New insecticides for control of the invasive cactus moth, Cactoblastis cactorum (Lepidoptera: Pyralidae), in Florida

Full text: Cactoblastis cactorum (Berg) has successfully controlled several species of invasive prickly pear cacti (Cactaceae: Opuntioideae - Opuntia) in Australia and in many other parts of the world. However, in 1989 C. cactorum was detected in the Florida Keys. Its rapid spread along the Atlantic and Gulf Coasts has raised concerns about its unavoidable impact on native Opuntia cacti in the southern United States and in Mexico. The current infestation of C. cactorum in Florida is affecting native Opuntia species distributed throughout large expanses of natural lands (O. stricta [Haworth] Haworth, O. humifusa [Raf.] Raffinesque and O. pusilla [Haworth] Nutall), as well as ornamental cactus plants (O. ficus-indica [L.] Miller and O. stricta) in urban settings. Even though chemical control would not be a practical or environmentally responsible tactic to protect the millions of ha of natural Opuntia vegetation, insecticide controls should be evaluated for their potential use in urban settings and in culturally managed plantings of Opuntia (nurseries, backyards, landscaped public lands) either alone or in combination with other suppression tactics. Furthermore, insecticides could be used to treat ornamental Opuntia in nursery settings to ensure that no infested plants are being transported and sold to the public. We conducted laboratory assays of nine products registered for use on ornamentals in Florida for their ovicidal and larvicidal activity against the invasive cactus moth C. cactorum. One hundred percent mortality (or 0% survival) of one-day-old eggs was obtained when egg stick sections were treated with cypermethrin, spinosad or imidacloprid. These products were equally as effective when assayed against eggs that were fully embryonated (28 days old) or when cladodes of O. stricta were exposed to neonates 24 hours after dipping or to cladodes that were dipped and stored for 30 days before exposure. When Bacillus thuringiensis (Dipel) was used to prevent neonate penetration into treated cladodes of O. stricta, 100% mortality (or 0% survival) was recorded in the laboratory. (author)