Overall probability of entry, establishment and spread
The overall probability of entry, establishment and spread is determined by combining the probabilities of entry, of establishment and of spread using the matrix of ‘rules’ for combining qualitative likelihood shown in Table 2.2.
The overall likelihood that A. viennensis will enter Australia as a result of trade in the commodity from the country of origin, be distributed in a viable state to suitable hosts, establish in Australia and subsequently spread within Australia: LOW.
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Consequences
The consequences of the establishment of A. viennensis in Australia have been estimated according to the methods described in Table 2.3.
Based on the decision rules described in Table 2.4, that is, where the consequences of a pest with respect to one or more criteria are ‘E’, the overall consequences are estimated to be MODERATE.
Reasoning for these ratings is provided below:
Criterion
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Estimate
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DIRECT
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Plant life or health
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E – Significant at the regional level
Amphitetranychus viennensis is an important pest in apple, peach, pear, apricot, plum, hawthorn, and cherry in a number of countries in Europe and Asia. In China, it can reduce the yield of the fruit during that current year by more than 10% and in the subsequent year up to 70-80%, due to the impact on the formation of flower buds (Cai et al. 1992; Sun et al. 2004). The mite causes a reduction in fruit size and weight, but not in the number of fruit produced (Cai et al. 1992).
Amphitetranychus viennensis may cause particular damage in dry years. Photosynthetic activity is also sensitive to mite damage. Heavy infestations of A. viennensis may cause water loss, premature leaf drop, impaired fruit formation, and lower the resistance of the host to winter conditions (Li et al. 1998).
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Other aspects of the environment
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B – Minor significance at the local level
There are no known direct consequences of this species on the natural or built environment, but its introduction into a new environment may lead to competition for resources with native species.
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INDIRECT
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Control, eradication, etc.
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D – Significant at the district level
Indirect consequences of eradication or control as a result of the introduction of hawthorn spider mite may include: (i) an increase in the use of acaricides for control of the pest due to the difficulties involved in estimating optimum times for application; (ii) disruption to Integrated Pest Management (IPM) programs because of the need to increase the use of acaricides; (iii) the development of resistance to acaricides as a result of the use of numerous acaricides to control A. viennensis (see (CAB International 2008)) for details); (iv) increases in control measures and impacts on existing production practices; (v) increases in costs of production due to increases in the use of acaricides may alter the economic viability of some crops; (vi) increased costs for crop monitoring and consultant services to producers.
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Domestic trade
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D – Significant at the district level
If A. viennensis becomes established in areas of Australia, it is likely to result in interstate trade restrictions on many commodities such as apples, pears and cherries, potential loss of markets and significant industry adjustment.
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International trade
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D – Significant at the district level
The presence of A. viennensis in commercial production areas of a wide range of commodities (e.g. apples, pears and cherries) may limit access to overseas markets, such as the USA, where this pest is absent.
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Environment
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B – Minor significance at the local level
Pesticide applications or other control activities would be required to control this pest on susceptible crops, which would have a minor impact on the environment.
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Unrestricted risk estimate
Unrestricted risk is the result of combining the probability of entry, establishment and spread with the estimate of consequences. Probabilities and consequences are combined using the risk estimation matrix shown in Table 2.5.
Unrestricted risk estimate for hawthorn spider mite
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Overall probability of entry, establishment and spread
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Low
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Consequences
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Moderate
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Unrestricted risk
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Low
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As indicated, the unrestricted risk for hawthorn spider mite has been assessed as ‘low’, which exceeds Australia’s ALOP. Therefore, specific risk management measures are required for this pest.
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Flat scarlet mite - Cenopalpus pulcher
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Introduction
Cenopalpus pulcher (flat scarlet mite) belongs to the mite family Tenuipalpidae which are eight-legged mites. They are small but obvious due to their intense scarlet colour (Jeppson et al. 1975).
Cenopalpus pulcher has five life stages: egg, larval, two nymph stages (protonymphal, and deutonymphal) and adult (Zaher et al. 1974). Adult females are about 0.32 mm long and 0.16 mm wide (Jeppson et al. 1975) and deposit eggs on the striations and natural indentations of leaves and fruits. The adult male is shorter and paler than the female and its abdomen is almost transparent and curves upward. Mating occurs in August and September, after which the males die and the females go into hibernation. Cenopalpus pulcher prefers the lower leaf surface and may cause stippling of injured tissue, leaf and fruit drop or twig die-back (Jeppson et al. 1975). These mites can also feed on fruit (Bajwa and Kogan 2003). Beside adults, the nymphal stage may overwinter (Elmosa 1971). Cenopalpus pulcher produces from one generation a year in Europe (Dosse 1953) to three generations a year in Iran and Iraq (Elmosa 1971; Sepasgosarian 1970).
