(Lichtenstein, 1881)
Taxonomic note
Diaspidiotus pyri belongs to a group of species that are difficult to assign to distinct genera - see Genus Diaspidiotus, Background.
Diagnosis
Scale cover of adult female in life circular, 1.8-2.1 mm in diameter, moderately convex, dark brown with central or subcentral exuviae DIASPYL.jpg . Scale cover of male not recorded, but probably smaller than that of female, oblong, brown, with exuviae near one end. Body of adult female in life pyriform, light or dark yellow (Zahradník, 1990a).
Body of slide-mounted adult female membranous, approximately pyriform, 1.2-1.5 mm long, sometimes with slight constriction between meso- and metathorax DIASPYO.jpg . Anus smaller than a median lobe, situated at least 2.4 times its own length from base of median lobes; perivulvar pores present in five groups. Pygidium with median and second lobes well developed, slightly convergent, second lobes each slightly notched on outer margin, usually as shorter than associated marginal seta; third lobes usually represented by points, occasionally absent; fourth lobes absent DIASPYP.jpg . Paraphyses present between positions of third lobes only, shorter than the lobes, usually thickened towards their inner ends. Plates between lobes fimbriate; inner basal angle of median lobe with thick paraphysis, as large or larger than parapysis on outer basal angle of median lobe DIASPYMG.jpg .
Host range
Diaspidiotus pyri has been recorded from hosts (mostly trees) belonging to 9 plant families (Borchsenius, 1966). Hosts include species of: Aesculus, Betula, Carpinus, Crataegus, Ficus, Fraxinus, Juglans, Malus, Mespilus, Olea, Platanus, Populus, Prunus, Pyrus, Salix, Sorbus, Spiraea and Tilia.
Affected plant stages: vegetative growing, flowering, fruiting and post-harvest stages
Affected plant parts: on trunk, twigs and fruit
Biology and ecology
Reproduction may be either sexual or parthenogenetic; there is one generation per year, and the species overwinters as second instar larvae. Each female lays 41-165 (usually about 70) eggs that hatch in a few days (Schmutterer, 1952; Kosztarab and Kozár, 1988; Zahradník, 1990a).
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
Balachowsky ,1950, recorded D. pyri causing serious damage that was often attributed to D. ostreaeformis. Diaspidiotus ostreaeformis infests branches and causes drying of the tissues (Zahradník, 1990a). Sometimes it can be found on the fruits, where it causes red spots. Presumably the damage caused by D. pyri is similar, although no description of the damage caused has been found in the literature.
Economic impact
In Central Europe, D. pyri is a pest of fruit trees (Kosztarab and Kozár, 1988). In North Africa, Balachowsky,1950, recorded it causing serious damage, maily to rosaceous fruit trees, that was often attributed to D. ostreaeformis. It was regarded as one of the most important pests of apple in the southern USSR (Konstantinova, 1976). Danzig and Pellizzari, 1998, said that this species is sometimes a pest in the Palaearctic region. Foldi, 2001, lists D. pyri as an occasional pest in France.
Detection and inspection methods
Examine trunk, twigs and fruit closely for circular, moderately convex, dark brown scale covers with central or subcentral exuviae. Infested fruits may show red spotting.
Natural enemies
The list of natural enemies below is based on Kosztarab and Kozár, 1988, and CABI, 2000.
Parasitoids:
- Ablerus atomon
- Ablerus marchali
- Aphytis aonidiae
- Aphytis mytilaspidis
- Aphytis proclia
- Encarsia citrina
- Habrolepis dalmanni
- Pteroptrix bicolor
- Pteroptrix dimidiata
- Pteroptrix lauri
- Pteroptrix longicornis
Predators:
- Chilocorus bipustulatus
- Chilocorus renipustulatus
- Cybocephalus politus
- Hemisarcoptes malus
Distribution
See Diaspidiotus pyri distribution.
Microscopic examination of slide-mounted adult females is required for authoritative identification to species.
