If you have really bad outbreaks of OE, I suggest cutting back your plants so they will produce new leaves that are (hopefully) OE free. And if you raise the caterpillars inside, wash everything that comes into contact with them with a vinegar solution. We got it really bad at the museum once and that's what we did. I've heard it gets worse in late summer since it has had several generations to pass to at that point. I haven't had too many problems with OE in a while, but those parasitic flies get way too many of my Monarchs.
