"Native Beneficial Organisms"
By Mario Lanthier and Tania Jensen, CropHealth Advising & Research,
July 2001.
Prepared for the B.C. Ministry of Agriculture, Fisheries and Food.
A modified version was published in the 2002 version of the "Nursery
& Landscape Pest Management & Production Guide".
- Lady beetles
- Twice-stabbed lady beetles
- Stethorus lady beetles
- Syrphid flies
- Aphid midges (Aphidoletes a.)
- Minute pirate bugs (Orius)
- Pirate bugs (Deraeocoris and Anthocorids)
- Lacewings, green and brown
- Predatory mites
- Parasitic wasps
See also the page Using beneficials.
Identification
The adults are oval, rounded beetles, with more than 500 species known to
occur in the United States and Canada. They
vary in length between 4 to 10 mm and display a variety of
colours, including black, red,
orange-red, and yellow. Many
species have a characteristic wing colour and number of black spots on their
wings, but other species show a large variation in colour and number of
spots.
The larvae have an alligator-like shape.
At first they are black with short hairs and spines on their backs, and well-developed legs. The later
instars are grey to blue-grey with orange markings.
Pupae are often found hanging from leaves and bark and are orange-red
with black markings.
Lady beetles are also called “lady bugs” and “ladybird beetles”.
Preferred
food
Both adults and larvae feed on
aphids, spider mites, scales and mealybugs.
The adults chew the body parts and can eat up to 3,000 aphids in their
lifespan. Full-grown larvae can
suck the body fluids of approximately fifty aphids per day.
When prey is in short supply, the adults can survive on pollen and nectar
for a short period of time.
Life cycle
Lady beetles overwinter as adults and emerge early in the spring.
An adult female will lay 10 to 50 yellow to orange elongated eggs in a
cluster, often on the underside of a leaf.
The time span from egg to adult is usually 20 to 35 days. The adults can live one to two months and under ideal outdoor
conditions, there may be up to six generations per year.
Status in
ornamental plants
The lady beetle adult is the first predator of the season and can be seen
in early April. They can multiply
to large numbers in a short time and continue to forage for aphids all through
the summer. The public easily
recognizes this predator.
Nursery and landscape managers should learn to recognize the larval stage
of lady beetles. The
alligator-shape, blue to black with orange markings, is typical of this
predator. There are many situations
where toxic pesticides are applied to control “the bugs” that turn out to be
lady beetle larvae.
Different species are available
from insectaries for commercial release. The
species collected in the mountains of California often fly away from the point
of release before searching for food, making them less useful in open areas.
Recently, the Asian lady beetle became available through some suppliers
and is said to remain at the site of release.
Identification
The twice-stabbed lady beetle
exhibits the standard lady beetle body shape, is 1.5 to 5 mm in size, but has a
characteristic shiny black body with two red spots on the wings.
The larvae are alligator-shaped with prominent spines and often go
unnoticed as they hide under the body of their prey.
Preferred
food
Chilocorus species commonly feed on scale insects. They will also prey on aphids, adelgids, and other
soft-bodied insects.
Life cycle
The twice-stabbed ladybeetle overwinters as an adult and appears very
early in the spring, often in April.
It is commonly seen on plants with a high population of overwintering
scale.
Status in
ornamental plants
This pretty lady beetle is a joy for landscape managers.
It is a common sight in juniper plantings affected by juniper scale. Feeding by adults and larvae can provide reasonable control
of the scale crawlers.
Stethorus
lady beetles (Stethorus picipes, S. punctum, S. punctillum)
Identification
The Stethorus lady
beetle, also called “the spider mite destroyer”, is 1.5 mm long or smaller.
It exhibits the standard lady beetle body shape but has a typical shiny
black body with pale, tiny hairs.
The larvae are dark grey to brown and covered with a plentitude of fine
hairs. The pupae are dark orange to
black and covered with fine hairs.
Preferred
food
Stethorus lady beetle adults and larvae prey almost exclusively on spider mites.
An adult may consume 20 to 60 spider mites and lay up to ten eggs per day
over a three-month period. The
older larvae can eat up to 250 mites per day.
Life cycle
Stethorus lady beetles overwinter as adults in leaf litter.
The females will lay their eggs in the midst of a spider mite colony.
Development from egg to adult takes two to four weeks, depending on
temperature, resulting in two to three overlapping generations during the year.
