All summer I’ve been watching and waiting to see a flock of Monarch butterflies soaring through the air to lite upon our abundant field of milkweed. So far I’ve been disappointed. The Monarch butterflies on our property have only numbered one. I was mowing along our driveway when I saw it and I thought, maybe there will be more coming. Surely this is the first one of many.
That was several weeks ago and while butterflies are abundant on our property the Monarchs are not. So where have they gone? A recent article I read may have some insight. According to NPR a parasite in Florida may be the cause. Essentially a protozoa called Ophryocystis elektroscirrha (OE) is infecting the Monarch butterflies in Florida. Spores from this parasite spreads from butterfly to milkweed which then get eaten by the larvae. The parasite kills the larvae which is destroying the Monarch butterfly population.
Milkweed is the Transmission Vector
According to the article the tropical milkweed was part of the problem. Tropical milkweed can grow year round in Florida. Since native milkweed in our area (Tennessee Zone 7) is a perennial and dies back in the winter cold the parasite and its spores would not survive through the cold winters. In Florida however the the weather won’t kill it off which allows the parasite to thrive and spread.
Monarch butterflies perform a migration every year from the southern hemisphere to the north. That migration has several stops along the way where they lay eggs and propagate a new group of butterflies to continue the next leg of the journey. If that journey gets interrupted by a parasite it makes sense why our monarch population seems so small. There aren’t enough butterflies that survive to continue the journey.
Milkweed is the Larval Food Source for Monarch Butterflies
On our property we have allowed common milkweed to populate the property for years. I have intentionally cut around large stands of milkweed (Asclepias syriaca and A. tuberosa) and created pathways for us to walk around these areas. Milkweed is used by the larval stage of Monarch butterflies as a food source. It’s essential to have 2 things for the these butterflies to thrive: a larval food source and an adult food source (other native flowers). Adults will land on the nectar flowers they enjoy and lay their eggs on the milkweed plants nearby. Planting native perennials near your milkweed is an excellent way to attract and help the Monarch butterflies. We’ve seen swallowtails, fritillaries, silvery checkerspot butterflies, and others but, this summer, only the 1 monarch.
It was my hope to be a refuge for these beautiful butterflies along their journey. Where we could enjoy their presence and simultaneously help them along the way. The NPR article recommends that gardeners in Florida refrain from planting milkweeds of any kind as the parasite can use every type of milkweed in its cycle. That won’t stop milkweed from germinating and growing in uncontrolled areas though so the parasite problem it is likely to persist for some time.
Hopefully Monarch butterflies can find other routes for their migration in the future. Or maybe parasite resistant butterflies will emerge through natural selection. It would be a very sad thing not to witness even one in a summer. In the meantime we’ll just keep on planting milkweed in Tennessee in the hopes that we’ll be able to help these beautiful creatures.
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