it sounds like you are able to grow the dendrobs outside in all weather.
This link http://www.anbg.gov.au/emblems/qld.emblem.html
is to the state flower of Queesland Austrailia as I feel that it gives good info on this species and it is used in breeding the hard cane dendrobs like you grow.
When misting ,mist the whole plant not just the roots as if that red mite is the same as we get here ,it is an indication that the humidity is not high enough (they dislike water).
During the dry season there is now water and humidity could be quite low.BTW in the natural habitat from about the 1/2 way point in the dry season these plants can be subjected to bush fires.In the wet season it is quite common for a tropical down pour everyday in the mid to late afternoon.
I found this artical and it may also help
Dendrobium bigibbum (Lindley 1852 ) by Len Field
Common name of Cooktown orchid.
This species was first named by Lindley in 1852 and since then has had over 40 name changes but these have now been reduced to just two in recent times by Clements who has reduced all synonyms to just three species Dendrobium bigibbum is one and sub variety compactum is now known as Dendrobium liphocola (growing on rocks) with D.phalaenopsis the third.This may reduce some confusion but can also lead to more confusion especially when one considers the many hybrids that have these species as one of the parents,so I will continue to refer to them by the names of Dendrobium bigibbum var.bigibbum , Dendrobium bigibbum var. superbum and the sub variety compactum.
(Editor - the new names are gaining recognition. It would be best to use the new names as the differences warrent species rank.)
While looking through old bulletins I came across the following article which I will reproduce here The name Dendrobium bigibbum was given to the species in 1852 by Lindley for a plant that had been collected on Mt Adolphus Island which lies about 18 kilometres north of Cape York. To confuse the issue , in 1880 Fitzgerald described a plant growing in the garden of a Captain Bloomfield at Balmain, Sydney and named it Dendrobium phalaenopsis this plant was reported as coming from Cairns. However, botanists to-day are convinced that no such plant fitting Fitzgeralds description has originated in Australia Fitzgeralds description better fits plants from Larat, An island in the Timor Laut group in Indonesia.This was further confused by a collector by the name of Micholit, who, to hide the true location had given North New Guinea as the location of plants fitting Fitzgeralds description that were sent to Sander by him, and apparently also came from Larat, as did plants collected by H.O.Forbes who was more honest about the location of collection. Most of Forbes plants finished in the collection of Baron Schroeder and became known as Dendrobium schroederianum.
In 1964 S.T.Blake, a Queensland botanist, successfully sorted out the identification of Queenslands floral emblem the "Cooktown orchid". His paper was published in the Proceedings of the Royal Society of Queensland 1964, and a condensed version can be found in the Australian Orchid Revue, March 1966. As many as forty names have been given to Dendrobium bigibbum and its variations. However, it is now considered there are only two valid varieties, one with two sub varieties.
Dendrobium bigibbum var bigibbum
Occurs on Cape York Peninsular from the Archer River northward and extends to the Torres Strait Islands, preferring slender trees in dry scrub areas. the flowers of this variety are usually smaller than the next variety and usually have a white crest on the labellum.
Dendrobium bigibbum var. superbum
Has two sub-varieties. Subvariety superbum is the one considered to be the "Cooktown orchid"and is found from the Archer River south to Mt. Molloy, and grows under similar conditions to Dendrobium var. bigibbum
Dendrobium bigibbum subvariety compactum is apparently confined to the Macalister Range between the Barron and Mossman Rivers, and grows on rocks quite often exposed to the sun. It differs from the others in its short robust stems. All varieties are usually autumn bloomers. The above extract was taken from An article written for A.N.O.S Newcastle Group March 1977 by George Hillman. When Dendrobium bigibbum was made the floral emblem of Queensland in 1964 it caused great controversy as coming from one localized area many thought it did not truly represent the state also it almost led to its extinction in the wild due to extensive collecting. I can always remember the only time I went looking for Dendrobium bigibbum for having been told where I could find sub variety compactum I decided to make a solo expedition to find it and after walking for klms across reasonably flat country covered in Ti tree where I found one very small plant on a rock face overlooking a gully but while trying to get a closer look I made the mistake of climbing a small tree and was immediately covered in green ants which was not a very pleasant experience. After that I lost most of my enthusiasm for looking for this species. Flowering can take place from January through to November but is usually in the Autumn months. Flowers can range in colour from white (rare) through to deep purple with 3 to 15 on peduncles 15-20 cm long and can vary greatly in size but usually about 3 to 5 cm in diameter. Many beautiful hybrids both natural and man made with this species as one of the parents have been made with one Dendrobium x. superbiens (Dendrobium bigibbum x Dendrobium discolor coming to mind as one of the better known natural crosses.
Cultivation Some warmth may be needed in the colder areas but I have found that D. sub variety compactum does seem to be more cold tolerant, this no doubt is due to there lithophytic nature. Years ago it was unusual to find anyone growing any of these species in pots ,usually it was tied to a tree fern slab or a piece of hardwood etc, but now the better grown plants seem to be found growing in pots with a well drained compost. This can be partly due to the fact that many of these plants have Sub variety compactum in there ancestry and being lithophytic adapt better to this environment. As a point of interest a lot of growers are now growing many types of species in pots which years ago was unheard off for instance Dendrobium tetrogonum to name one. Watering is also very important while they need a good supply in our summer months a good way to ruin a plant is to water in the winter remember they come from a tropical area where the winters are very dry.