Status in
ornamental plants
This lady beetle species is
very common on plants with a high population of spider mites.
It provides relatively good control on mature plants in landscape areas
but it usually appears too late in the season to prevent damage on young nursery
plants.
Identification
Adult syrphid flies, also called "hover flies", resemble bees or wasps in their colour pattern but
are usually smaller and have only one set of wings.
The surname “hover fly” comes from their distinguished ability to
hover in flight. The body length ranges from 8.0 to 15.0 mm.
Hundreds of species have been identified in North America.
The white elongated eggs are normally laid singly among aphid colonies.
The larvae are legless, have a tapered flattened body 10 to 15 mm in
length, and exhibit varying colours of yellow, green and brown.
These maggots sway their pointed heads from side to side to search for
prey or when disturbed.
The pupal stage is a smooth cigar-shape, light to dark brown in colour.
Preferred
food
Syrphid adults feed strictly on flower pollen and nectar but the larvae
are voracious aphid feeders. Despite
being legless, the larva is very efficient at finding its prey and can consume
200 to 800 aphids in a 10-day period. When
aphids are in short supply, some species can survive on flower pollen.
The syrphid larvae can also feed on caterpillars, thrips and sawfly
larvae.
Life cycle
Syrphid flies overwinter as mature larvae, pupae or adults.
The adults can be seen as early as April and both adults and larvae are
found in large numbers in May.
The females require pollen to produce their eggs, laying 400 to 1000
single eggs amid aphid colonies over a lifespan.
The eggs require only a few days to hatch, and the larval stage last
seven to ten days. Pupation occurs
in a dark place such as a rolled leaf or in the soil litter and takes
approximately one
week.
The total duration from egg to adult is two to four weeks with two to
four generations occurring per year.
Status in
ornamental plants
Syrphid flies are one of the most effective aphid predators
on ornamental
plants, both in nurseries and in landscape settings.
They can be found in large numbers throughout British Columbia at all times
between April and October. When
they are present on a plant, they can provide control of an aphid problem within
a few days.
Older larvae can be mistaken for caterpillars.
However, they are legless, usually in the middle of an aphid colony, and
have a characteristic tapered body shape.
Having plants in bloom is a good method to increase the resident
population of this predator, as the adult females feed on the flower pollen
before laying eggs. Plants such as yarrow, flowering buckwheat, and members of
the carrot and dill family have shallow nectaries that provide accessible food
sources for the adults.
Aphid midges (Aphidoletes aphidimyza)
Identification
The adult is a small (2 to 3
mm), night-flying fly resembling a mosquito, with long slender legs and beaded
antennae often curled back over their heads.
Bright-orange larvae are legless and very small, less than 3 mm in
length. Their tiny eggs are also orange
and oval. Aphidoletes are
always found amid an aphid colony, whereas a similar looking pest of Malus
trees, the apple leaf
midge, is usually found inside rolled leaf edges.
Preferred
food
Only the larval stage is
predaceous and is known to feed on over sixty species of aphids.
The adults do not prey on insects but feed on honeydew and nectar.
The larvae puncture the leg joint of aphids and inject a paralyzing
poison before sucking the body fluids, leaving only a shriveled, black corpse.
They are voracious, eating up to fifty aphids per day and often killing
more aphids than they eat.
Life cycle
Aphidoletes overwinter as pupae in soil or debris, emerging in
early June when daylight is longer. Female
adults will lay 150 to 200 eggs within aphid colonies over a lifespan.
The eggs take two to five days to incubate and the larvae will feed for
one to two weeks before dropping to the ground to pupate.
Pupation requires one to three weeks.
The duration from egg to adult is very rapid, approximately 20 days.
Adults live for about ten days with three to five generations occurring
per year.
Status in
ornamental plants
Aphidoletes are very effective predators that can bring an aphid problem under
control within a few days. When
present on a plant, they should be allowed to do their work without interference
from toxic pesticides.
For nursery and landscape managers, the difficulty is to find them.
The adults fly mainly at night, and the young larvae are so tiny they are
often hidden beneath aphids.
Aphidoletes are available from insectaries for commercial
releases. Since they require open
soil at the base of the plant for pupation, they are more appropriate for
greenhouses, flower beds and rose gardens.
Their impact can take up to one year to manifest but is sustained for
many years.
