The aftermath of Hurricane Dolly has set up South Texas as a potential hot bed for mosquito production and the diseases they transmit.
There are two common backyard biters in South Texas that are included in the flood water group of mosquitoes that play a significant role in disease transmission.
The yellow fever mosquito and Asian tiger mosquito are black and white in coloration, lay their eggs in artificial containers (cans, children's toys, tires, potted plants, or any object that holds water for more than seven days), and prefer to feed on humans. These facts make them excellent vectors for the dengue virus which is endemic (found yearly) in northern Mexico and has caused several outbreaks in South Texas.
The last dengue outbreak was in 2005 and resulted in 24 confirmed cases of dengue fever and one case of dengue hemorrhagic fever in Texas.
After the initial wave of flood water mosquitoes disperses, a new group of mosquitoes move into the new pools of standing water left after the flood waters begin to recede.
This new group of mosquitoes prefer habitats with calm, temporary or permanent pools of standing water to lay their eggs. Many of the most important disease vectoring mosquitoes in Texas belong to this group of standing water mosquitoes and compose the second wave of mosquito invaders. The most important standing water mosquito species is the southern house mosquito, the primary vector of West Nile virus and St. Louis encephalitis in Texas.
While there are vaccines available to protect horses against WNV, there is currently no human vaccine for this virus, or for St. Louis encephalitis, or dengue virus and treatment is limited to treating the various symptoms caused by the pathogen.
The best defense against this disease is to practice the four "Ds" of mosquito control. These include:
1. DEET - Wear DEET or another mosquito repellent (Picaridin, Oil of Lemon Eucalyptus, or IR3535) when outside.
2. Dusk and Dawn - Restrict activities during the hours of peak mosquito activity.
3. Dress - Wear loose fitting, light colored, long sleeved shirts and pants.
4. Drain - Dump, clean, or cover all containers that can hold water for over three days
To control mosquitoes effectively around the home, it helps to know about their life cycle. There are different control strategies for different life-cycle stages.
Adult mosquitoes typically live for about a week to a month, but this can vary, depending on a number of environmental factors. Some adult mosquitoes seldom travel more than 200 yards from the breeding sites, while other species can travel for more than a mile.
This ability to travel long distances can create problems in management. If the source of the mosquito problem is far from your home, you may not be able to control them without cooperation from other individuals or groups.
Here are some ways to alleviate mosquito problems around your home:
Eliminate breeding sites for larvae
- Reduce standing water that provides breeding sites. Eliminate containers such as old tires, buckets, cans and bottles that collect and hold rainwater and become good breeding sites for mosquitoes. Drain water from flower pots, bird baths, rain gutters, rain barrels, birdbaths, pet dishes, livestock watering troughs, etc. at least once a week. Empty your plastic wading pool weekly and store it indoors when not in use. Fill holes or depressions in trees with sand or mortar, or drain them after each rain by drilling holes into the tree, and finally repair leaky pipes and outside faucets.
Reduce adult mosquito populations
Mow tall grass or reduce the amount of brush and other foliage in your area to reduce the resting sites for adult mosquitoes. For temporary relief in yards or high traffic
areas, use fog treatments or surface treatments of insecticides that are labeled for that use and apply them following directions on the product label.
Avoid contact with mosquitoes
- Use screening in your homes and pet kennels. Keep the screens in good repair and be sure that they seal around the frames of the door or window. Schedule outdoor activities during times when mosquitoes are not active. Mosquito species that are active at dusk and dawn can often be avoided. Species that bite throughout the day are more difficult to avoid.
- Wear long, loose-fitting clothing to avoid mosquito bites. Use head nets when mosquitoes are very abundant. Use repellents whenever in a mosquito infested location. Products that contain DEET have been shown to be the most reliable repellents. Protect your pets with drugs that eliminate heartworm.
Treat larval breeding sites
- Use mosquito fish or other fish species in permanent bodies of water whenever the water will support them. Mosquito fish can be found in other ponds, pet shops or bait stores.
- Use Bacillus thuringiensis israeliensis products such as Mosquito Dunks(r) to treat permanent water bodies to eliminate larvae. You can use oil treatments on the surface of standing water to kill larvae. Use commercial products according to the instructions on the product label.
The first step in reducing the mosquito problem is to take a walk in your backyard, and make sure you are not contributing to your own problem. All a mosquito needs to breed are a few leaves or organic matter and water.
So, lets all do our part to help reduce the mosquito problem.
More information about mosquito control and biology can be found at the following Web site: http://www-aes.tamu.edu under the vector control tab.
Jeffrey Stapper is the Agricultural and Natural Resources Agent for Nueces County. Readers may contact him at (361) 767-5217.