Classifications

• • A—HUMAN NECESSITIES
  • A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
  • A01N—PRESERVATION OF BODIES OF HUMANS OR ANIMALS OR PLANTS OR PARTS THEREOF; BIOCIDES, e.g. AS DISINFECTANTS, AS PESTICIDES OR AS HERBICIDES; PEST REPELLANTS OR ATTRACTANTS; PLANT GROWTH REGULATORS
  • A01N25/00—Biocides, pest repellants or attractants, or plant growth regulators, characterised by their forms, or by their non-active ingredients or by their methods of application, e.g. seed treatment or sequential application; Substances for reducing the noxious effect of the active ingredients to organisms other than pests
  • A01N25/30—Biocides, pest repellants or attractants, or plant growth regulators, characterised by their forms, or by their non-active ingredients or by their methods of application, e.g. seed treatment or sequential application; Substances for reducing the noxious effect of the active ingredients to organisms other than pests characterised by the surfactants

Definitions

• the invention relates to oil compositions for pest control in general, and to a mosquito larvicidal oil composition in particular.
• the composition according to the present invention is free from toxic chemicals / pesticides, has improved stability of the oil film on water and gives very high mortality rate (>90%) against Anopheles, Culex and Aedes mosquito larvae.
• Mosquito is a common insect in the family Culicidae. Mosquitoes go through four stages in their life-cycle: egg, larva, pupa, and adult or imago.
• Adult females lay their eggs in standing water, which can be a salt-marsh, a lake, a puddle, a natural reservoir on a plant, or an artificial water container such as a plastic bucket.
• the first three stages are aquatic and in the last 5-14 days, depending on the species and the ambient temperature, eggs hatch to become larvae, then pupae.
• the adult mosquito emerges from the pupa as it floats on the water surface.
• Adults live for 4-8 weeks. Larvae breathe through spiracles located on the eighth abdominal segment, or through a siphon, and therefore must come to the surface of water frequently.
• Mosquitoes are a vector agent that carries disease-causing viruses and parasites from person to person without being infected with the disease themselves.
• This mosquito is a vector of malaria and mosquito control is a very effective way of reducing the incidence of malaria.
• the principal mosquito borne diseases are the viral diseases yellow fever, dengue fever and Chikungunya, transmitted mostly by the Aedes aegypti.
• Mosquitoes are estimated to transmit disease to more than 700 million people annually in Africa, South America, Central America, Mexico and much of Asia with millions of resulting deaths. At least 2 million people annually die of these diseases.
• mosquito control There are many methods used for mosquito control. Depending on the situation, source reduction (e.g. removing stagnant water), biocontrol (e.g. importing natural predators such as dragonflies), trapping, use of Mosquito Larvicidal Oil (MLO) for killing mosquito larvae and pupae in the aquatic stage itself and/or insecticides to kill larvae and/or adults may be used.
• source reduction e.g. removing stagnant water
• biocontrol e.g. importing natural predators such as dragonflies
• MLO Mosquito Larvicidal Oil
• US 3,499,969 discloses an oily composition which is applied to water surfaces. The composition is toxic towards the aquatic stages of insect life, in particular to the larvae and pupae of mosquitoes. A promoter is added to mosquito oil, which turns toxic to mosquito larvae.
• the mosquito larvicidal oil according to the present invention is not fish toxic (toxicity to fresh water fish, LC 50 : > 100 mg/1 of water as per OECD Guideline No. 203 for Testing of Chemicals).
• the composition disclosed in the US patent depends on a promoter added to the oil for killing larvae, which turns toxic. It is a chemical action. But the invented oil is free of toxic chemicals and larvae mortality is due to cutting off oxygen to larvae i.e. suffocation. It is a physical action.
• US 4,166,112 discloses a buoyant colloidal bacterial larvicide composition containing bacteria which, when applied to water surface, remains just below water surface in the feeding zone of larvae and pupae and kills them when they feed on the composition.
• the method of killing is by contamination of the food taken in by the larvae and pupae. It is not mentioned whether the composition is bio-degradable.
• the invented oil composition makes a thin oil layer on the water surface and kills mosquito larvae by oxygen cut off i.e, suffocation.
