I sprayed my clover today with a boomless atv sprayer and some of the spray hit my small trees that are in tree tubes, the tubes have vent holes and I'm afraid some of the clethodim hit the leaves, will it kill them?
Since Clethodim is a grassy plant killer, I don't think you have anything to worry about. I know how you feel though. I have several oaks that I planted too close to a crop field and the last 3 years they have been sprayed accidentally with RoundUp. It kills them back for about a month then they recover and continue to grow. But it scares me each time. My trees are older and larger than yours though. They are about 2 or 3 feet above the tubes with a lot of leaves to absorb the poison - and it still doesn't really kill them. I think you are OK.
Absolutely. If you don't keep the grass and weed competition down, they will soak up most of the water and hurt your tree growth. Mulch would be the best way to take care of this problem permanently if you can get it to your trees. I keep meaning to try it myself.