1.0 INSECTICIDES (General Overview)
Insecticide is a substance or a mixture of substances used for killing insects. It is well known fact that many protozoal bacteria diseases are transmitted from man to man by insects. One may combat these diseases not only by means of prohylactic drugs but also by the destruction of the insects carriers.
Insecticide is a chemical compound that is lethally toxic to insects either by ingestion or by body contact. It is applied to vegetation, crops and insect breeding areas either as liquid spray or as dry powder.
They are used in agriculture, medicine, industry and household. The use of insecticides is believed to be one of the major factors behind the increase in agricultural productivity in 20th century.
Nearly, all insecticides have the potential to significantly after ecosystem, many are toxic to human and others are concentrated in food chain. It is necessary to balance agricultural needs with environmental and health issues when using insecticides. It is crucially important that all the rural areas in Nigeria are being educated on the need to eradicate insects especially mosquitoes that might breed around the environment and transmit malaria to people living within the enclave.
Integrated Pest Management (IPM) in the home being with restricting the availability of insects of three vital commodities; shelter, water and food. If insects become a problem despite such measures, IPM seeks to control them using the safest possible methods targeting the approach to the particular pest.
Years now, efforts are geared towards controlling malaria infestation both in urban and rural areas. A lot of measures are being taken to reduce the number of death as a result of malaria.
We hear now and then that numbers being quoted by the analyst that died of malaria attack. Thus, free mosquitoes treated nets are always distributed to families and individuals all in a bid to reduce malaria attack from mosquito bite.
In the light of this, it is necessary to study God-given substances in this case, plant that has embedded substances that will help man combat mosquitoes or at least reduce infestation to the barest minimum.
1.1 OBJECTIVES OF THE STUDY/WORK
The purpose of this work is to produce mosquito repellants using orange peels (cestrum) wastes perse, which will save the cost of production and purchase, thereby increasing its availability especially in the rural areas. If the work is successful, production of mosquitoes repellants using orange peels will provide source of employment to our teaming youths and also make mosquito repellant within the reach of everybody, thereby reducing the number of death due to malaria caused by mosquito bite.
1.2 SCOPE OF THE STUDY
Orange peels (cestrum) will be prepared and used for the production of mosquito coil, which ignited, will repel mosquitoes within the limit of the smoke. The produced coil will be tested for the effectiveness performance. Cost analysis should also be taken to know weather mass production will be more effective or not.
1.3 LITERATURE REVIEW
1.3.1 HISTORY ASPECT OF MOSQUITO REPELLENT
Traditionally, various types of substances have been used to repel mosquitoes. These include such things as smoke, plant extracts, oil, tars, muds, etc.
As insects repellants technology became more sophisticated, individual compounds were discovered and isolated. This allows the formulation of new and more efficient forms of mosquito repellants.
The first truly effective active ingredient used in mosquito repellants was citronella oil. This material is a herbal extract derived from the citronella plant, an Asian grass. While citronella has been used for centuries for medical purposes, its repellence was only accidentally discovered in 1901, when it was used as a hairdressing fragrance. Since citronella oil is a fragrant material, it is thought that the chemical terpenes of which it is composed are responsible for its repellant activity.
Citronella oil does repel mosquitoes, but it has certain characteristics which limit its effectiveness. For example, it is very volatile and evaporates so quickly from the surface to which it is applied. Also, large amount are needed to be effective. The disadvantages of using citronella oil prompted researchers to study alternative synthetic compounds many of the early attempt at creating synthetic insect repellants were initiated by the Unites State military. Out of this research, the discovery of the repellant dimethylphthalate in 1929. This material showed a good level of effectiveness against certain insect species, but it was ineffective against others. Indalone was found to repel insect in 1937 and Rutgers 612 (2-ethyl-1,3-hexane diol) was synthesized soon after. Like dimethylpthalate, these materials had certain limitations which prevented their widespread use.
