Anyone living in North Central Texas is keenly aware of the treat that awaits him or her when venturing outside - hordes of hungry, big mosquitoes.
The onslaught is greatly magnified during morning and evening hours. Residents concern is certainly not unwarranted, after all mosquitoes are noted carriers of dreaded diseases such as West Nile neuroinvasive disease and West Nile fever and others.
At least for now, these hungry hordes consist primarily of floodwater mosquito species, which are not carriers of West Nile encephalitis. Species that lay eggs singly on the moist soil usually near the edge of temporary pools of water are known as floodwater mosquitoes. These eggs only hatch after they have been flooded by water.
Psorophora and Aedes mosquitoes are floodwater mosquitoes which are most abundant shortly after heavy spring rainfall. Floodwater species in the eastern part of the state can carry disease, but are mainly an annoyance and are not part of the cycle of West Nile or Saint Louis encephalitis.
Floodwater mosquitoes lay their eggs in low lying areas and pasture lands prone to flooding or standing water, where they remain dormant until heavy rains produce flooding conditions favorable for hatching. Recent rains over the past 17 days have caused eggs to hatch that may have been laid as far back as two to four years ago, according to Dr. Jim Olson, entomologist with the Texas Agricultural Experiment Station.
Suddenly, we are overwhelmed pesky mosquitoes. The good news, at least for now, is that all the flooding rains we received in various parts of the eastern half of Texas — and maybe beyond — have flushed out the breeding sites of the species of Culex, the primary vectors of the urban outbreaks of West Nile disease, according to Olson, noting, “It’s disrupted that cycle to some degree, if not to a great degree.”
The bad news, though, is the rain has hatched millions of eggs of floodwater mosquito species.
The males feed only on nectar, plant juices and other sources of liquid carbohydrates. Female mosquitoes also feed periodically on nectar, plant sap and other sources of plant carbohydrates for energy. However, females of most mosquito species require a blood meal as a source of protein before they produce eggs.
Control measures are not going to have a great impact, since some of these floodwater mosquito species can travel 25 to 30 miles in search of blood meals. With widespread heavy rains we are in the middle of a vast floodwater mosquito hot bed.
A bit of wisdom: Residents are encouraged to cover up, stay inside and providing no more heavy rainfall falls for a while, the situation will get better in about 10 days.
Although control measures may be limited in managing a large scale flood mosquito outbreak, I encourage residents to administer control/suppression measures such as the eliminating breeding sites (standing water) or the addition of a larvicide such as Bt (Bacillus thuringiensis - israeliensis), which is found in Vectobac briquets, Summit B.t.i Briquets or Mosquito Dunk.
These small donut-shaped briquettes kill mosquito larvae and provide up to 30 days control.
To avoid being bitten, cover up with clothes and repellent or move your parties inside. It’s to a point where you can spray everywhere and hit a mosquito, but you can’t get them all. Protect yourself by wearing protective clothing and a repellent of choice, and avoid being outside when mosquitoes are active. Wear clothing that is loose-fitting. With tight-fitting clothing, mosquitoes can drill right through the fabric. Clothing should cover arms and legs completely and be light-colored because mosquitoes are attracted to darker hues.
Prevention and the use of an effective repellent can greatly minimize the threat of the disease. If possible limit outdoor activity at dusk and dawn when mosquitoes are most active. Dress appropriately when venturing outside; long sleeve shirt and long pants. For extra protection clothing can be treated with a repellent. Use an insect repellent that contains DEET as the active ingredient. Do not use repellents containing more than 10 percent DEET on children. Always wear a repellent when outdoors.
Pets should be treated with a labeled repellent or brought inside if possible during hours of heavy mosquito activity. Consult your veterinarian for information on effective repellents.
With all the rain, it’s nearly impossible, but eliminate mosquito breeding around the house by removing all sources of standing water. Pet watering bowls, should be changed frequently. Often sites of standing water that are overlooked include old tires, boat covers, flower pots and clogged rain gutters. Prevent mosquitoes from getting inside by properly screening and sealing doors and windows.
“The floods are actually playing to our benefit in regard to disease (in the eastern half of the state) because most of the vectors of disease agents that are mosquitoes are of the standing water variety. They required stabilized, stagnant water for breeding sites,” according to Olson, who adds, “But, once the flooding rain stops, the puddles left will stagnate. Then it will be, ‘Katy, bar the door.’ We may be in disease trouble. The standing water mosquitoes aren’t going to have to look far to find a breeding site.”
Glen Moore serves as entomologist for the Ellis County Extension Service.