Update: Dutch inspection identifies fern mite

The Netherlands Food and Consumer Product Safety Authority reported finding Hemitarsonemus tepidariorum at a fern plants producer in March. Now they have updated their finding, confirming it was in fact Hemitarsonemus ganeo (fern mite) that affected the greenhouse.

The identity of Hemitarsonemus ganeo could be confirmed on plants for planting of Platycerium alcicorne (fern plants) in a production greenhouse, which was detected in November 2015. Early September the mite was also detected outdoors on ferns (Polypodium vulgare, Dryopteris carthusiana, Dryopteris filixmas, and Athyrium filixfemina) in public green and natural forests at great distance from the first finding (approximately 100 km). No apparent damage was observed on the outdoor ferns, as opposed to the indoor ferns of Platycerium alcicorne. It is presumed that the mite has been present for a prolonged period in the Netherlands.

The mite may have escaped detection in the Netherlands due to the limited number of experts on Tarsonemidae. The identity was initially incorrectly determined as Hemitarsenomus tepidariorum.

The fern mite H. ganeo has been earlier reported outdoors in Poland (Magowski, 2012), and is closely related to Hemitarsenomum tepidariorum which has been recorded in the USA, UK and Costa Rica before, but its pest status worldwide is highly uncertain. Both species can cause damage on various fern species. No official eradication measures are considered at present, in view of outdoor presence both in the Netherlands and in Poland. Follow-up measures consist of communication to stakeholders.

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