Biological Control
In Landscapes
Dr. David Shetlar
The Ohio State University
OARDC/OSU Extension
Columbus, OH
© October, 2004, D.J. Shetlar, all rights reserved
Integrated Pest Management
(IPM)
Chemical
Biological
Cultural
NOTES:
While using the Integrated Pest Management (IPM)
approach, ALL control options should be considered –
cultural, chemical and biological. Many believe that
most landscape plants can “defend” themselves from
most pests if the plants are given proper care –
suitable location, nutrition and food. Under these
conditions, most pests have parasites, predators or
pathogens that keep their populations below serious
damage levels. However, urban landscapes often
cause plant stress and intervention may be necessary
to reduce pest attack. In these situations, most pest
management specialists suggest using the least
intrusive methods – plant health care and low impact
pesticides. These methods help conserve biological
controls.
Classic Biocontrols
P Predators
Ants & Wasps
Beetles
Spiders
Bugs (damsel, bigeyed, stink)
Mites
Others
P Parasites
Wasps
Flies
P Pathogens
Bacteria
Fungi
Virus
Entomopathogenic Nematodes
NOTES:
In general, BIOLOGICAL CONTROL includes the “three
Ps” – Predators, Parasites and Pathogens. Predators
are animals that capture and eat their prey. Parasites are
animals that infest their prey, usually killing it. Insects
that are parasites of other insects are called Parasitoids.
Pathogens are usually microbes that are generally lethal
to their insect hosts – mainly, bacteria, fungi, virus and
protozoa. Some include nematodes in the pathogen
category, but they are technically parasites (multicellular
organisms).
Biocontrol or "BioBased"?
! Paenibacillus popillae –
grub milky disease
! Bacillus thuringiensis - *-endotoxin
! Saccharopolyspora spinosa spinosyns (=ConserveJ)
NOTES:
True biological controls are either predators, parasites
or pathogens. Many microbes produce chemicals that
are lethal to insects if ingested or absorbed. In the
previous case, the bacterium, Paenibacillus popillae,
infects white grubs and it reproduces inside the grub
body. Resistant spores are produced to infect future
grubs. The bacterium, Bacillus thuringiensis, (BT)
actually lives in soil, but it produces a protein toxin
that can be lethal to insects if it is ingested. BT does
NOT “infect” insects! Saccharopolyspora spinosa is
another soil-dwelling microbe that produces a group
of toxins that are lethal to some insects and mites.
This toxin is extracted from the growing medium. BT
and S. spinosa toxins are considered BIOBASED, not
biological.
Chinese mantis, a
common imported
predator
NOTES:
Is the Preying Mantis a “good bug”?
Many would say “yes,” but I would then ask “why”?
What do preying mantids eat? When their egg cases
hatch, the nymphs prey on each other and often there is
a 50% mortality rate in the first 24 hours! Mantids are
generally large predators that feed on larger insects –
flies, grasshoppers, honey bees, etc. In other words,
they are indiscriminate predators, eating anything that is
the right size, whether pest or beneficial.
Do preying mantids eat aphids? Scales? Spider mites?
White flies? NO!
The better question to ask is, “Are preying mantids
USEFUL biological controls?” (probably not!)
Convergent lady
beetle eating
aphids
NOTES:
Is the Lady Beetle a “good bug,”? Oops, a useful
predator?
Lady beetles are usually called “general predators,”
but each species usually specializes on certain limited
groups of prey – aphids, scales, spider mites, etc.
Lady beetles have multiple generations each year and
they can often “react” to pest build-ups. They rarely
eat each other and the adults are commonly
considered “resistant” to many groups of insecticides,
a good IPM trait!
Therefore, lady beetles can be considered USEFUL
biological controls!
However, do you know its complete life cycle?
What is this?
NOTES:
While many recognize the lady beetle, few recognize its
larva! In order to use biological controls effectively, one
must be able to recognize all the stages of a useful
biological control.
In fact, the larvae of lady beetles are often two to three
times more efficient (eating more prey per unit time) than
the adults! However, because the larvae are often
considered “ugly,” they may be destroyed by unknowing
persons.
Polistes wasp
eating black
cutworm
NOTES:
Unfortunately, many biological controls are not as “cute”
or aesthetically pleasing as lady beetles.
As an example, many social wasps are considered to be
beneficial predators by entomologists, but are not
“appreciated” by the average gardener. During most of
their life cycles, social wasps (including yellowjackets)
prey on caterpillars, sawfly larvae and various flies. It is
only during the end of the season when these wasps turn
to feeding on sweets that they then become nuisance
pests.
