Invasive Species Compendium

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Chionaspis pinifoliae
(pine leaf scale)

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Datasheet

Chionaspis pinifoliae (pine leaf scale)

Summary

  • Last modified
  • 08 November 2017
  • Datasheet Type(s)
  • Invasive Species
  • Pest
  • Preferred Scientific Name
  • Chionaspis pinifoliae
  • Preferred Common Name
  • pine leaf scale
  • Taxonomic Tree
  • Domain: Eukaryota
  •   Kingdom: Metazoa
  •     Phylum: Arthropoda
  •       Subphylum: Uniramia
  •         Class: Insecta
  • Summary of Invasiveness
  • As this species can be a pest on conifers within its native range, it is likely to be invasive and problematic in countries where it is accidentally introduced in the absence of its usual natural enemies.
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    UK
    compend@cabi.org
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Identity

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Preferred Scientific Name

  • Chionaspis pinifoliae (Fitch, 1856)

Preferred Common Name

  • pine leaf scale

Other Scientific Names

  • Aspidiotus pinifoliae Fitch, 1856
  • Leucaspis pinifoliae García Mercet, 1912
  • Mytilaspis pinifoliae LeBaron, 1872
  • Phenacaspis pinifoliae Ferris, 1937: Sl-93
  • Polyaspis pinnaefoliae Lindinger, 1935: 140
  • Trichomytilus pinnaefoliae Lindinger, 1933: 166

International Common Names

  • English: pine leaf, scale; pine needle scale; pine needle, scale; white pine needle scale
  • French: chermes du pin; cochenille des aiguilles du pin

Local Common Names

  • : white pine scale
  • Cuba: guagua de las hojas del pino

EPPO code

  • PHECPI (Phenacaspis pinifoliae)

Summary of Invasiveness

Top of page As this species can be a pest on conifers within its native range, it is likely to be invasive and problematic in countries where it is accidentally introduced in the absence of its usual natural enemies.

Taxonomic Tree

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  • Domain: Eukaryota
  •     Kingdom: Metazoa
  •         Phylum: Arthropoda
  •             Subphylum: Uniramia
  •                 Class: Insecta
  •                     Order: Hemiptera
  •                         Suborder: Sternorrhyncha
  •                             Unknown: Coccoidea
  •                                 Family: Diaspididae
  •                                     Genus: Chionaspis
  •                                         Species: Chionaspis pinifoliae

Description

Top of page When intact and alive, the first instar (crawler) is less than 0.5 mm long, yellow to orange and mobile. The intermediate immature female is sessile, similar to the adult female but smaller, and has only one cast skin incorporated in the scale cover. The scale cover of the adult female is 2-3 mm long, mussel-shaped, pure white, slightly convex and has two yellow-brown or translucent cast skins situated terminally. See Watson (2002) for an illustration of the adult female. The male scale cover, if present, is about 1 mm long, elongate and white with three longitudinal ridges and terminal, yellow or translucent, cast skins.

Beneath the scale cover, the body of the living adult female and the eggs are dark orange or red (Zahradník, 1990; Gill, 1997). When mounted on a microscope slide, the body of the adult female is elongate, 1.3-1.7 mm long, membranous and has a narrow prosoma. Gland spines and macroducts are present anterior to abdominal segment I. The pygidium has zygotic median lobes, inset and broadly rounded (with the inner margins longer than the outer margins) and any setae or gland spines between their bases are absent. Submedian macroducts are present on both the pygidial and prepygidial segments; those on segments III, IV and V are all of a similar size.

The adult male possesses one pair of colourless wings with very simplified venation; three pairs of legs; long, many segmented antennae; long genitalia; several pairs of simple eyes; and lacks mouthparts. See Bullington et al. (1989) for an illustration of the adult male.

Distribution

Top of page C. pinifoliae is a temperate species that probably originated in North America. In spite of records published in Nakahara (1982) and Danzig and Pellizzari (1998), C. pinifoliae is not present in the UK (Watson, 2002). The species has not been recorded from Europe, Asia, Australia or the Pacific islands.

The distribution map includes records based on specimens of C. pinifoliae from the collection in the Natural History Museum (London, UK): dates of collection are noted in the List of countries (NHM, various dates).

