Extension Service: Do elegant bromeliads serve as mosquito farms? Yes, and no

Strange looking things, and for four years I had avoided them. But finally after seeing some creative landscapes with different sizes and colors, placed together in a captivating plant collage, I finally surrendered and invested in about 20 bromeliads.

A few months later, while I was hosing some of them, as one needs to maintain their "cups" with a certain degree of fresh water, I noticed — a small wattage, "light bulb" epiphany moment here — some mosquito wrigglers floating out as if they were on a waterslide and some were still happily bobbing around in the cup. I never thought about it (me, an entomologist!), but could the water contained in these plants harbor the immature stages of West Niles virus and other disease vectoring mosquitoes? What am I doing with these things?

Dare we place a horticultural stigma on bromeliads and put them in the same category as castoff old tires in the backyard? Must we now mandate that we remove them quickly, as they could serve as breeding sources for mosquito larvae? Surely someone has studied the wildlife inhabiting these plant parts. Wasn't there a PBS special about how some other insect predators and tadpoles, etcetera, move in to these micro-niches and gobble up the little wrigglers? Maybe we horticulturists should not recommend bromeliads that have cups (phytotelmata) that have standing water?

Apparently not to worry. There has been research on this issue by J. Howard Frank, University of Florida-Gainesville, and also by Phil Lounibos, UF-Florida Medical Entomology Laboratory in Vero Beach, see: fmel.ifas.ufl.edu/index.htm.

Our native bromeliads (about 16 species) provide harborage for the immature larvae of several daytime biting mosquito species. These are in the genus Wyeomia (say, WHY-OH-MY-AH). Fortunately, these do not vector diseases and are just a biting nuisance. Frank estimates that 100 adult native mosquitoes are produced each year in one of the most common imported bromeliads, Billbergia pyramidalis. For information on this, see:

bromeliadbiota.ifas.ufl.edu/mosbrom.htm

Lounibos demonstrated that the invading "forest day mosquito," AKA, "Asian tiger mosquito," Aedes albopictus, is excluded by the native mosquito larvae. One theory is that the native species are vastly better at foraging for food than are Aedes albopictus, which are generalists. So Wyeomyia wins the competition for food. An old ecology rule, "CCCC" — complete competitors cannot coexist — holds true, perhaps. More research is still underway.

So, the good news is that it appears that bromeliads will not be become an outcast plant group that harbors the bad skeeters that vector diseases. If you don't like the native mosquitoes, Jeff Stivers with the Collier Mosquito Control District, replied, "When people ask about bromeliads I generally recommend that they get a can or Raid Yard Guard with permethrin as the active ingredient (there is another version with, I think, allethrin as the active) and treat the plant opening with that. The permethrin gives a little residual and helps knock down the adults as they try to oviposit or emerge as adults. Another thing they can do is get the Mosquito Dunks at Home Depot or Lowes and put a few very small pieces of that in each plant."

Anyway, I feel relieved and will continue to gather in more bromeliad species into my landscape collage.

Doug Caldwell is also a landscape entomologist and works for the Cooperative Extension Service. E-mail dlcaldwell@ifas.ufl.edu Call 239-353-4244 x203. For updates on the Southwest Florida Horticulture Learning Center and more landscape pest management details, visit collier.ifas.ufl.edu.

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