Keys to Successful Biocontrols
! Easy to recognize
! Easy to use
! Public acceptance
! Cost effective
! Shelf life
NOTES:
Biological controls that are “successful” usually need to
fulfill several criteria. They must be recognizable, i.e., if
you can’t tell what is a useful agent, then it is susceptible
to being mistaken as a pest! Biological controls that are
easy to use are more likely to BE used! Many do not
“like” wasps, spiders, ground beetles and other “yucky”
critters. These are less likely to be accepted by most
people.
Commercially useful biological controls must be effective
AND economically feasible. If the best biological control
is too expensive to use, it will not be used!
Many potential biological controls can not be easily
packaged and delivered to users. They have no shelf life!
Classic Landscape
Biocontrols
• Predators
Spiders
Predatory Mites
Lady Beetles
Predatory Bugs
Lacewings
Syrphids & Other Flies
NOTES:
Spiders consistently end up as one of the top ten of
useful landscape predators. Unfortunately, many
people do not like spiders and have trouble
considering them useful.
To overcome this this problem, many recommend
training and education about the diversity and behavior
of spiders.
Jumping spider
Lynx spider
Wolf spider with egg mass
NOTES:
Predatory mites are some of the best control agents that
battle spider mites, thrips and other small insects.
They are often misidentified as plant feeding mites, but
they can be easily differentiated because most
predatory mites run rapidly over the plant surface.
Predatory mite
NOTES:
Lady beetles are some of the most popular, acceptable
and useful biological controls found in urban landscapes.
However, the group is a large and diverse one, and some
of the adults are often not recognized since they are not
the typical red-orange beetles with black spots.
One group is generally black with red spots. These are
often called twice-stabbed lady beetles (several species)
and most are scale predators.
Many small lady beetles are simply tiny black beetles
with or without spots. These are often scale or mite
predators.
Each lady beetle has a characteristic larva that is often
not recognized as being a “baby” lady beetle!
Transverse lady beetle adult.
Coleomegilla maculata, often called simply “C-mac” lady beetle.
A twicestabbed
lady beetle adult
feeding on pine
needle scales.
Convergent lady
beeltle larva, a typical
form.
Beetle larvae
Scales
Twicestabbed
lady beetle larvae
eating magnolia
scales. They
look like
mealybugs, the
classic “wolf in
sheep’s
clothing”!
Tiny
Stethorus
lady beetle
larva, a mite
predator.
Multicolored Asian lady beetle,
eggs, larva, pupa and adult forms.
NOTES:
There are many “bugs” (insects in the Order Hemiptera)
that are predators of other insects and mites. While less
recognized than Lady beetles, many of these are
extremely important in keeping a variety of ornamental
and turf pests in check. The group is a large and diverse
one, with adults ranging from the large wheel bug (about
1.25-inches long) to the tiny minute pirate bugs (less than
0.1-inch long).
Unfortunately, some of the beneficial bugs belong to
families that also contain pest species, e.g., stink bugs
and plant bugs. In such cases, an expert may be needed
to help identify the good bugs from the bad bugs!
Bigeyed bugs are common
predators of turf infesting pests,
like chinch bugs. They also
occasionally climb up ornamental
plants in search of prey. They run
and fly rapidly. They are identified
by having the head width as wide
or wider than the body width.
Damsel bugs are
common on perennials
and flowers where they
are generalist
predators.
These lace bugs are running
away from a minute pirate
bug. These tiny bugs
normally feed on eggs and
mites, but they will take on
larger prey.
This predaceous stink bug is
feeding on a pine sawfly larva.
These stink bugs specialize in
feeding on caterpillars and
sawflies.
A predatory bug feeding on a gypsy moth larva. Many
predatory bugs use toxic saliva that rapidly kills large
prey. Bites from such bugs can be very painful.
NOTES:
Lacewings (Order Neuroptera) include several families
insects that have predatory larvae though some adults
also feed on other insects. The green lacewings and
brown lacewings are the most commonly seen landscape
neuropterans. Both groups have lizard-shaped larvae
that are armed with a pair of sucking mandibles. The
mandibles of the green lacewing larvae are curved and
the brown lacewing larvae have straight mandibles.
A little known group of lacewings, the dustywings, are
small insects that feed primarily on mites. The adults
have white powder on their wings and may be mistaken
for a whitefly or bark louse adult. The larvae look like
overweight, miniature brown lacewing larvae.
