Ecology and Management of Mindarus kinseyi Voegtlin (Aphidoidea: Mindaridae) on White-Fir Seedlings at a California Forest Nursery
AuthorsL. E. Ehler
M. G. Kinsey
Authors AffiliationsL. E. Ehler was Professor of Entomology &; Entomologist in the Experiment Station, Department of Entomology, University of California, Davis, CA 95616; M. G. Kinsey was Staff Research Associate IV, Department of Entomology, University of California, Davis, CA 95616.
Hilgardia 62(1):1-62. DOI:10.3733/hilg.v62n01p006. September 1995.
In recent years, an aphid identified as balsam twig aphid, Mindarus abietinus Koch, was observed on seedlings of white fir (Abies concolor [Gord. &; Glend.] Lindl.) at the USDA—Forest Service Nursery near Placerville, California. Both first- and second-year seedlings were infested and aphid-induced stunting of seedlings was observed. Investigations during 1989-92 revealed that the aphid had a life cycle that differed from that reported for M. abietinus. The following stages were detected: egg, fundatrix, vivipara (apterous and alate), sexupara (apterous and alate), and sexualis (male and ovipara). Third and subsequent generations of apterous viviparae were observed; these, plus the alate viviparae and the apterous sexuparae, have not been recorded for other Mindarus species. Aphid populations first appeared in spring, but persisted throughout the summer, fall, and well into winter. The aphid was recently described as Mindarus kinseyi Voegtlin.
Ecological studies of M. kinseyi revealed that initial infestation of first-year seedlings was coincident with the discrete flight period of alate viviparae. Alates presumably originated in nearby plantings of second-year seedlings, or in white fir growing at other nearby sites. Alate colonization generally led to an aphid population that was distributed in patches in first-year seedlings. Mean aphid density peaked at replacecodegt25 per seedling (replacecodegt100 per infested seedling), and up to 21% of the first-year seedlings were infested. Initial infestation of second-year seedlings was due to either overwintering eggs (deposited on first-year seedlings), alate viviparae, or both. Early infestations were also patchily distributed, and in some cases, over 50% of the seedlings were eventually infested. Aphid eggs were also present on about 20% of the harvested seedlings destined for outplanting. Naturally occurring predators and parasites were not able to maintain aphid populations at low levels. The aphid’s major enemies at the nursery were aphidophagous predators, primarily larvae of syrphid flies.
Survival of marked seedlings from emergence to harvest was very high (97.3%). However, cull-rate at harvest was independent of previous aphid infestation. Mean height, stem diameter, and dry weight of marked seedlings at harvest were not significantly reduced by aphid infestation. However, for marked seedlings infested early during the first season, both final height and dry weight were significantly reduced. Thus, aphid infestations can have a significant impact on growth of seedlings, but this does not necessarily lead to an increase in cull-rate at harvest. However, aphid caused mortality of first-year seedlings must also be considered. Additional seedlings were monitored at outplantings in the Eldorado and Stanislaus National Forests during 1991 and 1992. Seedlings were infested with aphids during the first year; however, seedling mortality was independent of aphid infestation during the season.
A management program for M. kinseyi was developed and evaluated at the nursery. The program was based on careful monitoring, particularly during the aphid flight season, and spot treatment with compatible suppressive measures. The use of reflective lath fencing (placed horizontally over first-year seedlings) was not effective in reducing alate colonization. Larvae of the lacewings Chrysoperla carnea (Stephens) and C. rufilabris (Burmeister) were released in infested patches and provided good aphid suppression in most cases. Safer® insecticidal soap was also successfully employed as a spot treatment. In a management demonstration, about 10% of the first-year seedlings in the control group (without treatment) were infested by the end of the season compared to only about 1% in the management plot; all infestations in the latter were treated with either larvae of C. rufilabris, Safer® soap, or both. During the second season, all infested patches in the management plot were treated with Safer® soap; by the end of the season, about 20% of the seedlings in the control showed aphid damage compared to approximately 3% in the management plot. At harvest, the cull rate for both plots was relatively high, but independent of aphid infestation. The management program was evaluated again in 1992 with similar results. The pest status of M. kinseyi should be evaluated on a case-by-case basis and the management program implemented as needed. The primary aphid-suppression tactics (soap sprays, lacewing larvae) that were effective in a nursery setting could also be employed against M. kinseyi at Christmas-tree farms.