Minute pirate bugs (Orius tristicolor, O insidiosus, O.
minutus)
Identification
The Orius adult is oval,
flat, and has a narrow, pointed head. The
wings are held flat on the body at rest and are black, with white diamond marks
vaguely resembling a pirate flag. Adults
are quite small, ranging in size from 2 to 5 mm, and tend to move rapidly.
These tiny insects range in size from 1.8 to 3.7 mm, but are still visible to
the naked eye.
Preferred
food
Both the adults and nymphs are predaceous sucking insects.
The nymphs will feed on thrips, whiteflies, small caterpillars, insect
eggs, aphids and adelgids. They can
consume up to 30 spider mites per day. When
prey is abundant, the nymphs will kill more thrips than it needs to consume.
Life cycle
The adults overwinter under bark or in ground litter.
Emerging in late spring, the female adult can live for three to four
weeks and lays her eggs into plant tissue.
Development time from egg to adult is three to six weeks, producing three to
four generations per year.
Status in
ornamental plants
Orius are the unknown heroes of nursery production, both in the
field and in containers. Adults and nymphs can be very abundant on plants that have thrips, spider mites
or aphids. Producers of flowers,
shrubs and trees would gain to recognize this small predator, as it can survive
on flower pollen when there is no prey.
Minute pirate bugs are available from insectaries for commercial release.
They have proven to be effective for greenhouse release to control thrips.
Orius should not be used in conjunction with predatory mites, as
they will also consume the mites.
Pirate
bugs (Deraeocoris and Anthocorids)
Identification
The adult has an oval-shaped,
flat body that is 4 to 6 mm in length. They
have a black head and body and a tan wing pattern.
The adult Deraeocoris is twice as large and stouter than the adult
Anthocorid. Pirate bug
nymphs are pinkish-grey when they first emerge and turn to a light grey with
darker marking as they grow. They
resemble the minute pirate bug larvae but are larger, roughly 4 mm in length.
Preferred
food
Pirate bugs will consume aphids and other soft-bodied insects, but their
preferred diet includes mites (30 or more a day) and pear psylla (especially the
eggs).
Life cycle
Pirate bugs overwinter as adults and become active when daily
temperatures exceed 100C. Egg
incubation usually takes three days, and development from egg to adult requires
approximately twenty days.
Nymphs can be present in late spring and late summer as two overlapping
generations can occur during the growing season.
Status in
ornamental plants
Pirate bugs are occasionally seen in landscape settings and in nurseries.
However, they are far more common in commercial tree fruit orchards and
are an important predator of pear pests.
Green and
brown lacewings (Chrysoperla carnea, Chrysopa oculata,
Hemerobius pacificus)
Identification
There are three common species of lacewings in British Columbia, two
green and
one brown.
The adult green lacewing is bright green with a long thin body 10 to 20
mm in length. The eyes are golden or red incandescent, the antennae are
long and delicate, and the wings are large, green and lacy.
The adult brown lacewing has a brown body with pale brown wings.
It is typically smaller and less common than the green lacewing.
The eggs of all species are white and laid singly or in groups.
Those of the green lacewing are typically attached by a stem 8 mm long to
the underside of a leaf, whereas the eggs of the brown lacewing are not.
The larvae have an alligator-shape with distinctive legs and mandibles,
and a long, pointed head. When
mature, the larvae are 6 to 10 mm in length, and are pinkish brown to cream in
colour with darker markings.
Preferred
food
Although aphids and mealy bugs
are their preferred source of nourishment, both green and brown lacewings will
also feed on mites, scale, thrips, leafhoppers, psylla and small caterpillars.
When prey is scarce, the adult Chrysopa species will feed on
honeydew, nectar, and pollen. The lacewing larvae puncture their prey and suck out the
internal fluids. Green lacewing
larvae are capable of consuming 20 to 100 aphids per day.
Life cycle
Lacewings overwinter as pupae or adults.
They are usually seen during the summer months, more often at night
around lamps, as they are attracted to light. The
females can lay 100 to 200 eggs over a lifespan, with development time from egg to adult being
approximately one month. Some
lacewing adults can live for many months.
The larvae are sometimes seen as early as April, being one of the first
active predators in the spring. However,
this insect is more common in August and September.
Status in
ornamental plants
The adult green lacewing is among the prettiest insects of nature.
