Be especially thorough on cut ends. Creosote could be used but it tends to fade quickly and you must follow sensible precautions and allow at least one month for harmful chemicals to subside before using the bench for trees. To extend the life of your bench it should be treated with a plant friendly preservative every other year. Metposts or short steel rod legs raise the timber, preventing rotting at the most vulnerable point where it would otherwise constantly be in contact with damp soil. If steel rods are used, they can also stop many crawling insect pests.
All container plants are therefore at risk.
This is filled with beer, water or insecticide. It will stop Vine Weevils and help prevent slugs from reaching their favoured victims such as Mulberry, Laburnum and Maples. Another alternative is to spread a band of sticky grease around each bench leg. Neither will stop flying pests, like greenfly, but will help prevent crawlers and sliders. Construction A willing and able helper will make the job much more manageable and should also more than double your rate of progress.