Wednesday, March 20, 2013

The hunt for the toatoa gall mite

Here's an interesting challenge for everyone on NatureWatch NZ from entomologist Nicholas Martin. Nicholas is the creator of the Plant-SyNZ website of the insect herbivores on New Zealand plants. He's an expert on invertebrate herbivores, especially galling species. And he's found something surprising in Auckland and is keen for your help.

The toatoa bud gall mite, Aceria victoriae (Acari: Eriophyidae), lives on the common native plant, toatoa (or shrubby haloragis), Haloragis erecta (Haloragaceae). The mite was first discovered in a greenhouse at Victoria University, Wellington in 1956 and named and described by Graeame Ramsay in 1958. (Here's the holotype specimen at Te Papa museum.) Remarkably, it was not seen again, until Nicholas found it in 2012 in Auckland, despite his spending decades in Auckland documenting invertebrates feeding on native plants.

Nicholas first found bud galls on toatoa in October 2012 at Whatipu on the southwest tip of the Waitakere Ranges. He found them again in December, this time in the heart of urban Auckland in a native reserve in St Helliers.

The host plant is common in native bush, and the galls are obvious to a trained eye, so why is it so rare in Auckland? And where has it been all these years? Is it more common elsewhere in the country? This is an opportunity for other naturalists in New Zealand to see if they can find the toatoa bud gall mite.

The galls are easily recognisable (see the photos with Nicholas's observations at Whatipu and St. Helliers). The galls are red. Toatoa flowers and fruit are normally green, but may be red, so you need to look closely at the shoot with suspected galls to make sure they are not red fruit or flower buds.

If you find what you think are toatoa bud galls, please add your observations to our new project, the Hunt for the toatoa gall mite. Please be sure to include photo(s) with your observations. Nicholas would also appreciate a specimen if you're interested. And if you find some toatoa and there are no galls on it, that would be very useful to know too. In this case, you can enter an observation of the species and tick the "Sought but not found" box.

Good hunting!

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