepare the soil well
in advance of planting. Damage can also be prevented by placing
a paper or plastic "sleeve" over the plant and pressing the
bottom into the soil. (Paper cups with the bottoms removed or 4"
high sections of 1/2 gallon paper milk cartons are ideal.) Place
sections or sleeves around newly-set transplants or
newly-emerged seedlings so that 1" inch is below ground and 3"
is above ground. Tuna cans with the bottoms removed may also
work. Back to Top
Flea Beetles
Flea beetles are most numerous in the spring.
Plant susceptible crops like eggplant and radish later in the
season or use row covers. Weeds bordering the garden may serve
as alternate hosts; removing weeds will reduce flea beetle
populations. Unless flea beetle populations are heavy, their
feeding will not kill plants or reduce yields; control is
usually unnecessary. However, last year many of our gardens
suffered a severe infestation by flea beetles. We attributed
this to the warm winter (a prolonged cold spell will
significantly set back insect populations) and the grass mulch
we applied over the winter to our growing beds. Both Rotenone
and Pyrethrum sprays worked relatively well in eliminating the
population, though we tried Diatomaceous Earth first, with
limited success, and wood ash, with more success. (If you use
Diatomaceous Earth, make sure to use a non-pool grade kind - the
pool grade variety can cause serious lung problems if inhaled -
and to wear a mask while applying.) Also, make flea beetle traps
by erecting yellow boards and covering them with Tanglefoot
(replace Tanglefoot weekly). And till the soil during frosts to
expose any overwintering adult flea beetles or larvae. We've
recently seen a recommendation to sprinkle flour on the leaves
as an alternative control, or to sprinkle cayenne pepper mixed
with an equal part of corn starch. Repel flea beetles by
spraying a mixture of 2 tsp. hot pepper, 2 cloves garlic, 1 tsp.
liquid soap (DO NOT use anti-bacterial soap!) and 1 quart of
water. Peppermint soap sprays are said to work well - 1 T to a
gallon of water. Also try a garlic spray - soak 3 ounces of
finely minced garlic cloves in 2 tsp. of mineral oil for 24
hours. Stir well and strain into a glass jar for storage.
Combine 1-2 T of this concentrate with 1 pint of water. Spray
directly on the bugs. Plant catnip to deter flea beetles (but be
careful - catnip, like the mints, is a relatively invasive
plant). Back to Top
Grasshoppers
Trap grasshoppers by using a 1 quart
container half filled with a 10% molasses and water mixture.
Grasshopper populations are most damaging in late summer; a
floating row cover can be used to protect late-season plantings.
Fall plowing of the garden including fence rows and garden
borders exposes grasshopper eggs to the weather and insect
predators. Back to Top
Harlequin Bugs
Try a mix of 1 quart water, 1 tsp. baking
soda, 1 tsp. cooking oil, and a few drops of dish soap. Shake
well and spray, making sure to make contact with the bugs.
Pyrethrum and Rotenone sprays also work - but all require
repeated application. Rodale advised to gather as many of the
offending bugs as one can, and whir, with water, in a blender.
After the mixture is strained, one should spray it on and around
the infested plants. The theory is that the dying bugs release a
chemical, warning the other bugs away (this also works with
other bugs, such as Japanese Beetles). One treatment we have not
yet tried involves what’s known as "peppering". Again,
gather as many bugs as you can. The bugs are then burned, and
the ashes are applied during certain alignments of the planets,
which is thought to enhance their pesticidal effect. We will
experiment with this treatment this year, should we suffer (as
we did in 1999) another Harlequin Bug infestation. Back to Top
Japanese Beetles
Avoid planting gardens near lawns or in land
previously containing lawn. If you use a Japanese beetle
pheromone trap, locate the trap at least 50 feet upwind of crop
plants. Protect plants with floating row covers. See, also, the
recommendation for Harlequin Bugs, above. Back to Top
Leafhoppers
Protect plants with cheesecloth or another
fine, mesh row covering. Make leafhopper traps by erecting
yellow boards and covering them with Tanglefoot (replace
Tanglefoot weekly). Spray plants with insecticidal soap.
