Most gardeners are anxious to get out into their gardens
as soon as the weather warms up and the first green sprout appears.
Unfortunately, plant-eating insects are just as anxious as we are to get
into the garden. They seem to think that our beautiful shrubs and tasty
vegetables were planted for their benefit!
There are many fine products available in catalogs and
garden centers to control insects. But for health or environmental
reasons, some gardeners are hesitant to use chemicals in their garden,
especially in a vegetable garden.
So what can you do to avoid sharing your beautiful
flowers, shrubs and vegetables with every insect that passes through the
neighborhood without using potentially harmful chemicals?
Practicing good garden housekeeping should be your first
defense in the battle of gardener versus insects. In other words, keep a
clean garden and don’t give the insects a place to hide and reproduce.
Rake up any dead leaves from the ground and discard them, or better yet,
add them to your compost. Harvest vegetables as soon as they ripen, and
don’t leave over-ripe vegetables in the garden. Clear out all dead
foliage from your gardens in the fall. Prune out any dead or damaged
branches from your trees and shrubs, making clean cuts without ragged
edges where insects can hide.
If you find insect damage on your plants, there are a
large number of organic products that work in a variety of ways to kill
insects or discourage them from eating your garden plants. Because many
organic insect controls are used for specific types of insects, it is very
important to know what insects you are dealing with before choosing the
correct organic insecticide. Carefully examine the damaged plant to find
the culprits, looking under the leaves and along the stems where they may
be hiding. Your county’s Ag Extension Agent can help identify specific
insects, or you can also do an online search for insect identification
sites.
Butterflies often lay their eggs on plants, and when those
eggs hatch the little caterpillars will stay and feed on the plant as they
grow. Caterpillars can be controlled using a common organic insecticide
known as Bacillus thuringiensis, or Bt. Bt is a naturally occurring
bacteria that causes caterpillars to stop eating and die. There are
several varieties of Bt that can be used, depending on the type of
caterpillar you’re after, including one specific to Colorado potato
beetle larvae and another for corn earworms. Bt is also effective against
tomato hornworms, the little green worms that like broccoli and cabbage,
and bagworms. Bt should be applied at 1-2 week intervals to kill
succeeding generations of insects. Gardeners with butterfly gardens should
avoid using Bt on their plants because it is harmful to butterfly
caterpillars. However, Bt is completely harmless to pets and people.
Diatomaceous earth is another natural insecticide that may
be used on a variety of insects. Diatomaceous earth is a fine powder that
feels like talc, but it is actually the fossilized skeletal remains of
small aquatic critters called diatoms. It is completely harmless to people
and pets, but when soft-bodied insects come in contact with it, the tiny
sharp edges of the diatoms lacerate the insects, making them dehydrate and
perish. Apply diatomaceous earth in the early morning or evening when the
plants are wet with dew, which will make the powder stick to the surface
of the leaves and doom the insects that walk through it. Diatomaceous
earth can be used to control ants, aphids, beetle grubs, box-elder bugs,
flea beetles, those nasty little earwigs and many more insects. It’s
also safe to use on houseplants, and can even be sprinkled on the ground
to control slugs.
Insecticidal soap is another favorite organic insect
control. Safe to use around bees, birds, and animals, insecticidal soap is
made of fatty acid salts. It can be used in the garden and on houseplants
to control aphids, spider mites, whiteflies and some leafhoppers and
caterpillars. The drawback to insecticidal soap is that it must be sprayed
directly onto the offending insects to be effective. Insects breathe
through their shells, and insecticidal soap suffocates insects by coating
their shells so they cannot breathe. Insecticidal soap must be applied
thoroughly and repeatedly for the best results.
There are also plant-based insecticides available. The
seeds of the Neem tree produce an oil that disrupts insects’
reproductive cycle, preventing them from multiplying. The Neem tree is
native to Southeast Asia and is also grown now in Australia for its
insecticidal properties. Neem works quickly and is effective against a
variety of caterpillars, beetles, aphids and borers.
Many insects are actually fussy eaters and they won’t
eat plants that are distasteful to them. If you’ve grown garlic you may
have noticed that insects leave it alone. You can find insect repellants
made with garlic that can be sprayed onto plants to prevent insects from
eating them. These garlic-based insect repellents become odorless within
five minutes after they’re applied and leave no aftertaste on food
crops. The plants actually absorb the garlic and stay distasteful to
insects for up to a month. There are also garden insect repellants
available that are made with hot peppers. Like the garlic-based
repellants, the hot pepper repellants are sprayed on the plants to make
them distasteful to insects.
Organic insecticides and insect repellants are becoming
available at more garden centers and gardening catalogs every year. It is
not difficult to control insects with organic insecticides, but the
organic gardener must be diligent with frequent plant inspections and take
prompt action to avoid infestations when insect damage is found in the
garden.
By Kathy Anderson
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