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GARDENER'S
READING ROOM
Fertilizers,
Pest Control and Soil Management
Organic Gardening
Good
Bugs Bad Bugs
 It’s
spring, and as the weather warms and the daylight increases
with each passing day, so does the insect populations in our
gardens. As Martha would say, this is a good thing. As the
insect "pest" populations rise, so do (or should!)
the insect "beneficials" (predatory and parasitic
insects). It is a balance that we must work to achieve rather
than resorting to chemicals every time we encounter an insect.
Most
insecticides and pesticides are not "insect exclusive"—most
kill a variety of insects, the good along with the bad. If
predatory and parasitoid insects didn’t control other
insects, we would find the earth uninhabitable. As the saying
goes: if we killed all the spiders, we would be waist deep
in other insects. Sounds pretty uninhabitable to me! The key
to "pest" insect control is attracting and keeping
the "good" insects: predators such as praying mantises,
damselflies and dragonflies, lady beetles, and lacewings;
and parasitoids like wasps that derive their nourishment from
the body of a host insect.
The
best way to attract beneficial insects to your garden is to
plant as diversely as possible, perhaps even leaving a weed
or two. Pests flourish in a monoculture (where only one type
of plant is grown) and can make control by natural or chemical
means almost impossible. Many beneficial insects need pollen
to eat if their target peat insect population is low or prefer
certain plants to lay their eggs on. Green lacewings (voracious
aphid eaters), for example, will lay their eggs on scented
geraniums. A number of herbs are excellent for attracting
beneficials: coriander, dill, lavender, lemon balm, lovage,
mustard, parsley, spearmint, fennel, thyme, and white sage.
Flowers good for attracting beneficials include baby’s
breath, cosmos, lemon gem marigolds, nasturtiums, sunflowers,
and Queen Anne’s Lace.
If
you find one type of pest insect in abundance, look for natural
means of control. You can buy lady beetles to control aphids;
beneficial nematodes to control root weevils, crane fly larvae,
and flea larvae; Worry Free™ Slug Bait if your ground
beetle population is too low to control your slugs; and apple
maggot or codling moth traps for your apple tree (note: these
items contains different pheromones so one trap will not attract
both pests).
If
you are buying or trying to attract beneficial insects, it
is important to avoid the use of disruptive chemicals. It
is also important to note that totally eliminating pests is
not required to grow good crops or beautiful flowers. It’s
only necessary to reduce pests below the damage threshold.
Remember, too, when you see a caterpillar lunching on a favorite
plant and kill it, you may have eliminated the butterfly that
you’d been trying to attract! You might have to sacrifice
a little bit of plant for the pleasure of watching the butterflies
float throughout your garden.
By Susan Ragan-Stuart
Skylights Spring/ Summer 2000, Vol 14, No. 2
Other
articles on fertilizers, pest control and soil
management
Other
articles on organic gardening
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