The prickly-pear cactus moth (Cactoblastis cactorum) is one of five species belonging to the genus Cactoblastis that occurs naturally in northern Argentina, Uruguay, Paraguay and southern Brazil (Map a). Females of this species lay eggs on the leaves of several cacti species (genus Opuntia, Cactaceae), which upon hatching produce gregarious larvae that feed voraciously on leaf tissue. Larvae generally cause severe damage (both in terms of tissue losses and as a result of secondary pathogen infections), which often lead to the death of cacti, mostly in young specimens (Zimmerman et al., 2007).

Given its ability to infest cacti, the prickly-pear cactus moth was released in 1925 in Australia in an attempt to use it as a biological control for eradicating the populations of Opuntia stricta, a species with a widespread distribution in over 25 million hectares across Queensland and New South Wales. By 1940, the prickly-pear cactus moth had eradicated nearly all cacti in Australia, except for some scattered areas across the littoral and in southeast Queensland. Given this success as a biological-control agent for cacti, the prickly-pear cactus moth was also introduced in South Africa, New Caledonia, Hawaii, Antigua, Monserrat, Kenia and Caiman Islands, among other countries (Map a).

In Mexico, however, the prickly-pear cactus moth poses a serious hazard, not only because of the enormous species richness of cacti living in the country and their ecological importance, but also because of their economic value (as they are used as human food and fodder in the dry season), as well as in terms of their cultural importance. More than 80 cacti species are recorded in Mexico, 19 of which are considered susceptible to be affected by this insect (Conabio, 2008). The natural areas most susceptible to the prickly-pear cactus moth are located in the states of Coahuila, Nuevo Leon, Tamaulipas and the San Luis Potosi-Zacatecas highlands; as for areas where this cactus is grown as food, the most susceptible areas are located in the states of Mexico, Morelos, San Luis Potosi, Puebla and the Federal District.

In August 2006, the presence of the prickly-pear cactus moth was confirmed in Isla Mujeres, followed soon after by Playa Ballena in Cancun and Playa del Niño, also in Quintana Roo. However, thanks to the rapid implementation of eradication measures in the zones where this species was detected, along with monitoring measures for detecting its presence, this outbreak was eliminated before it became established. In September 2008, Sagarpa officially announced that this outbreak had been eradicated.

Although Cactoblastis cactorum has not yet become established in Mexico, the possibility that it may do so in the future through the northern border or as a result of hydrometeorological phenomena transporting insects from the Caribbean Islands cannot be ruled out. In order to implement actions should an invasion occurs, monitoring and surveillance activities in potential entrance routs continue; additionally, a public awareness campaign has also been implemented, along with training courses and inter-agency cooperation agreements at both national and international levels.

References

Zimmermann, H., S. Bloem y H. Klein. The Biology, History, Threat, Surveillance and Control of the Cactus Moth, Cactoblastis cactorum. FAO-IAEA. Austria. 2007.

Conabio. Sistema de información sobre especies invasoras. Palomilla del nopal en México. Available at: www.conabio.gob.mx/invasoras/index.php/Palomilla_del_nopal_en_M%C3%A9xico Consulted on: 21 -12-2008.