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Mosquito Season Is Here PDF Print E-mail
Written by Jeff Shimonski, BT Contributor   
May 2020

Consider a biorational, not a chemical, solution

APix_YourGarden_5-20s I write this column, we’ve had a nice rainfall that my garden appreciates. It has been so dry lately. Well, maybe the rainy season has started and we can irrigate our gardens a bit less.

But the rainy season and our warm temperature bring also mosquitoes, the over 60 species of mosquitoes that can be found in Miami-Dade County, and they’re suddenly more active and beginning to breed more readily.

Now of all those mosquito species, only a handful are real concerns for us as biters and disease vectors. In fact, not all mosquito species go after humans for their blood meal; some prefer reptiles or birds. There are even mosquito species that do not draw blood at all. But of the species that do go after a blood meal, it is only the female that draws blood, which she needs to produce her eggs.

Look at the cool photo of a blue land crab that accompanies this article. I took this photo while pumping out the water from inside the holes that land crabs dig and live in. There’s an endemic species of mosquito, Deinocerities cancer, whose larval stage takes place in the water at the bottom of the land crab holes. I was collecting this species of mosquito larvae to add to the handful of mosquito larvae species that my interns and I used to collect at Jungle Island.

I was collecting mosquito larvae at the park to determine what species were breeding, where they were breeding, and how to control their larvae, utilizing a biorational method so that we could halt the daily spraying for adult mosquitoes. Mosquito spray had been the only chemical broadcast into the park landscape since its construction, and the initial landscaping was done. I’d overseen the creation of a completely sustainable landscape -- no commercial fertilizers, no pesticides, no fungicides had ever been used on the landscape. So if I could determine how to safely control the mosquitoes in the park, we could stop spraying the one chemical used in the landscape. My goal was to create a habitat that would sustain natural insect predators that could respond to any insect outbreaks, like the whitefly infestations that we had here in south Florida.

Initially, my high school interns and I were only sampling our large bromeliad collection for the mosquito larvae that sometimes can be found in the impounded water at the base of the bromeliad leaves. We found four species of mosquito that bred in the leaf axils regularly and soon had a control program that treated all the bromeliads in the park with a biorational larvicide.

The mosquito larvae sampling was done every Saturday morning. The collected larvae would be left in my office in little containers of water. I would then identify the individual species under a microscope and then test those larvae with the different biorational larvicidal products I was testing.

After several months we had controlled the mosquito larva in the bromeliads! I was quite proud of myself, except that we still had a mosquito problem in the park. I was stumped. The park is on an island, and mosquitoes don’t typically fly too far. What was going on?

So every Saturday I began to test all the 30-odd storm drains in the park. The interns would continue sampling the bromeliads while I was sampling all the drains. The water level in those drains was typically 10 to 12 feet below grade, so I used a long PVC pole with a small net on the end to sweep the water and pull up any larvae that I found. I’d empty the net into a small bucket and from there into small sample containers so that I could bring them into my office to identify.

Once the species of mosquito larvae was determined, I started treating the storm drains with larvicide. Again, success! The storm drains were the issue, much more so than the bromeliads. No more spraying for mosquitoes!

The two main species of mosquito that I found in the storm drains are notorious disease vectors, Culex quinquefasciatus and Aedes aegypti, found around the world.

What viral diseases can they and other mosquito species transmit? Well, Zika virus, West Nile virus, Chikungunya virus, Yellow fever virus, and Dengue viruses, and don’t forget the non-virus malaria.

We were able to stop spraying for mosquitoes for the last six or seven years that I was at the park. And our outbreaks of white fly were controlled by insect predators that had colonized the landscape ecosystem. These predators responded to and ultimately completely controlled our insect outbreaks.

What are you doing to control the mosquitoes on your property?

 

Jeff Shimonski is an ISA-certified arborist municipal specialist, retired director of horticulture at Parrot Jungle and Jungle Island. Contact him at This e-mail address is being protected from spambots. You need JavaScript enabled to view it .

 

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