C. pinifoliae has been intercepted at plant quarantine on pine trees on several occasions but has never become established in Bermuda (Hodgson and Hilburn, 1991; Bermuda Department of Agriculture & Fisheries, 1997).

Distribution Table

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The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Continent/Country/RegionDistributionLast ReportedOriginFirst ReportedInvasiveReferenceNotes

Africa

EgyptPresentIntroducedNewstead, 1907; Hall, 1923
LibyaPresentIntroduced Invasive Lal and Naji, 1979; Danzig and Pellizzari, 1998

North America

BermudaAbsent, intercepted onlyHodgson and Hilburn, 1991
CanadaWidespreadNative Not invasive Gill, 1997
-AlbertaPresentNative Not invasive Maw et al., 2000
-British ColumbiaPresentNative Not invasive
-New BrunswickPresentNative Not invasive Magasi, 1992
-Nova ScotiaPresentNative Not invasive Magasi, 1992
-OntarioPresentNative Not invasive Cooley, 1899
-Prince Edward IslandPresentNative Not invasive Magasi, 1992
-QuebecPresentNative Not invasive Martel and Sharma, 1975
-SaskatchewanPresentNative Not invasive Maw et al., 2000
MexicoPresentNative Not invasive Miller, 1996
USAWidespreadNative Not invasive Gill, 1997
-AlabamaPresentNative Not invasive Williams, 1977
-ArizonaPresentNative Not invasive
-CaliforniaPresentNative Not invasive Gill, 1997
-ColoradoPresentNative Not invasive Cooper and Cranshaw, 1999
-ConnecticutPresentNative Not invasive McClure and Fergione, 1977
-District of ColumbiaPresentNative Not invasive Cooley, 1899
-FloridaPresentNative Not invasive Cooley, 1899
-GeorgiaPresentNative Not invasive Beshear et al., 1973
-IdahoPresentNative Not invasive
-IllinoisPresentNative Not invasive Tooker and Hanks, 2000
-IndianaPresentNative Not invasive Dean, 1909
-IowaPresentNative Not invasive Burden and Hart, 1990
-KansasPresentNative Not invasive Hunter, 1900
-KentuckyPresentNative Not invasive Mussey and Potter, 1997
-MainePresentNative Not invasive Cooley, 1899
-MarylandPresentNative Not invasive Kosztarab, 1963
-MassachusettsPresentNative Not invasive Cooley, 1899; Driesche and Elkinton, 1987
-MichiganPresentNative Not invasive Cooley, 1899
-MissouriPresentNative Not invasive Hollinger, 1923
-MontanaPresentNative Not invasive
-NevadaPresentNative Not invasive Herrick, 1929
-New JerseyPresentNative Not invasive Cooley, 1899
-New MexicoPresentNative Not invasive Cooley, 1899
-New YorkPresentNative Not invasive DeBoo and Weidhaas, 1976
-North DakotaPresentNative Not invasive Herrick, 1929
-OhioPresentNative Not invasive Kosztarab, 1963
-OregonPresentNative Not invasive Schuh and Mote, 1948
-PennsylvaniaPresentNative Not invasive Sleesman, 1945
-TennesseePresentNative Not invasive Lambdin, 1995
-TexasPresentNative Not invasive McDaniel, 1972
-UtahPresentNative Not invasive Jorgensen, 1934
-VirginiaPresentNative Not invasive French, 1942
-WashingtonPresentNative Not invasive Cooley, 1899
-WisconsinPresentNative Not invasive Severin and Severin, 1909

Central America and Caribbean

CubaPresentIntroduced Invasive Alayo Soto, 1976
El SalvadorPresentIntroduced Invasive Nakahara, 1982
HondurasPresentIntroduced Invasive Nakahara, 1982

South America

Chile
-Easter IslandPresentIntroduced Invasive

Risk of Introduction

Top of page The occurrence of a parthenogenetic/uniparental strain of C. pinifoliae increases the potential for this species to establish if it is introduced to a new territory. A single, unmated adult female could give rise to an established population if unchecked.

Hosts/Species Affected

Top of page C. pinifoliae has been recorded from hosts belonging to two families of evergreens: Taxaceae and Pinaceae (Borchsenius, 1966). In California it is common on species of Pinus (Gill, 1997).

