FOREST ENTOMOLOGY Survival and Development of Lymantria monacha (Lepidoptera: Lymantriidae) on North American and Introduced Eurasian Tree Species M. A. KEENA1 Northeastern Research Station, Northeastern Center for Forest Health Research, USDA Forest Service, Hamden, CT 06514 J. Econ. Entomol. 96(1): 43Ð52 (2003) ABSTRACT Lymantria monacha (L.) (Lepidoptera: Lymantriidae), the nun moth, is a Eurasian pest of conifers that has potential for accidental introduction into North America. To project the potential host range of this insect if introducedintoNorth America, survival anddevelopmentof L. monacha on 26 North American andeight introducedEurasiantree species were examined.Seven conifer species (Abies concolor, Picea abies, P. glauca, P. pungens, Pinus sylvestris with male cones, P. menziesii variety glauca, and Tsuga canadensis) andsix broadleafspecies ( Betula populifolia, Malus x domestica, Prunus serotina, Quercus lobata, Q. rubra, and Q. velutina) were suitable for L. monacha survival and development.Eleven of the host species testedwere ratedas intermediatein suitability, four conifer species (Larix occidentalis, P. nigra, P. ponderosa, P. strobus, and Pseudotsuga menziesii variety men- ziesii) andsix broadleafspecies ( Carpinus caroliniana, Carya ovata, Fagus grandifolia, Populus gran- didentata, Q. alba, and Tilia cordata) andthe remaining 10 species testedwere ratedas poor ( Acer rubrum, A. platanoidies, A. saccharum, F. americana, Juniperus virginiana, Larix kaempferi, Liriodendron tulipfera, Morus alba, P. taeda, and P. deltoides). The phenological state of the trees hada major impact on establishment, survival, anddevelopmentof L. monacha on many of the tree species tested. Several of the deciduous tree species that are suitable for L. monacha also are suitable for L. dispar (L.) and L. mathura Moore. Establishment of L. monacha in North America wouldbe catastrophic because of the large number of economically important tree species on which it can survive anddevelop,and the ability of matedfemales to ßy andcolonize new areas. KEY WORDS Lymantria monacha, host plant suitability, development, survival Lymantria monacha (L.) (Lepidoptera: Lymantri- The best defenses currently used against this potential idae) (nun moth) is a Eurasian pest of conifers that pest are to monitor its abundance in Eurasian ports poses an ever-present threat of being introduced into (Munson et al. 1995), develop a good pheromone trap North America. Adults are readily attracted to artiÞ- to monitor for it (Morewoodet al. 1999), andeducate cial lights andhave been observedin Russian Far East people on how to identify it (Keena et al. 1998). ports (Munson et al. 1995). L. monacha has a high However, there is little useful information that ad- potential to be transportedvia commerce because, dresses the problems that would be encountered although eggs are normally laidin bark crevices, they should L. monacha be introduced into North America. also couldbe depositedincrevices on containers, To predict the risk of successful establishment in var- pallets, andships. L. monacha feeds primarily on nee- ious North American forest ecosystems andthe po- dles and male cones of conifers (Picea, Pinus, Abies, tential damage to those systems, knowledge of the nun and Larix spp.) but also can develop on leaves of mothÕs ability to survive anddevelopon various North deciduous trees and shrubs (Fagus, Carpinus, Betula, American host plants is required. and Quercus spp.) (Sliwa 1987). Its establishment in In Europe, the two species L. monacha prefers and North America wouldbe disastrousbecause of its most often damages are Picea abies (L.) (Norway polyphagous feeding habits, ability to colonize new spruce) and Pinus sylvestris L. (Scots pine) (Lipa and habitats, andcapacity to be spreadrapidlyby ßying Glowacka 1995). Sliwa (1987) provides an extensive adult females. Literature on the pheromones, micro- list of the intensity of natural feeding of L. monacha bial control, andgeneral biology andbiological control larvae on trees andshrubs in Polandduringthe last of L. monacha exists (Gries et al. 1996, Glowacka 1989, major outbreak there between 1978Ð1984. Laboratory Sˇvestka 1971, Jensen 1991, Silwa 1987, Grijpma 1989). investigations of nun moth preferences andutilization of Eurasian host plants providelimitedandcontradic- 1 E-mail: [email protected]. tory information (Bejer 1988). For example, labora- 44 JOURNAL OF ECONOMIC ENTOMOLOGY Vol. 96, no. 1 tory studies rank the preferred speciesÑspruce, pine, randomlyassignedto each foliage type andany larvae andlarchÑas intermediateto low in foodvalue (Bejer that haddiedwerereplacedwith extra larvae from the 1988). Most of the host plant work done on L. monacha same hatch removal date. has concentratedon