Chomping & Chewing

I had two lovely Conifers in my garden but they both went brown and had to pull them out, also another one is going brown. Why do they do this I thought that they were an everlasting tree. I am thinking of planting more, so some good advice would be helpful thanks.
This kind of damage is quite often caused by a caterpillar. It can be accompanied by leaf webbing and browning. If you suspect that a caterpillar is the cause, then spray with Confidor every 2 to 3 weeks until browning stops.

We have two ponytails that have developed a little white bug on them and there is like a cottonwool appearance on the leaves. It looks like white powder. How do we get rid of these?
The white "cotton wool" is mealy bug. Small sap sucking insects that are quite difficult to control, but not impossible. For convenience, there is an aerosol spray available called Confidor that is effective against mealy bug. It can be used indoors and is odourless. Repeat sprays will be required.

My lemon tree has little piles of sawdust under some of the branches. The leaves on these branches are also quite yellow. Is this lemon tree borer?
It would appear so. The giveaway is the sawdust underneath. Borer larva tunnels and destroys stem tissues, eventually causing them to weaken and die - which is what is making the leaves look yellow. Spray with Conqueror Oil at any time of the year, or inject the holes that you can see with Kiwicare borer injector fluid.

I have a passionfruit plant that is growing over the fence between our house and my neighbours. When I walk down the fence line, hundreds of small browny coloured moth type insects fly everywhere. What are these insects, and how do I stop them from sitting all over my passionfruit?
These are passionvine hoppers. Spray with Mavrik - which is also a bee friendly product. Alternatively, you can use Natures Way Pyrethrum. A natural insecticide derived from the flowers of a chrysanthemum species.