Biological Control In Landscapes

Dr. David ShetlarThe Ohio State UniversityOARDC/OSU ExtensionColumbus, 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

P Parasites

P Pathogens

Ants & WaspsBeetlesSpiders

Bugs (damsel, bigeyed, stink)MitesOthers

Wasps Flies

VirusFungiBacteria

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

! Public acceptance

! Cost effective

! Shelf life

! Easy to use

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

• PredatorsSpidersPredatory MitesLady Beetles

Predatory BugsLacewingsSyrphids & 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.

Twicestabbed lady beetle larvae eating magnolia scales. They look like mealybugs, the classic “wolf in sheep’s clothing”!

Beetle larvae

Scales

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 are very common in urban landscapes. They should not be confused with the plant pests – lace bugs.

Green lacewings lay stalked eggs so that the cannibalistic larvae don’t kill each other.

Green lacewing larvae have curved mandibles.

Green lacewings pupate within small barrel-shaped 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.

• Predators

• ParasitesWasps Flies

Classic Landscape Biocontrols

SpidersPredatory MitesLady Beetles

Predatory BugsLacewingsSyrphids & Other 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 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!

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.

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.

• PathogensBacillus thuringiensis

Paenibacillus popilliaeBeauveria

Entomopathogenic Nematodes

• Predators

• ParasitesWasps Flies

Classic Landscape Biocontrols

SpidersPredatory MitesLady Beetles

Predatory BugsLacewingsSyrphids & Other Flies

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

Metarhizium spp. "Green" Fungus

Naturalis-T®

(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

S. riobravis

S. scapterisci

Heterorhabditis bacteriophora

VectorJTL, ExhibitJ, SaviorJ

VectorJMC, DevourJ

BioControl'sJ Nematode

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 thuringiensisBt -endotoxins

Variety Target Examples

Bt. kurstakiBt. aizawaiBt. israelensisBt. tenebrionis

(=san diego)

Bt. japonensis(strain 'Buibui')

caterpillarscaterpillarsmosquitoesleaf beetles

scarab grubs

Dipel®, MVP®Mattch®Vectobac®M-one®

M-press®

Using Biocontrols in Landscapes

! Introduction

! Conservation

! Augmentation

Conserving Biological Controls

! Learn to recognize biocontrols

! Use least toxic chemicals

! Target chemicals WHERE needed

! Educate customer

! Provide food and habitat

! BE PATIENT!!

Selecting Least Toxic Insecticides

! Soaps and Oils (kill by contact only)

! Use IGR-type products (very selective)

! Use chloro or thianicotinoids

! Use microbial products

! Use short residual products

! ??

Other Things to Consider!

! PLANT HEALTH CARE

! Use root uptake systemics

! Apply at BEST time, not when convenient.

! Consult – replace pest-prone plants

! Consult – customer wants to knowwhat is going on!

More Information?

http://entomology.osu.edu