Biological control is a tool to be considered in constructing an integrated pest management scheme for an interior environment. Biological control is a method of pest management in which a naturally occurring disease, parasite, or predatory organism is manipulated to control a pest.
A parasitic insect grows on or feeds off another organism. Adult parasitic insects lay eggs inside or on the surface of a host insect. As the egg develops, it consumes the host. These parasitic organisms are typically limited to a very narrow range of insect pest, and results are not quickly apparent; pests may live much of their lives before dying.
The life cycle of a parasitic insect must coincide closely with that of their host to achieve optimum suppression of the pest. Timing the release of parasites to coincide with increasing damage levels may be tricky, but successful establishment consistently results in pest death. Braconid wasps are parasitic insects that have been used successfully in interiorscape environments.
Predatory insects consume a large number of both adult and immature stages of a pest. These organisms feed on a wide range of prey. When the population of one prey declines, they will shift to feeding on an alternate prey species present in the area. Predatory organisms can consume a large number of pests daily and may act quite rapidly. In many instances a significant proportion of pest populations may be controlled by parasites and predators.
The life cycles of predatory insects do not have to coincide with their prey for successful establishment, but unless a population of prey exists, the beneficial organisms will disperse to find prey elsewhere. If predators are released before the pest population builds up, the beneficial insect or mite will starve or disperse.
Examples of predatory insects that have been used in the interiorscape environment include: mealybug destroyers, and predaceous mites. Natural enemies can be manipulated in many ways to control pest insects. Three definitions that are used to describe the manipulation of natural enemies are listed below. All three manipulation techniques can be used in interiorscape biological control programs.
|Biological Control Definitions
Augmentation: The periodic release of artificially produced natural enemies to supplement those that occur naturally.
Conservation: Managing an environment so that it provides
Importation: Introduction and permanent establishment of a naturally
occurring enemy into
|Biological Control Implementation
Biological control can be an effective, environmentally sound method of managing pests. However, when using natural enemies it may be helpful to consider the following suggestions:
Table 1. Natural Enemies for the Top 5 North Carolina Interiorscape Insect Pests
|PEST||NATURAL ENEMY||RATE||UNIQUE CHARACTERS|
|Citrus Mealybug||Mealybug Destroyer
|2-8/yard of foliage every
3-2 weeks, 2-4 times to
|Mealybug destroyer larvae
can be confused with
|As above.||Mealybug destroyers need
cottony egg mass to lay their
eggs in. Long-tailed
mealybugs don't produce a cottony mass.
|2-5/yard every 2 weeks,
|Need to release lacewing
|Spider Mite||Anblyseius Mites
|10-32/yd, every 3-2 wks,
2-4 times. 3-6/yd/month
|Effective under a variety of
conditions. Can live on
pollen as well as mites.
|Scale (soft or
|1-4/yard of foliage every
3-2 weeks, 2-4 times to
start. 1-3/yd/quarter to
|Release of lab-raised
Harmonia in interiorscapes
will not cause pest problem
associated with wild
populations of this beetle.
|Fungus Gnats||Soil Dwelling Mites
predator, scavenger mite
|1-4/yard of foliage every
3-2 weeks, 2-4 times to
start. 1-3/yd/quarter to
|Will also feed on thrips
pupae in the soil.
|2-8/yd/week, 2-4 times to
start. 2-3/yd monthly to
|Shipping as live adults, ready
to parasitize aphids.
|2-5/yd every 2-1 weeks,
2-5 times to start. 2-3/yd
monthly to maintain
|Drop from plants into soil to
pupate. If soil is not directly
beneath foliage, they will
|The Green Spot||CibaBunting North America||Koppert USA|
|93 Priest Rd.||PO Box 2430||2856 South Main St.|
|Nottingham, NH 03290-6204||Oxnard, CA 93034-2430||Ann Arbor, MI 48103|
|Tel: 603-942-8925||Tel: 805-986-8265||Tel: 313-998-5589|
|Fax: 603-942-8932||Fax: 805-986-8267||Fax: 313-998-5557|
Selecting Natural Enemies
If you decide to use biological control, you should choose your product and supplies carefully, as you would any consumer product. The number and rate of natural enemies to release, as well as the timing and method of application can be determined through consultation with a reliable supplier or your local Cooperative Extension Service.