The delicate, transparent green wings stand up high above the insect's
body. Many field workers will
recognize their egg clusters hanging on threads on the underside of leaves.
This predator is usually found in low numbers and cannot provide a
stand-alone control of aphids or mites.
Lacewings are available from
insectaries for commercial releases. Cannibalism
is a problem, as the larvae are generalist feeders and the first to emerge will
happily consume the other larvae in the shipment. Many field experiments indicate that releasing adults is not
a practical option as they immediately fly away before depositing eggs.
Predatory mites (Amblyseius species,
Hypoapsis species, Phytoseiulus persimilis, Typhlodromus species,
Zetzellia mali, and others)
Identification
Most predaceous mites have a pear-shaped body and translucent colour,
although they can also be opaque white when they are not feeding.
They are larger than their prey, the adult being 0.25 to 0.4 mm in
length, and are typically more motile, active, and shinier than the pest mites.
Predatory mite eggs are shiny, oval, and colourless to opaque white.
Preferred
food
Predatory mites feed on all
stages of plant-feeding mites, including rust mites, two-spotted spider mites,
McDaniel mites, and European red mites.
Life cycle
Predatory mites overwinter as adults under the bark and other refuges.
They emerge early in the spring and feed on early-season rust mites and
two-spotted spider mites. The
development time from egg to adult is seven to twenty-one days depending on
temperature, allowing for six to ten generations over the course of the year.
Status in
ornamental plants
Predatory mites are very common
in all nursery and landscape settings and provide more benefits than most
managers realize. Many outbreaks of
spider mites can be traced back to an application of pesticide that eliminated
the predatory mites, allowing pest mites to cause damage in the absence of
natural control.
The population of predatory mites can build to large numbers when there
is an abundant supply of prey. In
some situations, a ratio of 1 predator mite to 30 or 40 spider mites is
sufficient to obtain effective control within a few days.
Various species of predatory
mites are available from insectaries for commercial release. Each species has a preferred range of relative humidity,
temperature, and prey. The supplier
can suggest the predatory mite that would be the most effective for each
situation.
Parasitic wasps (Braconids,
Chalcidids, Trichogrammas, Ichneumonids)
Identification
There are thousands of
parasitic wasp species, which differ in biology, host, and appearance.
Some parasitic wasps are endoparasitic, developing within their host,
while others are exoparasitic, developing on the outside of the host.
The adult wasps are very small, ranging from 1 to 35 mm in length, and
often difficult to see with the naked eye.
The damage done by the larvae or emerging wasp is usually more obvious
than the adult. Infected or
parasitized aphids appear swollen, tan or black in colour, and shell like.
An exit hole will be present if the adult wasp has already emerged or the
larva has left to make a cocoon
Preferred
food
Parasitic wasps are grouped in three insect families.
The Ichneumonid wasp is parasitic to the egg and larvae of caterpillars
and beetles. The female adult has a long, needle-like egg-laying structure
at the back of the abdomen.
Braconid wasps inject their eggs into a broad host range, including
caterpillars, flies, beetles and aphids. In
some cases, they emerge early to pupate in cocoons adjacent to the host carcass.
Chalcid wasps are very small and parasitize a wide range of
caterpillars, flies and some beetles. A
well-known member of this family is the Trichogramma wasp, which lays its
eggs inside the eggs of many moths and butterflies.
Life cycle
The life cycle and number of generations per season varies depending on
the parasite species.
In general, the female deposits one or more eggs into the body of a host
insect. Upon
hatching, the larvae feeds on the internal organs of the host in such a way that
the host remains alive during the parasite development.
In some cases, the dead host serves as a house for pupation.
Later, the adult parasite emerges, leaving behind a mummified host carcass
or a cocoon.
The presence of “mummies” amidst an aphid colony is an indicator that
other “healthy” aphids may also be parasitized and will soon die.
Status in
ornamental plants
Parasites are efficient warriors that can devastate an aphid colony
within days. The presence of a few mummified aphids is a sign of doom and
gloom for the pest colony.
Unfortunately, the parasitic wasps tend to arrive after the aphid
population has built to large numbers. Landscape
and nursery managers must show patience to allow the parasites to establish.
Most pesticides are detrimental to parasitic wasps.
Using a toxic product to control an aphid outbreak will destroy the
resident parasite population and may trigger future aphid flare-ups.
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