A Parasitic Flythat Kills Mole Crickets Identifying Natural Parasites for Mole Crickets As Part of a Long-Term Control Strategy

Home , Larra analis, Ormia, Ormia depleta, Scapteriscus abbreviatus

A Parasitic FlyThat Kills Mole Crickets Identifying natural parasites for mole crickets as part of a long-term control strategy.

BY HOWARD FRANK

of Florida Mole Cricket Research Pro- gram began to investigate and import those natural enemies in the 1980s. Currently, two of those imported natural enemies are established year- round in the Gainesville, Florida, area. Together they provide about 95% control of tawny 'and short-winged mole crickets.2 Numbers of tawny and southern mole crickets in the Gainesville area are about 95% less than they were in the 1980s due to action of another wasp (Larra bicolor) and another beneficial nematode (Steinernema scapterisCl) from South America. What is remarkable about these imported wasps and nematodes is that they now occur all around the Gaines- An Ormia depleta pupa next to a dead adult mole cricket. The mole cricket was killed by an Ormia depleta larva that then became this pupa. Up to five fly larvae may develop successfully in an adult mole ville area and provide area-wide control cricket, and the process is always fatal to the mole cricket regardless of the number of fly larvae. for free.Year by year the area occupied by this wasp and nematode keeps rom coastal North Carolina south enemies that keep its numbers in check. increasing naturally, so that the area to Florida and west to Texas, mole These natural enemies include a wasp where mole crickets are controlled Fcrickets are major problems on (Larra analis) and a beneficial nematode expands. golf courses. Huge sums of money are (Steinernema neocurtillae) that seems to This article is about a third biological spent on pesticides every year to control attack only this species of mole cricket. control agent, a fly called Ormia depleta them, and this seems only to give tem- The services of these parasites are free that was imported by the University of porary relief from the problem. What wherever they occur naturally and Florida Mole Cricket Research Program would it take to get some level of provide permanent control. in 1987 and released in 1988. By having permanent control? The tawny mole cricket (Scapteriscus a third biological control agent for Not all mole crickets are pests.3 vicinus), southern mole cricket (Scapteris- mole crickets, the overall level of con- Although the northern mole cricket cus borellit), and short-winged mole trol for mole crickets may be improved. (Neocurtilla hexadactyla) gets into turf, it cricket (Scapteriscus abbreviatus) are not In addition, this fly may help establish seldom becomes numerous enough to native to the USA. All three of these biological control of mole crickets in do any damage. At least one of the pests arrived about 100 years ago and states north of Florida, such as the reasons for that is because it is native to left their natural enemies in their South Carolinas, where mole crickets are also the eastern USA and has native natural American homelands. The University a serious problem.

SEPTEMBER-OCTOBER 2002 9 THE FLY:ORMIA DEPLETA release in other southern states. Despite ten gravid female flies. Recipients were The initial stock of flies imported to extensive efforts to obtain the flies in expected to release the flies and after a Florida came from Piracicaba, a sub- 1998, the necessary permit was not few months begin monitoring the tropical city at about 23°S in Brazil. processed in time by the Brazilian release area for establishment of a popu- Rearing methods were devised,9 and government, and no flies were brought lation. To date, no recipient has reported flies were initially released at three back to the United States at that time. establishment of the flies. Nonetheless, localities: Gainesville (north Florida), However, Dr. Howard Frank, University attempts to establish populations in Bradenton (central Florida), and Miami of Florida, returned to Brazil early in other states continue. Additional flies (south Florida). Establishment of popu- February 1999. He was able to collect were shipped to Louisiana in May lations occurred at all three places. Re- seven gravid (pregnant) females and 2002. search sponsored by the Florida Turf- remove hundreds oflarvae from these grass Association in 1990-1991, which flies. Laboratory-reared mole crickets in DISCOVERIES ABOUT THE FLY included 28 participating golf courses, Gainesville were inoculated In the laboratory, adult flies failed to allowed for releases to be made at these with these larvae, and a survive long unless they were provided golf courses in 16 counties covering all culture was with artificial plant nectar (a mixture of regions of Florida. started. sugars). It had been expected that adult By the end of 1994, a continuous flies in the wild need nectar from some population of this fly had been estab- unknown plant or group of plants. lished in 38 contiguous peninsular Identifying those plants was difficult counties,4 but not farther north. because the flies are active only at The fly seemed to be poorly night. One attempt made by the adapted to survive the University of Florida Mole winters north of Cricket Research Program about 28°N. This was to identify pollen seems reasonable since grains attached to the it had come from a bodies of field-trapped subtropical area.7 Ormia depleta (old strain) in Lack of expansion of the Florida in hopes of identifying Ormia depleta population in plants from which adult flies obtain north Florida suggested that nectar. its origin was too tropical and that Ormia A second attempt to understand it could not survive winters in north depleta adult. the flies' diet was made by entomology Florida because it was unable to Adults are nocturnal. graduate student Craig Welch. He diapause. Diapause is a condition (like Gravid females are trapped adult flies at Bradenton (central attracted to the song of pest hibernation) in which individuals enter Florida), took samples of their gut con- mole crickets and lay living larvae dormancy during winter (or other (not eggs) on their hosts. tents, and analyzed the sugars present by periods when resources are not chromatography, a technique that allows available). It was hoped that additional The new (Osorio) strain of Ormia each sugar present to be identified. Sur- flies could be collected from farther depleta has been maintained in culture prisingly, the main sugar present was south in South America, in an area with since. The flies have been reared using melezitose.8 This sugar is not normally colder winters, where the local popula- laboratory-reared short-winged mole present in plant nectars, but it is the tion of flies can diapause. These hardier crickets as hosts. When generations of principle component of honeydew: flies could then be used to expand flies were produced that contained Honeydew is the sugary excretion of biological control of mole crickets in more than 10% gravid females, the homopterous insects (aphids, mealy the U.S. to states north of Florida. "surplus" (those that were not essential bugs, etc.). This means that the success to maintain the culture) was shipped to of using this type of biological control HOW NEW ORMIA DEPLETA other states for release. In 2000-2001, depends on having honeydew- WERE OBTAINED shipments of flies were made to col- excreting insects in the area. In 1998, the USGA funded a project laborating entomologists in North The principle is the same for butter- that would explore the southernmost Carolina, Georgia, Louisiana, and Texas fly gardening where, if we want to part of Brazil for a stock of Ormia for release in those states. enhance butterfly populations locally, depleta, bring that stock back to quaran- Each shipment consisted of either we must provide the plants from which tine in Florida, and provide flies for approximately 200 fly pupae or six to butterflies obtain nectar. This work is

