(Linnaeus, 1758)
Diagnosis
Scale cover of adult female in life 2.5-3.0 mm long, pyriform or broadly mussel-shaped, white with yellow terminal exuviae CHISAL6.jpg . Scale cover of male 0.7-1.0 mm long, slender, white, tricarinate with yellow terminal exuviae CHISAL3.jpg . Body of adult female in life with broadly rounded posterior end, yellowish initially, becoming red later in life (Zahradník, 1990a). Both winged and wingless forms of male known (Ghauri, 1962).
Body of slide-mounted adult female elongate, membranous, with prosoma narrow; with gland spines and macroducts present anterior to abdominal segment I CHSALS.jpg . Pygidium with median lobes zygotic, often divergent distally, without any setae or gland spines between their bases; submedian macroducts present on pygidial and prepygidial segments CHSALP.jpg ; those on segments III, IV and V of various sizes CHSALVAR.jpg . On trees and shrubs, but not on conifers.
The first instar nymph was described and illustrated by Howell and Tippins, 1977.
Host range
Chionaspis salicis has been recorded mainly from deciduous trees and shrubs, belonging to 17 plant families (Kosztarab and Kozár, 1988). Hosts include species of: Acer, Alnus, Andromeda, Arctostaphylos, Betula, Cornus, Corylus, Cotoneaster, Cytisus, Erica, Euonymus, Fraxinus, Genista, Helianthemum, Hippophae, Jasminum, Laburnum, Ligustrum, Loranthus, Lyonia, Myrtus, Paeonia, Populus, Pyrus, Quercus, Rhamnus, Rhododendron, Ribes, Rosa, Salix, Sophora, Sorbus, Syringa, Tamarix, Tilia, Ulmus, Vaccinium spp., Viburnum and Vitis.
Affected plant stages: vegetative growing, flowering, fruiting and post-harvest stages
Affected plant parts: on trunk and branches CHISAL2.jpg ; sometimes on fruits of Vaccinium
Biology and ecology
Reproduction by sexual and parthenogenetic means have both been recorded. This is a univoltine species that overwinters as eggs beneath the scale of the parent female. Each female lays between 8 and 60 eggs in summer, depending on host quality and environmental conditions (Schmutterer, 1959; Kosztarab and Kozár, 1988; Zahradník, 1990a). Chionaspis salicis occurs from lowlands up to mountains, often on banks in humid localities (Zahradník, 1990a).
In Germany, the sex ratio in C. salicis was found to be moderately biased in favour of males (Nur, 1990).
Crawlers are the primary dispersal stage and move to new areas of the plant or are dispersed by wind or animal contact. Mortality due to abiotic factors is high in this stage. Dispersal of sessile adults and eggs occurs through human transport of infested plant material.
Symptoms
Heavy infestations can cause wilting and drying of branches; on ornamental plants the scale covers can be unsightly, forming a white coating on the twigs and branches.
Economic impact
In Central Europe, C. salicis is often a pest on forest trees in the northern parts of its range, and causes significant damage to Ribes (Kosztarab and Kozár, 1988). Yanin, 1975, listed it as one of the more injurious species in the Caucasus; Kuznetsov, 1987, mentions it as a pest in Sakhalin I. In Hungary, it is one of the most important scale insect pests of ornamental trees and shrubs (Ripka, 1999). Danzig and Pellizzari, 1998, mention that C. salicis is a pest in colder parts of the Palaeartic region. Foldi, 2001, lists this species as an occasional pest in France. Sometimes it is of economic importance on Vaccinium myrtillis (Zahradník, 1990a).
Detection and inspection methods
Examine branches, twigs and fruits for white, broadly mussel-shaped scale covers.
Natural enemies
The following species are listed by Kosztarab and Kozár, 1988 and CABI, 2000.
Parasitoids:
- Ablerus celsus
- Aphytis fuscipennis
- Aphytis mytilaspidis
- Aphytis proclia
- Aphytis stepanovi, in former USSR
- Aphytis sugonjaevi
- Arrhenophagus chionaspidis
- Cheiloneurus microphagus
- Encarsia gigas
- Epitracnemus zetterstedtii
- Pteroptrix dimidiata
- Pteroptrix longicornis
- Thomsonica amathus
- Zaomma lambinus
Predators:
- Anthocoris minki
- Brysoptera rufifrons
- Chilocorus bipustulatus, in Russia
- Chilocous kuwanae, in Sakhalin I. (former USSR)
- Chilocorus renipustulatus, in Russia
- Cybocephalus politus
- Hemisarcoptes malus
- Histiogaster entomophagus
- Pilophorus clavatus
- Platybunus pinetorum
- Scymnus ater, in Switzerland
- Tyrophagus dimidiatus
Distribution
See Chionaspis salicis distribution.