Using natural enemies in augmentative biological control will require a bit of experimentation on your part. Professional plant managers are used to experimenting with plant varieties, fertilizers, watering schedules, etc. What works and what doesn't is somewhat dependent on your situation. So, too, for natural enemies!
Table 2 summarizes the primary predators and parasites of major interiorscape plant pests.
The booklet Biological Pest Management for Interior Plantscontains guidelines for choosing and distributing natural enemies that will maintain pests below a visible plant damage threshold.
Bacterial and nematode organisms can be readily integrated into a traditional pest management scheme, whereas others require a fairly high level of management. Bacillus thuringiensis israelensis and Steinernema carpocapsae nematodes suppress dark-winged fungus gnats. Except for Bacillus thuringiensis pesticides, the use of biological organisms is usually not compatible with the use of chemical sprays.
It is possible to integrate sprays of soaps and oils with Encarsia formosa by timing pesticide applications to coincide with the "black scale stage" of the parasite's development. Also the "brown mummy" stage of aphids infected with Aphytis wasps are resistant to soaps and oils.
Purchasing Natural Enemies
The majority of natural enemies used in augmentative biological control programs are produced commercially.
One of the most common questions people ask when they purchase natural enemies is, "Am I getting the number I paid for?" This is a very important question, as the chances for control are very much related to the number of natural enemies released. Evaluation of quality control increases an end-user's confidence in the ability of natural enemies to control insect pests. Other important factors to consider when ordering from a commercial supplier include the survival, vigor, and availability of a natural enemy.
When purchasing natural enemies the first question you need to ask is, "Do I need natural enemies?" If you do not know what pest you have but you know that it is, or soon will be a problem, put your checkbook away. It is very important to order the right natural enemy to do the job. This can only be done if you have correctly identified your pest. Your local Extension service and the companies selling natural enemies are good sources of information.
Order from a reputable firm; one that either specializes in natural enemies or has been selling them for a long time. Check with your local Cooperative Extension Service. You can also call the company (most have 800 numbers) and ask them. Companies usually provide lots of free information right over the phone, so ask away. They should be able to tell you what natural enemies they have in stock, what they are used for, how many to use, and under what conditions you should use them (e.g., when and how to release).
Finally, once you receive your natural enemies, look at your order. Did it come on time? If you ordered eggs (e.g. for lacewings), do you see larvae crawling around in the shipment. If you ordered parasites, do you see lots of "mini-wasps" flying out of the shipping container. A small magnifying glass will come in handy for observing smaller natural enemies. If you suspect you did not get what you paid for, call the company. They are usually helpful and friendly and will replace shipments. If neither, use someone else next time!
Sources of Biological Control Agents
Natural enemies are available from numerous commercial suppliers. A directory of suppliers can be obtained by contacting the following two resources.
Directory of Least-Toxic Pest Control Products
Published annually by Bio-Integral Resource Center, P.O. Box 7414, Berkley, CA 94707,
Beneficial Organisms in North America.
Charles D. Hunter, California Environmental Protection Agency.
Department of Pesticide Regulation, Environmental Monitoring and Pest Management Branch,
1020 North Street, Room 161,
Sacramento, CA 95814-5604
Table 2. Summary of Primary Predators and Parasites of Major Plant Pests
|None||Encarsia formosa||Size of a spider mite, readily available from insectories.|
|Green Peach Aphid
|Various lady beetles. Some results with Aphidoletes aphidimyza a predaceous midge larva.||Braconid and Chalcid wasps||The adult midge lays 100-200 tiny orange eggs near the aphid colonies which hatch in two to three days. The larva is orange or red and depending on temperature and food supply, matures in three to five days.|
|Chilocorus nigritus and Lindorus lophanthae (two small lady beetles)||Metaphycus helvolus,
a tiny black and yellow wasp.
|Both beetles will control soft scale and ornamental scale. Chilocorus nigritus development time is approximately one month.|
|Twospotted Spider Mite
|.||Adults can consume 5-20 eggs or mites per
day. These mites avoid bright lights.
