J. Appl. Ent. 114 (1992), 110-112 0 1992 Verlag Paul Parey, Hamburg und Berlin ISSN 093 1-2048

Laboratoire de Biologie animale et cellulaire CP 160, Universiti Libre de Bruxelles, Belgium, and Institut fir Organische Chemie, Universitat Hamburg, FRG Semiochemicals and the management of grandis Gyll. (Col., Rhizophagidae) for the biocontrol of micans Kug. (Col., Scolytidae)’

By J.-C. GR~GOIRE,D. COUILLIEN, A. DRUMONT,H. MEYERand W. FRANCKE

Abstract Semiochemicals can be exploited for rearing and monitoring natural enemies involved in biological control. The predator , which is used against , is now artificially mass-produced using synthetic oviposition stimuli. Recent results from the laboratory and the field also suggest that R. grandis population levels could be monitored using synthetic attractants.

1 Introduction

The predator Rhizophagus grandis is widely used for the biological control of the greater Eurasian , Dendroctonus micans. It is, or has been, mass-cultured and released on thousands of hectares in the USSR (KOBAKHIDZE1965), France (GRBGOIREet al. 1984), the United Kingdom (KING and EVANS1985) and Turkey (N. USLU,pers. com.). This specific predator needs precise chemical signals to locate its prey, and semiochemicals are also needed as oviposition stimulants. These compounds have been recently identified and bioassayed. Synthetic oviposition stimulants are now used in mass culturing R. grundis, whilst release-recapture experiments suggest that the predator could soon be successfully monitored in the field using synthetic kairomones.

2 Oviposition stimulants

A comparative analysis of the larval frass of D. micans and D. valens (an American species which elicited oviposition by R. grandis), led to the identification of seven compounds involved as oviposition stimulants (GREGOIREet al. 1991a): (-)-fenchone, (-)-isopinocam- phone, (-)-pinocamphone, rac. verbenone, rac. camphor, (+)-fenchol and (-)-borneol. These compounds have since been used in connection with mass-rearing of the predators. Cultures were made in “oviposition boxes” (GREGOIREet al. 1986), where live D. micans larvae and spruce bark were replaced by Calliphora frozen maggots and synthetic stimulants. Yields of 3 successive cultures are given in table 1.

3 Long-range attractants

Starting from the oviposition stimulants, successive bioassays selected a mixture of (-)- fenchone, (-)-verbenone, rac. camphor, (+)-terpinene-4-01, (+)-fenchol, (-)-borneol, and

’ Contribution to the Workshop ‘Semiochemicals in the Pest Management of Bark ’, Hann.- Miinden, 19. 8. 1991-22. 8. 1991. Dedicated to Prof. Dr. J. P. VIT~on the occasion of his retirement.

U.S. Copyright Clearance Center Code Statcment: 0931-2048/92/1401-0110 $ 02.50/0 Semiochemicals and the management of R.grandis for the biocontrol of D. micans 11 1

Table 1. Mass cultures of Rhizophagus grandis using synthetic stimulants

1 Date No boxes Total no larvae Total no pupae Total no adults Adultslbox 1 I I March 91 45 2592 2058 1749 32.4 April 91 35 6668 4580 3681 105.2 May 91 39 unknown 9401 8840 226.7

(-)-a-terpineol, which elicited 97% of the response to frass in a flight windtunnel (GR~GOIREet al. 1991b). Field trials were run in Dendroctonus-free sites in France (Somail and Espinouse Mountains, Department of Htrault). Groups of about 400 beetles were released in the middle of two concentric rings of traps. The first ring had a 50 m radius, there were 4 traps in this ring. The second ring had a 100 m radius and consisted of 8 traps. Distance between traps in any ring was 80 m. Traps were commercial Kreins traps (four black PVC vanes crossing at 90", 50 cm long and 18 cm wide, over a funnel 30 cm in diameter). 100 mg of the synthetic attractant were enclosed in each trap, within a polythene bag serving as a controlled release dispenser. Each experiment was run for two days and the traps were examined daily. The results of these release-capture experiments are given in table 2. The high recapture rates need to be carefully checked. If they prove consistent, we shall have a powerful way to monitor R. grandis, either to prepare releases in areas where it is supposedly lacking, or to assess the success of releases. Another possible use of attractants for R. grandis could be monitoring for the presence of D. micans in areas still supposedly uncolonised by the but threatened by population movements of this latter. As D. micans itself does not respond to pheromones, and as the damages of incipient populations are difficult to spot, R. grandis could be used as a marker, being released in areas of unknown status. Recaptures would indicate the presence of D. micans since R. grandis had obviously been able to survive on its prey. Large scale trials are planned next year in the French Departments of Htrault and Aude, which are adjacent to areas already colonised by D. micans (Gard and Aveyron to the East; Ariege to the West), but are still supposedly safe from the bark beetle.

