Beetle Infestation

Beetle infestation impacting oyamel fir trees inside the Monarch Reserve

Current knowledge regarding the Bark Beetle outbreak in the Monarch Butterfly Biosphere Reserve, as of 1 December 2009, from Dr. Lincoln Brower:

In mid-October, MBF learned that there was an outbreak or plague (‘La Plaga’) of a wood boring beetle attacking the oyamel fir trees (Abies religiosa) inside the core zone of the Monarch Butterfly Biosphere Reserve in Michoacan, Mexico.  The oyamel forests provide a microclimate, similar to a blanket and umbrella, which is absolutely essential for monarch butterflies to overwinter successfully. We were told that the beetle is Scolytus mundus; several species in the genus Scolytus are known forest pests. We are still in the process of obtaining detailed information from Mexican authorities.

Typically, the beetles are attracted to trees that have been stressed in some way. The beetles bore through the bark and excavate ‘galleries’ in which the females lay eggs.  The resulting larvae then tunnel as they eat through the sapwood.  If there are high numbers of beetles they effectively girdle, weaken, and can eventually kill the trees. If the trees are healthy and not stressed, the flow of the resinous sap entraps and kills or weakens the beetles.

According to the very preliminary report that we have received, the summer of 2009 was extremely dry, and this drought stressed the oyamel trees, and the beetle attack became an outbreak that was deemed to require control measures. The usual manner of control is to cut down the trees, strip the bark off and spray the trunks and cut up the branch-wood and bury it along with the bark. The resulting bark-stripped trunks are, we understand, to be taken to sawmills.

We were told that separate infestations have occurred in the very midst of key monarch butterfly overwintering areas, on both Chincua and Campanario near Rosario. Several thousand trees were scheduled to be removed, and the operation was planned to be completed before the opening of the butterfly colonies to tourists in mid-November. The extent of the operation, the specific areas where the trees have and will be cut, and plans for restoration are currently unknown to us.

As soon as we find out any new information, we will update our website.

Additional information regarding the beetle infestation includes the following:

1.  Stevenson, M. (2009) Mexico fells trees to save butterfly reserve. In: The Associated Press, pp. 1, Washington, D.C. 19 October 2009 (click here).

2. Rodriguez, R.R. (2009) Talan mil arboles en la Reserva de la Monarca, para combatir plaga. In Cambio de Michoacan, pp. 1, Morelia. 21 October 2009 (in Spanish: click here). 

3. Llana, S.M. (2009) Butterflies versus beetles. In Christian Science Monitor, pp. 2. (click here)