- 3.6.1 Probability of entry
- 3.6.2 Probability of establishment
- 3.6.3 Economic consequences
- 3.6.4 Overall assessment of risk
3.6 Thrips obscuratus
3.6.1 Probability of entry
In the draft IRA there is very little information about the status of this pest on apple fruit. The majority of information presented by AFFA is related to the status of the pest on stonefruit crops. AFFA has assessed the probability of entry as high based on the assumption that the pest could hide in the calyx of the apple and would not be detected at on-arrival inspection. The assumption has also been made based on
information from stonefruit exports, that storage and transport would not affect the status of the pest. As mentioned previously, the storage and transport conditions of apples are unlikely to be equivalent with those of stonefruit and any assumptions made on the basis of this data are pure speculation by AFFA.
| New Zealand requests that AFFA take into account the differences in the pathways between stonefruit and apple crops exported to Australia. |
3.6.2 Probability of establishment
In assessing the risk of establishment, AFFA admits that although this pest has "probably already had many opportunities to reach the Australian environment", it has failed to establish. Despite this, AFFA have not taken into account this extremely low likelihood or the possible reasons for this. McLaren and Fraser (1998) suggested that summer temperatures above 34oC reduced either female fertility or egg viability. In laboratory experiments these authors found that mortality occurred above 35oC, with an LT95 at 35oC ranging from 1.6 hours in spring to 26 hours in April. Such temperatures are common in many parts of Australia from early spring, so low thermal tolerance may be partially responsible for the failure of this pest to establish in Australia.
AFFA assessed there to be a moderate risk of establishment (i.e., an even probability). However New Zealand suggests that the risk of establishment is very low.
| New Zealand suggests that the failure of T. obscuratus to establish in Australia and the low thermal tolerance of the pest demonstrates a very low risk of establishment. |
3.6.3 Economic consequences
AFFA has not presented any documented information on the damage to apple fruit or apple trees caused by T. obscuratus. Therefore it is difficult to estimate the economic consequences. New Zealand submits that this lack of information indicates this pest is not of economic importance and the economic consequences are not significant enough to warrant documenting.
| New Zealand believes that the economic consequences of T. obscuratus are negligible. |
3.6.4 Overall assessment of risk
AFFA has concluded that the overall unrestricted risk estimate for this pest is low. MAFNZ suggests that this pest should actually fall below the ALOP on apples as it does when intercepted on other crops from New Zealand. This is supported by the failure of the pest to establish in Australia and the very limited economic consequences.
| New Zealand believes that T. obscuratus presents an unrestricted risk estimate of negligible. |
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