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1.14Citrophilus mealybug [Hemiptera: Pseudococcidae]

Pseudococcus calceolariae ^EP

Pseudococcus calceolariae (citrophilus mealybug) is not present in Western Australia and is a pest of quarantine concern for that state.

Pseudococcus calceolariae belongs to the mealybug family Pseudococcidae which consists of small, soft-bodied insects that are covered with a mealy wax secretion (Charles et al. 2000). Mealybugs can rapidly increase to large numbers and cause significant damage by extracting plant sap, excreting toxic salivary compounds, and secreting honeydew which serves as a substrate for the development of sooty moulds (El-Sayed et al. 2010; RBG 2012b). Pseudococcus calceolariae is native to Australia (RBG 2012b) and is a serious pest of citrus in South Australia (Smith et al. 1997; Gullan 2000) and a minor pest of citrus in Victoria and New South Wales (Gullan 2000).

Eggs are laid in a cottony sack containing up to 500 eggs (Smith et al. 1997). Female mealybugs develop from an egg through three nymphal (instar) stages before undergoing a third moult into the adult form (Smith et al. 1997). Adult females are slow moving, oval-shaped and 3-4 mm long (Smith et al. 1997). Males develop from eggs through first and second instar stages, form pupa, and undergo a third and fourth moult into small, winged adults with long tail filaments (Smith et al. 1997). Females, prior to egg laying, and males, after the second instar stage, stop feeding and find protected locations under vegetation or bark (CABI 2011). In Australia, the lifecycle takes around 2 months in summer and 3-4 months in winter (Smith et al. 1997).

The risk scenario of concern for P. calceolariae is the presence of nymphs or adults on table grapes from California.

Pseudococcus calceolariae has been assessed in the existing import policies for table grapes from Chile (Biosecurity Australia 2005). The commercial production practices in Chile and California are similar, and although table grapes are harvested at different times of year, this mealybug does not overwinter and the risk of distribution is comparable for table grapes from both regions being imported to Australia at any time of year. The wide climatic variation across Australia means that conditions are suitable for entry, establishment and spread somewhere in Australia all year round. Furtheremore, the probability of distribution, establishment and spread of P. calceolariae in Australia and the consequences it may cause will be comparable for table grapes imported into Australia from any country as these probabilities relate specifically to events that occur in Australia and are independent of the importation pathway. Accordingly, there is no need to reassess these components, and the risk ratings for distribution, establishment, spread and consequences, as set out for P. calceolariae in the final import risk analysis report for table grapes from Chile (Biosecurity Australia 2005) will be used for this assessment.

1.14.1Probability 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 P. calceolariae will arrive in Western Australia with the importation of table grapes from California: LOW.

Supporting information for this assessment is provided below:

• 
  Pseudococcus calceolariae is present in the state of California (Smith et al. 1997; Waterhouse and Sands 2001; Daane et al. 2008; Ben-Dov et al. 2010). It was first detected in California in 1913 and had become a serious pest by 1928. Effective control of the pest was achieved when two parasitoids, Coccophagus gurneyi and Tetracnemoidea brevicornis, were introduced from the Sydney area (Waterhouse and Sands 2001). Although these parasitoids reduced the pest to low numbers (Waterhouse and Sands 2001), it is still considered to be a pest of citrus in California (Grafton-Cardwell et al. 2012) and could therefore be present on table grapes grown in California.
  
• 
  Pseudococcus calceolariae has a wide host range, infesting plants belonging to 40 families, including grapevine (Ben-Dov et al. 2010).
  
• 
  Although P. calceolariae is present in the USA and is a pest of citrus in California (Grafton-Cardwell et al. 2012), it is reported to be rarely found in North American vineyards (Daane et al. 2011).
  
• 
  Juvenile and adult stages of P. calceolariae seek out fruit and sheltered sites (Smith et al. 1997). On grapevine, mealybugs are most prevalent in dense canopies and tend to be located in sheltered positions such as the underside of leaves, inside curled leaves, between bud scales, under bark, and inside grape bunches (Furness and Charles 1994). If P. calceolariae are present in sheltered locations inside grape bunches, such as between touching fruit, they are likely to be overlooked during pre-export sorting and packing processes.
  
• 
  Although native to eastern Australia (Smith et al. 1997; RBG 2012b), P. calceolariae has invasively spread and now has a world-wide distribution due to trade in plants and plant products.
  

The presence of this pest in California, its association with grapevines and its cryptic nature are moderated by low pest prevalence in California and infrequent detections in North American vineyards. This support a likelihood estimate for importation of ‘low’.

Probability of distribution

The probability of distribution for P. calceolariae is being based on the assessment for table grapes from Chile (Biosecurity Australia 2005). That assessment used the same methodology as described in Chapter of this report. The rating from the previous assessment was MODERATE.

Overall probability of entry (importation  distribution)

The overall probability of entry is determined by combining the probabilities of importation and of distribution using the matrix of rules shown in Table 2.2.

The likelihood that P. calceolariae will enter Western Australia as a result of trade in table grapes from California and be distributed in a viable state to a susceptible host is: LOW.

1.14.2Probability of establishment and spread

The probability of establishment and of spread for P. calceolariae is being based on the assessment for table grapes from Chile (Biosecurity Australia 2005). That assessment used the same methodology as described in Chapter of this report. The ratings from the previous assessment are:

Probability of establishment: HIGH

Probability of spread: HIGH

1.14.3Overall probability of entry, establishment and spread

The overall probability of entry, establishment and spread is determined by combining the probability of entry, of establishment and of spread using the matrix of rules shown in Table 2.2.

The likelihood that P. calceolariae will enter Western Australia as a result of trade in table grapes from California, be distributed in a viable state to a susceptible host, establish in Western Australia and subsequently spread within Western Australia is: LOW.

1.14.4Consequences

The consequences of the establishment P. calceolariae in Western Australia have been estimated previously for table grapes from Chile (Biosecurity Australia 2005). That assessment used the same methodology as described in Chapter of this report. The ratings from that assessment can be used in this review for Western Australia because the geographic level in the consequence impact scores did not exceed Regional. The estimate of impact scores from that analysis is provided below:

Plant life or health D Significant at the district level

Any other aspects of the environment A Indiscernible at the local level

Eradication, control, etc. D Significant at the district level

Domestic trade D Minor significance at the regional level

International trade D Minor significance at the regional level

Environment A Indiscernible at the local level
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 ‘D’, the overall consequences are estimated to be LOW.

1.14.5Unrestricted 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 Pseudococcus calceolariae
Overall probability of entry, establishment and spread	Low
Consequences	Low
Unrestricted risk	Very low

As indicated, the unrestricted risk estimate for P. calceolariae has been assessed as ‘very low’, which achieves Australia’s ALOP. Therefore, no specific risk management measures are required for this pest.