Potential for Biological SECTION TWELVE Control of Dendroctonus . and Ips Bark Beetles

Edited by David L. Kulhavy Center for Applied Studies School of Forestry Inoculative Release of An Exotic Predator Stephen F. Austin State University for the Biological Control Nacogdoches, Texas USA of the Black Turpentine ijectle

and John C. Moser Southern Forest Experirnent S tntion Mitchel C. Miller USDA Forest Service Southern Forest Experiment Station Pineville, buisiana USA USDA Forest Service Pineville, Louisiana ABSTRACT An inoculative release of the Eurasian prcdatori a1 bcctle, Rhizoplingn.~ grandis, was made for control of the black turpcntiric bcctlc. Dendroctt~nic~ terebranr Olivier, a prominent native pest of southern pines. If this central Louisiana release proves successhl, and rcaring programs arc pcrfcctcd. further releases should expand the geographical range of X. grandis. Bc- cause the larval frass of other species of Dendroctonirs is highly attractive Center for Applied Studies to R. grandis, this exotic predator may also attack the bmod of some or all School of Forestry of the South's Dendroctonur species, including that of thc southern pine Stephen F. Austin State University beetle, Dendructonus frontalis . Nacogdoches, Texas USA 1989 BACKGROUND The black turpentine beetle (BTB), Dendroclonirs tcrchrtzrls Olivicr, is a native pest of pines in southern United States. It is pnflicularly injurious in Georgia and Florida where gum naval stores operations arc an impoflant industly (Smith and Lee 1967). During turpcntinc opcrat ions, sl;lsl~pine Moser, J.C. 1989. An exotic predator for the biological control (Pinus elliottii Engelmann) and longleaf pine (Pinus palicrtris hliller) arc of the black turpentine beetle. pp. 189-200. In Kulhavy, D. L. and Miller, M. C. , (eds. ) Potential for ~iolo~zalControl of B1OUX;ICAL CONTROL OO .droctonus and Bark Beetles. centdr for Applied Studies, School of Forestry, Stephen F. Austin ~t+teUniversity, Nacogdoches, TX. 255 pp. 190 Inoculative Release of An Exotic Predator Inoeula tive Release of An Exotic Predator 191 commonly attacked and killed by the beetle. Additiondy, the BTB quickly and Bogenschutz 1984, Moser et al. 1978). Although the native natural attacks trees damaged during logging operations and trees located near enemies may have a considerable impact on bectle populations, they still do comtmction sites in urban areas. Apparently normal healthy tws may also not always control epidemic levels of the Dendroctonus bark beetles. It is he attacked, although BTB damage usually involves less than 10% of a possible then that the best hope in this area lies with the release of exotic stand during a single season. One "epidemic," however, in the 1950's, natural enemies. One exotic insect predator, Rhizophagus grandis ~prtcdlyaKccted more than 25% of a single healthy stand (Smith and Lee Gyllenhal (Coleoptera: Rhizophagidae), appears to have potential as a 1967). control agent (Miller et al. 1987). Although not as aggressive or wide spread as the southern pine beetle: (SPB), Dendroctomfrontalis Zimmermann, the BTB shows a preference The Biological Control Approach for weakened trees, such as those damaged by fire, tapped for naval storcs, or injured during logging operations. The BTB ranks third as over- Rhizophagus grandis is a specific predator, attacking only the spruce bark all damage agent among 10 major forest pests in the 13 southern states. beetle, Dendroctonus micans (Kugelann). The distribution of both host and However, according to USDA Forest Service and university researchers predator now extends westerly from eastern Siberia to France and Eng- worliing in norida and Georgia where the turpentine industry is important, land, south to Turkey, and to the northern tip of Norway (Bevan and King UTB ranks as the most destructive pest. 1983). D.micans is the only species of Dendroctonus within this vast area. In the recent past, D. micans has expanded westerly from its Siberian ori- Current Control Strategies gin. As the beetle invaded Europe during the past 100 years, population explosions coincided with this advance (Carle 1975). Apparently these A rlumber of control strategies are currently used to reduce bark beetle outbreaks occurred when D. micans temporarily "outran" its predator, R. population numkrs and/or to manage outbreaks. These strategies can be grandis; but once the predator-prey balance was achieved, D. rnicans again categorizxd as I) spot control by salvage, 2) chemical treatment, and 3) became endemic (J-C. GrCgoire, personal communication). Presently. preventive management of susceptible stands by silvicultural methods. Of large-scale programs are under way to introduce the predator in spruce the first two categories, rapid salvage is the preferred alternative (Swain stands in parts of England, France, Russia, and Turkey where the scolytid arid Remion 1981). Except for urban areas, chemical control is not widely is still epidemic (Grdgoire et al. 1985). Efforts are espccially intense in practiced because it is not cost effective and because of environmental England, where D. micans was first discovered in 1982 (Bevan and King conam. 1983). In 1984.30.000 R. grandis adults were produced in large breeding Currently. preventive control by silvicultural treatment is the best units for distribution in England's outbreak areas of D.rnicans (Evans overall strategy in combating outbreaks. Research over the past decade has 1985). In 1985,29,000 were reared in Belgium (J-C. Gregoire, personal provided successful silvicultural prevention methods that are now widely communication). accepted (Belanger 1980, Lorio 1980). Unfortunately, economic con- Within the palearctic spruce forests, R. grandis is,.found in association strai nts sometimes preclude use of prevention methods by many landown- only with D. micum, there being no records of its having attacked other ers in the souG~ernUnited States. scolytids. But perhaps this is because no other Dendroctonus species may Applied biological control of bark beetles is still an ignored and be available to it within the predator's natural range in Eurasia. R. grandis undcrdcvelupcd technique. Of the many organisms and allied beetle has a high searching efficiency and is found in more than 80% of D. mi- species associated with Dendroctonus, only native insects, mites, cam galleries (Gregoire et al. 1985). R. grandis is able to detect both larval nematodes, and ftrngi have received much attention (Berisford 1980). and adult allomones of D. micanr (Tondeur and Gregoire 1979). but R. Recent studies have been oriented toward determining specific roles and grandis females will not oviposit unless larval frass of D.micans is present impacB of native associ atcs so that computer models can be developed to (Gdgoire et al. 1984). The key allomones attracting R. grandis to D.mi- forecast population trcnds. Studies have been designed to implement cans galleries appear to be em-brevicomin, which may be produced by D. control strategies that cncapitalize on population suppression by native micans adults, and (-)-verbenone, produced by D. micans larvae natural cncr~iics(Kinn 1984, Moser and Dell 1980). Other studies are Wmmerh et al. 1985). searching for exotic or extrarcgional natural enemies (Moser 1981, Moser 192 Inoculative Release of An Exotic Predator Inoculative Release of An Exotic Predator 19.3

