Last ticket sold at 4:00 PM
Miami Dade County
X (presumed extirpated)
Green Antelopehorn Milkweed
Who else uses milkweed?
Many other species of insects use milkweed. Queen and soldier butterflies as well as some moths use milkweed.
Isn’t there OE on native milkweed, too?
Yes, however, native milkweeds die back naturally. When the native plants die back, the parasite will too. Non-native tropical milkweed does not die back naturally and can accumulate heavy infestations of the parasite.
Does Florida have resident populations of monarchs?
Yes, Florida has resident monarch populations. However, monarchs are largely year round residents BECAUSE of the tropical milkweed. Monarchs sense the chemicals from the tropical milkweed and break their diapause/migration to mate and lay eggs. One study found that 91% of the monarchs tested in Miami had consumed tropical milkweed. (Knight and Brower, 2009). Diapause means that monarchs do not mate for a period of time, as reproduction costs a lot of energy. Instead, monarchs are able to live longer as adult butterflies so that they are able to migrate towards their overwintering locations.
Are monarch populations declining?
Monarchs are in decline in their overwintering locations which include Mexico and southern California. However, a study published in 2022 shows that monarch populations across the U.S may have actually been increasing about 1.3% each year since the mid 1990’s! (Crossley et al., 2022) One reason why the overwintering populations are declining is because of the parasite OE. It either kills the monarch or makes them weaker and therefore can’t make it to the overwintering location. In Florida, the monarch populations have also been increasing due to the large amount of available non-native tropical milkweed.
Are monarch butterflies endangered?
Monarchs were declared endangered by the International Union for Conservation of Nature (IUCN). They have not been listed by U.S Fish and Wildlife.
What about pesticides and milkweeds?
Large box stores and local nurseries carry the non-native tropical milkweed, which often has either topical or systemic pesticides. These pesticides will most definitely kill monarchs. Search for local, native plant nurseries where you can purchase native milkweeds to your area and be sure to ask if they use any pesticides.
Can I just wash my tropical milkweed or treat it with bleach to prevent the OE?
Washing your tropical milkweed is not really practical. You might try to be very diligent about washing your milkweed to lower OE amounts but if neighboring properties do not, the high amounts and rates of transmission will continue. Bleach is good at killing many bacteria, fungus, and a few protozoa parasites with enough contact time. But, many protozoal parasite cysts like the form of OE on plants, can be resistant to bleach. Bleach is also readily inactivated when it comes in contact with organic matter and can cause plant damage. Even with all of these possible measures, cleaning tropical milkweed does prevent the other damaging effects of tropical milkweed such as halting migration and spreading invasively to surrounding areas.
Dr. Andy Davis discusses the parasite OE: https://www.monarchscience.org/single-post/monarchs-have-a-growing-parasite-problem-and-it-s-not-from-natural-causes
Zoom interview with Dr. Andy Davis and Zoo Miami: https://www.monarchscience.org/single-post/what-to-do-about-monarchs-and-their-parasites-in-florida-a-zoom-conversation-with-miami-zoo-expert
Find out where the parasite OE occurs: https://www.monarchparasites.org/maps
A University of Florida webpage that shows the Florida native milkweeds: https://gardeningsolutions.ifas.ufl.edu/plants/ornamentals/milkweed.html
Crossley, M., Meehan, T., Moran, M., Glassberg, J., Snyder, W., Davis, A., 2022. Opposing global change drivers counterbalance trends in breeding North American monarch butterflies. Glob. Change Biol. 28, 4726–4735.
Davis, A., 2021. Captive-reared migratory monarchs fly in the wrong direction: a critique of Wilcox et al. Conserv. Physiol. 9.
Davis, A., Smith, F., Ballew, A., 2020. A poor substitute for the real thing: captive-reared monarch butterflies are weaker, paler and have less elongated wings than wild migrants. Biol. Lett. 16. http://dx.doi.org/10.1098/rsbl.2019.0922
Harvey, R., Howell, P., Morgenstern, C., Mazzotti, F., n.d. Native Habitats for Monarch Butterflies in South Florida. University of Florida.
Howard, E., Davis, A., 2015. Investigating Long-Term Changes in the Spring Migration of Monarch Butterflies (Lepidoptera: Nymphalidae) Using 18 Years of Data From Journey North, a Citizen Science Program. Ann. Entomol. Soc. Am. 108, 664–669.
Knight, A., Brower, L., 2009. The Influence of Eastern North American Autumnal Migrant Monarch Butterflies (Danaus plexippus L.) on Continuously Breeding Resident Monarch Populations in Southern Florida. J. Chem. Ecol. 35, 816–823. https://doi.org/10.1007/s10886-009-9655-z
Majewska, A., Altizer, S., 2019. Exposure to Non-Native Tropical Milkweed Promotes Reproductive Development in Migratory Monarch Butterflies. Insects 10.
Majewska1, A., Davis, A., Altizer, S., de Roode, J., 2022. Parasite dynamics in North American monarchs predicted by host density and seasonal migratory culling. J. Anim. Ecol. 91, 780–793.
Oberhauser, K., Nail, K., Altizer, S., 2015. Monarchs in a Changing World : Biology and Conservation of an Iconic Butterfly. Comstock Publishing Associates, Cornell University Press.
Solis-Sosa, R., Semeniuk, C., Larrivee, M., Cox, S., 2022. Investing in monarch conservation: understanding private funding dynamics. Front. Conserv. Sci. 3. https://doi.org/doi: 10.3389/fcosc.2022.903132
Zanden, H., Chaffee, C., Gonzalez-Rodriguez, A., Flockhart, D.T.T., Norris, R., Wayne, M., 2018. Alternate migration strategies of eastern monarch butterflies revealed by stable isotopes. Anim. Migr. 5.