Host Plants and Other Plants Affected

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Plant nameFamilyContext
Abies (firs)PinaceaeOther
Cedrus (cedars)PinaceaeOther
Cupressus (cypresses)CupressaceaeOther
Juniperus (junipers)CupressaceaeOther
Picea (spruces)PinaceaeOther
Pinus (pines)PinaceaeMain
Pinus mugo (mountain pine)PinaceaeMain
Pinus resinosa (red pine)PinaceaeMain
Pinus sylvestris (Scots pine)PinaceaeMain
Pseudotsuga (douglas-fir)PinaceaeOther
Taxus (yew)TaxaceaeOther
TorreyaTaxaceaeOther
Tsuga (hemlocks)PinaceaeOther

Growth Stages

Top of page Flowering stage, Fruiting stage, Vegetative growing stage

Symptoms

Top of page C. pinifoliae may cause the foliage to turn yellow, then brown, and the branches may die (Kosztarab, 1990; Kosztarab, 1996). Feeding by the pest destroys the mesophyll cells, leading to chlorosis of the foliage. This chlorotic condition and/or light interception by the insects decreases the photosynthetic capacity of the foliage. The decline in assimilation rate reduces the vigour of severely infested trees (Walstad, 1972).

List of Symptoms/Signs

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SignLife StagesType
Leaves / abnormal colours
Leaves / abnormal leaf fall
Leaves / external feeding
Leaves / necrotic areas
Leaves / yellowed or dead
Stems / dieback

Biology and Ecology

Top of page Apparently there are two races of C. pinifoliae, one is parthenogenetic and the other is biparental. In California, USA, the parthenogenetic race has one generation per year and overwinters as eggs; the biparental race has two generations per year and overwinters as gravid females (Gill, 1997). In California, USA, 53% of the population are male (Nur, 1990). In Iowa, USA, Burden and Hart (1989) found that at 18.5°C, there were 136 day-degrees accumulated to hatching and the time to 50% hatching was 17.25 days. The developmental threshold was between 10.8 and 11.8°C. Kosztarab (1963) mentions that there are two generations per year in Ohio, USA. In Virginia, USA, each female lays eight to 32 eggs, there are two generations per year, and overwintering is as eggs and females (Kosztarab, 1996).

On Pinus mugo in the USA (New York), C. pinifoliae infested only the lower quarter of the crown (DeBoo and Weidhaas, 1976). This may indicate that this scale species has a preference for the shade.

Walstad et al. (1973) reported that the stylets enter the needle through a stoma and terminate in the mesophyll tissue.

The crawlers are the primary dispersal stage. Mortality due to abiotic factors is high during crawler dispersal.

Natural enemies

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Natural enemyTypeLife stagesSpecificityReferencesBiological control inBiological control on
Aphytis diaspidis Parasite Adults/Nymphs
Aphytis mytilaspidis Parasite Adults/Nymphs
Azotus atomon Parasite Adults/Nymphs
Chilocorus kuwanae Predator
Chilocorus orbus Predator Adults/Nymphs
Chilocorus stigma Predator Adults/Nymphs
Closterocerus phenacaspia Parasite Adults/Nymphs
Coccidophilus marginatus Predator Adults/Nymphs
Coccobius howardi Parasite Adults/Nymphs
Coccobius varicornis Parasite Adults/Nymphs
Cryptoweisea atronitens Predator Adults/Nymphs
Encarsia bella Parasite Adults/Nymphs
Marietta pulchella Parasite Adults/Nymphs

Notes on Natural Enemies

Top of page Burden and Hart (1990, 1993) discussed the natural enemy communities associated with C. pinifoliae in North America.

Means of Movement and Dispersal

Top of page Natural dispersal (non-biotic)

The crawlers are the primary dispersal stage. They walk up to a few metres, to new areas of the host plant, or from one plant to another if the plants are touching.

Vector transmission

The crawlers are dispersed over longer distances by wind (Greathead, 1990) or animal/human agencies. The dispersal of sessile adults and eggs occurs through human transport of infested plant material.

Movement in trade

The dispersal of sessile adults and eggs occurs through human transport of infested plant material (Greathead, 1990).