GnSgoire et al. (1981) suggested that other Dendvctonus species with troduced into Britain until 1982. Moreover, other known cpcics of Rhi- gregarious larvae, such as BTB, might also be attractive to R. grandis. In a zophagus are much less species specific and their predatory quali ties arc series of bioassays performed in February, 1985, J-C. GnSgoire demon- questionable (J-C. GrcSgoire, personal communication). Specimens of R. strated that larval frass of three native North American species of Den- grandis were sent to the United States on three occasions (1976-78) for droctonus (D. terebrans, D.frontalis, and D. rufpennis (Kirby), the laboratory tests against North American Dendrcrrtcl~wspecies, but nonc spruce beetle) were highly attractive to both males and females of R. gran- were released (Coulson 1981). The Canadim Forcstry Scrvicc at Victoria dis. The most surprising find was that the frass of D,Jicontalis (whose lar- B. C. has imported individuals to control De&actonrrr ponrierosae )Top vae are not gregarious) was also highly attractive (Miller et al. 1987). This kins (i.A. Moeck, personal comunication). suggests that if R. grandis was intmduced into the United States and suc- cessfully established as a predator on D. terebrm, then the predator might also impact the SPB. D. terebrans, however, remains the primary target because it has an ecology similar to that of D. micans. Both BTB and D. micans have a long life cycle and gregarious larvae, facilitating prey ex- ploitation by R, grand&.

Fig. 2. Young BTB larvae feeding gregariously in phloem sandwich. Below are an adult and two larvae of Rtrizophagus grandis (USDA Forest Service photo).

, This biological control agent, if successfully established, should spread throughout the host's range, effecting widespread control that is cost effective. Theoretically, R. grandis should also attack broods of the Fig. 1. Male Rhizophagus grandis in gallery of Ips grandicollis inside phloem more aggressive SPB, because the predator adults are highly attracted to sandwich (USDA Forest Service photo). larval frass of the scolytid (Miller et al. 1987). Indeed, R. granciis adults entered SPB galleries through holes made by them, and consumcd the 1nr- It should be mentioned at this point that in 1933 and 1934 about 800 vae in phloem sandwiches. These sandwiches (Moser and Roton, unpub- specimens of an unidentified Rhizophagw from England were released in lished) had been previously attacked by SPB in the field. fIowcvcr, R. Quebec, Canada, against the spruce beetle in an outbreak area, but the in- grandis egg laying was not observed. The same phenomenon was ob- troduced beetles failed to become established. Tumock et al. (1976) classi- served in another sandwich field-attacked by Ips grdcollis (Fig. 1). fied this release as a futile colonization attempt, doomed by inadequate selection of natural enemies and by poor handling and release techniques,.. This species could not have been R. grandis because it was not introduced 194 Inoculative Release of An Exotic Predator Inoculative Release of An Exotic Predator 195