Green lacewings
lay stalked eggs
so that the
cannibalistic
larvae don’t kill
each other.
Green lacewings are very
common in urban
landscapes. They should
not be confused with the
plant pests – lace bugs.
Green lacewing larvae have
curved mandibles.
Green lacewings pupate
within small barrelshaped cocoons.
Brown lacewing adult (left) and larva feeding on aphid (right).
Dustywing adult near spruce
spider mites, a favorite prey.
NOTES:
There are many predatory flies, both as adult flies and
larvae (maggots). One of the most common groups is the
hover flies or syrphids. These brightly colored flies are
commonly mistaken for sweat bees or other bees since
they commonly hover around nectar-producing flowers.
The adults are harmless, but the larvae have a pair of
sharp hooks with which they latch onto aphids, their
favorite food.
Many other flies feed on other insects while in the adults
stage and many more flies have larvae that are parasitic,
not predatory.
Syrphid larva
feeding on an
oak aphid.
Typical adult
syrphid on a flower.
Most of these flies
are excellent bee
mimics.
Syrphid eggs
next to birch leaf
aphids.
Some syrphid maggots are
elaborately colored and
have fleshy extensions
along the body side.
This tiny maggot is the larva
of the predatory aphid
midge. These flies feed on
aphids and spider mites.
An anthomyiid fly feeding on a leafhopper nymph.
NOTES:
There are many groups of beetles, other than lady
beetles, that are also general predators, both as adults
and/or larvae. Ground beetles and rove beetles are often
in the top 10 of common landscape predators.
Unfortunately, many people do not like these large,
rapidly running predators. Such people are likely to kill
these beetles rather than let them help control other
insects.
Ground beetles
range from brown
and black to
iridescent blues
and greens. Most
are predators, but a
few feed on plants.
Ground beetle larvae are
often better at seeking
out and preying on other
insects than the adult
stage.
Classic Landscape
Biocontrols
• Predators
Spiders
Predatory Mites
Lady Beetles
Predatory Bugs
Lacewings
Syrphids & Other Flies
• Parasites
Wasps
Flies
NOTES:
While one of the largest and most important groups of
biological controls, parasitic insects are often disliked
because of peoples’ general fear of wasps and flies.
Insects that are parasites of other insects are commonly
called parasitoids because they eventually kill their host.
Unlike their social bee and wasp cousins, parasitic wasps
generally do not posses a sting. However, a few do have
stings, but they will not use them unless severely
provoked.
Many parasitic flies have larvae that enter their hosts’
bodies. The maggots eat most of the body contents
before the host dies. These larvae may emerge to pupate
while some remain in the host body to pupate. Talk about
the model for the movie “Aliens”!
Aphid wasps are small black
wasps that lay eggs in the
bodies of aphids. Upon
completing development, the
wasp larva causes the aphid
body to swell into an aphid
“mummy.”
This cutworm has parasitic
wasp larvae that are feeding
externally.
This hornworm was parasitized
by a parasitic wasp with larvae
that fed inside the body but they
have pupated on the surface.
This is the larva of an
imported cabbageworm
which has just been
killed by wasp parasites.
The parasites have
emerged and pupated in
a mass next to the host
body.
This remains of a cabbage
looper is filled with the
mature larvae of a unique
wasp. Only one egg was
laid! The embryos divide
until they fill the body
cavity!
The Tiphia wasps dig into the
soil to locate white grubs. Their
larvae feed from the outside of
the body (above), eventually
consuming the entire grub. The
mature larvae pupate in brown
cocoons in the soil.
Tiny parasitic wasps are some of the most efficient scale
controls. Can you find all the adults in this picture? (ans: 3)
These large ichneumon
wasps can have two-inch
long bodies and ovipositors
that exceed five inches!
Fortunately, they can’t
sting. The use the long
ovipositor to locate insect
larvae burrowing in wood.
This tachinid is an
imported parasite
of the gypsy moth.
The adults “lay”
larvae on host
caterpillars. The
larvae burrow into
the caterpillar and
eat its internal
organs.
Classic Landscape
Biocontrols
• Predators
Spiders
Predatory Mites
Lady Beetles
Predatory Bugs
Lacewings
Syrphids & Other Flies
• Parasites
Wasps
Flies
• Pathogens
Beauveria
Bacillus thuringiensis
Paenibacillus popilliae Entomopathogenic Nematodes
Entomophaga
Nuclearpolyhedrosis virus
NOTES:
Pathogens are merely diseases, fungi, bacteria, and virus
(among others), that usually kill their host insect.
