Problems From to Much Tropical Milkweed

OE Disease

 

A Protozoan Problem

That’s because of a protozoan parasite called Ophryocytis elektroscirrha(OE). This parasite, if eaten by monarch caterpillars, causes wing deformities in the adult butterfly and shortens their lifespan. Infected butterflies shed spores that can then go on to infect other youngsters.

OE isn’t usually a problem, though, because of two things: the butterflies’ annual migration, and the type of milkweed they eat. Infected monarchs will generally perish on the trip to Mexico, which helps control OE’s spread. And by the time they return, the native milkweed plants have died and new ones have grown up — another natural check on spreading the infection. But the tropical type of milkweed survives cold winters, and so does its pestilent guest.