Distribution and dispersal of Cactoblastis cactorum (Lepidoptera: Pyralidae), an exotic Opuntia-feeding moth, in Florida

The recent arrival of Cactoblastis cactorum Berg in Florida has raised concern for Florida's native Opuntia cacti. Moreover, the potential for movement of the moth across the gulf states and into the southwestern United States may endanger cacti in the Opuntia-rich areas of Texas, Arizona, New Mexico, and Mexico. However, the spread of the moth northward through Florida has either slowed since the invasion or the rate of spread for the first two years was over estimated. The mortality rate of pads and the distribution of egg sticks at six sites in Florida were recorded on O. stricta Haworth, the most common host in Florida. While the percentage of cactus pads with C. cactorum damage is as high as 60%, the data indicates that most mature cacti are not being reduced in size. However, small cacti and new growth pads are particularly susceptible to mortality by C. cactorum, thus, over time we may expect to see a reduction in the number of plants as a result of an increase in the mortality rate of recruits.