Adams J. B., Drew M. E., MacGillivray M. E. The aerial aphid plankton over the Research Station, Fredericton, New Brunswick, 1967-1969. Can. Entomol. 1976. 108:1069-78. DOI: 10.4039/Ent1081069-10 [CrossRef]
Allison D., Pike K. S. An inexpensive suction trap and its use in an aphid monitoring network. J. Agric. Entomol. 1988. 5:103-7.
Bigler F., Canard M., Semeria Y., New T. R. Biological control by chrysopids: integration with pesticides. Biology of Chrysopidae. 1984. The Hague: Dr W. Junk Publishers. p. 233-45.
Blackman R. L., Campbell R. K., Eikenbary R. D. Specificity in aphid/plant genetic interactions, with particular attention to the role of the alate colonizer. Aphid-Plant Genotype Interactions. 1990. Amsterdam: Elsevier. p. 251-74.
Blackman R. L., Eastop V. F. Aphids on the World’s Trees. 1994. Wallingford, UK: CAB International. 1025p.
Branham S. J., Hertel G. D. Integrated Forest Pest Management Symposium: The Proceedings. 1984. Athens, Georgia: University of Georgia. 281p.
Breene R. G., Meagher R. L. Jr., Nordlund D. A., Wang Yin-Tung. Biological control of Bemisia tabaci (Homoptera: Aleyrodidae) in a greenhouse using Chrysoperla rufilabris (Neuroptera: Chrysopidae). Biol. Contr. 1992. 2:9-14. DOI: 10.1016/1049-9644(92)90069-P [CrossRef]
Carter C. I., Maslen N. R. Conifer Lachnids in Britain. Forestry Commission Bulletin No. 58. 1982. London: Her Majesty’s Stationery Office. 75p.
Carter C. I., Nichols J. F. A. Some resistance features of trees that influence the establishment and development of aphid colonies. Z. Ang. Entomol. 1985. 99:64-67. DOI: 10.1111/j.1439-0418.1985.tb01961.x [CrossRef]
Carter C. I., Eastop V. F. Mindarus obliquus (Chol.) (Homoptera, Aphidoidea) new to Britain and records of two other aphids recently found feeding on conifers. Entomol. Mon. Mag. 1972. 108:202-4.
Cavalloro R. Aphid Migration and Forecasting ‘Euraphid’ Systems in European Community Countries. 1987. Luxembourg: Commission of the European Communities. 264p.
Chambers R. J., Minks A. K., Harrewijn P. Syrphidae. Aphids: Their Biology, Natural Enemies and Control. World Crop Pests, Vol 2B. 1988. Amsterdam: Elsevier Science Publishing Co. Inc. p. 259-70.
Chambers R. J., Polgar L., Chambers R. J., Dixon A. F. G., Hodek I. Oviposition by aphidophagous hoverflies (Diptera: Syrphidae) in relation to aphid density and distribution in winter wheat. Behaviour and Impact of Aphidophaga. 1991. The Hague: SPB Academic Publishing. p. 115-21.
Connor M. D., Hoffard W. H. Aphids. Forest Nursery Pests. USDA Agric. Handbook No. 680 1989. pp.134-35. Washington, D. C
Croft B. A. IPM systems that conserve pesticides, pest-resistant plants and biological controls, including genetically altered forms. J. Entomol. Soc. Sth. Afr. 1992. 55:107-21.
DeHayes D. H. Genetic variation in susceptibility of Abies balsamea to Mindarus abietinus. Can. J. For. Res. 1981. 11:30-35. DOI: 10.1139/x81-005 [CrossRef]
Dixon A. F. G. Aphid ecology: life cycles, polymorphism, and population regulation. Annu. Rev. Ecol. Syst. 1977. 8:329-53. DOI: 10.1146/annurev.es.08.110177.001553 [CrossRef]
Dixon A. F. G. Structure of aphid populations. Annu. Rev. Entomol. 1985. 30:155-74. DOI: 10.1146/annurev.en.30.010185.001103 [CrossRef]
Dixon A. F. G., Minks A. K., Harrewijn P. The way of life of aphids: host specificity, speciation and distribution. Aphids: Their Biology, Natural Enemies and Control. World Crop Pests, Vol 2A. 1987. Amsterdam: Elsevier Science Publishing Co. Inc. p. 197-207.