Pathway Vectors

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VectorNotesLong DistanceLocalReferences
Land vehicles Yes

Plant Trade

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Plant parts liable to carry the pest in trade/transportPest stagesBorne internallyBorne externallyVisibility of pest or symptoms
Bark nymphs Yes Pest or symptoms not visible to the naked eye but usually visible under light microscope
Flowers/Inflorescences/Cones/Calyx nymphs Yes Pest or symptoms not visible to the naked eye but usually visible under light microscope
Fruits (inc. pods) nymphs Yes Pest or symptoms not visible to the naked eye but usually visible under light microscope
Leaves adults; eggs; nymphs; pupae Yes Pest or symptoms not visible to the naked eye but usually visible under light microscope
Seedlings/Micropropagated plants nymphs Yes Pest or symptoms not visible to the naked eye but usually visible under light microscope
Stems (above ground)/Shoots/Trunks/Branches nymphs Yes Pest or symptoms not visible to the naked eye but usually visible under light microscope
Plant parts not known to carry the pest in trade/transport
Bulbs/Tubers/Corms/Rhizomes
Growing medium accompanying plants
Roots
True seeds (inc. grain)
Wood

Wood Packaging

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Wood Packaging not known to carry the pest in trade/transport
Loose wood packing material
Non-wood
Processed or treated wood
Solid wood packing material with bark
Solid wood packing material without bark

Impact

Top of page Tooker and Hanks (2000) describe C. pinifoliae as a common pest of conifers in the USA, especially in urban environments and Christmas tree plantations. It is considered to be one of the most serious pests of ornamental pine trees, especially Pinus mugo and Pinus sylvestris. Lal and Naji (1979) found that C. pinifoliae was the most injurious pest on pines in Libya. In California, heavy infestations are unsightly and reduce host vitality, weaken and kill branches, and sometimes the whole tree. This species can cause problems on Christmas tree plantations and is considered to be one of the most serious pests of ornamental pines (especially Scotch and mugo pines) in the USA (Kosztarab, 1996). Heavy outbreaks have been recorded after widespread spraying against mosquitoes (Gill, 1997), which presumably eliminated the natural enemies. Zahradník (1990) described C. pinifoliae as noxious or very noxious to conifers. Walstad et al. (1973) found that percentage reduction in chlorophyll content and in net photosynthetic rate were approximately equal to the percentage of foliage surface area covered by the scale insects. Feeding by the pest destroys the mesophyll cells, leading to chlorosis of the foliage. This chlorotic condition and/or light interception by the insects decrease the photosynthetic capacity of the foliage. The decline in assimilation rate reduces the vigour of severely infested trees (Walstad, 1972).

Diagnosis

Top of page Microscopic examination of slide-mounted adult females is required for an authoritative identification to species. Williams and Watson (1988) described a method for preparing microscope slide mounts of Diaspididae.

Detection and Inspection

Top of page The needles/foliage should be closely examined for mussel-shaped, pure white scale covers with terminal yellow-brown or translucent exuviae. The foliage should also be inspected for chlorosis and browning, in association with the scale infestation.

Similarities to Other Species/Conditions

Top of page Microscopic examination of slide-mounted adult females is required for an authoritative identification to species.

Chionaspis corni (dogwood scale, cochenille de cornouiller) could be misidentified as C. pinifoliae, but differs in having the median lobes divergent, with each one shorter than it is wide. In contrast, C. pinifoliae has median lobes that are not strongly divergent, and each one is longer than it is wide. These species also have different host plants, with C. corni feeding on Cornus species and C. pinifoliae feeding on Pinus species.

Prevention and Control

Top of page Cultural control

Outbreaks of C. pinifoliae can be discouraged by increasing the structural and species diversity of the plants in ornamental landscapes and Christmas tree farms, to favour natural enemies (Tooker and Hanks, 2000).

Eliason and McCulloch (1997) found that the abundance and fecundity of C. pinifoliae varied on different varieties of Pinus sylvestris, being higher on the varieties, 'Riga' and 'Pike Lake Improved' compared with 'Belgium' or 'Land O'Pine'.

