You know what I use is those 55 gallon plastic drums and I'll cut those in half and I cut a bunch of drain holes in the very bottom of it.... nothing can borrow through that plastic that lives in the ground between 0 and the bottom of the Barrel there's not a whole lot of things that are cruise around below 6 or 7 in anyways so if you got that Barrel in the ground with a couple inches above the ground you got plenty of dirt in there to do the job and nothing's going to get through it unless it can crawl up and over the side.I was just guessing how big I dug the hole before I added my soil, I didn't use a pot. Looks like 25 gallon works pretty good. My thinking is they can't borrow threw the pot to get to the stem. They eat right threw the stalk at ground level or just below and thats all they eat.
If you don't have access to plastic barrels like that then you could use plastic totes just get the big ones drill holes in it put in the ground do the same job.