The cactus moth, Cactoblastis cactorum has become the textbook example of successful biological weed control of invasive Opuntia species in many countries, including some Caribbean islands. However it has now turned, and is now threatening not only the lucrative cactus pear industry in Mexico, but also the rich diversity of all Opuntia species in most of the North America mainland. The moth is now present on most Caribbean islands as a consequence of either deliberate or accidental introductions by man or by means of natural spread. Although there is convincing evidence that Cactoblastis reached Florida through the nursery trade, there also exists the possibility of natural spread by means of cyclonic weather patterns. The different pathways that could result in the arrival of the moth in Mexico are analyzed. With few exceptions, little is known of the impacts of the cactus moth on the native Opuntia species in the Caribbean. The main target species, namely Opuntia triacantha and O. dillenii have become very scarce and may now need protection status. The long-term impact on non-target species is unknown but some species may have been drastically affected. Recently regional and international efforts have been launched to prevent the further spread of Cactoblastis to the species rich native Opuntiae flora of the southern United States and of Mexico. These include an intensive monitoring program of resident populations at the leading edge near the Florida/Alabama borders and monitoring of large cultivated plantations in Mexico, which are focal points for possible early invasions. An awareness campaign that sensitizes farmers and government officials to the insect and its damage is aimed at interception and early detection to allow eradication in the event of establishment in Mexico. Research also is underway in Florida to develop an SIT (Sterile Insect Technique) program to halt the westward spread of the moth and to create a biological barrier. The involvement and co-operation of plant health and quarantine personnel in these Caribbean islands has become crucial in the campaign to keep Cactoblastis out of Mexico.