Bonsai Boy of New York
Beneficial Insects for Your Garden’s
Adapted from “Natural Enemies are Your
Allies” by the University of California.
Photos courtesy Regents of the University of California
Remember the three “P’s” of beneficial insects:
pollinators, predators and parasites.
Pollinators, such as honeybees, fertilize flowers, which increases
the productivity of food crops ranging from apples to zucchini.
Predators, such as lady beetles and soldier bugs, consume pest
insects as food.
Parasites use pests as nurseries for their young. On any given
day, all three “P’s” are feeding on pests or
on flower pollen and nectar in a diversified garden.
If you recognize these good bugs, it’s easier to appreciate
their work and understand why it’s best not to use broad-spectrum
herbicides. Here are 10 worth knowing:
mummies are the bodies of aphids that have been killed by
parasites such as mini wasps. The hole was made when an
adult mini wasp emerged from the aphid. You can tell if
beneficial mini wasps are present by looking closely for
the mummies in aphid colonies. To allow the mini wasps to
thrive, avoid spraying pesticides.
beetles (Coleoptera) are large, often black, shiny beetles
that frequently are encountered beneath mulch. About 2,500
species are native to North America. Ground beetles are
most active at night. They consume soil-dwelling, soft-bodied
pests, including slugs, snails and caterpillars. Although
they are called ground beetles, some species do climb trees
to feed on caterpillars. Ground beetles need a stable habitat
because they do not move around very much. They also grow
more slowly than many other insects; a complete life cycle,
from egg to larvae to pupae to adult, takes one year, and
most adults live two to three years.
(Neuroptera) may be brown or green, and adults are usually
one-half to three-fourths-inch long, with delicate, transparent
wings. Eggs are often seen stuck to leaves on short threads.
The larvae, known as aphid lions and aphid wolves, feed
on aphids, mealybugs, scale, thrips, mites, and other larvae
and eggs. The predacious period lasts 15 to 20 days, during
which a larva will eat 100 or more insects a day. Adults
need pollen, nectar and honeydew (secreted by aphids and
other sucking insects), as well as water.
beetles (Coleoptera) are yellow-orange to red, with black
spots. Adults are one-fourth-inch long. Both adults and
larvae, which look like tiny blue-black and orange alligators,
feed on aphids, scale, thrips, whiteflies, spider mites,
mealybugs and other soft-bodied pests. Adults are attracted
to nectar and pollen plants. Lady beetles overwinter as
adults in leaf litter, tree crevices and homes.
pirate bugs (Orius tristicolor ) attack mites and any tiny
insects, especially thrips.
flies include more than 1,300 species of tachinid fly (Diptera),
which look like hairy houseflies. They lay their eggs on
a number of caterpillars, including corn earworms, cabbageworms,
cutworms and many other garden pests. Closely related humpback
flies parasitize ants, bees, beetles and scale insects.
include soldier bugs, which look like squash bugs but have
sharp spines on their shoulders, and big-eyed bugs (above),
which have large bulging eyes on the sides of their heads
and no shoulder spines. Both types of predators eat leaf
beetle larvae, small caterpillars and many other insects.
A third type of predatory bug, the one-fourth-inch-long,
black-and-white minute pirate bug, feeds on thrips, mites
and insect eggs. Adults of all three species overwinter
in perennial weeds or other debris.
(Arachnida) have eight legs rather than six, and they probably
are the most abundant predators in home landscapes. The
3,000 species found in North America include web spiders,
jumping spiders, crab spiders and many others. Spiders are
general feeders that help keep many other insects in check.
flies or syrphid flies (Diptera) are brightly colored flies
that resemble bees and that hover and dart like hummingbirds.
They don’t sting. The larvae, cylinder-shaped maggots
with tapered heads, feed on aphids, mealybugs and other
small insects. A larva may consume 400 aphids before pupating.
Adults feed on pollen and flower nectar. Hover flies overwinter
as pupae in the soil.
(Hymenoptera) include numerous species of predators and
parasites. Large paper wasps are predators, but many parasitic
species such as braconids look like tiny flying ants. Some
“micro-wasps” that parasitize eggs are so small
you may never see them. Braconids lay eggs in the bodies
of other insects, including caterpillars, tomato hornworms,
aphids, thrips, Mexican bean beetle larvae and various borers.
The eggs hatch and the larvae feed on their hosts’
body fluids. Braconids and other parasitic wasps are most
active in warm weather, and they like humid conditions.
They are attracted by nectar in small flowers.