Table 2. Release-recapture experiments with R. grandis using synthetic attractants (Hirault, France, July 91)

Number released % caught Yo recalculateda

140 1.8 49 150 0.9 2.3b 256 0 0' 407 12.3 30.9d 382 5.2 12.9d 43 1 11.2 23.8d 437 13.3 28.4: 422 12.4 31.1 430 11.7 24.gd 420 20.6 51.4 415 26.3 65.7 446 26.8 57.0

a Basis for recalculation: (Noreleased - dead individuals) x flight capacity coefficient. Flight capacity coefficient decreases linearly with age of beetles and is affected by the use of oviposition stimulants in cultures (COILLIENand GRLGOIRE,in prep.). Its value for beetles used here varied

from 0.4 to 0.47. ~ One single trap, SO m from release point. - No attractant. - One ring of traps only, 50 m from release point. 112 /.-C. Grigoire, D. Couillien, A. Drumont, H. Meyer and W. Francke

4 Conclusions

The results presented here demonstrate the high potential of semiochemicals in an area of bark beetle integrated management that has yet been less intensely researched: the use of natural enemies. A better understanding of the chemical ecology of predator-prey and parasitoid-host relationships among bark beetles and their associates might considerably increase our capacity to manipulate harmful scolytids.

Acknowledgements Thanks are due to ANDYFOGGO for help with the English, and to LETICIACHRBTIEN and JOELLEVAN BAMBEKEwho helped with the rearings. Parts of this work was financed by a grant to J.-C. G. from Region Languedoc-Roussillon/FEOGA Special Programme F.2.89, Project 5.6.1.1.d. W.F. thanks the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie for financial support. J.-D. G. thanks the Fonds National Belge de la Recherche Scientifique for financial support.

Zusammenfassung Verhaltensmodifzierende Duftstoffe im Management von Rhizophagus grandis Gyll. (Col., Rhizophagidue) zur biologischen Bekampfung von Dendroctonus micans Kug. (Col., Scolytidae) Duftstoffe konnen in der Zucht und in der Uberwachung natiirlicher Feinde bei der biologischen Bekampfung eingesetzt werden. Der rauberische Rhizophagus grundis, der gegen Dendroctonus micuns eingesetzt wird, ist heute Gegenstand kunstlicher Massenzuchten, bei denen synthetische Eiablagestimulantien verwendet werden. Neuere Ergebnisse aus Labor und Freiland weisen darauf hin, daB die Populationsdichten von R. grandis mit synthetischen Lockstoffen ermittelt werden konnen. References GR~GOIRE,J.-C.; BAISIER,M.; DRUMONT,A,; DAHLSTEN,D. L.; MEYER,H.; FRANCKE,W., 1991a: Volatile compounds in the larval frass of and Dendroctonus micuns (Coleo- ptera: Scolytidae) in relation to oviposition by the predator, Rhzzophugus grandis (Coleoptera: Rhizophagidae). J. Chem. Ecol. 17(10), 2003-2019. GRBGOIRE,J.-C.; COUILLIEN,D.; KREBBER,R.; KONIG,W. A,; MEYER,H.; FRANCKE,W., 1991b: Oxygenated monoterpenes in predator-prey relationships: oviposition stimulants also mediate long-range orientation of Dendroctonus mzcans by Rhizophagus grandis (Coleoptera: Rhizophagidae and Scolytidae). Chemoecology (in pr.). GRBGOIRE,J.-C.; MERLIN,J.; JAFFUEL,R.; DENIS,PH.; LAFONT,P.; SCHVESTER,D., 1986: Elevage h petite et moyenne ichelle du pridateur Rhzzophugus grundis Gyll. en vue de la lutte biologique contre Dendroctonus micans Kug. Rev. Forestikre Franpise XXXVIII (5), 457464. GRBGOIRE,J.-C.; MERLIN,J.; PASTEELS,J. M.; JAFFUEL,R.; VOULAND,G.; SCHVESTER,D., 1984: Mass-rearings and releases of Rhizophagus grandis. In: Proc. EEC Seminar Biol. Control of Bark Beetles (Dendroctonus micans), Brussels, 34/10/1984. pp. 122-128. Ed. by GRBGOIRE,J.-C.; PASTEELS,J. M. KING, D. J.; EVANS,H. F., 1984: The rearing of Rhzzophugus grandis and its release against Dendroctonus micans in the United Kingdom. In: Proc. EEC Seminar on the Biol. Control of Bark Beetles (Dendroctonus micans), Brussels, 34/10/1984. pp. 87-97. Ed. by GR~GOIRE,J.-C.; PASTEELS,J. M. KOBAKHIDZE,D. N., 1965: Some results and prospects of the utilization of beneficial entomophagous in the control of pests in Georgian SSR (USSR). Entomophaga 10 (4), 323-330.

Authors’ addresses: JEANCLAUDE GRBGOIRE, DANIEL COUILLIEN and ALAINDRUMONT, Laboratoire de Biologie animale et cellulaire CP 160, UniversitC Libre de Bruxelles, 50 av. F. D. Roosevelt, B-1050 Bruxelles, Belgium; HOLGERMEYER and MITTKO FRANCKE,Institut fur Organische Chemie, Universitat Hamburg, Martin- Luther-King-Platz 6, W-2000 Hamburg 13, FRG