The microbes that are most useful in actively controlling
insects are ones that form some kind of resistant spore
or have a resistant stage. These spores allow for
packaging and spreading of the disease in pest control
efforts.
Entomopathogenic Fungi
Beauveria spp. "White" Fungus
Naturalis-T®
Metarhizium spp. "Green" Fungus
(none registered in US)
NOTES:
Beauveria bassiana is called the white fungus of insects
because most of the strains produce external spores that
make the infected insect appear coated with a white
powder or cottony material.
Metarhizium is usually called the green fungus of insects.
The fungus has white mycelia within the body, but when
it is ready to form spores, the spores coat the killed host
with a velvety covering of olive-green.
A bluegrass billbug adult (above)
and Japanese beetle larva (right)
infected with Beauveria.
Green June
beetle grubs
killed by
Metarhizium.
Japanese beetle
grub infected with
Metarhizium.
A gypsy moth
larva infected
with another
fungus,
Entomophaga
maimaiga.
A gypsy moth larva
killed by a virus
disease.
NOTES:
There are numerous bacteria that can infect and kill
insects. The most common ones encountered in
landscapes are the ones that kill white grubs – milky
disease and amber disease bacteria.
The milky disease bacterium, Paenibacillus popillia,
causes the blood of white grubs to turn a milky white
color. Eventually, the bacteria overwhelm the grub.
Though milky disease spores are commercially available,
there is little evidence that use of such products actually
increase infection over the long run.
Amber disease is caused by Serratia which is available
commercially in New Zealand, but not in the United
States. This disease is often found naturally.
Normal grub (left) and a milky disease infected grub (right). Note
color of blood droplet where the tip of the leg was pinched off.
A Japanese beetle grub with amber disease (left) and a normal
one (right.
NOTES:
Insect parasitic nematodes are often called
entomopathogenic (=insect killing). There are many
species of these nematodes and several are
commercially available. In the small space available
here, only some of the more common species will be
mentioned.
You are directed to an excellent web site on these
nematodes located at:
http://www.oardc.ohio-state.edu/nematodes/
Entomopathogenic Nematodes
Steinernema carpocapsae
VectorJTL, ExhibitJ, SaviorJ
S. riobravis
VectorJMC, DevourJ
S. scapterisci
BioControl'sJ Nematode
Heterorhabditis bacteriophora
CruiserJ, ScanmaskJ
Insects infected with
Steinernema nematodes are
usually light tan in color.
Note the adults (larger
nematodes) and the infective
juveniles (the tiny nematodes
forming a cloud around the
grub.
Insects infected
with Heterorhabditis
nematodes are
usually a reddish
color.
NOTES:
Technically, the bacterium, Bacillus thuringiensis (Bt), is
not a true biological control. This is because the
bacterium does not cause an infection within the insect.
The bacteria actually grows in soils. However, many
strains of this bacterium contain a protein toxin crystal
that is released if the bacterium is digested. The protein
toxin destroys the insect gut lining which causes a
secondary infection or starving of the insect.
Many strains of Bt are known and only a few have been
found to have insect killing properties.
Bacillus thuringiensis
Bt *-endotoxins
Variety
Bt. kurstaki
Bt. aizawai
Bt. israelensis
Bt. tenebrionis
(=san diego)
Bt. japonensis
(strain 'Buibui')
Target
Examples
caterpillars
caterpillars
mosquitoes
leaf beetles
Dipel®, MVP®
Mattch®
Vectobac®
M-one®
scarab grubs
M-press®
Using Biocontrols in Landscapes
! Introduction
! Augmentation
! Conservation
Conserving Biological Controls
! Learn to recognize biocontrols
! Provide food and habitat
! Use least toxic chemicals
! Target chemicals WHERE needed
! Educate customer
! BE PATIENT!!
Selecting Least Toxic Insecticides
! Soaps and Oils (kill by contact only)
! Use short residual products
! Use IGR-type products (very selective)
! Use chloro or thianicotinoids
! Use microbial products
! ??
Other Things to Consider!
! PLANT HEALTH CARE
! Consult – replace pest-prone plants
! Use root uptake systemics
! Apply at BEST time,
not when convenient.
! Consult – customer wants to know
what is going on!
More Information?
http://entomology.osu.edu