The estimated likelihoods and consequences of entry, establishment and spread for quarantine pests are presented in this section. The results of these estimates are summarised in Table 4.4, together with the overall unrestricted risk estimates.
Pink citrus rust mite
In previous policy developed for the importation of sweet oranges from Italy into Australia (BA 2005), Aculops pelekassi, the pink citrus rust mite, had an unrestricted risk rating of LOW. This exceeds Australia’s ALOP. A summary of the risk assessment for Aculops pelekassi is listed in Table 4.4. This risk rating has been reviewed. On the basis of similar commercial production practices in Italy and Japan, it has been concluded that the risk rating is valid for this risk analysis.
The unrestricted risk estimate for A. pelekassi of ‘low’ exceeds Australia's ALOP. Therefore, specific risk management measures are required for this pest.
Citrus red mite
(*of quarantine concern to Australia; distribution restricted to Orange, Gosford and Sydney in New South Wales, where it is subject to quarantine restrictions)
In previous policy developed for the importation of sweet oranges from Italy into Australia (BA 2005), Panonychus citri, the citrus red mite,had an unrestricted risk rating of VERY LOW, which achieves Australia’s ALOP. A summary of the risk assessment for Panonychus citri is listed in Table 4.4. This risk rating has been reviewed. On the basis of similar commercial production practices in Italy and Japan, it has been concluded that the risk rating is valid for this risk analysis.
(*of regional quarantine concern to Western Australia, #of regional quarantine concern to South Australia)
Armoured scale insects are sessile, small (2–4 mm long), their body is covered with hard, waxy ‘armour’ and they are relatively inconspicuous. The armour covers adult females and immature males. First instars or crawlers are mobile and are the dispersal stage. The reproductive rates for armoured scales are temperature dependent and more generations are produced in tropical climates.
In previous policy developed for the importation of sweet oranges from Italy into Australia (BA 2005) and Tahitian limes from New Caledonia into Australia (BA 2006), the armoured scales Parlatoria pergandii, Parlatoria ziziphi,Unaspis yanonensis, Lepidosaphes gloverii,Morganella longispina, Parlatoria cinerea and Pseudaonidia trilobitiformis were assigned an unrestricted risk rating of VERY LOW, which achieves Australia’s ALOP. A summary of the risk assessments for these armoured scales is listed in Table 4.4. These risk ratings have been reviewed. On the basis that similar commercial production practices are used in Italy, New Caledonia and Japan, it has been concluded that these risk ratings are valid for this risk analysis.
The armoured scales considered further in this import risk assessment are Howardia biclavis,Ischnaspis longirostris, Lepidosaphes pinnaeformis,Lopholeucaspis japonica, Parlatoria theae,Pseudaonidia duplex and Unaspis euonymi. These species have been grouped together because of their related biology and taxonomy. In this assessment, the term ‘armoured scales’ is used to refer to these species, unless otherwise specified.
Probability of entry
Probability of importation
The likelihood that armoured scaleswill arrive in Australia with the importation of fresh unshu mandarin fruit from the production area in Japan is: HIGH.
Armoured scales are sessile, often inconspicuous and feed on fruit.
First instar nymphs (or crawlers) of armoured scales can move onto fruit. Second instars are permanently attached to fruit by embedding mouthparts into the host tissue for feeding purposes (Beardsley and Gonzalez 1975; Hely et al. 1982; Smith et al. 1997; Fasulo and Brooks 2004). Subsequent instars are sessile and usually remain attached to their host, including fruit (Taverner and Bailey 1995; Fasulo and Brooks 2004).
Armoured scales have a relatively hard, impermeable, external covering or ‘scale’ (Smith et al. 1997) that can protect them from physical and chemical damage (Foldi 1990a). Commercial fruit cleaning procedures may not eliminate all viable scales present on the fruit surface (Taverner and Bailey 1995).
Given that fruit would provide an ample food supply during transit, adults and crawlers are likely to survive storage and transport.
The small size, sessile nature of most life stages, and hard external covering of almost all life stages that provides protection to scales insects all support a risk rating for importation of ‘High’.
Probability of distribution
The likelihood that armoured scaleswill be distributed within Australia in a viable state, as a result of the processing, sale or disposal of fresh unshu mandarin fruit from the production area in Japan is: LOW.
Unshu mandarin fruit is intended for human consumption and adults and immature stages may remain on the fruit during retail distribution. Infested fruit is likely to be consumed. Disposal of waste fruit or peel is likely to be via commercial or domestic rubbish systems. However, some fruit waste may be disposed of in the home garden which provides an opportunity for these pests to transfer to susceptible hosts in the vicinity.
