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Plantwise Technical Factsheet

small emperor moth (Saturnia pavonia)

Host plants / species affected
Alchemilla (Lady's mantle)
Alnus incana (grey alder)
Betula nana (dwarf (arctic)- birch (UK))
Betula pendula (common silver birch)
Betula pubescens (Downy birch)
Calluna vulgaris (heather)
Carpinus betulus (hornbeam)
Cistus (rockrose)
Crataegus laevigata
Crataegus monogyna (hawthorn)
Erica (heaths)
Fragaria ananassa (strawberry)
Frangula alnus (alder buckthorn)
Hippophae rhamnoides (sea buckthorn)
Lythrum salicaria (purple loosestrife)
Malus domestica (apple)
Populus tremula (aspen (European))
Prunus salicina (Japanese plum)
Prunus spinosa (blackthorn)
Pyrus communis (European pear)
Quercus robur (common oak)
Rhamnus cathartica (buckthorn)
Rosa (roses)
Rosa majalis (cinnamon rose)
Rubus (blackberry, raspberry)
Rubus chamaemorus (yellow berry)
Rubus fruticosus (blackberry)
Rubus idaeus (raspberry)
Salix aurita (eared willow)
Salix caprea (pussy willow)
Salix cinerea (grey sallow)
Salix phylicifolia (tea-leaved willow)
Salix starkeana
Salix viminalis (osier)
Sorbus aucuparia (mountain ash)
Spiraea
Ulmus (elms)
Vaccinium myrtillus (blueberry)
Vaccinium uliginosum (bog whortleberry)
List of symptoms/signs
Leaves  -  external feeding
Description
Egg: Oval, 1.4 x 2.2 mm, greyish-white with olive-brown gum.

Larva: Fully-fed 60-75 mm. The newly hatched, 2-3 mm-long larvae consume part of their eggshells before clustering together. At this stage they are black and bristly, with an orange line down each side. As they grow, patches of orange appear around the base of the tubercles. These spread and coalesce with further growth, and gradually turn green. Most fully-grown larvae are grass-green with a yellow sub-spiracular line on the abdominal segments. Each segment bears dorsally a half-ring of six yellow, pink or orange, spine-topped tubercles. These may have a black ring around their base which, in some individuals, link up to form a black band. Some larvae may be completely black, particularly those from high altitudes (Novák, 1980), and many have varying degrees of black pigmentation (Pittaway, 1998).

Pupa: 20-25 mm. Dark brown to black with reddish-brown highlights, noticeably dorso-ventrally flattened, and 'comma'-shaped. Formed in a coarse, thin-walled, pear-shaped, double, unsealed brown cocoon. This is the overwintering stage, and many pupae overwinter more than once (Harris, 1766; Novák, 1980).

Adult: Wingspan (males) 40-65 mm, (females) 48-90 mm. The main characteristic of this species is a large, well-developed, multi-ringed eyespot placed in the white centre of each wing, with the latter being crossed by a number of wavy or curved grey, white or reddish-brown bars. Tips of forewings with incipient snake's-head pattern (Gardiner, 1982). Thus like a small version of Saturnia pyri, but differing in being sexually dichromatic, much greyer, and lacking any of the chocolate-brown of that species. The sexes are similarly marked, but males are more brightly coloured, with rosy, tawny and orange hues, and bear huge, pectinate antennae. There is little variation, but sometimes the eyespots are missing from all wings (ab. obsoleta Tutt), or abnormally shaped. High altitude populations may be small and marked very contrastingly (de Freina and Witt, 1987); many of these are also very thinly scaled (ab. alpina Favre) (Vorbrodt and Müller-Rutz, 1911). In some individuals the white surrounding the eye-spots is rose-red (ab. rosacea Newham). Occasionally, a female may be coloured as per the male, or be very dark grey.

Subspecies ligurica is larger, yellower and paler than subsp. pavonia, with males spanning 45-70 mm, females 50-95 mm. Subspecies josephinae is the same size as subsp. pavonia but paler, with the males lacking almost all brown and orange pigmentation so that they appear whitish-grey. The females are more like those of subsp. pavonia.

Prevention and control
Most of the standard chemical pesticides used to control insect pests on fruit trees will control this species, for example, carbaryl or chlorpyrifos (Bertucci, 1983).

Impact
S. pavonia has little economic impact. In Italy, where it is usually only a very minor pest it can, when the occasional outbreak occurs, rapidly defoliate pear and apple trees (Bertucci, 1983) causing a reduction in fruit yield.
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