While there are a number of milkweed varieties that one can grow in Missouri, many of them don’t last very long and could be expensive if you want to grow a large patch. Asclepias curassavica is an annual variety that blooms all summer long and is both a great nectar plant and host plant. There have been a number of questions about it so I thought I’d review some of the research.
Ophryocystis elektroscirrha, or OE is a disease that Monarchs get and will kill them. The problem is theorized that OE will last over the winter on plants in southern states where the plants will over-winter. That’s not a problem in Missouri when you start your milkweed from seed. I do take cuttings from some plants later in the year and root them for new plants the next year. I cut off almost all the leaves so there shouldn’t be many or any possible spores. I also get so few Monarchs these days so OE should definitely not build up. In 2012 I didn’t get a single Monarch larvae. I’m not concerned about this potential problem in Missouri.
Dr. Lincoln Brower says this, “Another problem with establishing what becomes a continuously breeding population of monarchs is that the incidence of the protozoan parasitic disease (Ophryocystis elektroscirrha) increases with time. If the diseased individuals then somehow end up breeding with or joining the overwintering clusters of monarchs, then the incidence of the disease will very likely rise with detrimental effects on the migratory monarch populations.” Professor Sonia Altizer at the University of Georgia, who is the World expert on O. e., agrees with me.
Does Curassavica cause Monarchs to leave Diapause?
Diapause is the period of time when the last generation of Monarchs stop maturing sexually. They need to use all their energy for their flight to Mexico and their hibernation while there. Leaving diapause will probably not be a good thing for any Monarch on its journey to Mexico.
Dr. Karen Oberhauser replied to an email I sent to her and said this. “There is fairly good evidence that milkweed in good condition in the fall causes monarchs to break diapause, at least in TX.”
Karen sent me to a great website which has lots of great Monarch butterfly material. http://monarchjointventure.org/
Dr. Lincoln Brower also corresponded with me and gave me this information, “When monarchs are in their non-reproductive phase (gonads repressed in the fall), they will be almost irresistibly attracted to curassavica, remain near the plant, and come into reproductive condition. When this happens, as far as we know, monarchs lose their migratory urge…….and probably, as individuals, never get it back.”
Now that I have two experts in the field recommend that we not have Curassavica available to Monarchs in the fall – what am I going to do with this great plant? At a minimum, I’m going to cut it down around September 10th. The migration usually occurs around September 20th, so I should be safe. I like having a good supply of milkweed to raise Monarchs during the summer, although that didn’t happen at all last year.