Controlling Mosquitoes

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A comprehensive mosquito control program is a carefully planned and executed operation aimed at ensuring effective and continuous control of mosquitoes in a given area. It follows an integrated approach using methods or combinations of methods that give maximum control of mosquitoes with minimal impact on non-target organisms and the environment. The approach must consider cost/benefit ratios and be sound from an economic standpoint.

CHEMICAL CONTROL

Adulticiding:
The term "adulticiding" is used to describe the procedure of applying insecticides to kill flying adult mosquitoes or those adults resting in vegetation, buildings, or similar harborage. Only EPA approved insecticides are utilized, with applications following label directives for their use. Application methodology is Ultra Low Volume (ULV), generally implying the application of materials at the rate of ounces per acre. Applications generally begin around sunset and resume into the evening hours. This normally coincides with the peak activity period of adult populations allowing for the most cost effective control efforts. Weather conditions are a major factor as to the success of these operations. Conditions such as rain, high winds, cool temperatures and fog have an adverse effect on spray operations and may actually shut it down.

Ground Application: The fleet consists of 12 permanently rigged spray trucks, with the ability to add 2 portable units during times of need. These machines arespray truck carefully calibrated to dispense 0.6 - 1.4 ounces of insecticide per acre depending on which type of insecticide is being used. On board computers regulate flow application rates allowing drivers to legally spray at speeds ranging from 7 - 18mph. The machines are also calibrated to deliver small droplets of 10 - 15 microns in size, which allows for proper drift to contact and kill adult mosquitoes. GPS tracking units in each truck give detail information of spray route, speed of travel, time and spray on/off.

Aerial applications: There are two aircraft in the fleet utilized to treat large and/or airplaneinaccessible areas quickly and thoroughly. Computerized flow controls, as well as GPS, are also employed to assure accurate applications of insecticides at ULV rates of 0.5 – 1.0 ounce per acre. Time of applications normally begin around sunset into the evening hours coinciding with peak mosquito activity. Aerial applications are usually conducted at altitudes below 300 feet.

Portable/Off-Road: Each inspector is equipped with a hand-held ULV sprayer that can be used to combat adult populations inaccessible by vehicle or confined to a very limited space that does not warrant the use of a truck or aerial unit. There is also an ATV unit equipped with an ULV sprayer for larger off-road needs. These units give quick solutions to localized problems.

Larviciding: The term "larviciding" involves treating the immature stages of mosquitoes in standing water while they are still pupae or larvae. Products utilized are either oils or bio-rational products. Oils generally give a broad range of control of both pupae and larvae, while the biorational products are effective primarily against larvae. As with adulticides, all products used for larviciding are used according to their label. Following are examples of the type of habitats that are regularly monitored and larvicided when appropriate.

  • Roadside Ditches
  • Catch Basins
  • Flooded Woodlots
  • Buckets, tires, boats, bird baths or any other item collecting water

Application: Most all larviciding is accomplished using ground and hand-held techniques. There are 3 trucks rigged permanently for larviciding application: 2 for granular and 1 for liquids. These are used primarily for roadside ditches. Calibration and GPS tracking assures proper verification of application. One ATV unit can also be rigged for off-road applications and inspectors have hand-held tanks for custom application when needed. Catch basins in the parish are larvicided by placing a slow release (last about 90 days) product in a custom made PVC holder and suspending it from the top of the basin by a string into the water. Aerial applications can also accomplished by when deemed feasible.

PHYSICAL CONTROL

Source Reduction: This refers to any method of physically altering a mosquito breeding site to render it useless for the completion of the mosquito life cycle. It mostly takes the form of drainage, but can also be filling, water level management, and emptying/storing containers. Residents should be aware of areas around the premise that hold water and alter these habitats to assist in the reduction of mosquitoes around their properties. Below is information on accomplishing these objectives.
 
Emptying Containers: The most practical control strategy around the hotrash canme is to remove containers from environmental factors (rain) that contribute to them collecting water and become mosquito production sites. For those containers where water is desired, flushing them every 4 -5 days is essential. Eliminating the water source where mosquitoes breed is a must for homeowners. Remember, anything holding water around the home is a potential mosquito breeder (common breeding sites).

Ditching/Filling: Both of these methods are effective in eliminating breeding sites from around the residence. Low areas can be identified after rains and either ditched for rapid drainage or filled to allow for the proper runoff into drainage systems. Where runoff is not possible, a pond may be dug and stocked with minnows to provide control.

BIOLOGICAL CONTROL    dragonfly            mosquito fish

Naturally Occurring: The most important biological control of mosquitoes is happening continuously in nature. Birds, bats, spiders, and various flying insects prey to some degree on adult mosquitoes. Beetles ants, isopods (pill bugs), cockroaches, and other scavenging animals prey on their eggs. Many kinds of aquatic animals such as fish and miscellaneous invertebrates prey on mosquito larvae and pupae. Larvae are vulnerable to a number of parasites and pathogens.

Bio-Rational Products: A bio-rational product is any product that is naturally occurring that will kill mosquitoes in nature. Many were discovered accidentally through research processes on mosquitoes. Once discovered, these naturally occurring organisms are now commercially reproduced and used as part of an IPM program. One of the main benefits of using these products is that they are very environmentally friendly. This means they have little to no effects on other organisms inhabiting areas utilizing the same breeding areas, including animals that may drink from the water. In fact, some of these products are labeled for use in potable water sources.

As mentioned in the larviciding section, our program utilizes bio-larvicides like Bacillus thuringiensis (Bti) and Bacillus sphaericus, both spore and crystal forming soil bacterium in control efforts. The bacterial spores/crystals are poisonous to mosquito larvae, but harmless to most all other forms of aquatic and terrestrial life. Another bio-product utilized is methoprene, an insect growth regulator. This product disrupts the developmental cycle of the mosquito preventing it from completing its transformation from pupa to adult. It too is extremely safe to use in most all breeding situations.