Chemical control

Natural enemies are important in helping to control C. pinifoliae populations. The mosquito control programmes that involve fogging with insecticide can cause outbreaks of C. pinifoliae by suppressing its natural enemies (Luck and Dahlsten, 1975). Unless scale populations have reached very high numbers, it is advisable not to use pesticides because these kill hymenopteran parasitoids at lower concentrations than are needed to kill the scales. The use of pesticides is likely to make the problem worse. If spraying is essential, the oil emulsion sprays are least harmful to the natural enemies (Nielsen, 1990).

References

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Alayo Soto R, 1976. Introducci=n al estudio de los Coccoideos de Cuba. (In Spanish). Academia de Ciencias de Cuba Serie Biologico (Instituto de Zoologia), 61:1-25.

Bermuda Department of Agriculture and Fisheries, 1997. Unwelcome visitors to the island at Christmas. Monthly Bulletin - Department of Agriculture, Fisheries & Parks, Bermuda, 68(1):8 pp.; 3 ref.

Beshear RJ; Tippins HH; Howell JO, 1973. The armored scale insects (Homoptera Diaspididae) of Georgia and their hosts. Research Bulletin, University of Georgia College of Agriculture Experiment Stations, No. 146:15 pp.

Borchsenius NS, 1966. A Catalogue of the Armoured Scale Insects (Diaspidoidea) of the World. (In Russian). Leningrad, Russia: Akademii Nauk SSR Zoologicheskogo Instituta, 449 pp.

Britton WE, 1922. The pine leaf scale. Chionaspis pinifoliae Fitch. (21st Report of the State Entomologist for 1921). Bulletin of the Connecticut Agricultural Experiment Station, No. 234:181-183.

Bullington SW; Kosztarab M; Jiang GZ, 1989. Adult males of the genus Chionaspis (Homoptera: Coccoidea: Diaspididae) in North America. Bulletin - Virginia Agricultural Experiment Station, No. 88-2:127-198

Burden DJ; Hart ER, 1989. Degree-day model for egg eclosion of the pine needle scale (Hemiptera: Diaspididae). Environmental Entomology, 18(2):223-227

Burden DJ; Hart ER, 1990. Parasitoids of Chionaspis pinifoliae (Homoptera: Diaspididae) in Iowa. Great Lakes Entomologist, 23:93-97.

Burden DJ; Hart ER, 1993. Parasitoids associated with Chionaspis pinifoliae and Chionaspis heterophyllae (Homoptera: Diaspididae) in North America. Journal of the Kansas Entomological Society, 66(4):383-391

Charlfn R, 1973. Coccoidea de Isla de Pasvua. Revta chil. Ent., 7:111-114.

Cooley RA, 1899. The coccid genera Chionaspis and Hemichionaspis. Massachusetts Agriculture Experiment Station, Special Bulletin, 1899:1-57.

Cooper DD; Cranshaw WS, 1999. The natural enemy complex associated with pine needle scale, Chionaspis pinifoliae (Fitch) (Homoptera: Diaspididae), in north central Colorado. Journal of the Kansas Entomological Society, 72(1):131-133; 10 ref.

Danzig EM; Pellizzari G, 1998. Diaspididae. In: Kozßr F, ed. Catalogue of Palaearctic Coccoidea. Hungarian Academy of Sciences. Budapest, Hungary: Akaprint Nyomdaipari Kft., 172-370.

Darling DC; Johnson NF, 1984. Synopsis of Nearctic Azotinp (Hymenoptera: Aphelinidae). Proceedings of the Entomological Society of Washington, 86(3):555-562.

Dean GA, 1909. Coccidae of Kansas. Transactions of the Kansas Academy of Science, 22:265-275.

DeBoo RF; Weidhaas JA Jr, 1976. Plantation research; XIV. Studies on the predation of pine needle scale, Phenacaspis pinifoliae (Fitch), by the coccinellid, Chilocorus stigma (Say). Chemical Control Research Institute, Canada, Report No. CGX-119.

Driesche RG van; Elkinton JS, 1987. Potential for increased use of biological control agents against pests of woody landscape plants in Massachusetts. Research Bulletin, Massachusetts Agricultural Experiment Station, No. 718:112-141

Eliason EA; McCullough DG, 1997. Survival and fecundity of three insects reared on four varieties of Scotch pine Christmas trees. Journal of Economic Entomology, 90(6):1598-1608; 41 ref.

French GT, 1942. Division of Plant Industry. Department of Agriculture and Immigration of Virginia, Bulletin No. 403, 8-9.