Rearing Procedures immediate objective was to obtain eggs of R. grandis so that they could be surface-sterilized in White's solution (Banas 1972), thus reducing the Attempts will be made to determine the best way to rear the predators in I chances of microorganisms being introduced from Europe. R. grandis order to build up populations for release in central Louisiana. Experience readily laid eggs in phloem sandwiches (Fig. 2) inoculated with about 20 in Europe has show that large numbers of R. grandis for release in the BTB larvae, and one male and two females of R. grandis (only one pair ficld can be artificially reared on brood of D. micans (Fig. 1) in spruce was needed, but the extra female doubled the egg production). Young BTB bolts, and by a semiartificial breeding method (Gdgoire et al. 1986). This larvae fed gregariously (Fig. 3) similar to those of D. rnicans, but older latter rearing method was first developed in Russia Kobakhidze et al. lalvae became solitary (Fig. 2). Individual females laid as many as 133 1968) and is currently being used in England. In 1985, the British eggs per sandwich. After 5 to 8 days the sandwiches were opened, and the Forestry Commission reared adults of R. grandis in spruce billets at a cost 1 easily visible eggs (Fig. 4) were collected. of about $2.50 per beetle, counting materials and labor (H. F. Evans, per- 1 After surface sterilization, the eggs were placed in polystyrene boxes sonal communication). For that project, a constant temperature of 20 de- where the resulting larvae were reared on the alternate food sources de- grees C., 65-7596 R. H., and an artificial lighting regime of 18 hours/day scribed by Gegoire et al. (1986). This method conserved BTB lalvae that were maintained in rearing moms (Evans 1985). were sometimes scarce and were needed as oviposition stimuli for R. grandis. Although the R. grandis larvae would readily feed gregariously on BTB larvae inside the sandwiches (Fig. 5). the predator larvae (as well as adults. Fig. 6) could be conveniently fed a variety of foods including frozen dipterous maggots and even commercial cat food. Prepupae were placed in moist sand to pupate, after the technique described by G~goireet dl. (1986).

Fig. 3. Phlocm sandwich with mame BTB larvae, some of which are constructing pupal cells. Young larvac were inaoduced at right. They feed gregariously at first; later the older larvae disperse (USDA Forest Service photo).

111 1986 arid 1987, three shipments totaling 300 hundred pairs of R. grundis, reared by J-C. GrCgoire in Belgium, were shipped to the Alexan- dria Forcsq Ccntcr in Louisiana to test methods of rearing the predator on B7B and SPB AlU~ough preliminary tests showed that the predator could Flg. 4. Portion of phloem sandwich with eggs of Rhizophgus grundis (arrows) in be rcarcd or1 BIB, using both the bolt and the semimificial methods, the B?TB &ass (USDA Forest Service photo). laucr nlctlltd was chosen because using bolts was too labor intensive. Our-- 196 Inoculative Release of An Exotic Predator Inoculative Release of An Exotic Predator

Whereas Beauveria barsiuna (Balsamo) Vuillcmin cnuscd rn;rjor rearing losses to D. micans and R. grandis brood in Europe. another pathogen [probably Metarhizium anisopliae (Mctschinikoff) Sorokirl] soon cnuscd 100% losses to both host and predator larvae in thc lirst Alcxaildria Forestry Center rearing containers. The discasc iv;t s CO~r01Ied in 1at or rearings by using 0.5 g each of sorbic acid and mctliyl parakn, rnircd with 400 g of the bark dust medium used to fill the pol ystyrenc ho~i~

