University of Vermont Extension
Department of Plant and Soil Science
GOOD BUGS IN THE GARDEN
Dr. Leonard Perry, Extension Professor
University of Vermont
Most may not realize that over 97 percent
of insects, spiders, and similar bugs (better known as “arthropods”) in home
gardens and landscapes are beneficial.
That is, they either do no harm, provide food for desirable species such
as birds, or prey upon insects we consider bad and destructive to our
crops. Knowing some of the most common
good bugs, and how to help and not harm them, will help minimize pest problems
and the use of pesticides.
There are two main groups of beneficial
insects. The predators, such as spiders
and lady beetles, are generally larger than their prey, killing and feeding on
them. The parasitoids, such as parasitic
wasps and flies, are generally smaller than their hosts and lay eggs on or
within them. When these eggs hatch, the
resulting larvae (like small caterpillars) kill the host insects by feeding on
A University of Maine
Extension bulletin provides ten tips to attract
and sustain these beneficial insects.
a tolerance to some damage to your plants. Most plants tolerate low levels with
no lasting harm.
shelter for your good bugs from adverse weather such as extreme heat. This just might be
leaf litter and debris under shrubs (don’t be too tidy around them).
the diversity of plantings in your landscape.
A wide range of plants will support a wide range of beneficial
insects. Avoiding monoculture with only
one species of plant ensures that if you do get a problem, it wont get out of
control and wipe your plantings out.
use bug zapper lights, those bluish ones that attract insects with ultraviolet
light, then electrocute them. A University of Delaware study found these lights kill
mainly harmless insects and not biting flies.
In fact, most mosquito species are not attracted to ultraviolet
before you spray. This often kills
beneficial insects as well as bad ones.
Cutting out webworm nests from trees, picking off Japanese beetles, and
improving airflow to deter slugs are examples of simple, non-toxic physical
inspect plants for pests. It is much
easier to control them as they just appear.
your insects before you make a decision on whether to control. Extension services, garden stores with
trained staff, books, and online websites are useful in identification.
plants for predators. These include
flowers with umbels (umbrella-like clusters) such as yarrow, composites such as
daisies, spikes such as lavender and goldenrod, and flat cups such as
buttercups. Many predators like what we
don’t and call weeds. It may be helpful
to have a nearby patch for such “wildflowers.”
plants healthy. Pests usually attack
weakened or stressed plants. These
stresses can be created by improper watering (too much as well as too little in
a drought, or sandy soil), improper placement of plants according to light and
soil needs, mulching too close and deep around plants, and improper
fertilization. Too much fertilizer,
especially nitrogen, may be worse than too little. Lush plants from excess fertilizer are
favorite targets for pests such as aphids, mites, and the black
addition to the above tips concerning managing your yard or garden for
beneficial insects, some consider buying and bringing more in. These can be purchased from specialty
catalogs and websites. Importing
beneficials can be complex in order to have success. You must determine the proper beneficial,
best time to release it for the life cycle of the pest, how many are needed, and
proper release requirements such as time of day, food, and water needs. Use of imported beneficials is much easier in
a greenhouse, as often outdoors they fly away.
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