Question and Answer

What are common monarch diseases or problems?

It can be difficult to identify exactly what the problem with any specific monarch is, but here are a few common ailments that affect monarchs.

Monarch caterpillars often turn black or darkish in color when they are sick with bacterial infections. This is often referred to as 'black death.' There are a number of other bacterial infections or viruses that monarchs can get as well. If the chrysalis has darkened, it could either have an infection, like previously mentioned, or it could have been parasitized by a fly or a wasp.

Monarchs also may have O.E. (Ophryocystis elektroscirrha). OE is a protozoan parasite that infects monarchs. You won't be able to tell if a monarch has OE until it's in the pupal, or even adult, stage. Sometimes adult monarchs infected with OE appear normal. You cannot be sure that a monarch is infected without testing it.

OKIf you are raising monarchs, and do notice that something is wrong, you should isolate the monarch from others, if you aren't already raising them in separate containers. In between caterpillars, be sure to bleach everything, regardless of whether or not they appear "sick." You can read the 'Rearing Monarchs Responsibly' handout for more information.

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