Dixon W. N., Foltz J. L., Branham S. J., Hertel G. D. Integrated pest management in nurseries—insects and mites. Integrated Forest Pest Management Symposium: The Proceedings. 1984. Athens, Georgia: University of Georgia. p. 226-37.
Doane R. W., Van Dyke E. C., Chamberlin W. J., Burke H. E. Forest Insects. 1936. New York: McGraw-Hill Book Company, Inc. 463p.
Duryea M. L., Landis T. D. Forest Nursery Manual: Production of Bareroot Seedlings. 1984. The Hague: Martinus Nijhoff/Dr W. Junk Publishers. 386p.
Eastop V. F., Lowe A. D. Biotypes of aphids. Perspectives in Aphid Biology. 1972. Entomol. Soc. of New Zealand (Inc.). p. 40-51. Bulletin No. 2
Essig E. O. A new aphid of the genus Mindarus from white fir in British Columbia. Pan-Pacific Entomol. 1939. 15:105-10.
Ferrell G. T. Differential susceptibility of white fir provenances to balsam twig aphid. USDA—Forest Service, Research Note PSW-403. 1989. Berkeley, CA: Pacific Southwest Forest and Range Experiment Station. 4p.
Fox R. C., Griffith K. H. Pine seedling growth loss caused by cinaran aphids in South Carolina. J. Georgia Entomol. Soc. 1977. 12:29-34.
Frazer B. D., Minks A. K., Harrewijn P. Coccinellidae. Aphids: Their Biology, Natural Enemies and Control. World Crop Pests, Vol 2B. 1988. Amsterdam: Elsevier Science Publishing Co. Inc. p. 231-47.
Furniss R. L., Carolin V. M. Western Forest Insects 1977. p.654. USDA Misc. Publ. No. 1339. Washington, DC
Furuta K., Takai M. Population dynamics of Cinara bogdanowi ezoana Inouye (Horn., Lachnidae) in plantations of Picea glehnii Masters and P. jezoensis Carriere. Z. Ang. Entomol. 1983. 95:238-49. DOI: 10.1111/j.1439-0418.1983.tb02638.x [CrossRef]
Gibson R. W., Rice A. D., Minks A. K., Harrewijn P. Modifying aphid behaviour. Aphids: Their Biology, Natural Enemies and Control. World Crop Pests, Vol 2C. 1989. Amsterdam: Elsevier Science Publishing Co. Inc. p. 209-24.
Hagen K. S. Role of nutrition in insect management. Proceedings Tall Timbers Conference on Ecological Animal Control by Habitat Management. 1976. 6:221-61.
Hallgren S. W., Helms J. A. The effects of summer shoot production on height growth components of seedlings of California red and white fir. Can. J. For. Res. 1992. 22:690-98. DOI: 10.1139/x92-092 [CrossRef]
Harrewijn P., Minks A. K., Minks A. K., Harrewijn P. Integrated aphid management: general aspects. Aphids: Their Biology, Natural Enemies and Control. World Crop Pests, Vol 2C. 1989. Amsterdam: Elsevier Science Publishing Co. Inc. p. 267-72.
Hastings F. L., Hain F. P., Mangini A., Huxster W. T. Control of the balsam woolly adelgid (Homoptera: Adelgidae) in Fraser fir Christmas tree plantations. J. Econ. Entomol. 1986. 79:1676-80.
Heie O. E., Minks A. K., Harrewijn P. Palaeontology and phylogeny. Aphids: Their Biology, Natural Enemies and Control. World Crop Pests, Vol 2A. 1987. Amsterdam: Elsevier Science Publishing Co. Inc. p. 367-91.
Hett J. M., Loucks O. L. Application of life-table analyses to tree seedlings in Quetico Provincial Park, Ontario. Forestry Chron. 1968. 44:29-32.
Hille Ris Lambers D. Polymorphism in Aphididae. Annu. Rev. Entomol. 1966. 11:47-78. DOI: 10.1146/annurev.en.11.010166.000403 [CrossRef]
Holopainen J. K., Soikkeli S. Occurrence of Cinara pini (Homoptera, Lachnidae) in Scots pine (Pinus sylvestris) seedlings with disturbed growth. Ann. Entomol. Fenn. 1984. 50:108-10.
