Probability of establishment
The likelihood that R. auratus will establish, based on a comparison of factors in the source and destination areas that affect pest survival and reproduction: MODERATE.
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Probability of spread
The likelihood that R. auratus 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 pests: MODERATE.
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Adults of R. auratus can fly, but other natural dispersal mechanisms are limited (e.g. they have no known natural vectors) (Zherikhin and Gratshev 1995).
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Natural barriers such as arid areas, climate differences and long distances, exist in Australia and may limit the spread of R. auratus.
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Rhynchites auratus pupates in the soil and pupae may be spread with the contaminated soil on products or machinery that has not been properly cleaned.
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If infested apples and other hosts from Australian orchards where Rhynchites auratus become established are transported and sold on the domestic market, this could increase opportunities for the species to spread to and establish in other areas in the same manner as the initial introduction (e.g. disposal of infested apples intended for human consumption).
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An egg-eating parasite of R. auratus was reported in Turkestan (Troitzky 1913), but it is most likely not present in Australia.
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Effective control of Rhynchites species has been achieved in Greece with organophosphate compounds (Lykouressis et al. 2004), and in Siberia with endosulfan (Thiodan) and pirimiphos-methyl (Actellic) (Bashkatova et al. 1983). Endosulfan is registered for use in Australia and is sometimes used as part of integrated pest management programs for apples (APVMA 2005). Pirimiphos-methyl is used in Australia, but not on apples (NRA 1999).
Readily available commercial hosts and winged adults but otherwise limited natural dispersal mechanisms 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 overall likelihood that R. auratus 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 that area and subsequently spread within Australia: VERY LOW.
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Consequences
The consequences of the establishment of R. auratus 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
Adults and larvae of R. auratus attack fruit crops, requiring active management during the growing season. Adults feed on plants and fruit and oviposit in the fruit. Infestation can cause considerable fruit drop (Hanson 1963).
Rhynchites auratus can cause great damage to host plants. It is described from the USSR as one of the most injurious insect pests of fruit trees (Kharin 1916; Lozhaunikas and Yakovishena 1978). In Kazakhstan, R. auratus weevils present in large numbers damaged up to 60% of apples in some trees (Khairushev 1970). Rhynchites auratus was reported in 1914 to reduce yearly peach orchard outputs by nearly 90% in Turkestan (Plotnikov 1914), and is known to infest up to 98% of cherry crops in Serbia (Lazarevic 1955) and 10-85% of cherry crops in Turkey (Ozbek et al. 1996).
Larval Rhynchites feeding has also been shown to encourage infestation of the fungus Sclerotinia fructigena (a synonym of Monilinia fructigena) (INRA 2006).
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Other aspects of the environment
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A – Indiscernible at the local level
There are no known direct consequences of R. auratus for the natural environment.
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INDIRECT
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Eradication, control etc.
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C – Significant at the local level
Programs to suppress and control R. auratus by insecticide applications, should this species become established, would not add significantly to grower costs of crop production. Insecticides which would also control weevils are used to control existing insect pests in Australian apple orchards.
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Domestic trade
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D – Significant at the district level
The presence of R. auratus in commercial production areas may result in interstate trade restrictions on a range of commodities such as apples, pears and stone fruit. These restrictions may lead to a loss of markets.
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International trade
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D – Significant at the district level
The presence of R. auratus in the commercial production areas of a range of commodities (apples and stone fruit) may limit access to overseas markets where this pest is absent. These restrictions may lead to a loss of international markets.
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Environment
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B – Minor significance at the local level
Additional pesticide application and other measures to control R. auratus could have additional effects on the environment. It is noted that insecticides such as synthetic pyrethroids are already registered for and used in Australian orchards to control other weevil species.
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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 apricot weevil
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Overall probability of entry, establishment and spread
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Very low
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Consequences
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Moderate
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Unrestricted risk
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Very low
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