We do not recommend bleaching monarch eggs or milkweed.
Motivation is high to save monarch populations, but the MJV joins many other organizations and entities in discouraging the practice of informally rearing monarchs at home. While captive rearing has been successful in laboratory settings for other at-risk species, this approach is not yet warranted for monarchs, and recent research illustrates that informal captive rearing by individuals may pose significant risks to monarchs, including disease and lower migration success.
Of particular concern to conservation organizations is the practice of raising monarchs in groups without proper sanitizing procedures. In a healthy environment, there would be no reason to bleach monarch eggs or milkweed. The only time bleaching occurs in a laboratory setting is when disease has already been introduced to the rearing environment.
Monarchs did not evolve under high-density conditions, so larvae reared in close proximity are highly susceptible to disease, including OE. If the parasite goes undetected, an infected adult can easily transmit OE spores to its offspring or other larvae in the same container. Keeping adults and larvae together can lead to very high infection rates; inadequate sanitizing can result in OE spore transmission long after infected individuals are gone. While OE is a naturally occurring monarch parasite, captive rearing may inadvertently increase its spread.
If you are raising a few monarchs for enjoyment or education, please do so as part of an established community science program, so that your observations will contribute to that program's research objectives. If a monarch is exhibiting symptoms of OE, please report your observations to Project Monarch Health.
For more information on the risks associated with rearing monarchs, and a list of community science programs where tagging or small-scale rearing are part of the research objectives, please see our Rearing Monarchs: Why or Why Not? handout.