Microscopic examination of slide-mounted adult females is required for authoritative identification to species.
Chionaspis americana Johnson (elm scurfy scale, cochenille écailleuse de l'orme) CHAMS.jpg could be misidentified as C. salicis, but differs in having median lobes fused in their basal half, each one with the outer margin deeply notched CHAMMG.jpg ; and submedian macroducts absent from abdominal segment VI CHAMP.jpg . In contrast, C. salicis has median lobes separate, each one with the outer margin relatively smooth; and submedian macroducts present on segment VI CHSALP.jpg. Chionaspis americana is known from USA (Alabama, California, Colorado, Connecticut, District of Colombia, Delaware, Florida, Georgia, Iowa, Illinois, Indiana, Kansas, Louisiana, Massachussetts, Maryland, Missouri, Michigan, Minnesota, Mississippi, North Carolina, New England, New Jersey, Ohio, Oklahoma, Pennsylvania, South Carolina, South Dakota, Rhode Island, Tennessee, Texas, Virginia, Wisconsin, West Virginia), and is probably present in eastern Canada also; it is found mostly on Ulmus species, although the species is polyphagous (Kosztarab, 1996; Liu et al., 1989; Nakahara, 1982). This species can kill twigs, branches and even small trees; older trees can be seriously weakened (Kosztarab, 1996). The scale cover is pure white, with terminal exuviae (Gill, 1997). CHIAML1.jpg
Chionaspis furfura (Fitch) (scurfy scale, cochenille écailleuse) CHFURL.jpg,
CHFURS.jpg is similar to C. salicis, but lacks the submedian ducts on abdominal segment VIthat are present in C. salicis CHSALP.jpg. Chionaspis furfura occurs in North America (Canada (Ontario) and continental USA (including Maryland and Virginia but not California)) and possibly in Argentina (old literature records only); it has been recorded from bark, leaves and fruit of hosts belonging to the plant families [l][m]Host plants[/m][r]Betulaceae[/r]Betulaceae, Juglandaceae, Rosaceae, Rutaceae and Saxifragaceae, such as species of Crataegus, Cydonia, Malus sylvestris, Prunus, Pyracantha, Sorbus and other Rosaceae (Claps et al., 2001a; Gill, 1997; Kosztarab, 1996; Liu et al., 1989; Howard and Oliver, 1985; Nakahara, 1982; Dekle, 1976; Borchsenius, 1966; The Natural History Museum collection, London, UK). Hosts include fruit trees, and this scale was listed as a pest of deciduous fruit trees (mainly apple) of regional importance by Kozár, 1990b. Chionaspis furfura can cause reddish spots and small pits on the bark of apple and pear twigs, and can become a pest in untreated orchards (Kosztarab, 1996). This species is mentioned on quarantine lists (Burger and Ulenberg, 1990). Pygidial margin CHFURMG.jpg. Male CHFURM.jpg
Chionaspis salicisnigrae (Walsh) (black willow scale, willow scurfy scale, cochenille dartreuse du saule) CHSALNL1.jpg is a highly variable species with numerous, small submarginal macroducts on abdominal segments II or III-V that are often partially replaced by microducts. It could be misidentified as C. salicis, but differs in having median lobes either closely adpressed at the base, or, if separate, with 2 toothlike sclerotized projections on the margin between them. In contrast, C. salicis has divergent median lobes without any marginal projections between them (Kosztarab, 1996; Liu et al., 1989) CHSALP.jpg. Chionaspis salicisnigrae is known from Canada (Ontario), USA (Alabama, Arkansas, California (rare), Colorado, Florida, Iowa, Idaho, Illinois, Indiana, Kansas, Louisiana, Massachusetts, Michigan, Minnesota, Missouri, Mississippi, Montana, North Carolina, North Dakota, New England, New Jersey, New Mexico, New York, Ohio, Oklahoma, Pennsylvania, South Dakota, Tennessee, Texas, Wisconsin, Wyoming), Mexico, China (Inner Mongolia, Jilin), Japan (Honshu), former USSR on branches of species of Amelanchier, Cornus, Fraxinus, Liriodendron, Populus and Salix (1965 data from S. Kawai photograph; Kawai, 1980; Nakahara, 1982; Kosztarab, 1996; Miller, 1996; Tao, 1999). It is common on black willow in California. The scale cover of the adult female is mussel-shaped and white (Gill, 1997); the scale cover of the male is much smaller than that of the female, narrow, parallel sided, white with at least one longitudinal ridge CHSALNL1.jpg . There are two generations each year and the species overwinters as eggs (Zahradník, 1990a); Borchsenius, 1966, described it as a noxious species in North America. Heavy infestations can kill branches and trees (Kosztarab, 1996).
