Death and Decline of a Rare Cactus in Florida


June 2010


Peter Stiling

Additional Authors

ABSTRACT Conseola corallicola is a rare cactus that is known from just two islands in Florida, Little Torch Key and Swan Key. The appearance of the cactus-eating moth, Cactoblastis cactorum, in the 1980s, threatened its survival. Outplantings at various locations were made in the 1990s and early in the 21st century to try to boost population sizes in the field and to determine optimal outplanting conditions. Here, I examine the survival of these cacti and compare it to the survival of volunteers around the bases of parent plants at Little Torch Key. I correlate percent survival in all locations with soil nutrients. Survival of recruits in outplantings was lower than that of volunteers around parent plants. Transplant experiments showed the physical act of replanting did not reduce survival. Cacti planted close to individuals of prickly pear cactus, Opuntia stricta, suffered from attack by Cactoblastis as they spilled over from O. stricta onto C. corallicola outplantings. Survival of cacti planted far away from O. stricta was often low because of poor soil quality and high mortality from crown rot. Where cacti were not killed by Cactoblastis, survival was greatest where soil nutrient content and water content were highest. Soil fertilization did not increase survival rates, but did increase survivor growth. Future restoration of C. corallicola in the Florida Keys is likely to prove difficult. As Cactoblastis spreads throughout the United States and Mexico, these same issues will likely be faced by Cactoblastis-susceptible cacti in many other locations.