GB2376887A - Mosquito control using a surfactant which acts as a powerful larvicide - Google Patents

Abstract

By combining insect repelling oils, a Bacillus thuringiensis (Bti), and a suspension agent, in a monomolecular layer the solution is used to control the population growth of mosquitoes in an aquatic environment. The monomolecular solution is a non-toxic and biodegradable surfactant. Surface tension is reduced causing water to enter the breathing tubes of the Larvae or Pupae, drowning them. The Bti is toxic to both Pupae and Larvae and being in the monolayer suspension enhances its effectiveness. The repelling oils discourage the adult mosquito from laying eggs on the surface. The suspension agent, preferably fumed silica, acts as a flotation aid for the Bti.

Description

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Mosquito Control using a Surfactant which when applied to breeding grounds acts as a Powerful Larvicide Description In many parts of the world, populations of mosquitoes are on the increase, as they become resistant to insecticides and other methods of control. As a consequence of this, the malaria parasite, which is carried by the mosquito, is now a serious problem for the populations of many countries.

In the past there have been various attempts at controlling the mosquito at the beginning of it's life cycle by directly attacking the larvae or pupae This was done, In the early days, by introducing a film of oil on to the surface of the water where the mosquito larvae were breeding. This prevented the larvae from breathing, but it also affected many other species and polluted the environment.

This was later replaced by non-toxic materials including monomolecular films (monolayers), or foams which starved the larvae of oxygen, but were either difficult to apply, or were not effective at controlling the mosquito at all stages of it's development. They also had a short life span being dispersed quickly by the elements making it uneconomical Insecticides have been used to control the larvae and pupae in breeding grounds, however these affected fish and other species living in the water. The residual chemicals in the water would render the water unsafe to drink.

More recently, biological pest control agents have been developed which are very specific in targeting mosquito larvae One of these is Bacillus thuringiensis subsp. israelensis (Bti) which disrupts the intestinal gut lining of insect larvae by endotoxins. (Also known as BT H14)

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Using a Bti has proved effective, but the product in isolation, has several disadvantages Foremost, when it is applied to water it naturally sinks and loses much of its effectiveness. In this state it naturally degrades very quickly.

By using the above methods alone, the adult mosquito, could in certain circumstances, continue to lay eggs on the water surface.

The invention described solves the above problems by attacking the mosquito at all stages of its development in the aquatic environment.

Firstly, a non-toxic monolayer is used as a base.

Secondly, this is combined with a gelling agent, which is capable of holding the Bti in suspension on the surface of water.

Thirdly, insect repelling natural fragrances, citronella and eucalyptus, are added so that the adult mosquito will not lay eggs on the water surface It has been found that the effectiveness of this combination is far greater than that of the individual components in isolation The essential features are :- The monolayer works by reducing the surface tension around the breathing tubes of the larvae and pupae, which allows water to flood the respiratory system leading to drowning . The Bti suspension is particularly effective at terminating the larvae when ingested.

. The insect repelling oils will stop the adult mosquito from laying eggs on the water.

. For a given area, the quantity of the solution required is much less than conventional pesticides as the components are on the surface-where the larvae reside.

. The longevity of the Bti is extended because of the characteristics of the suspension.

. The solution is non-toxic to most other species including humans and is biodegradable.

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The monolayer component consists of molecules having a long water repellent (hydrophobic) tail attached to more compact water-attracting (hydrophilic) head. This asymmetry causes the molecules on a water-surface to form as sheet of molecules with hydrophobic tails in the air and hydrophilic heads under water in a monomolecular film.

The first component is the monomolecular film as described above, comprising :- 90% Oleyl Cetyl Alcohol 90/95 with 2 mol EO 10% Cetyl Stearyl Alcohol with 2 mol EO The second is the Biocide :-Bacillus thuringiensis subsp. israelensis (Bti) The third component is the gelling agent : - Fumed Silica- a water-Insoluble gelling agent, which, holds the Bti in suspension and does not cause agglutination.

The fourth is a combination of two insect repelling fragrant oils :-citronella and eucalyptus (0. 5%).

Claims (4)

1. Claims 1. That by using repellent oils within the solution, egg laying is inhibited.
2. 2. That by using fumed silica, Bti, monolayer and repellent oils, the mosquito's life cycle is interrupted during each of it's aquatic stages
3. 3. That the life of the Bti is extended due to the fact that it is held In a suspension.
4. 4. That the formulation of the monolayer described, the Bti and the repellent oils are a unique combination providing a non-toxic and biodegradable solution to mosquito control.