Since 2000, several messages have enquired about mites on taro exported from Pacific Island countries to those on the Pacific rim, Australia and New Zealand in particular. The concern is the extra cost of treatment (fumigation) and a reduced shelf life.
In 1999 or thereabouts, consignments of taro reaching Australia from Fiji were fumigated because of the presence of mites. Questions arose on PestNet on the identity of the mite and whether there is a particular species involved and if so “is it a quarantine pest according to the IPPC definition, and if not, is it being treated as a regulated non-quarantine pest by AQIS. If the latter, it might be possible to negotiate some degree of tolerance by AQIS.”
It was thought to be particularly important to ask a) AQIS for the identification of the mite; and b) the exporter to check for the presence of the mite prior to shipment.
At that time, it was suggested that the best long-term strategy would be to tackle the cause of the problem, particularly since methyl bromide will not always be an option and, anyway, methyl bromide treatment reduces taro shelf life. Another questions raised was whether the mite was simply feeding on fungi associated with the taro, in which case it might be controlled indirectly by a fungicide at the packing stage, or perhaps the taro could simply be washed and dried before storage at the correct temperature.
Later, it was made clear that there are two mites commonly found on taro. The Tetranychidae are the spider mites and the ones likely to be causing damage on leaves. The common genera are Tetranychus and Oligonychus. Rhizoglyphus is a genus of mites commonly found “attacking” stored products. There is some debate as to whether they cause primary damage or whether they are secondary to fungal attack or other damage. As such they are not “normally” seen.
Later, in August 2003, it was reported that an expert at Landcare, New Zealand, had done a full revision of the genus Rhizoglyphus and will be publishing it shortly. R. minutus is the mite that has been found on imports of taro entering Australia and New Zealand.
Q-H FAN & Z-Q ZHANG (2003) Rhizoglyphus echinopus and Rhizoglyphus robini (Acari: Acaridae) from Australia and New Zealand: identification, host plants and geographical distribution. Systematic & Applied Acarology Special Publications 16: 1-16
Open access of full text of this paper is available from:
A more detailed account of this species with world distribution and host plants is at:
Fan Q-H & Zhang Z-Q (2004) Revision of Rhizoglyphus Clapar??de (Acari: Acaridae) of Australasia and Oceania. Systematic & Applied Acarology Society, London. 374pp.
The book also reviews many several other important species of worldwide distribution.
Limited copies of the hardback edition of this monograph are still available and can be ordered from the Treasurer of Systematic & Applied Acarology Society ([email protected]).
Reviews of biology and control of Rhizoglyphus echinopus and other bulb mites can be found in the book:
Zhang (2003) Mites of Greenhouses: Identification, Biology and Control. CABI Publishing, Wallingford, UK, xii + 244 pp (hardback).
Later still (May 2011), a moderator repoirted the following:
Part of the revision of Rhizoglyphus can be found at: http://hbs.bishopmuseum.org/fiji/pdf/fan-zhang2004.pdf According to the New Zealand Biosecurity Organisms Register for Imported Commodities (BORIC) website: http://www.maf.govt.nz/biosecurity-animal-welfare/pests-diseases/boric taro mite Rhyzoglyphus minutus is not a quarantine pest (regulated organism) for New Zealand. The current New Zealand requirement for taro is a Phytosanitary Certificate validating that the consignment of taro: “been inspected in accordance with appropriate official procedures and found to be free from any visually detectable quarantine pests, specified by the New Zealand Ministry of Agriculture and Forestry.”