My plum tree is a baby. I noticed the leaves were being eaten and found these yellowish caterpillars that bite or sting. Are they the enemy? If so, how do I destroy them?
Cool (though maybe not the getting stung part). I'm fairly certain these are Io moths (scroll down to figure 12 in this page for comparison: io moth - Automeris io (Fabricius) -- you'll be best to judge, since the colour is a bit difficult to tell in the photo with them being shaded. That said, yes, it looks like Prunus (of which plum trees belong to) is one of the preferred host plants. Control option, if you are so inclined, looks like a Bt spray according to that article. I think they're pretty cool and insects are having a tough go of it right now--so I'd probably do something like *very* carefully moving them (with tools and gloves) to a different kind of host plant that they like (there are a number on that list). Or, since these are almost in the last stage of their caterpillar development, doing something like cheesecloth around unaffected branches for the next couple weeks to maintain the plant while allowing them to munch away on the leaves of a few other branches.