Hurlbert S. H. Pseudoreplication and the design of ecological field experiments. Ecol. Monogr. 1984. 54:187-211. DOI: 10.2307/1942661 [CrossRef]
Isard S. A., Irwin M. E., Hollinger S. E. Vertical distribution of aphids (Homoptera: Aphididae) in the planetary boundary layer. Environ. Entomol. 1990. 19:1473-84.
Johnson C. G., Taylor L. R. The development of large suction traps for airborne insects. Ann. Appl. Biol. 1955. 43:51-62. DOI: 10.1111/j.1744-7348.1955.tb02452.x [CrossRef]
Johnson J. W. A revision of the species of Praon Haliday in North America north of Mexico (Hymenoptera: Aphidiidae). Can. Entomol. 1987. 119:999-1025. DOI: 10.4039/Ent119999-11 [CrossRef]
Johnson N. E. Reduced growth associated with infestations of Douglas-fir seedlings by Cinara species (Homoptera: Aphidae). Can. Entomol. 1965. 97:113-119. DOI: 10.4039/Ent97113-2 [CrossRef]
Kawada K., Minks A. K., Harrewijn P. Polymorphism and morph determination. Aphids: Their Biology, Natural Enemies and Control. World Crop Pests, Vol 2A. 1987. Amsterdam: Elsevier Science Publishing Co. Inc. p. 255-68.
Keen F. P. Insect Enemies of Western Forests 1939. p.210. USDA, Misc. Publ. No. 273. Washington, DC
Kidd N. A. C., Berryman A. A. The large pine aphid on Scots pine in Britain. Dynamics of Forest Insect Populations. 1988. New York: Plenum Press. p. 111-28. DOI: 10.1007/978-1-4899-0789-9_6 [CrossRef]
Koehler C. S., Barclay L. W., Kretchun T. M. Pests in the home garden: soaps as insecticides. Calif. Agric. 1983. 37(9,10):11-12.
Koehler C. S., Kinsey M. G., Fouche C. F., Ehler L. E. Oil, soap sprays ineffective ovicides for control of balsam twig aphid. Calif. Christmas Tree Growers Bulletin. 1990. 141:24-25.
Klingauf F. A., Minks A. K., Harrewijn P. Host plant finding and acceptance. Aphids: Their Biology, Natural Enemies and Control. World Crop Pests, Vol 2A. 1987. Amsterdam: Elsevier Science Publishing Co. Inc. p. 209-23.
Kring J. B. Flight behavior of aphids. Annu. Rev. Entomol. 1972. 17:461-92. DOI: 10.1146/annurev.en.17.010172.002333 [CrossRef]
Leather S. R. Aspects of aphid overwintering (Homoptera: Aphidinea: Aphididae). Entomol. Gener. 1992. 17:101-113. DOI: 10.1127/entom.gen/17/1992/101 [CrossRef]
MacKauer M. A new genus and several new species of aphid parasites (Hym. Aphidiidae). Entomophaga. 1967. 12:139-147. DOI: 10.1007/BF02370610 [CrossRef]
Margolis H. A., Brand D. G. An ecophysiological basis for understanding plantation establishment. Can. J. For. Res. 1990. 20:375-90. DOI: 10.1139/x90-056 [CrossRef]
Mattson W. J., Haack R. A., Lawrence R. K., Herms D. A. Do balsam twig aphids (Homoptera: Aphididae) lower tree susceptibility to spruce budworm? Can. Entomol. 1989. 121:93-103.
Mexal J., Branham S. J., Hertel G. D. Integrated pest management in southern pine nurseries. Integrated Forest Pest Management Symposium: The Proceedings. 1984. Athens, Georgia: University of Georgia. p. 267-79.
Miyazaki M., Minks A. K., Harrewijn P. Forms and morphs of aphids. Aphids: Their Biology, Natural Enemies and Control. World Crop Pests, Vol 2A. 1987. Amsterdam: Elsevier Science Publishing Co. Inc. p. 27-50.
Moore W. S., Profita J. C., Koehler C. S. Soaps for home landscape insect control. Calif. Agric. 1979. 33(6):13-14.