Tolerates both high and low temperatures. Effective on hairy- leaved plants.
|Cryptolaemus montrouzieri, Austrailian lady beetle.||Leptomastix dactylopii||C. montrouzieri will consume all species of above
Will feed on aphids and immature scale insects when mealybugs are not available.
Biological Control in the Great Indoors: At the Mall of America
When most people think of biological control, they think of experiences in the great outdoors—fields, orchards, and forests. But biological control can also be an effective management tactic indoors, and there is no greater indoors than the Mall of America in Bloomington, Minnesota. This megamall has it all, including a seven acre amusement park at its center called Knott's Camp Snoopy. "Campers" and their parents are greeted at the entrance by a three-story tall Snoopy, and are thrilled with rides including Paul Bunyan's Log Chute, the Ripsaw Roller coaster, and the Kite Eating Tree, attractions such as Legoland, Wilderness Station, and the Ford Playhouse Theater, and several food and concession stands.
Within this urban entertainment area, lies 54,000 square ft. (1.2 acre) of a man-made forest. Over 100 temperate, subtropical, and tropical plants species grow in this arboretum, including black olive trees, Ficus trees, Norfolk Island pines, English ivy, oleanders, and ferns. Birds, reptiles, and mammals inhabiting the Wilderness Station, and Koi fish swimming in the pond near the Ford Theater, add to the forest experience.
Roxanne Rickert and Karla Richter, horticulturalists for McCaren Design, Inc., St. Paul, MN, have handled landscape design, plant maintenance, and pest control for Camp Snoopy since it opened in August of 1992. At that time, plants brought from field nurseries in Florida, Georgia, and California probably contained hitchhiking arthropod pests, therefore presenting the designers with pest management problems. Although chemical control is used in some areas (materials such as Safer's soap, 70% alcohol mixed with Ivory soap, and the insect growth regulator Enstar), one concern of Camp Snoopy officials is pesticide applications around the Wilderness Station and Koi fish pond. Ms. Rickert addresses this concern by using cultural control (washing down plants on a weekly basis) and augmentative biological control (see MBCN Vol. I, No. 4). The specialists now use inoculative releases in roughly 3/4 of the planted area (0.9 acre).
McCaren horticulturalists initially received management ideas and pest identifications from Jody Fetzer, a horticulturalist for the University of Minnesota's Landscape Arboretum. Arboretum staff have been using biological control in their greenhouses for over six years, and Ms. Fetzer worked directly with the McCaren staff in ordering and releasing beneficial arthropods. The University's Dial U Insect and Plant Clinic, the Minnesota Department of Agriculture (MDA) Biological Control Program, and interior landscape magazines also have provided information for the McCaren staff.
What are some of the arthropod pests in this interior forest? Pest species during the three years have included soft scales (brown soft scale, Coccus hesperidium, and black scale, Saissetia oleae), mealybugs (citrus mealybug, Planococcus citri, and longtailed mealybug Pseudococcus longispinus) , mites (spider mites, Tetranychus urticae and Panonychus citri; cyclamen mite, Phyonemus pallidus; and eriophyids), thrips (western flower thrips, Frankliniella occidentalis, and Cuban laurel thrips, Gynaikothrips ficorum), and various aphid species.
Scale and Mealybug Control
McCaren receives their beneficials from two sources, BioTactics, Inc. from Riverside, CA and IPM Laboratories, Inc. from Locke, NY (see MBCN Vol. II, No. 3). Initially, Metaphycus helvolus (Encyrtidae) was released for soft scale control. Although this parasite was effective in lowering scale population densities, parasite shipments were not always available. MDA entomologists got involved in the biological control project after meeting Ms. Rickert in late 1993. Scale populations were expanding on the black olive trees and shipments of M. helvolus were delayed. Dr. John Luhman and Dr. Dharma Sreenivasam mentioned that another parasite, Coccophagus lycimnia (Aphelinidae), was found parasitizing scale in a greenhouse and was being reared at MDA. In a much publicized media event, Dr. Luhman released about 300 C. lycimnia pupae and adults to the treetops via a powerlift in early January 1994.