Leafhoppers can transmit virus diseases; remove diseased plants
to avoid the spread to healthy plants. Back
to Top
Mealy Bugs
Mix 1-2 cups isopropyl rubbing alcohol with 1
quart water. Spray directly on the bugs. Be careful not to
overdo it. As we have not used this one yet, be very cautious -
test, test, test! Back to Top
Mexican Bean Beetles
Handpick and destroy yellow egg masses,
yellow larvae, and adult beetles (adults look like ladybugs, but
are brown with black spots). Interplant non-host crops among
bean plants to disrupt egg-laying. Consider planting soybeans as
a trap crop. Back to Top
Scale
Insecticidal soap works wonders! For small
infestations, consider swabbing it on - treating each leaf and
stem individually - with a cotton ball. Spray small bursts of
Pam or another vegetable oil onto the scale - but be careful
about overdoing this (too much oil will kill your plant). Keep
the plant out of the sun for a day or two. Again, test, test,
test! Back to Top
Slugs
Spade or till garden area in the fall and
again in the spring before planting. Hand pick slugs (this works
best at night), and place slugs into a solution of salt or soapy
water. Place beer (stale beer must be used) in small cups or
pans sunken in the soil so the lip of the container is slightly
below ground level. Slugs are attracted to the beer; once inside
they drown. The beer should be replaced about every 3 days for
best results. Try a spray made out of 1 part non-sudsing ammonia
to one part water (the spray dissolves the slugs, then breaks
down into nitrogen on the foliage). Be sure and test this first,
and do not use in hot weather or on drought-stressed plants. Use
Diatomaceous Earth, crushed up eggshells, sawdust, wood ash, or
cocoa bean shells as a barrier - the slugs won't crawl across
this rough surface. (If you use Diatomaceous Earth, make sure to
use a non-pool grade kind – the pool grade variety can
cause serious lung problems if inhaled - and to wear a mask
while applying. And replace DE and wood ash after each rain. A
further caution - be careful with sawdust and wood ash. The
sawdust, if from horse stalls, can contain fresh urine or
manure, which can burn plants. The wood ash and lime - being
alkaline - can raise soil pH significantly if overused.) Copper
strips placed around your plants has also been found to work.
The copper provides a shock to the slug's body, and it will not
attempt to cross it (unraveled copper scrubbies may work, too,
but this control has not been sufficiently tested). Predatory -
or Decollate - snails also work well. Try contacting
Applied Bio Pest for information and a supply. I've recently
read that slug infestations are a symptom of acidity in the
soil. (If this is so, concerns about raised pH would be
unfounded - and, in fact, one would want to raise soil pH.
Watering the soil with liquid seaweed also has an alkalizing
effect.) Slugs dislike strong smells - so try placing aromatic
herbs (including Artemisia, Mint, Tansy, or Lemon Balm) and
conifer twigs around your plants or between your rows. Constant
hoeing is another suggested control, as is tilling in quackgrass
during the fall. Back to Top
Spider Mites
Spray plants with insecticidal soap. Mites
don't like moist conditions, so keeping the foliage wet can
deter mites (but can also encourage plant diseases.) Wash your
plants with a mild soap solution, then spray the plants -
especially the underside of the leaves - with a strong spray of
water. Repeat weekly until the spider mites are gone. Back to Top
Squash Bugs
Remove and destroy clusters of oval,
orange-brown squash bug eggs. Place shingles or boards near
squash or pumpkin plants in spring or early summer to attract
squash bugs, then collect and destroy adult bugs under the
boards each morning. Nasturtiums and marigolds planted near
squash plants may deter squash bugs. Back to Top
Squash Vine Borers
Cover plants with a fine mesh cloth (such as
cheesecloth) or a row cover until female flowers appear. Plant
in late summer or fall to avoid heavy vine borer infestations.
Plant resistant varieties - the vines of winter squash tend to
be too hard for the borer to penetrate. Cut open borer entry
holes in the stem with a knife, then remove the worm and pack
moist earth around the stem (you can recognize borer entry holes
by the mass of "sawdust" on the ground below the hole). This
will help the plant produce additional roots at the site of the
slit. Place an aluminum foil mulch around the stems to
discourage adults from landing. Though it is labor-intensive,
wiping the stems every day with a piece of soft cloth will knock
off any eggs which have been laid. This has worked well for us.
Back to Top
Tomato Hornworms
Hand pick worms - which are quite large -
from plants. Bacillus Thuringiensis (Bt) is effective if sprayed
when the worms are still small. Dill planted next to tomatoes
will serve as a preferred trap crop; hand pick worms off the
dill. Do not destroy hornworms which have small, white cocoons
attached to their body, as these are the cocoons of parasitic
wasps. (The larvae feed on the hornworm, eventually killing it.
A greater benefit is the release of additional parasitic wasps
into your gardens.) Turning the soil in the fall will expose
hornworm pupae to weather and predators. Back to Top
Whiteflies
Whiteflies are rarely a problem in outdoor
gardens, but are a major problem in the greenhouse. Make sure
purchased transplants are not infested with whiteflies (or other
insects). Make whitefly traps by erecting yellow boards and
covering them with Tanglefoot (replace Tanglefoot weekly). Spray
plants with insecticidal soap. Back to Top
Wireworms
Wireworms are the slender, yellowish-brown,
hard-bodied larvae of click beetles. They can survive deep in
the soil for up to 5 years, and can move up to attack seeds or
young plants. Several wireworm species prefer plants in the
grass family, and are usually not a problem unless the garden is
planted into land that previously contained grasses or crops in
the grass family. Turning over the soil in the fall, and again
in the spring, well in advance of planting, will help to reduce
wireworm populations. Back to Top
Yellowjackets
Place a glass jar over the entry/exit hole
(do this in the evening or early in the morning, when hive
activity is decreased). The wasps become confused, and die
trapped in the jar. As others return to the hive and make new
entry holes, place another glass jar over that hole. This system
worked quite well for us last year, and we were able to
eliminate a very large yellowjacket hive - smack in the middle
of one of our pea beds - with neither pesticides nor stings!
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