The risk scenario of concern for C. pulcher is that the nymphs and adults can be found on the fruit and females can also deposit their eggs on the fruit (Bajwa and Kogan 2003).
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Probability of entry
The probability of entry is considered in two parts, the probability of importation and the probability of distribution, which consider pre-border and post-border issues, respectively.
Probability of importation
The likelihood that C. pulcher will arrive in Australia with the importation of the commodity: HIGH.
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Cenopalpus pulcher is present in several of China’s major apple production areas, including Beijing, Hebei, Liaoning, Shangdong and Shaanxi (Wang 1981).
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Apple is a major host for C. pulcher throughout its natural range (CAB International 2008).
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Eggs can be found on fruit and nymphs and adults can feed on fruit (Bajwa and Kogan 2003).
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Cenopalpus pulcher overwinters on structures remaining on trees during winter, and is known to occur on fruit (Bajwa and Kogan 2003; Elmosa 1971). A large proportion of the population of this mite would be dormant or seeking overwintering sites by the start of apple harvesting in China (Wang 1981), so it is anticipated that mites will shelter in the stem end and calyx of harvested apple fruit.
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Cenopalpus pulcher is unlikely to be detected or dislodged from fruit by harvesting and grading activities because of its small size.
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A large proportion of C. pulcher populations in China are already dormant when apples are harvested (Wang 1981). Accordingly, dormant mites present on apples are likely to survive cold storage during transport to Australia, as they may survive temperatures as cold as 30 °C in their native habitats (Jeppson et al. 1975).
The small size of the mite and the presence of eggs, nymphs and adults on apple fruit support a risk rating for importation of ‘high’.
Probability of distribution
The likelihood that C. pulcher will be distributed in Australia as a result of the processing, sale or disposal of the commodity: MODERATE.
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Apple fruit is sourced for human consumption and the mites may stay on the fruit during wholesale and retail distribution in Australia. Mites present on apples are likely to occupy sheltered positions, such as the stem attachment and the calyx.
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The cores of apple fruit include the stem attachment and calyx and are not normally consumed by humans and are disposed of as waste.
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Apple waste products disposed of as municipal waste and compost is unlikely to distribute C. pulcher into the environment.
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Apple waste disposed of as litter may be deposited into urban, peri-urban and agricultural situations, as well as areas of natural vegetation, throughout Australia.
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Cenopalpus pulcher cannot fly and is unlikely to move from fruit waste to a host by crawling because of its small size. However, C. pulcher may be able to access hosts in the environment via air currents (Pedgley 1982).
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Most of these environments are known to contain suitable hosts, including fruit crops (apple, apricot, pear, pomegranate, prune, quince and walnut) and amenity trees (sycamore and willow), which are commonly found in southern areas of Australia (Hnatiuk 1990).
The limited mobility of the flat scarlet mite, mitigated by the wide distribution of its hosts, supports a risk rating for distribution of ‘moderate’.
Overall probability of entry (importation × distribution)
The overall probability of entry is determined by combining the probability of importation with the probability of distribution using the matrix of rules shown in Table 2.2. The likelihood that C. pulcher will enter Australia as a result of trade in the commodity and be distributed in a viable state to a suitable host: MODERATE.
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Probability of establishment
The likelihood that C. pulcher will establish in Australia based on a comparison of factors in the source and destination areas that affect pest survival and reproduction: HIGH.
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Probability of spread
The likelihood that C. pulcher will spread, based on a comparison of factors in the area of origin and in Australia that affect the expansion of the geographic distribution of the pest: MODERATE.
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Cenopalpus pulcher occurs in many subtropical and temperate parts of Asia, Europe, North America and Africa (Elmosa 1971; Jeppson et al. 1975). This indicates that there would be suitable environments for its spread in temperate regions of Australia.
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Host plants are widely grown in six states of Australia. The distribution of hosts on the roadside and in home gardens, parks and orchards could assist the spread of this mite.
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Geographical areas such as arid regions between the western and eastern parts of Australia could be natural barriers for the spread of C. pulcher.
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Crawling is the common mode of movement of the mite on host plants and this limited mobility may limit its ability to spread.
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First instar nymphs of Cenopalpus pulcher may be able to access hosts in the environment via air currents (Pedgley 1982). However, there is no strong evidence that the mite has been transferred over long distances by unaided dispersal mechanisms (NAPPO 2008).
