Gymnandrosoma aurantianum is a polyphagous pest of fruit trees, which occurs in Central and South America. Economic damage has been reported on Citrus, macadamia, cocoa, guava and some other tropical crops. The pest has been recorded on different hosts in different countries (for example, only on macadamia in Costa Rica despite the presence of other hosts in the same area). The reasons for this are not known. 

The main risk of entry relates to larvae in fruit. The pest has been intercepted on various fruits (commercial consignments and traveller’s luggage) in the EPPO region and the USA. The pathway with the highest likelihood of entry is Citrus fruit. Entry on macadamia nuts and other fruits were rated low and very low respectively, and there was a high uncertainty attached to entry with other fruits. For macadamia nuts, this was mostly linked to the fact that nuts are imported processed, and that there would be a risk only if they are imported fresh with husks. Fruits transported by travellers in their luggage are also considered a risk.

Hosts are widespread in the endangered area. However, the availability of fruit in the field is critical for the life cycle (larvae) and for the establishment of the pest. It is likely that the pest can maintain populations only in areas where host fruits are present all year round. Within the endangered area, Citrus fruit are present all year-round in the field at least in Spain and Turkey. However, the pest has a wide host range, and even where Citrus fruit are not present all year-round, other fruits may allow the pest to maintain populations. In any case, the gap between availability of Citrus fruit on trees (in orchards or other environments) in other countries of the endangered area may only be a couple of months, and there may be other fruits on host plants, such as pomegranate, loquat (Eriobotrya japonica) or peach. Even in areas where host fruits are not present all year round, transient populations may establish and cause damage.

The magnitude of spread was rated as moderate with a moderate uncertainty. Adults have a low flight capacity. Spread would be mostly human-assisted, through infested fruit and plants, especially with larvae inside fruit. Host fruits and plants for planting with soil or growing medium are traded in large quantities in the EPPO region.

In the endangered area, high potential impact is expected mainly where Citrus is grown all year-round. Citrus and other hosts (known and yet unknown) may be attacked. The presence of G. aurantianum will have negative effects on export markets due to interceptions and additional phytosanitary requirements.

Overall the EWG considered the phytosanitary risk to the endangered area to be high with a moderate uncertainty. 

The EWG proposed that phytosanitary measures should be recommended for Citrus and other host fruits; however, there is no approved treatment, and the only systems approach identified is not considered to be sufficiently effective (see other recommendations below). Finally, measures for plants for planting with soil or growing medium are listed, although the EWG did not think they were necessary.