They're here: freshwater mosquitoes coming out in droves in some places, not a problem in others

Chad Gillis
Fort Myers News-Press

Grab the bug spray and get ready to slap yourself: freshwater mosquito season is here. 

Every year summer rains drench the landscape, and eggs that were long ago laid in drainage ditches and freshwater canals and ponds hatch. 

Blood-suckers emerge and feast on mammals like humans. 

It's starting to happen in places like Fort Myers, where nearly 5 inches of rain fell in one day earlier this month. 

"We were really kicking in our pretreatment for the saltmarshes for the tides (last month), but since then the rains have come and the service requests have come in right and left from really all over the county," said Eric Jackson, spokesman for the Lee County Mosquito Control District. "And we're finding larvae in ditches and stormwater drains." 

Mosquito season in Southwest Florida comes in waves. 

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First, hearty and aggressive saltwater species hatch with the high tides in May, and then the freshwater varieties show up about a week after the first few days of heavy rain. 

"If you’re noticing a mosquito problem, there’s going to be some out there and it’s part of life down here, but if it seems higher than normal don’t hesitate to go to our website and fill out a service request," Jackson said. "We treat anyway, but it’s helpful if we know someone is having a problem."

Scenes from Lee County Mosquito Control District at the headquarters at Buckingham Airfield on Monday. In August, the Florida Department of Health in Lee County issued an advisory stating there has been in increase in mosquito borne disease. Several sentinel chicken flocks have tested positive for West Nile virus infection. The risk of transmission to humans has increased. The chickens are used to detect mosquito borne diseases such as the West Nile virus.

Jackson said calls are coming in from around the county but that the south end seems particularly buggy. 

"The southern part of the county, in Bonita (Springs) and Estero, that’s where it seems to be heavier," Jackson said. "In the urban area of Fort Myers and Lehigh (Acres), water has accumulated in storm drains and areas where people have containers that will fill with water." 

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One of the most dangerous mosquito species (Aedes aegyptia) lays eggs in man-made containers, gutters and other places that collect rain.  

"They're container breeders that live around houses," Jackson said. "We don’t want to grow them. Those can really be taken care of at each household. They don’t fly far. If people keep their containers dry and their gutters clean it’s certainly helpful." 

Late summer is generally when disease will show up in sentinel chickens that are used to monitor the risk of mosquito-borne illnesses. 

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"Even though we don’t start to see these chickens with viruses until later in the summer or into the fall, it’s important to knock those mosquitoes down now so we can break that cycle," Jackson said. "And there's really a handful of mosquito (species) that (can transmit diseases to humans)."

Collier has yet to see much in the way of freshwater species, although the district there is treating saltmarsh areas that are within the district boundaries. 

"We've been really busy getting out into the coastal and southern parts of our district, where we know those saltmarsh mosquitoes are going to come," said Robin King, spokeswoman for the Collier Mosquito Control District. "The challenge in all of this is those saltmarsh mosquitoes, because once they come off the mangroves they can travel 40 to 60 miles on the winds. So there's nothing we can do in the Ten Thousand Islands area." 

Bti (Bacillus thuringiensis subspecies israelensis), a bacteria, is being used nowadays to treat the larvae. It is not harmful to humans or other mammals. So instead of trucks spraying during the night to kill adults, mosquito control district works to take care of the mosquitoes before they get a chance to hatch. 

"We stopped spraying for adults years ago," King said. "The only trucks we have now is to use the mist of Bti and we use it in Golden Gate, Immokalee, Naples in the city and we roll downtown at night and we want that mist to settle. We're targeting the larvae and anything that contains water." 

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Wade Brennan, who manages the Sarasota Mosquito Management Services, said that area hasn't seen many mosquitoes yet, either. 

"The summer rains started last week, so we anticipate that people may experience some mosquito problems stemming from containers around their homes," Brennan said. "We will have our crews in the woodlots, swamps, and other areas for treatments and inspection, but we need the public’s help to battle mosquitoes that lay their eggs in containers." 

Soon cattle fields and rural lands will flood, and inland areas like LaBelle and Immokalee will see swarms of blood-thirsty insects. 

But rain has been sparse inland, and the mosquitoes haven't quite made themselves known there. 

"So far there haven't been very much here," said Gene McAvoy, a University of Florida IFAS agent who lives in LaBelle and works in Immokalee. "It’s been kind of dry around here. We got rain a couple of weeks ago but it’s really turned off. I don’t see any water standing in ditches and waterways. So we have had much activity yet. We’ve got enough water to green up the grass but barely." 

So the freshwater mosquito season has started in much of Lee County but the bugs still haven't emerged in Collier or inland areas toward Lake Okeechobee. 

Soon the entire region will experience some level of freshwater mosquito activity, for at least the next several months. 

"It will probably slow down at the end of October," Jackson said. "But we could have a storm come in and saturate everything. Then again, a couple of years ago we had planes out on Christmas." 

Connect with this reporter: @ChadEugene on Twitter.