(Fitch, 1856)
Diagnosis
In life, scale cover of adult female 2.0-3.0 mm long, mussel-shaped, pure white, slightly convex with terminal yellow-brown or translucent exuviae CHPINL.jpg . Male scale cover, if present, about 1.0 mm long, elongate and white, with terminal, yellow or translucent, exuviae. CHIPINL2.jpg Body of adult female dark orange or red, eggs red or dark orange (Zahradník, 1990; Gill, 1997).
Body of slide-mounted adult female elongate, 1.3-1.7 mm long, membranous, with prosoma narrow; with gland spines and macroducts present anterior to abdominal segment I CHPINS.jpg . Pygidium with median lobes zygotic, inset and broadly rounded (with inner margins longer than outer margins), without any setae or gland spines between their bases; submedian macroducts present on pygidial and prepygidial segments; those on segments III, IV and V all of similar size CHPINP.jpg . On conifers.
The adult male was illustrated by Bullington et al., 1989.
Host range
Chionaspis 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). Hosts include species of: Abies, Cedrus, Cupressus, Picea, Pinus, Pseudotsuga, Taxus, Torreya and Tsuga.
Affected plant stages: vegetative growing, flowering and fruiting stages
Affected plant parts: on the needles CHIPINL1.jpg
Biology and ecology
Apparently there are two races of C. pinifoliae, one parthenogenetic and the other biparental. In California, 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, 53% of the population are male (Nur, 1990). In Iowa, Burden and Hart, 1989, found that at 18. 5°C, 136 day-degrees C accumulated to hatching and the time to 50% hatching was 17.25 days. The developmental threshold lay between 10.8 and 11.8°C. In Virginia, each female lays 8-32 eggs, there are two generations per year, and overwintering is as eggs and females (Kosztarab, 1996).
Walstad et al., 1973, reported that the stylets enter the needle through a stoma and terminate in mesophyll tissue.
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
Chionaspis pinifoliae may cause foliage to turn yellow, then brown, and branches may die (Kosztarab, 1990; Kosztarab, 1996). Feeding by the pest destroys the mesophyll cells, leading to chlorosis of the foliage; the chlorotic condition and/or light interception by the insects decreases the photosynthetic capacity of the foliage; and the decline in assimilation rate reduces the vigour of severely infested trees (Walstad, 1972).
Economic impact
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, weakening and killing branches and sometimes the whole tree; this species can cause problems on Christmas tree plantations and is considered one of the most serious pests of ornamental pines (especially Scotch and mugho 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 the % reduction in chlorophyll content and in net photosynthetic rate were approximately equal to the % of foliage surface area covered by scale insects. Feeding by the pest destroys the mesophyll cells, leading to chlorosis of the foliage; the chlorotic condition and/or light interception by the insects decrease the photosynthetic capacity of the foliage; and the decline in assimilation rate reduces the vigour of severely infested trees (Walstad, 1972).
Detection and inspection methods
Examine the needles/foliage closely for mussel-shaped, pure white scale covers with terminal yellow-brown or translucent exuviae. Look also for browning of foliage in association with scale infestation.
Natural enemies
Parasitoids:
- Aphytis diaspidis, in USA (Iowa)
- Aphytis mytilaspidis, in Canada (Quebec)
- Ablerus atomon, in Spain
- Closterocerus phenacapsius, in USA (California)
- Coccophagus flavifrons, in Colorado
- Coccobius howardi, in USA (California)
- Coccobius varicornis, in Colorado, Canada (Quebec)
- Encarsia sp., in Colorado
- Encarsia bella, in USA (California, Colorado, New York)
Predators:
- Chilocorus orbus, in USA (California)
- Chilocorus stigma, in USA (New York)
- Coccidophilus atronitens, in USA (California, Colorado)
- Microweisea marginata, in Canada (Quebec)
Distribution
See Chionaspis pinifoliae distribution.
Microscopic examination of slide-mounted adult females is required for authoritative identification to species.
Chionaspis corni Cooley (dogwood scale, cochenille de cornouiller CHCOS.jpg could be misidentified as C. pinifoliae, but differs in having median lobes divergent, each one shorter than wide CHCOMG.jpg. In contrast, C. pinifoliae has median lobes not strongly divergent, each one longer than wide CHPINP.jpg. These species also have different host plants, with C. corni feeding on Cornus species and C. pinifoliae feeding on Pinus species. Chionaspis corni is known from Canada (Ontario), USA (California, Idaho, Illinois, Indiana, Kansas, Louisinana, Massachusetts, Maryland, Michigan, Mississippi, New Jersey, New York, Ohio, Pennsylvania, Utah, Virginia and Wisconsin) on species of Cornus (Liu et al., 1989; Howard and Oliver, 1985; Nakahara, 1982). Scale covers white, with terminal yellow exuviae.Often on [l][m]Host plants[/m][r]Cornus[/r]Cornus sp. Probably a native of the east coast of North America (Gill, 1997), this species causes considerable damage to species of Ribes and Cornus in North America (Kozár, 1990b; Kosztarab, 1996). CHCOL.jpg
Comments
Chionaspis 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 United Kingdom (C.P. Malumphy, Central Science Laboratory, UK, pers. comm.). The species has not been recorded from Europe, Asia, Australia, or from the Pacific islands. Hodgson and Hilburn, 1991, remark that the species does not appear to have become established in Bermuda.
Africa
Libya: present, not further details (Lal and Naji, 1979; Danzig and Pellizzari, 1998)
Western Hemisphere
Canada: common in most of Canada (Gill, 1997)
British Colombia: present, no further details (Wood and Ross, 1972)
New Brunswick: present, no further details (Magasi, 1992)
Prince Edward I.: present, no further details (Magasi, 1992)
Nova Scotia: present, no further details (Magasi, 1992)
Quebec: present, no further details (Martel and Sharma, 1975)
Central America: present, no further details (Danzig and Pellizzari, 1998)
Chile
Easter Island: present, no further details (Charlín, 1973)
Cuba: present, no further details (Nakahara, 1982)
El Salvador: present, no further details (Nakahara, 1982)
Honduras: present, no further details (Nakahara, 1982)
Mexico: especially in the north (Zahradník, 1990; Miller, 1996)
North America: common (Gill, 1997; Danzig and Pellizzari, 1998)
South America: present, no further details (Danzig and Pellizzari, 1998)
USA: common in most of the USA where pines grow (Gill, 1997)
Arizona: The Natural History Museum collection, London, UK
California: present, no further details (Gill, 1997)
Colorado: present, no further details (Cooper and Cranshaw, 1999)
Connecticut: present, no further details (McClure and Fergione, 1977)
Illinois: present, no further details (Tooker and Hanks, 1999)
Iowa: present, no further details (Burden and Hart, 1990)
Kentucky: present, no further details (Mussey and Potter, 1997)
Massachusetts: present, no further details (Driesche and Elkinton, 1987)
Montana: The Natural History Museum collection, London, UK
New York: present, no further details (DeBoo and Weidhaas, 1976)
Ohio: The Natural History Museum collection, London, UK
Tennessee: present, no further details (Lambdin, 1995)
Utah: The Natural History Museum collection, London, UK