Look at a Hypro 9910-D813
Kevin if he is using a D30 pump or equivalant he cannot get enough volume to get 50 to 75 feet in a tree.
In order to get that high you must have the following;
Sure you can get high psi pumps but they wont give you the hight you need to spray trees. That takes volume. Both of these listed above will get you up there. The next thing is the right gun.
If you have a lesco you probably have a Hyrpo D30 pump. 580psi 8.5gpm max.
When you pressurize water, it brings the volume down a cosiderable amount.
Next you need horse power to run the pump. A 5.5hp Honda wont do it. Need around 8hp.
You will be lo0king in the range of $1500 for pump an engine.
$500 electric rewind hose reel
$350 for 300' of 800psi hose
Tank from a 200gal for $180 to .................
The rest is all lower costing parts that add up fast.
Also you will most likely need a skid aprox $400