What to do about mosquitoes?

One thing I have noticed this year is the increase in the mosquito population due to the above average precipitation we received this winter. Did you know there are at least 58 different species of mosquitoes found throughout the United State? Fortunately, only a few species cause annoyance.

Mosquitoes, whether in the home, yard, park or elsewhere, interfere with work and leisure activities. Some mosquitoes attack pets and even livestock, causing weight loss and decreased milk production. Others transmit diseases such as malaria to humans, encephalitis and West Nile Virus to humans and horses, and heartworm to dogs.

For personal protection, many people use repellants. Mosquito repellents work by interfering with the female mosquito’s ability to detect the environmental cues (for example heat, CO2, and water vapor) that she uses to find a host.

There are many studies comparing the effectiveness of mosquito repellents. However, it is difficult to compare among studies because of the variety of methods used in comparing products. 

One recent study (Tables 1. Products with the same Evaluation Letter are similar in their control) provides an idea of the variety of products available and of the range of efficacy of these products.

The main problem with mosquito control is it is impractical to eradicate all of the mosquitoes in an area. However, there are things we can do to help reduce their numbers. Water management to prevent mosquito breeding is essential for effective control. Eggs do not hatch unless they are on or in water. Tires, in particular, require special mention because they are primarily breeding places for vector mosquitoes. Tires are often next to dwellings in close proximity to people. Locate standing water and eliminate if possible and practical.

Solving the mosquito problem primarily through larval control is the most logical approach of reducing annoyance. This is the only time in the insect’s life cycle when it is truly confined, concentrated and most readily controlled. When standing water cannot be eliminated from the premises, it should be examined each week to determine whether larvae are present. Water can be dipped with either a pan or cup. A white utensil is preferred because brown larvae can be

seen easily against a white background. Should larvae be present, an insecticide should be applied at once.

Some insecticides labeled for control of mosquito larvae are:

• Bacillus thuringiensis israelensis (B.t.i.), product names- (Bactimos), (Vectobac)- There is a homeowner label of Bactimos 10 percent Briquet known as ³³Mosquito Dunks.²² (Kills mosquito larvae growing in bird baths, rain barrels, old automobile tires, ponds, ditches, unused swimming pools, tree holes, flower pots, roof gutters or wherever water accumulates.) (Altosid) - This product is an insect growth regulator (IGR), which acts by inducing morphological changes interfering with normal development. These effects are not immediately apparent and result in the failure of adult mosquitoes to emerge from pupae.

• Oil* (GB-1111), (Bonide), Petroleum distillate- Use high rate in areas of heavy vegetative cover and in waters high in organic matter. *Do not apply to fish hatcheries.

• Temephos* (Abate)- Use the high rate in polluted water and areas with organophosphate insecticide-resistant mosquitoes. For tire treatment, apply 1 lb. of 5 percent CCG per 100 square feet of tire pile service area. *Do not use on food, forage or pasture crops. Repeat as needed.

Adult control programs are necessary in disease situations such as encephalitis-stricken areas and in areas where a high density of pest mosquitoes occurs. The larger the area treated, the more successful the control. 

Adult mosquito populations can be temporarily reduced to less annoying levels. Thermal Fogging can be effective as a space treatment against adult mosquitoes. Mix the insecticide in oil (kerosene-type oils, fuel oils, diesel oils and other base oils suitable for insecticide use) and apply in late evening, at night or early morning when the air is calm (less than 5 mph). 

Do not fog during daylight hours. Fogging is effective as a contact application with no residual effect. Frequent applications are needed during heavy adult mosquito migrations. Always follow product label recommendations. Operate in a manner so the fog drifts with the wind through the target area.

Residual sprays are applied in water or oil, using mist blowers, pump sprayers, power backpacks or hand sprayers. They are designed to remain active for several days to several weeks, but environmental factors such as rain, high temperatures or exposure to strong sunlight may reduce their longevity. 

When applied to foliage, the rate of plant growth may also influence the efficacy of residual sprays. Residual sprays can be applied as barrier treatments to tall grasses, weeds, shrubs, fences, and other harborages surrounding parks, playgrounds, residences, or even subdivisions to help reduce adult mosquito populations. For best results, target areas just before the period of maximum use.

 Treat when adult mosquitoes are active in early morning or at dusk. Repeat at seven-to-10-day intervals. Do not allow public use of treated areas during application or until sprays have dried.

Avoid direct application to parked cars, trailers, watercraft, dwellings, and other non-target objects. Car finishes may be damaged if spray droplets are not washed off immediately, and always be sure to read the precaution and use labels for all products before application.