The adult bugs are quite large, about the size of a thumbnail, and change colour as they grow, from green to orange to brown and then black. 

If you haven’t see them you would certainly be aware of the caustic and foul smelling liquid they eject - which is usually as a defence against predators like birds.

The liquid not only smells awful on contact, but also stains an orangey brown colour and remains for days afterwards unless washed off immediately.

 If there are only a few on the tree the damage is controllable, but large infestations can really affect the whole year's harvest.  So its important to catch them when they are at their most vulnerable.

Control

Therefore, as with most things in life, the key is to catch the problem early.  The Bronze Orange Bug‘s most sensitive stage is the first Tissue Paper Stage.  The eggs hatch in late autumn and the small nymphs (that are almost transparent like tissue paper) take up home on the underside of the leaves until spring.  It is at this stage the nymphs are most sensitive and you have the best chance of controlling them.

Spraying the leaves, particularly the undersides, with Eco-Oil will smother and kill the nymphs. 

Application is best done on a dry windless day. 

If you feel you may not have covered the leaves completely you can spray again a week later.

If you have missed this (late autumn) golden opportunity you will have to use a stronger chemicals like Pyrethrums to control the larger nymphs, this is not always successful and will discriminently kill all insects living on the tree.

For those of us who would rather not use chemicals the only other options are removal of the nymphs either by hand or with a vacuum cleaner. 

If you are taking them off by hand make sure you protect your hands and face from the bug’s caustic spray.  Place the bugs in to a plastic bag or drop into soapy water.  For those who don't mind squashing the bugs, a good technique is to wear a plastic bag over your hand, grab the bug then turn the bag inside out, you can then squash it without fear of being sprayed. 

Its also recommended to wear rubber gloves too though its amazing how the fingers can still become stained.

So remember 'A Bug in time saves nine'.  Put a note in your diary to spray your citrus tree with Eco or Pest Oil in July.