A deadly blast of Dengue fever insecticide sprayed on trees just outside Monterrey this week cut the migration short for several hundred Monarch butterflies. The unfortunate massacre illustrates the challenges of balancing reasonable insect control and management with conservation efforts.
The report below by Gerardo Boruga of Info7, a news service of Azteca Noreste, shows hundreds of Monarch butterflies writhing in the street after a fumigation truck passed through the Santa Catarina neighborhood of Monterrey in Nuevo Leon province and sprayed their roost in an effort to control the spread of the sometimes fatal Dengue virus.
Dengue fever, caused by a virus carried by mosquitoes, continues creeping north from tropical climes to U.S. cities. “The global resurgence of Dengue virus is a real issue,” Dr. Marty Cetron, director of the Center for Disease Control’s division of global migration and quarantine, told a Boston news service this week.
No cure for Dengue fever exists, but scientists continue work on a vaccine.
The primary management tools for controlling the spread of Dengue fever–insecticide use and habitat removal–also threaten the health of the Monarch butterfly migration. Gardeners know this quandary well. Indiscriminate spraying of insecticides kills desirables as well as pests.
The Santa Catarina Monarch massacre serves as a sobering reminder of the complex aspects of conserving our beloved Monarch butterfly migration. As we butterfly fans detail daily sightings of late season stragglers throughout the eastern United States on Facebook and on the D-PLEX*, let’s not forget the conservation challenge at hand.
Fumigation programs combat dangerous diseases, but the fallout can be a pile of dead butterflies. Illegal logging at the Monarch roosts in Michoacan results largely from a lack of economic opportunity; people must feed their familes and heat their homes in those remote Mexican mountains. Some (not me) might cast the development of herbicide tolerant crops, a practice that has decimated native milkweed (the Monarch butterfly host plant) in our heartlands, as another economic development issue.
Education and coordination can make a big difference. As reporter Boruga says in his report, the episode could have been avoided with a simple change in the fumigation schedule. “They’re only here for a night or two,” Boruga points out, suggesting a day or two delay in fumigating could have allowed the Monarchs to make it to Michoacan.*The D-PLEX list, so-called for its namesake’s Latin designation, Danaus plexipus, is an old fashioned email listserv started by Monarch Watch founder Chip Taylor of the University of Kansas at Lawrence. The D-PLEX includes about 650 scientists, conservationists, enthusiasts, and others, including some very interesting characters. Anybody can sign up to receive Dplex emails on the Monarch Watch webpage.