Armoured scales lack a natural dispersal mechanism that allows for the movement of scale species from discarded fruit waste to a suitable host. This is a significant limiting factor in their distribution. Although first instar nymphs (or crawlers) are mobile, they only disperse over short distances. First instars would have to be present for armoured scales to move from waste material to a host plant. Of the adult stages, only the short-lived males are capable of short flight while females remain sessile (CSIRO 1991).
Armoured scales are likely to survive local storage and transportation because scale insects generally tolerate cold temperatures and overwinter at various stages of growth. For example, L. japonica, L. pinnaeformis, I. longirostris, U. euonymi and P. theae all occur in temperate regions of the world (refer to Appendix B). In north-eastern Asia, L. japonica readily overwinters at temperatures of -20ºC to -25ºC (CABI and EPPO 1997c; CAB International 2007).
The limited mobility of almost all life stages of armoured scales and the disposal of most waste by municipal garbage collection, support a risk rating for distribution of ‘Low’.
The likelihood that armoured scaleswill establish within Australia, based on a comparison of factors in the source and destination areas considered pertinent to its survival and reproduction, is: HIGH.
All seven assessed scale species have a wide host range. Lopholeucaspis japonica feeds mostly on temperate and subtropical tree species, including Acer, Pyrus, Ficus, Diospyros kaki (persimmon), and woody ornamentals such as Camellia spp. (Ben-Dov et al. 2005; Appendix B). This would favour its establishment in more southern regions of Australia.
Pseudaonidia duplex feeds on major crops in Asia and in the Pacific region, including citrus, litchi, tea and ornamental trees (e.g. Acer, Alnus, Castanea). The host range of U. euonymi includes Citrus, Prunus, Olea, Hibiscus and others. Hosts of P. theaeinclude Citrus, Diospyros, Pyrus, Ribes, Rosa and others (Ben-Dov et al. 2005; Appendix B). All of these scale species would adapt to large areas of similar climatic conditions in Australia, including temperate and tropical areas.
Howardia biclavis is already present on the eastern seaboard of Australia (Donaldson and Tsang 2006). Its host range includes many tropical fruit tree species such as mango, litchi and custard apple, native species such as Randia, Morinda and Psychotria, introduced ornamental vines (Lonicera), shrubs (e.g. Gardenia, Buddleia) and tree species (Castanea, Khaya) (Ben-Dov et al. 2005; Appendix B). Ischnaspis longirostris feeds on citrus,coconut,coffee, mango and other woody plants and L. pinnaeformis on Citrus,Prunus, Pyrus, Magnolia, Quecus and others (Ben-Dov et al. 2005; Appendix B). Many of these hosts occur in Western Australia and climatic conditions, in parts of this state, are similar to the eastern seaboard where these pests are already established.
Moderate to high humidity, without precipitation, favours survival of armoured scale crawlers (Watson 2005).
Howardia biclavis reproduces parthenogenetically (Brown 1965) which is advantageous for the establishment of a species into a new environment. In Japan, this species has one generation per year (Murakami 1970).
In Japan, Lopholeucaspis japonica overwinters in the fertilised female stage and oviposits at the end of spring. Winged males emerge in summer and mate with the females prior to the overwintering phase (Murakami 1970).
In Louisiana in the USA, Pseudaonidia duplex has three generations per year (Ben-Dov et al. 2005).
Reproduction of scale species coincides with warm spring and summer temperatures. It therefore can be expected that the reproductive rate for all seven scale species will be higher in Australia than in Japan, considering the expanse of suitable climatic regions.
Existing control programs may be effective for some hosts (e.g. broad spectrum pesticide application) but not all hosts, because of the wide host plant range of these scale species (see above).
The wide host plant range, adaptability of armoured scales over a wide climatic range and limited pesticide effectiveness to control these pests support a risk rating for establishment of ‘High’.
Probability of spread
The likelihood that armoured scaleswill spread within Australia, based on a comparison of those factors in source and destination areas considered pertinent to the expansion of the geographic distribution of the pest, is: MODERATE.
Adults and nymphs may be moved within and between orchards (or other commercial production sites) with the movement of equipment, personnel and infested plant material (Dreistadt et al. 1994).
