Late in the summer of 1999, many people were terrified by a small, flying insect.  Mosquitoes, most specifically the species Culex pipiens and Culex pipiens pipiens are the two believed responsible for the transmission of West Nile Like Encephalitis into a number of areas in the Eastern United States.  We now know that other mosquito species may also be a vector of this disease.

Mosquito Basics

     Mosquitoes go through complete metamorphosis.  This includes the egg, larva, pupae and adult insects.  Mosquitoes lay their eggs in "rafts" or groups in standing water or sometimes in dry areas that these insects are able to anticipate will become wet. While many species lay eggs in large bodies of standing water, Culex pipiens and Culex pipiens pipiens take advantage of microenvironments in areas such as blocked gutters, standing water in debris such as tires, wheelbarrows, planters, swimming pool covers, ditches, sink holes and other land depressions.  

     When the eggs hatch in response to a sufficient amount of water, the larva actually float on the surface of the water.  The water must remain fairly still or the larva will not survive.  After a development period of 4 to 10 days, the larvae will pupate (enter the cocoon stage) while still in the water. In as little as a day, but sometimes weeks later, the adult (biting) stage emerges and remains floating on the pupal case until ready to fly off for its first blood meal.

     Encephalitis is a disease vectored by migratory birds.  The two known Encephalitis related mosquitoes don't fly very far, but if they feed on an infected bird and then bite a person, there is potential for transmitting the disease.  

Monitoring

     As part of protecting the public health, officials in susceptible areas have purchased equipment to carefully monitor for mosquitoes carrying West Nile Like Encephalitis.  In some cases, caged chickens or other similar birds are placed in mosquito prone areas and their blood may be drawn and checked for the virus on a regular basis.  These birds are not affected by the virus but may have it in their bloodstream.  If dead (migratory) birds are found, they too are tested.  Finally, sophisticated monitoring traps using fans and carbon dioxide (dry ice or cylinders) to attracts the mosquitoes, help to determine if there is a level of mosquitoes present that requires control measures.   Testing mosquitoes for the presence of diseases is another part of the process.

IPM (Integrated Pest Management)

     One of the most important concepts that has been introduced into the realm of Pest Management in the last few years is the concept of Integrated Pest Management (IPM).  Though there is some disagreement as to how to implement this concept, the common goal is the reduced use of pesticides. With mosquitoes in particular, pest management may best be achieved using resource management.  

     The most effective control measures for mosquitoes pertain to environmental controls.  Because these mosquitoes breed in standing water and areas that are flood prone, eliminating these harborages as mentioned above, is essential.   Checking each property for ditches, clogged gutters, debris etc. is a key part of control.  Additional controls may include checking screens on buildings to be sure that biting adults are kept outside.

     Another facet of management includes insect repellents, larvicides (to kill the larval mosquitoes in standing water) and adulticides which complete the IPM picture. Because children and the elderly are most vulnerable to the effects of West Nile Like Encephalitis, those groups should consider using insect repellents to protect them from insect bites.  Since mosquitoes are most active at night, people going out at that time need to be cautious.  Wearing long sleeved garments and long pants if practical, can be helpful.

     The Bug Clinic offers Mosquito Dunks as a general use larvicide for the public.  This two inch round donut shaped product may be used to treat standing water in ponds, on top of swimming pool covers, in bird baths and in any other stagnant water.  This product is essentially non-toxic according to the manufacturer.  The active ingredient in the product is bacillus thuringiensis israelis or Bti.  This product is specific for mosquitoes and other insects whose larvae breed in standing water.

     Adulticides may be applied to lawns and wooded areas to help kill mosquitoes.  Several insecticide concentrates may be applied for this purpose (check the label).  

     We also offering an organic alternative to insecticides.  Dr T's Nature Products produces an entirely organic formula called Mosquito Repelling Granules.  This granular product is repellent to both mosquitoes and gnats and is poison free.  It contains oil of lemongrass, oil of peppermint and garlic as its active ingredients.  It is not a registered pesticide.  According to the  manufacturer, the product is actually beneficial to soil and the product has pleasant odor.  A single application will last for two to three weeks or more.  We have sold the product for years now and have had mostly positive feedback from people that have purchased the product.  We've also had repeat business which tells us that the product is effective.

To Summarize

     Mosquitoes have become a major issue in some areas of the United States.  Understanding the complete metamorphosis of mosquitoes and the mode of transmission of this disease is a key component in the management of this insect.  Many local governments will be monitoring for mosquitoes infected with West Nile Like Encephalitis.   Because the implicated species, Culex pipiens and Culex pipiens pipiens don't fly far from their breeding source, control of breeding sites using mechanical alterations, repairs and larvicide are very important.  Use of insect repellents by children and the elderly as evening approaches is a prudent action to take as for these two groups of people whom are most likely to be severely affected by this disease.

     Adulticides and repellents for the lawn may also help control biting insects and thus protect people from potential harm.

Though The Bug Clinic can answer questions for you regarding mosquitoes and their control, remember that your local health department is the most accurate source for information about mosquitoes around your area.  

     We offer free advice on any pest problem.  You may call us weekdays, toll free at 800-433-1128 between 8 am and 4 pm ET.  Locally, call us at 845-356-2837 or send us a fax at 845-746-9018.  We also try to answer any written questions promptly.  Feel free to click here and write to us.