Protecting rare Florida cacti from attack by the exotic cactus moth, Cactoblastis cactorum (Lepidoptera: Pyralidae)

Abstract

Cactoblastis cactorum (Berg) represents a threat to rare Opuntia cacti in the Florida Keys. Conservation of such species may depend upon successful outplantings of young cacti in places that minimize attack rates by Cactoblastis. This paper discusses how to maximize the success rates of such outplantings of the endangered semaphore cactus, O. corallicola Small. A 1998 outplanting of 180 cacti in the Lower Keys showed that planting close to Opuntia stricta (Haw.) Haworth infected with Cactoblastis results in heavy losses, as Cactoblastis bleed over from O. stricta to attack outplanted O. corallicola. Growth rates of outplanted O. corallicola are greatest in shade conditions, but attack rates by Cactoblastis are also greater in the shade. An outplanting of 240 O. corallicola cacti on six different Keys in 2000, all far away from O. stricta, had no Cactoblastis related mortality. The most successful conservation strategy for O. corallicola thus appears to be outplanting in the shade, possibly in tropical hammocks, far away from Opuntia cacti that might contain Cactoblastis.