Garcfa Mercet R, 1930. [Aphelinids of Spain.] Los afelinidos de Espa±a. Revista de Biologfa Forestal y Limnologfa, BG, 29-106 (in Spanish).

Gill RJ, 1997. The scale insects of California. Part 3. The armoured scales (Homoptera: Diaspididae). Technical Series in Agricultural Biosystematics and Plant Pathology, No 3. Sacramento, USA: Department of Food and Agriculture.

Greathead DJ, 1990. Crawler behaviour and dispersal. 1.4.3. In: Rosen D, ed. Armoured Scales, their Biology, Natural Enemies and Control. World Crop Pests, Volume 4A. Amsterdam, The Netherlands: Elsevier, 305-308.

Hall WJ, 1923. Further observations on the Coccidae of Egypt. Egypt: Ministry of Agriculture, Technical and Scientific Service, Bulletin 36:1-61.

Herrick GW, 1929. Two scale insects, their bionomics and control. Journal of Economic Entomology, 22:198-202.

Hodgson CJ; Hilburn DJ, 1991. An annotated checklist of the Coccoidea of Bermuda. Florida Entomologist, 74(1):133-146

Hollinger AH, 1923. Scale insects of Missouri. Missouri Agricultural Experiment Station Research Bulletin, 58:1-71.

Horning DS; Barr WF, 1970. Insects of Craters of the Moon National Monument, Idaho. Idaho University College of Agriculture, Miscellaneous Series, 8:1-118.

Huang J; Polaszek A, 1998. A revision of the Chinese species of Encarsia F÷rster (Hymenoptera: Aphelinidae): parasitoids of whiteflies, scale insects and aphids (Hemiptera: Aleyrodidae, Diaspididae, Aphidoidea). Journal of Natural History, 32:1825-1966.

Hunter SJ, 1900. Coccidae of Kansas, III. Kansas University Quarterly, 9:101-107.

Jorgensen DD, 1934. A study of some Utah Coccidae (scale insects). Proceedings of the Utah Academy of Sciences, Arts, and Letters, 11:273-284.

Kosztarab M, 1963. The armoured scale insects of Ohio (Homoptera: Coccoidea: Diaspididae). Bulletin of the Ohio Biological Survey (New Series), 2(2):1-120.

Kosztarab M, 1990. 3.1.2 Economic importance. In: Rosen D (Ed.), Armoured scale insects, their biology, natural enemies and control. Vol. 4B. World Crop Pests. Amsterdam, the Netherlands: Elsevier, 307-311.

Kosztarab M, 1996. Scale Insects of North Eastern North America: identification, biology, and distribution. Martinsville, USA: Virginia Museum of Natural History, 650 pp.

Lal OP; Naji AH, 1979. Observations on some new insect pests and parasites from the Socialist Peoples Libyan Arab Jamahiriya. Rivista di Agricoltura Subtropicale e Tropicale, 73(3/4):219-232

Lambdin PL, 1995. Release, development and establishment of Chilocorus kuwanae Silvestri for control of Unaspis euonymi (Comstock) in Tennessee. Israel Journal of Entomology, 29:327-330; 6 ref.

Luck RF; Dahlsten DL, 1975. Natural decline of a pine needle scale (Chionaspis pinifoliae (Fitch)), outbreak at South Lake Tahoe, California following cessation of adult mosquito control with malathion. Ecology, 56(4):893-904

Magasi LP, 1992. Pine needle scale in the Maritime Provinces. Technical Note - Maritimes Region, Forestry Canada, No. 264:2 pp.

Martel P; Sharma ML, 1975. Parasites of the pine needle scale, Phenacaspis pinifoliae (Fitch), in the Sherbrooke region, Quebec. Annals of the Entomological Society of Quebec, 20(1):11-14

Maw HEL; Foottit RG; Hamilton KGA; Scudder GGE, 2000. Checklist of the Hemiptera of Canada and Alaska. Ottawa, Ontario, Canada: NRC Research Press.

