I have some plants that I am rehabilitating... they were pretty big when they got topped and some of them have hollow open stems. Last year, I had a sickly underperforming pant in my blackbox and it turns out that an earwig had moved into the hollow stem. To avoid that happening on these plants, which are destined for another project, I am trying to find that black goop that you use to close up plant wounds. But I don;t know what it's called, making it a pain in the ass to source. Anybody?