To keep the netting off the trees we drive 4 star posts into the ground around the drip line of the tree
Then we slip 2 lengths of poly pipe (two inch) over the posts and over the trees as hoops.
The posts give you a nice bit of rigid vertical height
Two inch diametre pipe is easiest to use because it slips straight over the star posts
If you have a large tree the poly will not be able to support itself and might collapse in the heat. I this case you may need to thread a piece of PVC electrical conduit up the pipe to help keep it rigid. Conduit is one of those things you can find dumped somewhere. Coduit does brea down when left exposed to sunlight for more than a few years, whereas poly last for ages.
You can either crisscross the hoops and join them where they cross (this is easiest but reduces the total volume enclosed) or you can create a series of parallel arches and connect them with a piece of light weight rigid material (we use a type of framing steel call top-hat). You will probably need to do a little bit of diagonal bracing with wire to stop the structure collapsing.
If you have a row of trees this is best because you can carry on the pattern indefinitely.
Then all you need to do is get your bird netting over your structure. Spare bits of poly pipe are good for poking but you will need a friend or two to help.
You can buy the star posts and the black poly pipe from rural supply stores or maybe a hardware store.
have fun.
n