Diaspidiotus ancylus (Putnam) (convex scale, Putnam scale, cochenille de Putnam) DIASANS.jpg could be misidentified as D. pyri but differs in possessing parallel median lobes and only about 30 macroducts on each side of the pygidium DIASANP.jpg (although the number of macroducts is very variable). In contrast, D. pyri has divergent median lobes, and about 70 macroducts on each side of the pygidium DIASPYP.jpg. Diaspidiotus ancylus is dimorphic. The leaf form of this scale has 3 pairs of well-developed pygidial lobes and has been called Abgrallaspis [Hemiberlesia] howardi (Cockerell) in the past (Gill, 1997); it would key out as Hemiberlesia lataniae in the Picture Key. Diaspidiotus ancylus is a polyphagous species known from Canada (Ontario), USA (continental including Arizona, California, Indiana, Iowa, New Mexico, New York, Tennessee), Mexico, Central America, Brazil (Sao Paulo), Chile (first to eighth regions), Spain (Huelva), Portugal, Germany, South Africa and Australia; it is often found on the bark of branches and trunk, and sometimes on leaves, of basswood, elm and maple. Hosts include species of Acer, Aesculus, Betula, Carya, Catalpa, Celtis, Cephalanthus, Crataegus, Cydonia, Fagus, Fraxinus, Hydrangea, Juglans, Liriodendron, Maclura, Malus sylvestris, Muehlenbeckia, Olea europaea, Oxalis, Persea americana, Populus spp., Prunus spp., Pyrus, Quercus, Ribes, Robinia spp., Salix, Sorbus, Tilia, Ulmus, Viburnum and Vitis vinifera (Munting, 1971a; Konstantinova, 1976; Nakahara, 1982; Zahradník, 1990a; Amparo Blay Golcoechea, 1993; Kosztarab, 1996; Miller, 1996; Gill, 1997; Danzig and Pellizzari, 1998; Claps et al., 2001a; CSIRO, 2001; The Natural History Museum collection, London, UK). Immature stages of D. ancylus can be mistaken for D. perniciosus (Claps et al., 2001a). This species has been a pest on walnuts, cranberries, blueberries and on elms and other ornamentals in the USA in the past; it is probably native to North America (Gill, 1997). Diaspidiotus ancylus was listed as a pest of deciduous fruit trees of regional importance by Kozár, 1990b; heavy infestations can kill twigs and branches (Kosztarab, 1996). One or two generations per year have been recorded in the USA, and overwintering is as adult females (second instar females in Chile) (Kosztarab, 1996). This species does not occur in the former USSR, but featured on the list of quarantine pests for this region (Konstantinova, 1976).
Diaspidiotus gigas (Thiem and Gerneck) (willow scale, poplar armored scale, poplar scale) DIASGIS.jpg could be misidentified as D. pyri but differs in its large body size and in possessing parallel median lobes with inner and outer paraphyses of almost equal size, or the outer paraphyses longer than the inner ones DIASGIP.jpg . In contrast, D. pyri has divergent median lobes with the inner paraphyses longer and thicker than the outer ones DIASPYP.jpg. Diaspidiotus gigas is a trans-Palaearctic species known from Bulgaria, Cyprus, former Czechoslovakia, former USSR (Central European territory, South European territory, Transcaucasus, Kazakhstan, Far East), France, Germany, Hungary, Italy, Netherlands, Poland, Romania, Spain (restricted distribution), Switzerland, former Yugoslavia, Turkey, the Middle East, China (Hebei, Heilongjiang, Henan, Inner Mongolia, Jiangsu, Jilin, Qinghai, Shanxi, Xinjiang), Algeria, Turkey, Canada (New Brunswick, Nova Scotia, Ontario) and USA (Idaho, Montana, New York, Ohio, Oregon, Pennsylvania, Rhode Island, Utah, West Virginia, Wisconsin and Wyoming); it is often found on the trunk and branches of hosts in 5 genera belonging to four plant families (Davidson and Miller, 1990). Hosts include species of Populus, Salix and Tilia; infestations often cause deformations (pitting of the bark) and dieback of branches, in windbreaks, suburban and