Moran N. A. The evolution of aphid life cycles. Annu. Rev. Entomol. 1992. 37:321-48. DOI: 10.1146/annurev.en.37.010192.001541 [CrossRef]
Moran N. A., Munson M. A., Baumann P., Ishikawa H. A molecular clock in endosymbiotic bacteria is calibrated using the insect hosts. Proc. R. Soc. Lond. B. 1993. 253:167-71. DOI: 10.1098/rspb.1993.0098 [CrossRef]
Moran N., Baumann P. Phylogenetics of cytoplasmically inherited microorganisms of arthropods. Trends in Ecol. and Evol. 1994. 9:15-20. DOI: 10.1016/0169-5347(94)90226-7 [CrossRef]
Munson M. A., Baumann P., Clark M. A., Baumann L., Moran N. A., Voegtlin D. J., Campbell B. C. Evidence for the establishment of aphid - Eubacterium endosymbiosis in an ancestor of four aphid families. J. Bacteriol. 1991. 173:6321-24.
Muirhead-Thomson R. C. Trap Responses of Flying Insects. 1991. San Diego, CA.: Academic Press Inc. 287p.
National Research Council. Forestry Research: A Mandate for Change. 1990. Washington D. C.: National Academy Press. 84p.
Nettleton W. A., Hain F. P. The life history, foliage damage, and control of the balsam twig aphid, Mindarus abietinus (Homoptera: Aphididae), in Fraser fir Christmas tree plantations of western North Carolina. Can. Entomol. 1982. 114:155-65. DOI: 10.4039/Ent114155-2 [CrossRef]
Nordlund D. A., Vacek D. C., Ferro D. N. Predation of Colorado potato beetle (Coleoptera: Chrysomelidae) eggs and larvae by Chrysoperla rufilabris (Neuroptera: Chrysopidae) larvae in the laboratory and field cages. J. Entomol. Sci. 1991. 26:443-49.
Osborne L. S. Is soap a viable method for controlling Tetranychus urticae on plants in the interior environment? Proc. Fla. State Hort. Soc. 1982. 95:149-51.
Pickett J. A., Wadhams L. J., Woodcock C. M. The chemical ecology of aphids. Annu. Rev. Entomol. 1992. 37:67-90. DOI: 10.1146/annurev.en.37.010192.000435 [CrossRef]
Pike K. S., Allison D., Boydston L., Qualset C. O., Vogt H. E., Summers C. G. Suction trap reveals 60 wheat aphid species, including Russian wheat aphid. Calif. Agric. 1989. 43(6):22-24.
Pinnock D. E., Brand R. J., Milstead J. E., Coe N. F. Suppression of populations of Aphis gossypii and A. spiraecola by soap sprays. J. Econ. Entomol. 1974. 67:783-84.
Raddi P., Capretti P., Tiberi-Ist R. Diseases and insect pests in forest nurseries in Italy 1991. Proceedings of the First meeting of IUFRO Working Party S2.07-09 (Diseases and Insects in Forest Nurseries). Aug. 22-30, 1990, Victoria, B.C., Canada. Information Report (Pacific Forestry Centre) BC-X-331, 69-77
Rather M., Mills N. J. Possibilities for the biological control of the Christmas tree pests, the balsam gall midge, Paradiplosis tumifex Gagné (Diptera: Cecidomyiidae) and the balsam twig aphid, Mindarus abietinus Koch (Homoptera: Mindaridae), using exotic enemies from Europe. Biocontrol News and Inform. 1989. 10:119-29.
Ridgway R. L., Murphy W. L., Canard M., Semeria Y., New T. R. Biological control in the field. Biology of Chrysopidae. 1984. The Hague: Dr W. Junk Publishers. p. 220-28.
Robert Y., Minks A. K., Harrewijn P. Aphids and their environment. Aphids: Their Biology, Natural Enemies and Control. World Crop Pests, Vol 2A. 1987. Amsterdam: Elsevier Science Publishing Co. Inc. p. 299-313.
Robinson A. G., Chen Ya-Hwai. Cytotaxonomy of Aphididae. Can. J. Zool. 1969. 47:511-16. DOI: 10.1139/z69-090 [CrossRef]
Shrimpton G. M. Insects in British Columbia forest nurseries 1991. Proceedings of the First Meeting of IUFRO Working Party S2.07-09 (Diseases and Insects in Forest Nurseries). Aug. 22-30, 1990, Victoria, B. C., Canada. Information Report (Pacific Forestry Centre) BC-X-331, 207-14
Stary P. Pseudopraon mindariphagum gen. n., sp. n. (Hymenoptera, Aphidiidae)—Description and life history of a parasite of Mindarus abietinus (Homoptera, Mindaridae) in Central Europe. Acta Entomol. Bohem. 1975. 72:249-58.