Armoured scales lack active long range dispersal mechanisms which moderates their rate of spread by self-propelled dispersal. The first instar nymphs are the primary dispersal phase within the scale’s life-cycle and can disperse by crawling, and also by dispersal on wind currents or using other vectors (Beardsley and Gonzalez 1975; Greathead 1990). However, subsequent instars are sessile and do not actively disperse once a feeding site has been selected. Adult females are flightless and remain on the host (Hely et al. 1982), while males fly weakly and only persist in the environment for a few hours (Beardsley and Gonzalez 1975). Animal and human activities (e.g. transport of contaminated equipment and plant material) may aid distribution (Greathead 1990; Dreistadt et al. 1994; Smith et al. 1997).
The Australian climate is expected to be conducive to the spread of all seven scale species, of which H. biclavis,I. longirostris and L. pinnaeformis are already established along the eastern seaboard (Donaldson and Tsang 2006; APPD 2008). All of the seven assessed species have an extensive range of hosts, which also occur in Western Australia. Climatic conditions in parts of Western Australia are similar to the eastern seaboard.
The world distribution of I. longirostris, L. japonica, L. pinnaeformis, U. euonymi and P. theae all suggest that these species would spread, specifically in the southern temperate environments, once they became established in Australia. Similarly the distribution of P. duplex throughout Asia and the Pacific region suggests that suitable climatic conditions would exist in Australia (see Establishment, above; Ben-Dov et al. 2005).
Experience with the establishment of H. biclavis, I. longirostris and L. pinnaeformis on the eastern seaboard of Australia indicates that after two or more generations, armoured scales are likely to persist indefinitely and spread.
The lack of a natural mechanism for long distance dispersal and the restricted mobility to first instar nymphs support a risk rating of armoured scales for spread of ‘Moderate’.
Probability of entry, establishment and spread
The likelihood that armoured scaleswill be imported as a result of trade in fresh unshu mandarin fruit from the production area in Japan, be distributed in a viable state to a susceptible host, establish and spread within Australia, is: LOW.
Assessment of the potential consequences (direct and indirect) of armoured scales for Australia is: LOW.
Estimate and rationale
Plant life or health
Impact score: D – significant at the district level
Armoured scales can cause direct harm to a wide range of plant hosts, affecting fruit quality and plant health (Beardsley and Gonzalez 1975; Smith et al. 1997). Infestation by armoured scales can cause direct damage to fruit. The feeding of scales causes defoliation, reduced fruit size and green spots on mature fruit at places where scales were fixed (OEPP/EPPO 2004).
Infested hosts are often susceptible to secondary attack by fungi and wood-boring insects (CAB International 2007). Damage caused to plants includes damage to trunks, limbs and twigs and occasionally leaves and fruit (Murakami 1970). Damage caused by armoured scales in some instances can cause twig dieback and extensive drying and splitting of the bark on the trunk and main limbs (Smith et al. 1997).
All seven species assessed, like other members of the Diaspididae, do not excrete honeydew and there is no issue with associated sooty mould or ants (Foldi 1990b).
Other aspects of the environment
Impact score: C – significant at the local level
All seven species assessedhave a wide host range, including numerous garden plants and amenity trees in tropical, subtropical and some temperate regions (Beardsley and Gonzalez 1975; Ben-Dov et al. 2005). All seven species are therefore likely to become widespread if introduced due to extending their current distribution. These species could also compete with native scale species, disrupt natural biocontrol methods for other pests, and alter aspects of the biotic environment such as native invertebrates and species known to predate scales (Smith et al. 1997).
Eradication, control etc.
Impact score: D – significant at the district level
Additional programs to eradicate scales on their host plants may be necessary. Existing control programs may be effective for some hosts (e.g. broad spectrum pesticide applications) but not all hosts (e.g. Malus (apples) and Pyrus (pears) where specific integrated pest management programs are used (APAL 2008).
Existing IPM programs may be disrupted because of the need to re-introduce or increase the use of organophosphate insecticides. This may result in a subsequent increase in the cost of production. Additionally, costs for crop monitoring and consultant’s advice to manage these pests may be incurred by the producer.
Impact score: C – significant at the local level
The damage by scales to fruit is green spots, and such fruits are downgraded for fresh fruit markets (Beardsley and Gonzalez 1975; Brooks and Knapp 1983).
The presence of these pests in commercial production areas may have a significant effect at the local level due to resulting trade restrictions on the sale or movement of a wide range of commodities, including nursery stock, between areas in Western Australia and between states/territory. These restrictions may lead to a loss of markets.
Impact score: C – significant at the local level
The presence of these scales in commercial production areas of a range of commodities would have a significant effect at the local level due to limitations of accessing international markets where these pests are absent.
Environmental and non-commercial
Impact score: B – minor at the local level
Additional pesticide applications or other control activities would be required to control these pests on susceptible crops. Any additional insecticide usage may affect the environment.