the relationships between bud Voucher specimens of adults were deposited at the burst of the main hosts, P. abies and P. sylvestris, and Entomology Division, Yale Peabody Museum of Nat- hatching of L. monacha larvae. This work has shown ural History, New Haven, CT. that host phenology is as important as host preference Tree Species. Foliage of 1 to 7 trees of 26 North in determining the survival and successful develop- American and8 Eurasian tree species (Table 1) was ment of L. monacha larvae. For example, when larvae obtained, primarily from laboratory property at An- hatch before foliage budburst the presence of male sonia and Hamden (CT), for use in these studies. cones on Pinus spp. is critical to larval survival and Larvae were rearedto adultson 11 of the host species growth since Þrst andsecondinstar larvae cannot feed (A. rubrum, B. populifolia, F. grandifolia, Q. alba, on the previous yearÕs foliage because of the toughness Q. velutina, L. kaempferi, P. abies, P. glauca, P. strobus, of the needles and the secondary compounds they P. sylvestris (with male cones), and P. menziesii variety contain (Bejer 1988). glauca), which representeda range of genera and This studycomparedthe survival anddevelopment predicted suitability based on European literature, of L. monacha larvae during their Þrst 14 d on 26 North andservedas the basis for developingcriteria to pre- American and8 introducedEurasianhost plants. Lar- dict suitability of all the hosts after only 14 d of rearing. vae on 11 of the hosts usedfor the 14-dstudywere The setup period, 5Ð13 May, was chosen based on the allowedto complete their developmenton those predicted time of L. monacha hatch andbudbreak of hosts. The host plants usedwere from a broadrange trees at 41.3Њ N latitude. Because of the large number of tree genera, representing the major forest types of hosts that were to be tested, hosts on which the present in North America andincludedmanyof the larvae were to be rearedto adultsand12 of the 14-d major species of economic importance. Species from hosts were set up on 5 May (conifers) and6 May Eurasia provided a basis for comparison with the re- (deciduous) (Table 1). The remaining 12 of the 14-d sults of European research andprovidedinformation hosts were set up on 12 May (conifers) and13 May on exotic hosts commonly grown in urban areas of (deciduous)(Table 1). The only hosts included in North America. The risk of successful establishment both set up times were P. glauca and P. sylvestris (Þrst in various North American forest ecosystems, should setup without males cones andsecondsetup with L. monacha become established, is discussed. them); in both cases, the two sets are reportedsepa- rately in the results section. Initial Setup. Short branch tips (15Ð25 cm long) Materials and Methods with foliage were clippedfrom the trees. Clippings Insects. Eggs produced by 200 female L. monacha from conifers includedboththe current andprevious (thirdlaboratory generation) originally from Predin, yearÕs foliage, andßower buds/conesif available. Clip- Czech Republic, were pooledandchilledat 5 Ϯ 1ЊC pings from deciduous trees included both foliage and and Ϸ100% RH with L:D of 16:8 for 144 d(Þrst setup) ßowers, if available (see Table 1 for ßowering times or 151 d(secondsetup). From the pool of mixedeggs, relative to the setup for each species). For initial setup, 16 andeight packets of Ϸ500 eggs each were made for all branch tips came from the same tree andhad the Þrst andsecondsetups, respectively. The eggs foliage/ßowers of similar size andage present on were surface sterilizedto kill potential pathogens by them. For subsequent foliage changes, foliage was submerging the egg packets in 10% formalin for 15 min, collected from the other individual trees being used in rinsing in lukewarm tap water for 15 min andletting a sequential rotation. The trees usedvariedin their them dry in a hood for no longer than 60 min. The eggs phenology within each host species. The ends of the were incubatedat 25 Ϯ 1ЊC and60% RH a photoperiod branches that were clippedwere kept in de-ionized of 16:8 (L:H) h for 6Ð7 d. Date of Þrst hatch of egg water until usedlater in the day.Insects anddebris packets andtotal percentage hatch were recordedas foundon the foliage were removedor washedoff with quality control checks. de-ionized water. If the leaves were washed, they All larvae hatching from incubatedeggs were re- were allowed to dry before being used. movedevery other daywith a Þne camel hair brush The ends of each branch tip were inserted through into small, tight Þtting preweighedpetri dishes.Thirty a hole in a plastic lidof a 256-ml plastic cup that served larvae were placedin each petri dish,the larvae and as a de-ionizedwaterreservoir andthe tip recut un- petri dishwere