• US 4,155,995 teaches the use of a high boiling point refined petroleum oil fortified with two specific surfactants, each in a specific concentration. This oil combination is said to be very effective against mosquito pupae and it is required in very much lower quantities in comparison with other similar oils of the time.
• the MLO according to the present invention has been specified on the basis of kinematic viscosity and surface tension.
• the oil film of the MLO will remain on the water surface without cracking and uniform for 2 hrs minimum after application which conforms to the requirement for larvae mortality as per WHO specification.
• US 6,623,766 This patent discloses an insecticidal formulation for mosquitoes. It is derived from herbal sources, in particular from plant sources. It is therefore totally bio-degradable and environment friendly.
• This US patent apparently describes killing of only adult mosquito by the insecticidal effect.
• the formulation of our invention does not contain any insecticide and has a different application from that of this US patent. It is applicable for mosquito larvae, and not for adult mosquitoes as claimed in the US patent.
• the killing method is by way of oxygen cut-off i.e., suffocation of the larvae, which is purely a physical phenomenon.
• US patent application 2010/310685 is directed to a pupicidal and larvicidal composition which has a substantially negligible toxicity for animals, particularly for fish, and for human beings.
• the formulation according to the present invention contains base oil/s and surface active agents.
• the formulation requires certain specific kinematic viscosity and surface tension for formation and maintenance of a thin layer on the stagnant water and works as a barrier for oxygen supply for respiration of mosquito larvae, killing the larvae by suffocating them.
• the formulation does not contain any chemical pesticide or poisonous material which is responsible for the killing of the larvae.
• the formulation has negligible fish toxicity.
• An object of the invention is to provide a mosquito larvicidal oil composition which forms a thin layer on water and eliminates mosquito larvae and pupae by suffocating them.
• Another object of the invention is to provide a mosquito larvicidal oil composition which is non-toxic to plant and animals, particularly fish.
• Yet another object of the invention is to provide a mosquito larvicidal oil composition which is bio-degradable.
• a further object of the invention is to provide a mosquito larvicidal oil composition which is required to be sprayed in small quantities, and hence is very cost effective.
• Yet another object of the invention is to provide a mosquito larvicidal oil composition which forms a thin, unbreakable and long lasting layer on the water surface after spraying.
• a still further object of the invention is to provide a mosquito larvicidal oil composition which causes no harm to human beings by entering into the human food chain.
• a mosquito larvicidal oil (MLO) composition has been disclosed, which eliminates mosquito larvae and pupae by suffocating them, when the composition is applied on stagnant water surface in a target area. It is bio-degradable as well as nontoxic to plant and animals, particularly fish, in the area of its application. It poses no danger to human beings because it does not enter into the human food chain.
• MLO mosquito larvicidal oil
• the MLO according to the present invention forms an unbreakable thin film on the water surface, and prevents the larvae and pupae from breathing in oxygen from the air above. Consequently, they die of suffocation within a short period. It has proved to be very effective. Moreover, it is devoid of side effects like pesticide resistance, resurgence of pests and numerous undesirable effects on flora and fauna that are usually associated with mosquito larvicidal oil compositions.
• the mineral oil can be paraffinic or naphthenic, hydrocracked or mixture of these.
• the surfactants/emulsifiers are required for the spontaneous spreading of the oil layer over water surface and stability of the oil film after application on water surface.
• the mosquito larvicidal oil (MLO) according to the present invention spreads uniformly on stagnant water and forms an unbreakable oil layer. This oil layer suffocates the mosquito larvae / pupae and leads to their elimination at the infant stage itself.
• the oil according to the present invention is non-toxic and has high biodegradability. This oil does not contain any poisons, insecticides or harmful chemicals. Hence, this MLO can be used safely for mosquito control in a variety of habitats including marshes, pastures, ditches, sewers, waste ponds, and tree holes. It very effectively controls larvae of Anopheles, Culex and Aedes species.
