Wildflower Stories: Milkweed, Monarchs and Monsanto

Monarch butterfly populations have declined an estimated 90% over the past 20 years. [1] What’s going on?! The answer involves genetic engineering, protozoans and herbicide.

Milkweed (Asclepias syriaca), a member of the Dogbane family of plants, is closely associated with Monarch butterflies. Monarch caterpillars feed on milkweed and assimilate the plant’s chemical defenses, providing the Monarchs protection over the rest of their lives.

Milkweed grows in disturbed soils, like those used in agriculture. The plant is often found between rows of corn or soybeans. However, genetic modification of corn and soybean allows herbicides (such as Monsanto’s RoundUp) to be more efficient at killing other plants, like milkweed. Fewer milkweeds, fewer Monarchs.

So good-hearted people came to the rescue, planting Milkweed in their yards in an effort to help the butterflies. Unfortunately, many people planted the wrong species of Milkweed. Here in the U.S., native Milkweed dies back each year. This dieback limits the population of a Monarch parasite called OE (Ophryocystis electroscirrha). [2] However, the species of Milkweed people planted is evergreen, so the parasites keep proliferating and Monarchs get so sick they don’t survive their migration to Mexico and back.

If you’d like to find the right Milkweed for your neck of the woods, here’s a handy tool from Xerces.

1. http://news.nationalgeographic.com/news/2014/10/141010-monarch-butterfly-migration-threatened-plan/
2. http://monarchparasites.uga.edu/whatisOE/

Wildflower Stories – the Hercules of Plants

Cow Parsnip (Heracleum maximum) has a fascinating relationship with war, GMOs and sunscreen.

The plant’s scientific name probably points to its size – it’s taller than me (but that’s not saying much). It takes two years to grow that big. If you’re going to put that much time into growing, you’ll want to make sure nobody eats you; which leads us to the other possible reason for Cow Parsnip’s scientific name. Some claim Hercules used this plant medicinally.

Many plants contain chemicals to protect them from predators. This plant makes “furocoumarin”. In humans, furocoumarin combines with sunlight to cause a rash. This is where war comes in. During World War II, military organizations recruited plant and insect experts to investigate the defensive (or offensive) properties of these chemicals. Mustard Gas is similar in its blistering effect to furocoumarin.

Most plant predators, though, are not humans; they’re insects. As you can imagine, Cow Parsnip is very effective at deterring insect herbivores. So, the genes that will ultimately produce furocoumarin are prized. If you could insert those genes into another plant (how GMOs are made), the same protection will occur.

Beware the inevitable evolutionary “arms race” that results though. A few insects can eat Cow Parsnip, either due to mutations that let them break down the furocoumarins or behavioral shifts (like eating that plant only at night or when rolled in one of the plant’s leaves. Remember, the chemical has to be combined with sunlight to produce an effect.

And we get to sunscreens. A related chemical was used as a “tanning accelerator” up until 1996. Unfortunately, it caused rashes (“sun poisoning”), skin loss and even cancer. Turns out, furocoumarins can mutate DNA.

Cow Parsnip belongs to the Carrot family of plants. They tend to have hollow stems and flowers in “umbels” (like umbrellas). Some relatives are frequently on our dinner table (carrots, celery, parsley, dill, etc.); some, like hemlock (not hemlock), are deadly.