Emerging milkweed is needed to feed hungry monarch larvae

Tattered yet resilient monarch butterflies have returned to the Midwest early this spring, laying eggs as they migrate north from their overwintering grounds in Mexico. While the distinctive black and orange creatures are a welcome sight here in Missouri, the butterfly’s early appearance could mean that emerging milkweed plants won’t be sufficient to feed hungry larvae.

“In the past 10 days, we’ve received reports of early monarch remigrants from across the state,” said Jason Jenkins, coordinator for Missourians for Monarchs, the state’s monarch and pollinator conservation collaborative. “The egg-loading that’s being reported is nearly unprecedented for our state. To support the caterpillars, we’re going to need every stem of milkweed out there, so we’re encouraging landowners to hold off on any springtime mowing to help this first generation of monarchs thrive.”

Monarch populations have consistently been decreasing over the past 20 years due to habitat loss, changes in agricultural practices and untimely mowing. Milkweed is critical for monarchs because adult monarchs solely lay their eggs on these plants, and caterpillars only eat milkweed before morphing into a chrysalis. Monarchs returning to the states from their overwintering vacation in Mexico have been mating the entire flight up, and are ready to lay eggs on milkweed.

Journey North, a wildlife migration organization based in citizen science, has been reporting sightings of eggs, caterpillars, monarchs and milkweed since some of the adults participated in a mass departure from Mexico on March 23. On March 30, Elizabeth Howard, founder of Journey North, said that the next six weeks would be the most critical for populations.

“It’s a critical time as the monarchs race northward to produce the next generation. Now in reproductive condition, the biological clock is ticking. Most of these monarchs will reach the end of their lives by the end of April,” Howard said in a blog post.

The sightings continue, and have since spread to states including Missouri. Citizen scientists are excitedly reporting sightings, some claiming to barely remember seeing monarchs this early in the springtime. This early migration, partially due to storms and gusts of wind, has some new challenges for the population.

“Unfortunately, there are likely to be negative consequences in terms of reproductive success for those monarchs that have reached mid-Kansas and further north. Milkweed is scarce with only a few plants being found in gardens and burned over areas. Egg dumping [laying numerous eggs on a single plant] is likely and late frosts are still a possibility. Larval development will be slowed due to lower temperatures – relative to that which would have occurred had the eggs been laid further south with warmer temperatures,” said Dr. Chip Taylor, founder and director of Monarch Watch, in a Journey North blog post.

This is where Missourians can step in to do their part.

“Older roads have some of the best milkweed numbers and native flower diversity left in the state,” said Mervin Wallace, native plant expert and owner of Missouri Wildflowers Nursery. “It would be great if landowners waited until after mid-November to mow them to the fence.”

Jenkins echoed Wallace’s sentiment.

“Spring is a time of renewal, and while many landowners may feel the urge to tidy up by mowing roadsides and other odd areas around their homes and yards, these places are important as habitat for monarch caterpillars when there is milkweed present,” he said. “So we’re encouraging folks not to mow and let the milkweed grow.”

Monarch Joint Venture, a partnership of federal and state agencies, non-governmental organizations and academic programs working together to protect the monarch migration, offers a handout outlining best mowing practices for monarchs. This may be downloaded at http://bit.ly/2pGVubF.