10 GREEN SECTION RECORD continuing and is investigating what homopterous insects on what plant hosts can be used to enhance Ormia depleta populations locally. In other words, how can we provide those resources in the landscaping of golf courses that will lay the foundation for biological control of mole crickets without causing other problems such as unsightly insect-infested plants? The famed Doral golf course in Miami was one of the sites where Ormia depleta flies were released in 1990. Steve Kuhn, then superintendent, thought the fly had achieved about Florida counties in which permanent (dark blue) and seasonal (pale blue) populations ofthe old 90% control of pest mole crickets there. (Piracicaba) strain of Ormia depleta are established. In the counties shaded dark blue, Ormia depleta provides partial control of pest mole crickets at no cost. In the areas shaded pale blue, the old strain of Craig Welch's research findings offer an the fly seems not to survive the winters and it recolonizes from the south in most years. A strain that explanation of that high level of success. can diapause is necessary to occupy the area shaded light blue and northward. Doral has a rich landscape of tropical and subtropical plants which can sup- investigated. However, in view of the depleta (Diptera:Tachinidae). PhD dissertation, port homopterous insects (aphids, importance of mole crickets as a serious Univ. Florida, Gainesville. mealy bugs, etc.) throughout the year. It golf course pest, this should not be 2Frank,J. H. 2001. Statewide controls for mole is likely that these newly released flies ruled out. crickets? Florida Turf Digest. 18(4):44-45. had the honeydew sources needed for Wherever populations of the fly have 3Frank,J. H., andJ. P. Parkman. 1998. Integrated pest management of pest mole crickets with their diets from the homopterous become established, there is a strong insects living on those tropical and emphasis on the southeastern USA. Integrated and inexpensive option of enhancing Pest Management Reviews. 4:39-52. subtropical plants of the golf course their populations by providing honey- landscape. 4Frank,J. H.,TJ.Walker, andJ. P. Parkman. 1996. dew sources. It is hoped that by finding The introduction, establishment, and spread of the right plants to support honeydew- Ormia depleta in Florida. Biological Control. FUTURE RESEARCH producing insects, enough parasitic flies 6:368-377. The simplest and least expensive can be produced to effectively and sParkman, J. P., J. H. Frank, T J.Walker, and D.J. research is to determine whether the permanently control mole crickets. Schuster. 1996. Classical biological control of new strain of Ormia depleta can undergo Current research is aimed at this possi- Scapteriscus spp. (Orthoptera: Gryllotalpidae) in Florida. Environmental Entomology. 25:1415-1420. diapause. If this new fly strain can do so, bility in hopes of benefiting hundreds 6Stevens,L. M.,A. L. Steinhauer, andJ. R. it will immediately be useful in other of golf courses affected by mole Coulson. 1975. Suppression of Mexican bean states, and releases will continue in crickets. beetle on soybeans with annual inoculative other states until new populations of ACKNOWLEDGMENTS releases of Pediobius foveolatus. Environmental flies are established there. If the new Entomology. 4:947-952. strain cannot diapause, then one option USGA funding made possible collection 7Walker,T J., J. P. Parkman, J. H. Frank, and J. P. of the new strain of Ormia depleta from is to determine whether it can be pro- Schuster. 1996. Seasonality of Ormia depleta and duced in adequate numbers for annual southern Brazil, its maintenance in limits to its spread. Biological Controls. 6:378-383. inoculative release each spring in other culture in Florida, and shipment of 8Welch, C. H., and D.A. Carlson. 2002. Gas states. However, it will take improve- stock to other southern states. Dr. Luiz chromatographic analysis of crop sugars of ments in rearing methods for both Salles (EMBRAPA, Pelotas) provided Ormia depleta established in Florida. Environ- mole crickets and the flies, as well as essential help in southern Brazil. E. Buss mental Entomology. 31:In press. improvements in the proportion of flies and F. Slansky kindly reviewed an early ~ineriter, S.A., and TJ.Walker. 1990. Rearing phonotactic parasitoid flies (Diptera:Tachinidae, becoming gravid before such a strategy draft of this manuscript. Ormiinae, Ormia spp.). Entomophaga. 35:621- becomes viable. LITERATURE CITED 632. It might be possible to produce a dia- I Cabrera, H. 2002. Development of the fly pausing strain of the fly by genetic engi- HOWARD FRANK, PH.D., is an Ormia depleta. Chapter 4. In: Relationship neering, but undoubtedly this would be between temperature and development of the Entomology Prifessor in the Entomology a very expensive option because the ectoparasitoid Larra bicolor (Hymenoptera: and Nematology Department, University genetics of this fly have not yet been Sphecidae) and the endoparasitoid Ormia of Florida, Gainesville.

SEPTEMBER-OCTOBER 2002 II