lets take a look at red spider mites, these are nasty little spider like insects that in large or small infestations can be hazardeous to trees. although name red spider mite they can range in colour including but not limited to black or green. spider mites are just visible to the human eye, a magnifying glass may help in identifying them, but the simplest way is to get an A4 size piece of white paper and tap the foliage of the tree, you might see little dots about the size of a pin head that will start moving around, this will tell you, you have a problem, on some indestations they can be quite readily seen as in the picture below, it speaks for itself. they will also make a visible webbing that looks like debris on the underside of the foliage.
Mites by themselves are not aggressive movers. They pretty much stay on the same leaf or nearby leaves for their entire lives. They are usually worst in dry dusty conditions.
now that we have identified them how do they do damage and how quickly?
Mites usually start becoming a problem in late spring and reach a peak by late summer or just at the peak heat of the season. They are definitely hot weather pests. damage is caused as they feed, bruising the cells with their small, whiplike mouthparts and ingesting the sap. Damaged areas typically appear marked with many small, light flecks, giving the plant a somewhat speckled appearance.
these will generally be but not limited to the older leaves or foliage. spider mite can be hazardous to a tree and if left unchecked can lead to death.
the life cycle of spider mite isnt a long one, generally about 7-10 days but they can reproduce at a very fast rate with mites being mature by the fifth day and have eggs laid by the end of their lifecycle.
this is where the control and iradiaction comes into it.
controlling spider mite can be a touch and go thing, they do have natural predators in the ladybird beetle, minute pirate bugs, big eyed bugs and predatory thrips (which we dont want near our trees either).
due to the spider mites lifecycle and how they can reproduce rapidly sometime chemical sprays need to have several applications to eradicate them all.
in years past white oil was used but is now tended not to be as it can clog up the pores of the tree/plant and possibly push your plant over the edge ( i know this from first hand experience
) chemical control of spider mite generally involves using a specific pesticide specific to spider mite and a second or even third dose might be necessary as pesticides wont penetrate the eggs so it needs to get them after they have hatched but before they can reproduce again.other control methods include using a jet spray of water blasting them off the tree, or a product like natrasoap can do the trick.
in wrapping up spider mite is better prevented than control and iradication as once the infestation reaches 40 mites per leaf the population can explode and more drastic measures will have to be taken, it could be a case of losing a lot of trees too.
as mites are more a dry hot weather thing by keeping up humidity a bit and constantly checking your trees you shouldnt have it explode to these amounts, after all we have to water our trees daily in most cases so spend the time and check your trees out aswell
if you have any personal experiences or anything to add, or questions please feel free to post it here, if we can create a database on pests and disease it will be a really good reference for beginners and more advanced
jamie
information sourced from evergreengardenworks.com re written by me.
pictures sourced from various locations on the internet
taking the top half of trees of since 2005! 
. I removed about 2/3 of the foliage after severing, but maybe that wasn't enough. I will have to watch it patiently til spring.
although it has lost its blueish hue it still looks quite healthy and im hoping that the original colour will return in time. After reading some more info and talking to a few nursery guys the notion that pest oil is less harmful than white oil seems to be correct however i probably wouldnt recommend it on your conifers unless you are happy with the colour change that happens from the oil on the foliage