urban settings rather than in forests (Nakahara, 1982; Kosztarab and Kozár, 1988; Kosztarab, 1990; Zahradník, 1990a; Amparo Blay Golcoechea, 1993; Kozár et al., 1994; Longo et al., 1995; Danzig and Pellizzari, 1998; Tao, 1999; Foldi, 2001). The species is rather thermophilous; it is univoltine and overwinters as second instar larvae (Davidson and Miller, 1990; Zahradník, 1990a). Diaspidiotus gigas is an occasional pest in France (Foldi, 2001) and Central Europe, causing deformation and drying of branches (Kosztarab and Kozár, 1988). Outbreaks have occurred in Heilongjiang province in China (Liu et al., 1997). Scale cover of adult female circular, 1.7-2.8 mm in diameter, convex, grey with orange-yellow, subcentral exuviae; scale cover of male elongate oval, smaller than that of female, grey with orange-yellow, subterminal exuviae (Davidson and Miller, 1990); exposed body of living female light yellow (Kosztarab and Kozár, 1988). Reproduction is sexual and each female lays 86-215 eggs (Kosztarab and Kozár, 1988). DIASGIL.jpg
Comments
Diaspidiotus pyri is a temperate/subtropical species, probably of Mediterranean origin (Kosztarab and Kozár, 1988). It has not been recorded from the Western Hemisphere, or from the Pacific islands.
Europe
Belgium: present, no further details (Danzig and Pellizzari, 1998)
Bulgaria: present, no further details (Danzig and Pellizzari, 1998)
Former Czechoslovakia: present, no further details (Danzig and Pellizzari, 1998)
Former USSR
Armenia: present, no further details (Zahradník, 1990a; Danzig and Pellizzari, 1998)
Azerbaijan: present, no further details (Zahradník, 1990a; Danzig and Pellizzari, 1998)
Caucasus: present, no further details (Zahradník, 1990a; Danzig and Pellizzari, 1998)
Georgia, Republic of: present, no further details (Zahradník, 1990a; Danzig and Pellizzari, 1998)
Moldova: present, no further details (Zahradník, 1990a; Danzig and Pellizzari, 1998)
Turkmenistan: present, no further details (Zahradník, 1990a; Danzig and Pellizzari, 1998)
Ukraine: present, no further details (Zahradník, 1990a; Danzig and Pellizzari, 1998)
Former Yugoslavia: present, no further details (Danzig and Pellizzari, 1998)
France: present, no further details (Danzig and Pellizzari, 1998; Foldi, 2001)
Germany: present, no further details (Balachowsky, 1950; Danzig and Pellizzari, 1998)
Greece: The Natural History Museum collection, London, UK
Hungary: present, no further details (Balachowsky, 1950; Danzig and Pellizzari, 1998)
Italy: present, no further details (Longo et al., 1995; Danzig and Pellizzari, 1998)
Malta: present, no further details (Danzig and Pellizzari, 1998)
Netherlands: present, no further details (Danzig and Pellizzari, 1998)
Poland: present, no further details (Danzig and Pellizzari, 1998)
Romania: present, no further details (Danzig and Pellizzari, 1998)
Spain: present in Almería and Madrid (Amparo Blay Golcoechea, 1993)
Canary Is: present, no further details (Amparo Blay Golcoechea, 1993)
Switzerland: present, no further details (Kozár et al., 1994; Danzig and Pellizzari, 1998)
United Kingdom: present (C.P. Malumphy, Central Science Laboratory, UK, pers. comm.)
England: The Natural History Museum collection, London, UK
Asia
Iran: present, no further details (Seghatoleslami, 1977; Danzig and Pellizzari, 1998)
Israel: The Natural History Museum collection, London, UK
Turkey: present, no further details (Danzig and Pellizzari, 1998; The Natural History Museum collection, London, UK)
Africa
Algeria: The Natural History Museum collection, London, UK
Egypt: present, no further details (Balachowsky, 1950; Danzig and Pellizzari, 1998)
Morocco: present, no further details (Balachowsky, 1950; Danzig and Pellizzari, 1998)
Oceania
Australia
Tasmania: present, no further details (CSIRO, 2001; The Natural History Museum collection, London, UK)