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The movement of vegetative propagative material, such as nursery stock or budwood, could be a means of dispersal (NAPPO 2008).
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Apples and other fruits for human consumption would be distributed around the country. Such human assisted distribution would lead to spread of the mite.
The wide distribution of hosts and the ability of first instar nymphs to be carried by wind currents, mitigated by the restricted mobility of the mite and the lack of evidence of unaided dispersal over long distances support a risk rating for spread of ‘moderate’.
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Overall probability of entry, establishment and spread
The overall probability of entry, establishment and spread is determined by combining the probabilities of entry, of establishment and of spread using the matrix of ‘rules’ for combining qualitative likelihood shown in Table 2.2.
The likelihood that C. pulcher will enter Australia as a result of trade in the commodity from the country of origin, be distributed in a viable state to suitable hosts, establish in the PRA area and subsequently spread within Australia: LOW.
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Consequences
The consequences of the establishment of C. pulcher in Australia have been estimated according to the methods described in Table 2.3.
Based on the decision described in Table 2.4, that is, where the consequences of a pest with respect to one or more criteria are ‘E’, the overall consequences are estimated to be MODERATE.
Reasoning for these ratings is provided below:
Criterion
|
Estimate
|
DIRECT
|
|
Plant life or health
|
E – Significant at the regional level
Cenopalpus pulcher is an important pest in apple, pear, quince, loquat, walnut, oriental sycamore, apricot, prune, pomegranate and willow in Europe, Africa, Asia and north America (NAPPO 2008). The flat scarlet mites feed on leaves, soft twigs and fruits (Bajwa and Kogan 2003). Feeding symptoms may be confined to simple stippling of injured tissue, or the host plant may suffer leaf and fruit drop or twig die-back (Jeppson et al. 1975).
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Other aspects of the environment
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B – Minor significance at the local level
There are no known direct consequences of this species on the natural or built environment, but its introduction into a new environment may lead to competition for resources with native species.(Ma 2006; Yoder 1990)
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INDIRECT
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Eradication, control etc.
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D – Significant at the district level
Indirect effects of eradication or control as a result of the introduction of flat scarlet mite may include: (i) an increase in the use of acaricides for control of the pest due to the unclear critical time of application; (ii) disruption to integrated pest management; (iii) potential to develop resistance to acaricides as a result of the use of numerous acaricides to control C. pulcher; (iv) use of additional control measures and impacts on existing production practices; (v) increase in cost of production could alter the economic viability of some crops; (vi) additional cost of crop monitoring and consultative advice to producers
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Domestic trade
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D – Significant at the district level
If C. pulcher is established in Australia it is likely to result in interstate trade restrictions on many commodities such as apple, pear, quince, loquat, apricot, plum and pomegranate, and potential loss of markets. This could require significant industry adjustment.
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International trade
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D – Significant at the district level
The presence of C. pulcher in commercial production areas of a wide range of commodities (e.g. apple, pear, quince, loquat, apricot, plum and pomegranate) may limit access to overseas markets.
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Environment
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B – Minor significance at the local level
Safer pesticide applications would be required to control this pest on susceptible crops, which would have minor impact on the environment.
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Unrestricted risk estimate
Unrestricted risk is the result of combining the probability of entry, establishment and spread with the estimate of consequences. Probabilities and consequences are combined using the risk estimation matrix shown in Table 2.5.
Unrestricted risk estimate for flat scarlet mite
|
Overall probability of entry, establishment and spread
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Low
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Consequences
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Moderate
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Unrestricted risk
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Low
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As indicated, the unrestricted risk for flat scarlet mite has been assessed as ‘low’, which exceeds Australia’s ALOP. Therefore, specific risk management measures are required for this pest.
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Apricot weevil - Rhynchites auratus
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Introduction
Rhynchites auratus (apricot weevil) belongs to the weevil family Rhynchitidae which can be distinguished from other beetles by its long proboscis, called a snout, and mouth parts modified to allow it to chew into flower heads.
Rhynchites auratus has four life stages: egg, larva, pupa and adult. Adults are 5-7 mm long, hairy and gold-brown or bright red. Damage by adult weevils is visible as large holes on the fruit surface. Females deposit their eggs within the fruit pulp, where the larvae develop (Booth et al. 1990). Larvae are short, wide and curved and remain inside the fruit until ready to pupate. Mature larvae leave the fruit and pupate in the soil. Both the larvae and adults can overwinter (Lazarevic 1955). Rhynchites auratus has one generation per year (Lazarevic 1955).
The risk scenario of concern for R. auratus is the presence of eggs and developing larvae within apple fruit.
