In each issue of the Florida Council of Bromeliad Societies newsletter, Drs. Howard Frank, Ron Cave and Teresa Cooper publish a report on the Mexican bromeliad weevil and their progress in the effort to control this menace. What can the back yard grower do if the weevil makes its way into your collection?
Because the bromeliad community occupies such a small niche in the world of big chemical companies, there are no chemical solutions labeled for use against the Mexican bromeliad weevil. In the absence of research and solutions by the chemical companies, we have to rely on anecdotal evidence - according to those who have fought the weevil, what has worked best to eradicate the weevil from back yard collections.
First of all, you cannot fend off the weevil with preventative spraying. You never know when and where the weevil will visit your collection, and if you are doing preventative spraying, you are wasting expensive chemicals for no sure reason.
Among bromeliad growers who have successfully fought the Mexican bromeliad weevil, the chemical of choice is imidicloprid, made by Bayer and often called Merit; it is in Advantage Garden, which you can find at garden centers as a spray. This is a systemic chemical, which means that it will last for several months in the bromeliad leaves. The larvae of the Mexican bromeliad weevil will ingest imidicloprid as it eats the bromeliad leaves and will die. Imidicloprid is not harmful to birds or animals (it actually is an ingredient found in some flea medicine). You can use the rose formula straight from the bottle. For the tree and shrub formula, use 1-2 teaspoons per gallon. There is no point in treating your entire collection if you do not currently have a problem. Treat only new plants coming into your collection or only if you have a confirmed infestation.
By the way, one beneficial side effect of imidicloprid is that it works wonders on black scale.
Remember, the main way the Mexican bromeliad weevil is distributed is by people transporting bromeliads from an infested area. Do not take, swap or buy plants from areas of known infestation unless you know they have been inspected and treated for the Mexican bromeliad weevil. Most commercial growers already have a management program in place; many small growers and hobbyists do not. If you find that one fabulous bromeliad you just have to have and the source gives you no reassurance about the weevil, isolate it from your collection when you get home and treat it with imidicloprid.
Never take bromeliads from their habitat. Many of Florida's bromeliads are endangered or threatened. Collecting plants from lands such as parks is illegal. In addition, you could be helping to spread the Mexican bromeliad weevil.