McClure MS; Fergione MB, 1977. Fiorinia externa and Tsugaspidiotus tsugp (Homoptera: Diaspididae): distribution, abundance, and new hosts of two destructive scale insects of eastern hemlock in Connecticut. Environmental Entomology, 6(6):807-811

McDaniel B, 1972. The armored scale insects of Texas (Homoptera: Coccoidea: Diaspididae). Part V. The tribe Diaspidini. Southwestern Naturalist, 16:321-340.

Miller DR, 1996. Checklist of the scale insects (Coccoidea: Homoptera) of Mexico. Proceedings of Entomological Society of Washington, 98(1):68-86.

Mussey GJ; Potter DA, 1997. Phenological correlations between flowering plants and activity of urban landscape pests in Kentucky. Journal of Economic Entomology, 90(6):1615-1627.

Nakahara S, 1982. Checklist of the Armored Scales (Homoptera: Diapididae) of the Conterminous United States. Washington, USA: USDA, Animal and Plant Health Inspection Service, Plant Protection and Quarantine, 110 pp.

Newstead R, 1907. List of other known African species of scale pests. In: Draper W, ed. Notes on the injurious scale insects and mealy bugs of Egypt; together with other insect pests and fungi. Cairo, Egypt: National Printing Department, 15-16.

Nielsen DG, 1990. Evaluation of biorational insecticides for use in arboriculture. Journal of Arboriculture, 16:82-88.

Nikolskaya MN; Yasnosh VA, 1966. Aphelinidae of the European part of the USSR and Caucasus (Chalcidoidea, Aphelinidae). Akademii Nauk SSSR Zoologicheskogo Instituta Opredeliteli po Faune SSSR, 91:1-295 (in Russian).

Nur U, 1990. Chromosomes, sex-ratios, and sex determination. In: Rosen D, ed. Armoured Scale Insects, Their Biology, Natural Enemies and Control. Vol. 4A. World Crop Pests. Amsterdam, the Netherlands: Elsevier, 179-190.

Schuh J; Mote DC, 1948. Insect pests of nursery and ornamental trees and shrubs in Oregon. Oregon State Experiment Station Bulletin, 449:164.

Severin HC; Severin HHP, 1909. A preliminary list of the Coccidae of Wisconsin. Journal of Economic Entomology, 2:296-298.

Sleesman GB, 1945. The Coccidae or scale insects of Pennsylvania. Proceedings of the Pennsylvania Academy of Science, 19:43-48.

Tooker JF; Hanks LM, 2000. Influence of plant community structure on natural enemies of pine needle scale (Homoptera: Diaspididae) in urban landscapes. Environmental Entomology, 29(6):1305-1311; 46 ref.

Vea IM; Gwiazdowski RA; Normark BB, 2013. Corroborating molecular species discovery: four new pine-feeding species of Chionaspis (Hemiptera, Diaspididae). ZooKeys, No.270:37-58. http://www.pensoft.net/journals/zookeys/article/2910/corroborating-molecular-species-discovery-four-new-pine-feeding-species-of-chionaspis-hemiptera-diaspididae-

Walstad JD, 1972. Impact of the Pine needle scale, Phenacaspis pinifoliae (Fitch), on the physiology of Scots Pine, Pinus sylvestris. Dissertation Abstracts International, B 32, 5852.

Walstad JD; Nielsen DG; Johnson NE, 1973. Effect of the Pine needle scale on photosynthesis of Scots Pine. Forest Science, 19:109-111.

Watson GW, 2002. Arthropods of economic importance: Diaspididae of the world. An illustrated identification guide and information source. CD-ROM. Expert Center for Taxonomic Identification (ETI), University of Amsterdam, The Netherlands. ISBN No. 90-75000-48-0.

Williams DJ; Watson GW, 1988. The Scale Insects of the Tropical South Pacific Region. Part 1. The Armoured Scales (Diaspididae). Wallingford, UK: CAB International.

Williams ML, 1977. Scale insect pests of Alabama shade trees. Highlights of Agricultural Research, 24:13.

Wood; RO; Ross DA, 1972. Pine needle scale and black pineleaf scale in British Columbia. Pest Leaflet, Forest Insect and Disease Survey, Canada, No. 40.

Zahradnfk J, 1990. Conifers. In: Rosen D, ed. Armoured Scale Insects, their Biology, Natural Enemies and Control. Vol. 4B. World Crop Pests. Amsterdam, The Netherlands: Elsevier, 633-644.

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