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Probability of entry
The probability of entry is considered in two parts, the probability of importation and the probability of distribution, which consider pre-border and post-border issues respectively.
Probability of importation
The likelihood that R. auratus will arrive in Australia with the importation of the commodity: VERY LOW.
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To date, Rhynchites auratus is reported only from Xinjiang Uygur Autonomous Region in China (AQSIQ 2006) and apple is listed as one of its hosts (Booth et al. 1990). There is no evidence of official control measures in place to prevent its spread to other provinces.
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Females of R. auratus oviposit deep within the fruit pulp, where the larvae develop (Booth et al. 1990). Schreiner (1914) reported that R. auratus had a particular attraction to “the China variety” of apple, where they deposited their eggs.
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AQSIQ ( 2008) advised that R. auratus was listed as ‘not on pathway’ by the USDA in its pest risk analysis on Chinese apples.
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In Bulgaria, Tosheva-Tsverkova (1965) found that R. auratus larvae fed on the fruits of stone fruit for between 16-36 days, with most of the larvae feeding for 31-33 days before entering the soil to pupate or overwinter. The average period from the entry of the larvae into the soil to the emergence of the first adults ranged from 72-105 days, and adults emerged from August to November.
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After laying eggs in the fruit, female Rhynchites weevils often sever the stalk, causing much of the infested fruit to drop to the ground so that the larva can enter the soil for pupation (Booth et al. 1990). This reduces the chance of infested fruit being harvested. However, Podleckis (2003) reports that ‘Rhynchites sp. was intercepted once on Chinese pear [entering the United States]; presumably, these were larvae’ but it is not clear if the interception was on a commercial consignment or from fruit carried by passengers.
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Adults have chewing mouthparts and cause feeding damage to plant tissue. Damage by adult Rhynchites weevils is visible as large holes on the fruit surface. Fruit damaged by adults can be recognised and removed during harvest, quality inspection and packing (Podleckis 2003).
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Adults of R. auratus are approximately 5-7 mm long and easily visible to the naked eye (Booth et al. 1990), and this would increase the chance that they would be noticed and removed during harvesting, quality sorting and packing.
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Larvae and adults of R. auratus can overwinter in cold climates (Lazarevic 1955). It is likely that they can survive cold storage and low-temperature transportation.
The indication that, after laying their eggs the weevils often sever the stalk of the fruit causing much of the infested fruit to drop to the ground, and that damaged fruit can be removed during harvest, quality inspection and packing, and the evidence that this species is only reported in Xinjiang, support a risk rating for importation of ‘very low’.
Probability of distribution
The likelihood that R. auratus will be distributed in Australia as a result of processing, sale or disposal of the commodity: MODERATE.
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It is expected that after arrival in Australia, apples will be distributed widely throughout the country for repacking and/or retail sale.
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Because the larvae reside within the fruit, infested apples are likely to travel unnoticed to their destination.
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Rhynchites auratus larvae and pupae can live in soil and even if they are not distributed to a host immediately, they could still survive and be moved to a suitable host subsequently. They can also pupate in the soil and emerge as adult weevils.
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Unaided movement of the larvae to nearby hosts or soil would be limited to crawling distance. If adults are present they would be able to fly to reach new hosts (Zherikhin and Gratshev 1995).
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Apples are intended for human consumption in Australia. It is expected that during commercial transport, storage and distribution to the end destination, some apples will be discarded as waste material. Individual consumers will dispose of small quantities of discarded apples in a variety of urban, rural and wild environments. This waste may be disposed of close to soil or a suitable host. The presence of waste infested with larvae may increase the chance of dispersal of this pest.
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Two or three larvae of R. auratus ferganensis Nevskii have been reported in one apricot fruit (Nevskii 1928) and it is feasible that this would be the case for R. auratus on apple fruit. This would increase the chance of sexual reproduction, as one infested fruit may contain larvae of both sexes.
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Fruit tree hosts of R. auratus, such as apple and stone fruit, are widely and sporadically distributed throughout Australia in domestic, commercial and wild environments that could occur near the commodity’s transport pathway and/or end destination.
Evidence that larvae may reside unnoticed within the fruit increasing the chance of dispersal, moderated by the need to complete their development and find a mate for sexual reproduction, supports a risk rating for distribution of ‘moderate’.
Overall probability of entry (importation distribution)
The overall probability of entry is determined by combining the probability of importation with the probability of distribution using the matrix of rules shown in Table 2.2. The likelihood that R. auratus will enter Australia as a result of trade in the commodity and be distributed in a viable state to a suitable host: VERY LOW.
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