• Performance of MLO was evaluated by "National Centre for Disease Control (NCDC)" working under the Ministry of Family Welfare, Govt, of India, and was found to be extremely effective and to meet WHO/SIF/23.R1- Dec 1999 specification (100% 100% and 95% mortality for Anopheles, Culex and Aedes species larvae respectively @ 9.6 ml of oil per square meter surface area of water).
• Trial was conducted for MLO at various locations. Water samples were collected before and after the spraying of the invented MLO and the density of mosquito larvae was measured in each sample. More than 90 % mortality was observed after 24 hours. Hence, this oil was found to be extremely effective.
• MLO mosquito larvicidal oil
• the performance or non-performance of an MLO becomes quickly evident during its use on the water surface.
• the performance of water-insoluble MLO is dependent on the type of concentration of surfactant, and kinematic viscosity of the mineral base oil(s).
• a defect in the MLO formulation becomes immediately evident after its application on the water surface.
• An unstable and non-uniform oil surface can be detected by broken or cracked oil layer or oil droplets formation on the water surface.
• the factors affecting the performance of an MLO are the concentration of the surface active agents and optimum kinematic viscosity of mineral base oil/s. Performance of the same oil may also vary significantly depending upon the type and dosage of the surfactants/emulsifiers.
• a mere mixture of mineral oils and surfactant/ emulsifiers is not sufficient for making a good quality MLO with desired spreading and film formation characteristics. Therefore, an optimized combination of mineral oil/s and surfactants/emulsifiers was selected based on the chemistry and nature of the emulsifiers to get a composition of MLO suitable for spreading and film formation characteristics. Optimum concentration of surfactant/emulsifier along with required kinematic viscosity of base oil/s were observed to achieve good spreading and film characteristics of the MLO composition.
• the mineral oil is either paraffinic or naphthenic, hydrocracked or a mixture of all these.
• Base stocks may be of Gr I, II and III.
• the base oil typically has a viscosity from 2 to 20 cSt at 40°C. Viscosity of the formulation can be adjusted by mixing adequate quantity of the required different base oils. The spontaneous spreading and the film stability of the oil layer are greatly dependent on the kinematic viscosity of the mineral oil s and concentration of surfactant(s) and/emulsifier(s).
• the surfactants/emulsifiers are required for the spontaneous spreading of the oil layer over water surface and stability of the oil film.
• surfactant and dispersant are characterized as nonionic, anionic, cationic and amphoteric types, or a mixture of all them.
• the emulsifiers may be ethylene oxide, propylene oxide or its condensate, amine ethoxylate, alcohol ethoxylate, sulphonate etc.
• the HLB value of the nonionic emulsifiers present in the MLO is in the range of 2-14
• the base oil or mixtures of base oils is heated to 30-35°C while stirring.
• the MLO oil phase is prepared by adding adequate quantity of surfactant/emulsifier to the oil phase.
• the physicochemical properties of the MLO is determined by respective ASTM methods.
• the stability of the oil film and toxicity to the mosquito larvae are determined according to WHO/SIF/23.R1 norms.
• a good MLO is characterized by a film stability of more than 2 hrs and minimum larvae mortality of Anopheles stephensi and Aedes aegypti 90% and 75% respectively as per WHO/SIF/23.Rl .
• MLO composition is surfactant/s or emulsifier/s or mixture of surfactant/s and emulsifiers and its concentration varies from 0.001 wt % to 3.0 wt % preferably 0.01 to 1.0 wt%.
• the balance comprises of mineral base stock/s.
• Kinematic viscosity of an oil signifies its flow property. Higher kinematic viscosity means slow flow and lower kinematic viscosity means fast flow.
• the kinematic viscosity of the present MLO composition varies from 2-20 cSt @ 40°C.
• the MLO composition has a surface tension of less than 30 mN/m @ 25°C.

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• Life Sciences & Earth Sciences (AREA)
• General Health & Medical Sciences (AREA)
• Health & Medical Sciences (AREA)
• Toxicology (AREA)
• Pest Control & Pesticides (AREA)
• Plant Pathology (AREA)
• Agronomy & Crop Science (AREA)
• Engineering & Computer Science (AREA)
• Dentistry (AREA)
• Wood Science & Technology (AREA)
• Zoology (AREA)
• Environmental Sciences (AREA)
• Agricultural Chemicals And Associated Chemicals (AREA)

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Citations (5)

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• 2013
  • 2013-02-14 WO PCT/IB2013/051183 patent/WO2013140274A2/fr not_active Ceased

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