- 3.7.1 Pest categorisation
- 3.7.2 Probability of entry
- 3.7.3 Probability of spread
- 3.7.4 Economic consequences
- 3.7.5 Overall assessment of risk
3.7 Eriophyes mali
3.7.1 Pest categorisation
Eriophyes mali was separated from the closely related species Eriophyes pyri in 1970. According to Manson (1984) the most practical criterion for their separation is host specificity. It is recorded by Naumann (1993) that E. pyri (pearleaf blister mite) is present is Australia, and it is recorded by McMaugh (1986) as being present on pear, apple, quince, mountain ashes, hawthorn and cotoneaster. Burts (1970) reported that E. mali could only establish on apple and E. pyri could only establish on pear.
| New Zealand requests that AFFA provide documentation that taxonomists have examined specimens of E. pyri from apple and pear trees in order to confirm whether or not Australia has both E. mali and E. pyri. |
3.7.2 Probability of entry
The probability of entry of this mite into Australia has been assessed by AFFA as moderate (i.e., an even probability). New Zealand considers this risk to be overstated in light of the information presented here. The mites will only survive for a limited time on discarded fruit, they have limited mobility and would need to attach to other insects to be transferred to their only host.
E. mali occurs primarily on foliage and only occasionally on fruit. In the original data sheet prepared by Landcare Research it was noted that these mites were not likely to occur on fruit. Furthermore, the pest has never been found on harvested apples during the USDA pre-clearance program which has been running for over 20 years. The record on the New Zealand pest list is one from Malus domestica, with no part of the plant specified. This has been left on the pest list because of the "possibility" that it may also occur on fruit.
AFFA states that eriophyid mites have been found during on-arrival inspection of New Zealand cherries and suggest that this is a sign that the mite survives storage and transportation. AFFA failed to take into account that storage and transport systems are not equivalent between apples and cherries. It would be more correct to say that the effect of storage and transportation on E. mali is unknown.
Burts (1970) reported that it was very difficult to establish populations of E. mali on apple seedlings, concluding that these mites "do not become easily established on these trees". When the likelihood of these mites occurring on imported fruit, the effects of transportation and storage, of surviving in the environment, and of being transferred to their only host is taken into account New Zealand believes that AFFA has over-estimated the probability of entry. New Zealand believes that a more reasonable interpretation of the scientific evidence is that the risk is very low.
| New Zealand believes that the risk of establishment is very low |
3.7.3 Probability of spread
If established, the mites are likely to be detected because they cause blisters on the underside of leaves that are quite visible. This would likely lead to eradication of the population before spread. To spread to other apple trees, they would need to attach to other insects or plants, or be transferred through nursery stock. AFFA's statement that existing movement controls on nursery stock would control the spread supports this view. New Zealand believes that the probability of spread is very low.
| New Zealand believes that the probability of spread is very low. |
3.7.4 Economic consequences
Very little published literature is available on this pest, indicating that it is not a serious pest of apple. No information is available on the loss of yield (if any) caused by the mites, but the pest is not recognised as a serious concern for New Zealand apple growers. New Zealand suggests that AFFA could obtain some information on the impact of the closely related E. pyri which occurs in Australia.
AFFA's assumption that Asian trading partners may reconsider phytosanitary measures if this pest becomes established in Australia are unjustified. New Zealand exports apples to the same countries and no measures other than phytosanitary inspection are required. While AFFA's assessment of the economic consequences may take into account these unknown factors, in light of the minor status of this pest,
| New Zealand considers that the economic consequences of establishment of E. mali should be assessed as very low. |
3.7.5 Overall assessment of risk
| New Zealand believes that AFFA’s overall assessment that the unrestricted importation of New Zealand apples presents a low risk of the introduction of E. mali is an over-estimate. New Zealand believes that the risk is very low. |
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