Field Release Techniques In England single pairs of R. grandis are placed in small plastic cups each having about 50 ml capacity. A small amount of moist sand is added. Thc cups are then taken into the field where the contents, including thc prcda- tors, are carefully poured out at the bases of trccs that have bccn attacked by D. micans (King and Evans 1985). In France, about 50 predators arc placed at the base of each single infcstcd tree, and the predators quickly vanish, running into the bark or taking flight (Grtgoirc ct al. 1985). El~(l1 Fig. 5. Young and mature larvae of Rhizophagus grandis feeding gregariously on larva of B'I'B in artificial rearing chamber (USDA Forest Service photos). release methods take advantage of the extraordinary searching abilities of R. grandis. The minimum number needed for an inoculative rclcase is urlkr-io~\n, but it is probably less than the 2,350 individuals released per arca in France (Gdgoire et al. 1985). This is the lowest numbcr listed in pub- lished reports for areas in which individuals were rccovcrcd the next ycar. However, H. F. Evans (personal communication), in England, recovered a number of R. grandis lawae 6 months later after rcleases of only 10 and 25 individuals respectively. Adults, larvae, and prepupac have bccn found overwintering (GrCgoire, personal communication). Bci me (1 975) has shown that of species (none of which werc Rhizophajitc~)rclcnsed for bio- logical control in Canada, 60% of those averaging more than 800 individuals per release became colonized, but of tKosc averaging Iess than 800 per release, only 15% became colonized. Hence, a1 though ii nppcnrs possible to establish R. grandis by using small numbers, a large rclcasc may greatly increase chances of succ.css. In Europe, when populations of R. grandis arc establishcd, they tend to "stay put" and not move rapidly into new distant arcas. For this reason, a number of inoculative releases would have to bc madc tllrotlgliout tlic southern United States to quickly establish the predator tliroughor~(thc range of BTB. Fig. 6. Adult of khizophgus grandis feeding on pellet of commercial dry cat food. Although the BTB is ubiquitous in pine forests of central Louisiana, At left (arrow) is remains of BTB larva conswed peviously by the predator. high populations often occur in stumps after logging opcmtions. Emerging adults may also attack nearby trees. It is at the interface of one of these 198 Inoculative Release of An Exotic Predator Inoculative Release of An Exotic Predator 199 areas and the surrounding forest that would be the ideal habitat to release the large numbers of R. grandis adults. As of April 1, 1988, there were Gregoire, J-C., J. Merlin, and J. M. Pasteels. 1984. Mass-rearing of Rhizopha- about 150 pairs of adults being held in the refrigerator for release in the gus grandis for the biological control of Dendroctonus micanx An in- terplay between technical requirements and the species biological field. On April 7, the first 20 pairs were released in four localities of Grant characteristics. Med. Fac. Landbouww. Rijksuniv. Gent, 4913a: 763- Parish, Louisiana on two trees and 6 stumps similar to the method by King 769. and Evans in England. GrCgoire, J-C., J. Merlin, J. M. Pasteels, R. Jaffuel, €3. Vouland, and D. Schvester. 1985. Biocontrol of Dendroctonus rnicans by Rhizophagus ACKNOWLEDGMENTS grandis Gyll. (Coleoptera: Rhizophagidae) in the Massif Central (France): A first appraisal of the mass rearing and release methods. 2. I gratefully acknowledge the advice provided by H. F. Evans, J-C. Gdgoire, and ang. Entomol. 99: 182-190. C. 1. King in the preparation of this manuscript. and to D. L. Kulhavy and D. Gregoire, J-C., J. Merlin, R. Jaffuel, Ph. Denis, P. Lafont, and D. Schvester. M.Anderson for reviewing the original manuscript. 1986. Elevage a petite et moyenne echclle du predateur Rhizophagus grandis gyll. en vue de la lutte biologique contre Dendroctonus micans LITERATURE CITED Kug. Rev. For. Fran, 38: 457-464. King, C. J. and H. F. Evans. 1985. The rearing of Rhizophagus grandis and its Barras, S. 1. 1972. Improved White's solution for surface sterilization of pupae release against Dendroctonus micans in the United Kingdom. In Proc. of Dendroctonusfrontalis, J. Econ. Entomol. 