Stary P., Remaudiere G. New genera, species, and host records of aphid parasitoids (Hymenoptera, Aphidiidae) from Mexico. Ann. Soc. Entomol. Fr. (N. S.). 1982. 18:107-27.
Stein J. D. Biology of a white fir aphid nursery pest: biotype or new species 1991. Proceedings of the First Meeting of IUFRO Working Party S2.07-09 (Diseases and Insects in Forest Nurseries), Aug. 22-30, 1990, Victoria, B.C., Canada. Information Report (Pacific Forestry Centre) BC-X-331, 273
Stein J. D., Haverty M. I. Insecticides effectively control an aphid pest of white fir seedlings. Tree Planters’ Notes. 1990. 41:8-12.
Stein J. D., Haverty M. I. Experience with insecticides for control of Mindarus victoria: a new aphid pest of white fir nursery seedlings 1991. Proceedings of the First Meeting of IUFRO Working Party S2.07-09 (Diseases and Insects in Forest Nurseries), Aug. 22-30, 1990, Victoria, B. C., Canada. Information Report (Pacific Forestry Centre) BC-X-331, 275-81
Stein J. D., Smith R. S. Jr. Diseases and insects in United States forest nurseries 1991. Proceedings of the First Meeting of IUFRO Working Party S2.07-09 (Diseases and Insects in Forest Nurseries), Aug 22-30, 1990, Victoria, B. C., Canada. Information Report (Pacific Forestry Centre) BC-X-331, 109-15
Stein J. D., Trummer C. R. Effective control of a new woolly white fir nursery aphid (Homoptera: Aphididae) 1993. Proceedings, Western Forest Nursery Association. USDA—Forest Service, Gen. Tech. Report RM-221, 139-43
Stone E. C. Coniferous seedling survival. Calif. Agric. 1955. 9(2):7 15
Sutherland J. R., Duryea M. L., Landis T. D. Pest management in northwest bareroot nurseries. Forest Nursery Manual: Production of Bareroot Seedlings. 1984. The Hague: Martinus Nijhoff/Dr W. Junk Publishers. p. 203-10. DOI: 10.1007/978-94-009-6110-4_19 [CrossRef]
Sutherland J. R., Shrimpton G. M., Sturrock R. N. Diseases and Insects in British Columbia Forest Seedling Nurseries. 1989. Victoria, BC, Canada: Ministry of Forests, Research Branch. 85p. FRDA Report
Tauber C. A. Systematics of North American chrysopid larvae: Chrysopa carnea group (Neuroptera). Can. Entomol. 1974. 106:1133-53. DOI: 10.4039/Ent1061133-11 [CrossRef]
Tauber M. J., Tauber C. A. Life history traits of Chrysopa carnea and Chrysopa rufilabris (Neuroptera: Chrysopidae): influence of humidity. Ann. Entomol. Soc. Am. 1983. 76:282-85.
Taylor L. R., Palmer J. M. P., van Emden H. F. Aerial sampling. Aphid Technology. 1972. London: Academic Press. p. 189-234.
Tulisalo U., Canard M., Semeria Y., New T. R. Biological control in the greenhouse. Biology of Chrysopidae. 1984. The Hague: Dr W. Junk Publishers. p. 228-33.
Varty I. W. The seasonal history and population trends of the balsam twig aphid, Mindarus abietinus Koch in New Brunswick 1966. p.21. Internal Report M-12, Forest Res. Lab., Fredericton, New Brunswick, Canada
Varty I. W. The biology of the balsam twig aphid, Mindarus abietinus Koch, in New Brunswick: polymorphism, rates of development, and seasonal distribution of populations 1968. p.65. Internal Report M-24, Forest Res. Lab., Fredericton, New Brunswick, Canada
Voegtlin D. Notes on the Mindarus spp. (Homoptera: Aphididae). of North America with descriptions of two new species. Proc. Entomol. Soc. Wash. 1995. 97:178-96.
Waters W. E. The life table approach to analysis of insect impact. J. Forestry. 1969. 67:300-4.
Waters W. E., DeMars C. J. Jr., Cobb F. W. Jr. Analysis of early mortality of Douglas-fir seedlings in postharvest plantings in northwestern California. For. Sci. 1991. 37:802-26.
Watt A. D., Leather S. R., Hunter M. D., Kidd N. A. C. Population Dynamics of Forest Insects. 1990. England: Intercept: Andover. 408p.