ARTICLE : Biosecurity Watch – Unnamed Whitefly

Whitefly adults on Melicytus obovatus.

Whitefly on Melicytus lanceolatus.

Immature whitefly stages on Melicytus.

 December 2004 - Keep Watch for Unnamed Whitefly

It’s Biosecurity New Zealand’s mission to reduce the risk to New Zealand from introduced unwanted pests and diseases.   But it is not always obvious whether an organism is actually new to New Zealand, as many of our unique organisms are not known to many people, including scientists.

Potentially, one such insect is a recently discovered unnamed whitefly, found infesting some species of Melicytus in Christchurch.   Biosecurity New Zealand is now investigating other regions to see how widely distributed this whitefly may be and is particularly interested in the Wellington / Wairarapa and Marlborough / Nelson districts.

Very little is known about the biology of this whitefly or whether it is exotic or endemic. The new whitefly has however, been found only on the New Zealand endemic genus Melicytus (including the common mahoe / whiteywood).   Whitefly numbers have been observed to be highest on Melicytus flexuous and M. obovatus with lower numbers on M. alpinus, M. ramiflorus, and M. lanceolatus.

In general, whiteflies can cause direct damage to plants by sucking sap from leaves. Indirect damage is caused by the growth of sooty mould on the honey dew excretions of immature whiteflies which leads to physiological disorders in the plant.   Sooty mould is often the first sign of infestation.

If you are out and about, or if you have Melicytus in your garden, have a close look to see if whitefly is present.   Another clue may be the presence of black sooty mould which grows on sugary secretions excreted by immature whiteflies.   It is the nymphs or pupae stuck to the underside of the leaf that are required for identification.   If what you see looks similar to the pictures below or at www.biosecurity.govt.nz/whitefly, please collect a leaf sample into a plastic bag, place in a non-breakable container and send to:

Freepost 120201, Whitefly Survey, MAF Laboratory, PO Box 24, Lincoln, Canterbury 8152.

Please include your contact details, the date and location of collection, and the species of Melicytus.   Keep Watch and we can all protect New Zealand.

For further information see MAF web site www.biosecurity.govt.nz/whitefly.

 April 2005 - Update on whitefly

In a previous newsletter article, Biosecurity New Zealand asked for assistance in searching for a new whitefly on Melicytus.   Since this request, a Landcare Research Ltd Scientist, Rosa Henderson, found uncatalogued specimens of the same whitefly on Melicytus micranthus collected from Riccarton Bush, Christchurch, in 1954.   Rosa’s discovery clearly shows that the whitefly is not a new organism to New Zealand.   It also suggests that the whitefly has more features in common with an endemic species than an exotic.   Biosecurity NZ has decided to stand down its investigation given this new information.   It has also advised that control of the whitefly, where it occurs in high numbers and causes damage to plants, is at the discretion of affected parties.

Biosecurity NZ thanks all those who have searched for this whitefly and would be happy to receive any new distribution records if reported.