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 Rollercoaster, 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. 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.

Pest Species. 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, Phytonemus 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 ordering insects). 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.

Metaphycus helvolus Coccophagus lycimnia
Illustrations by Dr. John Luhman, Minnesota Department of Agriculture

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. 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 (= Metaseiulus, = Typhlodromus) occidentalis, the western predatory mite, Phytoseiulus persimilus, and Neoseiulus (= Amblyseius) californicus have been successful at reducing spider mite populations. Neoseiulus (= Amblyseius) cucumeris has been successful against western flower thrips and cyclamen mites. The generalist predator Orius insidiosus (Anthocoridae) 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, 2, 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.

Other Interiorscapes. 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.

It is now Christmas time and Santa Claus is going to be in Camp Snoopy this year. The McCaren staff are excited for this opportunity to show thousands of visitors their natural "man made" forest and thereby exhibit the benefit and success of using biological control. Hopefully Rudolf doesn't start eating the shrubbery. Ho Ho Ho!!

- Rob Meagher,University of Minnesota

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