Final non-regulated risk analysis report for table grapes from the Republic of Korea

1.26Phomopsis cane and leaf spot

Phomopsis viticola ^{EP, WA}

Phomopsis viticola is not present in the state of Western Australia and is a pest of regional quarantine concern for that state.

Phomopsis cane and leaf spot, or dead arm, is caused by the fungus Phomopsis viticola. It is an important disease in several viticultural regions of the world (Nair et al. 1994), especially where rain following bud break keeps grapevines wet for several days (Hewitt and Pearson 1994). Phomopsis viticola is established in New South Wales, Queensland, South Australia, Tasmania and Victoria (Mostert et al. 2001; APPD 2010) but is not known to be present in Western Australia. The fungus overwinters in infected canes and rachises on the vine (Ellis and Erincik 2005). Pycnidium germination and conidia production require at least 10 hours of wet with relatively low temperatures (Rawnsley and Wicks 2002). A further 8–10 hours of very high relative humidity or surface wetness is required for infection to occur (Emmett et al. 1992).

Phomopsis viticola infects leaves, young shoots, rachises, petioles and fruit (Hewitt and Pearson 1994). Grapevines are susceptible throughout the growing season. After infection of juvenile fruit, symptoms do not appear until the fruit matures. On the fruit, the early symptoms are browning and shrivelling (Ellis and Erincik 2005). On rachises, the symptoms are chlorotic spots with dark centres (Hewitt and Pearson 1994). These spots enlarge to form dark brown streaks and blotches that turn black (Hewitt and Pearson 1994). Rachises may become brittle from numerous infections and break, resulting in loss of fruit (Hewitt and Pearson 1994). Pycnidia are subepidermal. Yellowish spore masses are exuded and then the berries shrivel and mummify (Gubler and Leavitt 1992). P. viticola conidia are splash dispersed and usually spread only short distances, i.e. within a vine or adjacent vines. Long distance spread is usually by movement of infected or contaminated propagation material (Hewitt and Pearson 1994).

The risk scenario of concern for Phomopsis viticola is the presence of the fungus on mature bunches of grapes.

P. viticola was included in the final import policy for table grapes from China (Biosecurity Australia 2011), which built on the import policy for table grapes from Chile (Biosecurity Australia 2005a). The assessment of P. viticola presented here builds on the China pest risk assessment. However, differences in horticultural practices, climatic conditions and the prevalence of the pest across Korea and China make it necessary to re-assess the likelihood that P. viticola will be imported into Western Australia with table grapes from Korea. The probability of distribution for P. viticola after arrival in Australia with table grapes from Korea would be similar to that for table grapes from China. The probability of establishment and of spread in Western Australia and the consequences the pest may cause will be the same for any commodity or country from which the species is imported into Western Australia, as these probabilities relate specifically to events that occur in Western Australia and are independent of the importation pathway. Accordingly, there is no need to re-assess these components, and the likelihood estimates for distribution, establishment, spread and consequences as set out for P. viticola in the China table grape IRA (Biosecurity Australia 2011) will be adopted for this assessment.

1.26.1Reassessment of probability of importation

The likelihood that Phomopsis viticola will arrive in Western Australia with the importation of table grapes from Korea is: HIGH.

Supporting information for this assessment is provided below:

• 
  P. viticola has been reported in Korea on grapes (APHIS 2002; Farr and Rossman 2010).
  
• 
  Berry infection, either direct or via infected rachis tissues (Erincik et al. 2002) can occur throughout the growing season, but most fruit infections occur early in the season (Erincik et al. 2001). Once present inside green tissues of the berry, the fungus becomes latent (Erincik et al. 2002) and infected berries remain without symptoms until the fruit is mature (Ellis and Erincik 2005).
  
• 
  P. viticola forms splash-dispersed conidia that infect leaves, young shoots, rachises, petioles and fruit (Hewitt and Pearson 1994). The teleomorph is not known. Infection is favoured by 20–30 hour wet periods during flowering (Rawnsley and Wicks 2002).
  
• 
  Visual symptoms first appear close to harvest when infected berries turn brown and shrivel (Ellis and Erincik 2005), and black pycnidia are produced through the skin (Gubler and Leavitt 1992). These pycnidia exude yellowish spore masses before the berries finally shrivel and become mummified (Gubler and Leavitt 1992). Infected berries may abscise from the pedicel, leaving a dry scar (Hewitt and Pearson 1994).
  
• 
  Recently infected rachises and fruit may not display symptoms and may be packaged for export.
  
• 
  P. viticola has been intercepted using visual inspection on table grapes exported from South Africa to Lithuania (Raudoniene and Lugauskas 2005) but has not been intercepted using visual inspection on table grapes exported from Chile to New Zealand (MAF New Zealand 2005), or to the USA, or on table grapes exported to Australia from California where the pathogen also occurs (Biosecurity Australia 2005a).
  

Infected rachises and berries remaining without symptoms until they mature, the ability and susceptibility of the berries for infection throughout the growing season and interception on grapes exported from South Africa all support a likelihood estimate for importation of ‘high’.

1.26.2Probability of distribution, of establishment and of spread

As indicated above, the probability of distribution for P. viticola will be the same as that assessed for table grapes from China (Biosecurity Australia 2011). The probability of establishment and of spread for P. viticola will be the same as those assessed for table grapes from Chile (Biosecurity Australia 2005a) and adopted for table grapes from China (Biosecurity Australia 2011). The likelihood estimates from the previous assessment are presented below:

Probability of distribution: LOW

Probability of establishment: HIGH
Probability of spread: MODERATE

1.26.3Overall 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 shown in Table 2.2.

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

1.26.4Consequences

The consequences of the establishment of P. viticola in Western Australia have been estimated previously for table grapes from Chile (Biosecurity Australia 2005a) and adopted for table grapes from China (Biosecurity Australia 2011). This estimate of impact scores is provided below expressed in the current scoring system.

Plant life or health C

Other aspects of the environment A
Eradication, control etc. D
Domestic trade B
International trade B
Environment B

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.

1.26.5Unrestricted 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 Phomopsis viticola
Overall probability of entry, establishment and spread	Low
Consequences	Low
Unrestricted risk	Very low

As indicated, the unrestricted risk estimate for P. viticola of ‘very low’ achieves Australia’s ALOP. Therefore, specific risk management measures are not required for this pest.