During post-release sampling, Dr. Luhman recovered M. helvolus and C. lycimnia, and a third parasite species, Diversineruis sp. (Encyrtidae). This species apparently arrived with the scale population from the nursery. After one year, new oleander plant material was brought into Camp Snoopy. These plants apparently were infested with scale, and soon after introduction, M. helvolus, C. lycimnia, and Diversineruis sp. were all found to be colonizing the scale. Therefore, all three species became established and were able to search in a different architectural habitat for hosts.
Mealybug biological control has been accomplished through releases of the mealybug destroyer, Cryptolaemus montrouzieri (see MBCN Vol. II, No. 5). This predator was received from commercial insectaries and from Dr. Luhman when insectary shipments were delayed. McCaren staff have also released Leptomastix dactylopii (Encyrtidae) against mealybug, but indications thus far have suggested that this parasite hasn't become established.
Biological control management hasn't been effective against armored scale. The parasite Aphytis melinus (Aphelinidae) was released on Norfolk Island pines that were infested with armored scale, but the parasites either did not become established or did so at very low levels. Unfortunately, the trees had to be removed and were replaced with native Northern white pines.
Mite and Thrips Control
Predatory mites have been released to control spider mites, cyclamen mites, and thrips. Galendromus (= Metaseialus, = Typhlodromus) occidentalis, the western predatory mite, Phytoseiulus persimilus, and Neoseialus (= Amblyseius) californicus have been successful at reducing spider mite populations. Neoseialus (=Amblyseius) cacumeris has been successful against western flower thrips and cyclamen mites. The generalist predator Orius insidiosus (Anthocoridae) (see MBCN Vol. I, No. 1) has been released against Cuban laurel thrips, and though it is still found throughout the forest, this predator hasn't been able to bring the thrips under control.
Aphid and Whitefly Control
Aphid natural enemies that have been augmented into Camp Snoopy have included both a parasite and a predator. Aphidius matricariae (Aphidiidae) hasn't worked well, but the cecidomyiid predator, Aphidoletes aphidimyza has been effective whenever aphid numbers have increased. Shipments of Hibiscus plants introduced whitefly to the forest and a parasite, Eretmocerus californicus (Aphelinidae) and a predator, Delphastus pusillus (Coccinellidae) (see MBCN Vol. I, No. 2; Vol. II, Nos. 1-3), were released to manage populations. The small, black Delphastus beetles have been very successful in maintaining whitefly populations below aesthetic levels.
Augmentation, Thresholds, and Cost Effectiveness
McCaren horticulturalists say that spring is their busiest time for predator and parasite releases. "We may make releases on a weekly or biweekly basis during spring," says Rickert. This time period coincides with an increase in pest populations and the introduction of new plants with new pests.
Camp Snoopy officials and McCaren staff seldom disagree when considering at which time pest population levels have gotten too large. "When Cuban laurel thrips ride along with blue balloons or when aphids start appearing in face painter's paint, then we know pest levels are too high," says Rickert.
The McCaren staff believe that biological control is cost effective when a predator or parasite becomes established and reduces pest populations. "Labor and application costs and worker concerns are lower with biocontrol compared to using chemicals," says Richter. "Of course, biological control is the only option in sensitive areas such as the Wilderness Station and Koi fish pond," adds Rickert.
McCaren horticulturalists use biological control in other indoor landscapes. Hospitals, hotels, restaurants, office buildings, and some department stores are also common augmentation sites for beneficials. "There are sensitive areas in all these buildings, and that is where beneficials are released," states Rickert. Most of the public doesn't seem to notice the beneficials and McCaren doesn't advertise that they are using augmentative biological control, although it may be an advantage in the bidding process for future interiorscape contracts.
-Rob Meagher, University of Minnesota
Reprinted from Midwest Biological Control News Volume II, Number 12 December 1995