Glider

I had the same problem. I have one or two trees with wound sealant on large branch cuts and I noticed the sealent was being removed over a period of days and there were strange marks in it, sort of long shallow grooves carved into the sealant, but not big enough to be squirrels (my first thought).

Turns out to be snails. They'd been rasping away at the stuff for weeks. I don't know why they like it, but I'm not too bothered. They don't do any other damage and they actually do a very good job of cleaning algea off the pots.

I use terracotta 'Dutch' pots as training pots and they can get covered in algae. I noticed a couple of summers ago that they seemed to be cleaning themselves, but closer inspection revealed the same long meandering tracks as in the wound sealant and looking under the benches I found a bunch of snails nestling between the slats. I've never had to scrub a training pot since I moved here.

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