You may have seen thousands of those chinese-made tree guards staked-out alongside state highways, local roads and lifestyle-blocks, etc. The version that is either coir mat or some sort of recycled cardboard-fibre product are ok and do the job, although they can be expensive and cumbersome. However the green plastic ones don't make sense.
You may think we're biased and pushing our own product...well of course we are...but why not use a natural repellent instead of plastic? I mean why plant a tree then add more plastic, it seems counter-productive?
Here's some reasons why they are silly:
They are an eyesore and blight on the landscape
They often end up being ripped out by the wind then flap loose across the landscape as litter
Some of them purport to be biodegradable...well that's just green-wash bollocks! All they do is breakdown into smaller bits of shredded plastic and litter the ground for years, then at sometime in the future breakdown to small bits of micro-plastic that enter and pollute the soil. There is nothing "green" about them, except for the colour.
Despite the type of tree-guard used a decent sized hare/rabbit or deer can still eat the top of the seedling
Tree guards are sometimes over $4 per tree whereas FATBANG is 20c per tree.
Good management should necessitate a regular visit to your seedlings anyway to weed, replace missing guards, prune damage, etc so why not just do another spray every 6 months?