65: 1504. EEC Seminar on the Biological Control of Bark Beetles (Dendroctonus Beirne, B. P. 1975. Biological control attempts by introduction against pest in- micans) Brussels. J-C. Gregoire and J. M. Pasteels, eds. 3-4/10784,pp. sects in the field in Canada. Can. Entomol. 107: 225-236. 87-97. Bclanger, R. P. 1980. Silvicultural guidelines for reducing losses to the southern Kinn, D. N. 1984, Incidence of endoparasitic nematodcs in Ips engraver beetles pine bcetle. In The Southern Pine Beetle. R. C. Thatcher, J. L. Searcy, in Central Louisiana. J. Ga. Entomol. Soc. 19: 322-326. 1. E. Coster, and G. D. Hertel, eds. U. S. Dept. Agric. For. Serv. Tech. Kobakhidze, D. N., M. S. Tvaradze, G. U. Yashvili, and I. K. Kraveishvili. Bull. 1631, pp. 165-178. 1968. Artificial rearing of Rhizophagus grandis Gyll. for the control of Bei-isford, C. W. 1980. Natural enemies and associated organisms. In The Dendroctonus micans Kug. in Georgia (In Russian). Soobschenie Soulhem Pine Beetle. R. C. Thatcher, J. L. Searcy, J. E. Coster, and Akademii Nauk Gruzinskoi SSR. 51: 435-440. G.D. Hertel, eds. U. S. Dept. Agric. For. Serv. Tech. Bull. 1631. pp. Lorio, P. L. 1980. Rating stands for susceptibility to SPB. In The Southern 3 1-52. Pine Beetle. R. C. Thatcher, J. L. Searcy, J. E. Coster, and G. D. Her- Bevan. D. and C. I. King. 1983. Dendroctonus micans Kug., A new pest of tel, eds. U. S. Dept. Agric. For. Serv. Tech. Bull. 1631. pp. 153-164. Miller, M. C., J. C. Moser, M. McGregor, M. Baisier, D, L. Dahlsten, and R. spruce in U. K, Commonwealth Forestry Review. 62: 41-51. ' Carle, P. 1975. Dendroctonus micans Kug. (Coleoptera: Scolytidae), The giant A. Werner. 1987. Potential for biological control of native North spruce bark beetle or European spruce bark bcetle: A bibliographical re- American Dendroctonus beetles (Coleoptera: Scolytidae). Ann. Ento- view, Rev. For. Fr. 27: 115-128. mol. Soc. Am. 80: 417-428. Moser, J. C. 1981. Transfer of a Pyemotes egg parasite phoretic on western pine Coulson, I. R. 1981. The Soviet-American environmental agreement and ex- to change of beneficial organisms, 1972-1979. In Proceedings of the Joint bark beetles the southern pine bcetle. ~ntcrhat.1. Acarol. 7: 197-202. Moser, J. C. and H. Bogenschutz. 1984. A key to the mites associated with fly- American-Soviet Conference on Use of Beneficial Organisms in the 2. Control of Crop Pests. I. R. Coulson, ed. August 13-14, 1979. Ento- ing Ips typographus in South Germany. ang. Entomol. 97: 437-450. mological Scxiety of America, College Park, pp. 1-11, Moser, J. C, and T. R. Dell. 1980. Weather factors predicting flying populations of a clerid predator and its prey, the southern pine beetle. In Dispersal of E\tarrs, W. F. 1985. Great spruce bark beetle, Dendroctonus micans: An exotic forest insects: Evaluation, theory, and management imp1 ications. A. pest new to Britain. Antenna 9: 117-121. Berryman and L. Safranyik, eds. Proceedings of the second IUF'RO Grbgoirc, J-C,, J. C. Brackman, and A. Tondeur, 1981. Chemical communica- Conference, Sandpoint, Idaho. pp. 266-278. tion between the larvae of Dendroctonus micnns Kug. (Coleoptera: Moser, J. C., B. Kielczewski, J. Wisniewski, and S. Balazy. 1978. Evaluating Scolytidae). Lees Colloques de I'IN'RA, 7. Les Mediateurs Chimiques: Pyemotes dryas (Vitzthum 1923) (Acari: Pycmotidae) as a parasite of 253-257. the southern pine bcetle. Internat. J. Acarol. 4: 67-70. 200 Inoculative Release of An Exotic Predator

Smith, R. H. and R. E. Lee. 1967. Black Tuqxntinc Beetle. USDA For. Serv. For. Pest Leaflet 12.7 p, Swain, K, M. and M. C. Remion. 1981. Direct control methods for the southern pine beetle. USDA Agricultural Handbook 575. 15 p. Tornmerb, B. A., H. Mustaparta, and J-C.Grtgoire. 1985. Electrophysiological recordings from olfactory receptor cells in Dendroctonus micans and Rhizophagus grandis. In Animals and Environmental Stress. R. Gilles, ed. Pergamon Press, pp. 98-106. Tondeur, A. and J-C. Gregoire, 1979. Chemical orientation of Rhizophagus grandis (Coleopterx Rhizophagidae) towards mates, and towards prey: Dendroctonus rnicans (Coleoptera: Scolytidae). lir Animds and Envi- ronmental Sms. R. GiIles, ed. Pergamon Press, pp. 93-94. Turnock, W. J., K. L. Taylor, D. Schroder, and D. L. Dahlsten. 1976. BioIogi- cal control of pests of coniferous forests. In Theory and Practice of Biological Control. C. B. Huffaker and P. S. klesscngcr, eds. Academic Press. pp. 289-3 11.