SAVE FLORIDA'S BROMELIADS CONSERVATION PROJECT
Controlling the Mexican Bromeliad Weevil
When the Mexican bromeliad weevil (Metamasius callizona) was first discovered in Florida in 1989, it had already become established on native bromeliads growing wild in county parks in Broward County (Frank and Cave 2005). This made control of the weevil challenging because it was too late to attempt to eradicate the weevil and pesticides could not be used due to ecological, economical, and strategic reasons. Initially, a biological control program was attempted to control the weevil, but was not successful. Now we are looking at alternative methods of control in conjunction with conservation.
Biological Control of the Weevil
Field biologist releasing Franki fly
A biological control program was started in 1991 to control the Mexican bromeliad weevil (Frank and Cave 2005). In 1993, a potential biological control agent, Franki fly (Lixadmontia franki), was discovered in Honduras on a related bromeliad-eating weevil, Metamasius quadrilineatus (Wood and Cave 2006). The fly is a specialist parasitoid of bromeliad-eating weevils. After mating and internal development of her eggs, an adult female fly deposits maggots on a weevil infested bromeliad (Suazo et al. 2008; Cooper 2009; Cooper and Frank 2014). The maggots go into the bromeliad and find the weevil larva. Maggots use a sharp mouth hook to cut a hole in the weevil larva's skin. The fly maggot enters the body of the weevil larva and eats the larva from the inside out, eventually killing the larva. When the larva is dead, the maggot emerges and pupates and the cycle starts over. If the fly could become established in Florida's forests, then it could reduce weevil populations and therefore, potentially reduce the damage the weevil causes the bromeliads.
After many years of research and getting appropriate permits, flies were released in several natural areas in central and southern Florida (Cooper et al. 2011). After each release, pineapple tops with 3rd-instar weevil larvae were placed in the release site about 5 weeks after a release. By this time, the adults that were released (the F1-generation) would, hopefully, have deposited maggots (F2-generation) on weevil-infested bromeliads, and those maggots would have emerged as adults, mated, and the females would be ready to deposit their maggots on weevil-infested bromeliads; hopefully, one of those females would deposit their maggots on our pineapple tops and the maggots would parasitize the sentinel weevil larvae. The pineapple tops were retrieved about 2 weeks after being placed in the field and returned to the laboratory, where they were monitored for parasitism by the fly. Only once were 2 flies recovered from a single weevil larva. After many years of releases, no other flies were caught in the wild and there were no signs of the fly having an affect on the weevil. Because Franki fly was so expensive and difficult to rear and because there was no evidence of success, resources are now being directed towards conservation efforts and alternative methods of controlling the weevil.
Host Plant Resistance
While searching for biological control agents in Belize, a giant airplant population was discovered living with the Mexican bromeliad weevil, without the destruction our form of the giant airplant suffers from the weevil. Research is being done to understand why the giant airplant in Belize is resistant to the weevil and to see if that resistance can be imparted to the Florida form of the giant airplant in Florida.
Biopesticides, Repellants, and Insecticides
Biopesticides and natural repellants are being studied as alternative methods for controlling the weevil. These will be used in concert with the conservation effort. As well, information from these studies will be made available for bromeliad growers to use in their collections and landscapes.
Insecticides have been used by bromeliad growers in Florida for many years. Anectodal evidence showed that certain insecticides worked, usually with 3 - 4 month intervals between applications. Now, studies are being done to determine which insecticides work best for how long and at what concentrations. Insecticides are used in the conservation effort when giant airplants are transferred to Protected Sites.