Comments
Chionaspis salicis is a temperate species that originated in the Palaearctic; its distribution is now trans-Palaearctic (Kosztarab and Kozár, 1988). It has not been recorded from the Western Hemisphere, Australia, or from the Pacific islands.
Europe: present, no further details (Tao, 1999)
Albania: present, no further details (Danzig and Pellizzari, 1998)
Austria: present, no further details (Danzig and Pellizzari, 1998)
Belgium: present, no further details (Danzig and Pellizzari, 1998)
Bulgaria: present, no further details (Danzig and Pellizzari, 1998)
Cyprus: present, no further details (Danzig and Pellizzari, 1998)
Denmark: present, no further details (Gertsson, 2001)
Finland: present, no further details (Gertsson, 2001)
Former Czechoslovakia: present, no further details (Danzig and Pellizzari, 1998)
Former USSR
Caucasus: present, no further details (Yanin, 1975)
Central European Territory: present, no further details (Danzig and Pellizzari, 1998)
Eastern Siberia: present, no further details (Danzig and Pellizzari, 1998)
Far East: present, no further details (Danzig and Pellizzari, 1998)
Kazakhstan: present, no further details (Danzig and Pellizzari, 1998)
Middle Asia: present, no further details (Danzig and Pellizzari, 1998)
Northern European Territory: present, no further details (Danzig and Pellizzari, 1998)
Russia: present, no further details (Tao, 1999)
Southern European Territory: present, no further details (Danzig and Pellizzari, 1998)
Transcaucasus: present, no further details (Zahradník, 1990a; Danzig and Pellizzari, 1998)
Western Siberia: present, no further details (Danzig and Pellizzari, 1998)
Former Yugoslavia: present, no further details (Danzig and Pellizzari, 1998)
France: present, no further details (Foldi, 2001)
Corsica: present, no further details (Kosztarab and Kozár, 1988)
Germany: present, no further details (Danzig and Pellizzari, 1998)
Greece: present, no further details (Danzig and Pellizzari, 1998)
Hungary: present, no further details (Danzig and Pellizzari, 1998; Ripka, 1999)
Italy: present, no further details (Longo et al., 1995)
Sicily: present, no further details (Longo et al., 1995)
Luxemburg: present, no further details (Danzig and Pellizzari, 1998)
Malta: present, no further details (Danzig and Pellizzari, 1998)
Netherlands: present, no further details (Danzig and Pellizzari, 1998)
Norway: present, no further details (Gertsson, 2001)
Poland: present, no further details (Danzig and Pellizzari, 1998)
Portugal: present, no further details (Danzig and Pellizzari, 1998)
Romania: present, no further details (Danzig and Pellizzari, 1998)
Spain: fairly widespread (Amparo Blay Golcoechea, 1993)
Sweden: present, quite widespread (Gertsson, 2001)
Switzerland: present, no further details (Kozár et al., 1994; Danzig and Pellizzari, 1998)
United Kingdom: widespread (C.P. Malumphy, Central Science Laboratory, UK, pers. comm.)
Channel Is (Guernsey): The Natural History Museum collection, London, UK
England: present, no further details (Kosztarab and Kozár, 1988)
Northern Ireland: The Natural History Museum collection, London, UK
Scilly Is: The Natural History Museum collection, London, UK
Scotland: The Natural History Museum collection, London, UK
Wales: The Natural History Museum collection, London, UK
Asia
China
Inner Mongolia: present, no further details (Tao, 1999)
Jilin: present, no further details (Tao, 1999)
Kansu: present, no further details (Tao, 1999)
Liaoning: present, no further details (Tao, 1999)
Ningxia: present, no further details (Tao, 1999)
Shanxi: present, no further details (Xie, 1982)
Xijia: present, no further details (Tao, 1999)
Xingxia: present, no further details (Tao, 1999)
India
Bihar: The Natural History Museum collection, London, UK
Jammu and Kashmir: present, no further details (Masoodi and Trali, 1987)
Iran: present, no further details (Seghatoleslami, 1977; Danzig and Pellizzari, 1998)
Japan: present, no further details (Danzig and Pellizzari, 1998)
Korea: present, no further details (Danzig and Pellizzari, 1998)
Middle East: present, no further details (Kosztarab and Kozár, 1988)
Mongolia: present, no further details (Danzig and Pellizzari, 1998)
Pakistan: The Natural History Museum collection, London, UK
Southern Asia: present, no further details (Danzig and Pellizzari, 1998)
Turkey: present, no further details (Danzig and Pellizzari, 1998)
Africa
Algeria: present, no further details (Danzig and Pellizzari, 1998)
Morocco: present, no further details (Danzig and Pellizzari, 1998)
North Africa: present, no further details (Kosztarab and Kozár, 1988)