By LESLIE NESLON
Mairs Ryan is fascinated with butterflies. And she’s delighted to get the chance to help them, given their plight.
Monarch butterflies are facing numerous challenges, according to Mairs who leases a couple of plots at the San Carlos Community Garden (SCCG) and has taken over the management of the Butterfly Garden bed. She has learned a lot about these challenges and now she’s applying her knowledge at SCCG, which has become an official Monarch Waystation by the Monarch Watch Monarch Waystation Program.
These waystations provide resources necessary for monarchs to produce successive generations and sustain their migration. This includes the need for host plants for larvae and energy sources for adults applies to all monarch and butterfly populations around the world.
She first learned about the monarch’s plight when she was teaching sixth grade science 19 years ago. And more recently she took a workshop on monarch butterflies through the California Native Plant Society and became even more interested. Monarch’s main food supply is milkweed. Milkweed species are in the genus Asclepias and contain cardiac glycosides that are poisonous to humans, but they are also dangerous to grazing animals.
According to the Monarch Joint Venture, female monarchs use a series of cues to find milkweed and lay their eggs on the leaves of this plant. After the egg hatches, the caterpillar feeds on milkweed exclusively, and does not leave the host plant until it is ready to pupate. Therefore, milkweed is known as the “host plant” for monarchs.
As she began integrating them into her gardens, she noticed that the chrysalises sometimes turned black and she was horrified. This led her to learn more about some of the problems they are facing, including a parasite called OE. According to the Project Monarch Health website, “Ophryocystis elektroscirrha (OE) is a parasite that infects monarch, queen, and lesser wanderer butterflies. OE is not an animal or plant, but a single-celled organism known as a protozoan, a living thing that has many of the same characteristics as animals. OE must live within a host to grow and multiply. However, when it is not inside a host, OE survives in the environment as spores, which are resistant to extreme conditions.”
Another foe that the monarch caterpillars face is the larvae of the tachinid fly. Tachinid larvae are endoparasites (internal parasites) of caterpillars of butterflies and moths, meaning that they lay their eggs inside of the butterfly which become the host insect, and then the host eventually dies. Both fly and wasp parasitoids lay their eggs on monarch larvae but the most important larval parasitoid is in the family Tachinidae which includes 10,000 species, most of which parasitize Lepidoptera (butterflies and moths), though they also parasitize ants and bees, and true bugs and their relatives.
Through all of Mairs’ education on monarchs, she learned that when they breed year-round in the southern U.S., they face a greater risk of parasite infection. A study from Project Monarch Health’s lab showed that monarchs breeding year-round in the southern U.S. face a much higher risk of parasite infection compared to migratory monarchs. Mairs said they are especially sensitive to climate change and other weather-related cues in relation to their migration.
Another related problem is the expanded sales of tropical milkweed in the U.S. Tropical milkweed, with its orange and yellow flowers, instead of pink and cream, can interfere with the monarch’s migratory cycle because it encourages them to remain in the southern states (where is doesn’t die back in winter) and continue to breed and lay eggs instead of migrating to the Oyamel fir tree forests of central Mexico. Monarchs that don’t migrate face a much greater risk of parasite infection.
Pesticides and the reduction of wilderness that contains the milkweed plants that they need to subsist on has also had a negative impact on the monarch population. In fact, there were only 2,000 migratory Western monarchs during last year’s Thanksgiving weekend count. Monarchs typically travel to Mexico starting in early November and migrate back in March. Monarchs are very sensitive to pesticide use which is another reason for the population decline.
Butterfly garden tips
In order not to interfere with the monarch’s migratory cycle, in Southern California, Tropical Milkweed should be pruned back by Halloween down to 6-10-inches tall and the leaves should all be removed, according to MonarchJointVenture.org.
Mairs encourages gardeners to avoid tropical milkweed (Asclepias Curassavica) and stay with native milkweed (Asclepias fascicularis) if possible. Natives have flowers that are pink, white and cream.
Adult monarchs feed on the nectar from flowers, which contain sugars and other nutrients. Unlike the larvae that only eat milkweeds, adult monarchs feed on a wide variety of nectar bearing flowers. They will visit many different kinds of flowers in their search for food.
Also, remember to take steps to prevent accidental ingestion of milkweed, such as instructing children that the plant is poisonous and to avoid any contact with their eyes after touching the plant.
— Leslie Nelson serves on the education committee of the San Carlos Community Garden.