Host specificity of Cactoblastis cactorum (Lepidoptera: Pyralidae), an exotic Opuntia-feeding moth, in Florida

The recent arrival of the cactus moth, Cactoblastis cactorum (Berg) in Florida in 1989 has raised concern for the native Opuntia cacti. At particular risk is Opuntia spinosissima, whose entire U.S. population consists of 12 plants in the Florida Keys. We examined host choice of both C. cactorum larvae and ovipositing females to determine if any species of native Opuntia are preferred by C. cactorum. In addition, larval performance among Opuntia hosts was examined. Ovipositing moths showed no host preference in interspecific host choice experiments. Although larvae significantly preferred O. spinosissima over the other Opuntia species, larval survivorship on O. spinosissima was less than on O. stricta and O. humifusa. Mie also examined intraspecific host choice between pads of O. spinosissima to see if any of the 12 remaining plants is more resistant to attack than others. Such information is valuable for future restoration efforts to protect O. spinosissima. No adult or larval host choice was demonstrated in the intraspecific experiments.