Information note prepared by Richard Piper, Scientific Advisory Services
In November 2014, a red spider mite was found on several banana plantations around Innisfail and the Atherton Tablelands during crop monitoring, which looked quite different to the normal red spider, Tetranychus lambi that is found here. T. lambi will be referred to as ‘banana spider mite ‘ in the rest of this article.
The new mite was red in the adult stage and produced a silvering on the underside of the leaf, as a result of feeding, whereas the banana spider mite adult is greenish in colour and produces a lighter yellowish colour at the feeding site which later turns brown.
The mite was brought to the attention of Biosecurity Queensland who subsequently confirmed that the mite was a different species that had previously only been found in the Northern Territory. The mite was identified as Tetranychus gloveri and has no common name although it has been called the cotton red spider mite in the United States.
Damage is mostly confined to the undersides of the leaf and results in a silvering of the leaf.
The conditions that have occurred in the spring and early summer of 2014 have been unusually dry and hot. Innisfail has only received 5- 15% of its average rainfall for the 3 months from September to November.
Under these conditions banana spider mites have increased rapidly and it is not surprising that the T. gloveri populations have been found during these conditions. The conditions favouring the new mite will be likely to be the same as those favouring the banana spider mite.
The new mite produces a large amount of silk webbing on the leaf underside and tends to prefer to feed along the midrib of the leaf or in folds of the leaf. The eggs and the motile stages (nymphs and adults) are scattered amongst the webbing and when viewed through a magnifying glass can be seen to be distributed throughout the web, not just sitting on the leaf surface. The banana spider mite does not produce significant amounts of this webbing and all stages are on the leaf surface.
The adults of T. gloveri are dark pink to red in colour and are very obvious on the leaf surface compared to banana spider mites. The adults may be slightly larger than banana spider mite adults.
The younger nymphs of both species appear similar and are generally clear with green markings on each side of the body hence the common name “two-spotted mite”.
T. gloveri has previously been found in the Northern Territory and the finding of the species in north Queensland is regarded as a range extension so that Biosecurity Queensland (BQ) will be taking no action against this species. The mite is found on numerous weeds, crop and ornamental plants.
The control of T. gloveri is likely to be achieved using the same strategies as are used for banana spider mite control. The biological control agents including the mite eating ladybird, Stethorus sp. and predatory mites have been observed preying on T. gloveri, so that management practices should be performed to conserve these beneficials. The miticides currently registered for banana spider mite control appear to be providing control of T. gloveri. It is not considered that this species will be any more difficult to control than the banana spider mite, which is widely spread in north Queensland banana growing areas.
I would like to thank Paul Edwards, Cropwatch Information Services and Hannah MacKay for assisting with the photography of the mites in the field. Delina Connell (Scientific Advisory Services) assisted with production and upload of the article to web. I also wish to thank the grower who allowed me access to his property to inspect and photograph the mites.
Scientific Advisory Services Pty Ltd does not make any representations or warranties in respect hereof and expressly disclaims any liability for loss, damage or expenditure of whatsoever nature, which may result from reliance on the contents of any advice given.
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