Since none of the available materials were ideal repellents, research into new synthetic materials continued. In 1955, scientists synthesized DEET (n-n-diethyl-netatoluamide) currently the most widely used active ingredient for mosquito repellents.
After its discovery, repellent manufacturers developed many different forms in which to deliver DEET, such as creams, lotions and aerosols.
1.3.2 CLASSIFICATION OF INSECTICIDE
Insecticides are usually classified into the following three classes.
STOMACH OR INTERNAL INSECTICIDES
These insecticides which are taken up by the insects are called stomach poisons or insecticides. Example, Boric acid.
CONTACT OR EXTERNAL INSECTICIDES
These insecticides destroy the insect simply by external bodily contact. Example Rotenone.
These insecticides act on the insects through the respiratory system. Example hydrogen cyanide, carbon disulphide, nicotine, p-dichlorobenzene, etc. .
Insecticides may be applied as a spray, liquid or in suspension, as a dust or as a gas.
1.3.3 CHEMICAL INSECTICIDES MAY BE CLASSIFIED AS INORGANIC, NATURAL AND ORGANIC INSECTICIDES.
Before world war II nearly all the insecticides were inorganic compounds of which arsenic, fluorine, sulphur and cyanide compounds were the most important. In recent years, inorganic insecticides have been greatly displaced by organic compounds in many applications.
The major disadvantage of inorganic insecticides is their comparable toxicity to man and other warm blooded animals. Upon handling and so as residues on food products.
SOME INORGANIC INSECTICIDES ARE;
· Lead Arsenate
· Calcium Arsenate
· Paris green
· Flourine compounds
· Sulphur and sulphur compounds
· Hydrocyanide acid
NATURAL OR PLANT INSECTICIDES
Plant materials yield some of the most widely used insecticides and many of them are being supplemented by the synthetic organic insecticides. The roots stem, leaves or flowers may be finely grounded and used as such or active parts may be extracted and used either alone or with other toxicants and auxiliary materials.
SOME NATURAL INSECTICIDES ARE
A typical organic insecticide is DDT (Dichlor-Diphenyl-Trichloroethane) with IUPAC name 4,4-(2,2,2-trichloroethane-1,1-diyl)bis chlorobenzene.
DDT was first prepared by O. Zeidler, a German Ph.D. student in 1874. Its insecticidal properties were however discovered by a Swiss chemist Paul Muller in 1939. DDT kills lice and mosquitoes which carries germs of typhus and malaria fever respectively. DDT was the first chemical to have the property of killing insects only by means of contact. DDT is still the backbone of many insects control programs and is widely used as a household insecticide against leaf hoppers and potatoes and in cotton insect control. DDT is a remarkable powerful and persistent insecticide that is soluble in kerosene oil, petrol and ethyl alcohol but insoluble in water. DDT is manufactured by exothermic condensation of chlorobenzene with chloral at about 300C in the presence of oleum or 99% sulphuric acid.
DDT (Dichloro Diphenyl Tdrichloroethane) Fig II 
In the 1940s, the properties of the new insecticide DDT seemed close to miraculous. In tropic, DDT save millions of lives by killing the mosquitoes that spread malaria, increase crop yields resulting from DDT’s destruction of insects pests saved million or more from starvation
DDT and other substances that undergo biological manifestation have two properties that makes them dangerous;
§ They do not readily break down into harmless substances
§ They are fat soluble but not water soluble, therefore, they accumulate in the bodies of animals particularly in the fat, rather than being broken down and excreted in the watery urine. Because the transfer of energy from lower to higher tropic level is extremely inefficient, herbivores must eat large quantities of plant materials (which may have been spread with DDT), carnivores must eat many herbivores and so on.
In1951, the first DDT resistant strains of mosquitoes were reported from Greece, Panama and U. S. A. In many parts of the world, spraying no longer prevents transmission of malaria. In addition, the passage of persistent insecticides such as DDT though the food chain become an increasing problem to birds and mammals at the top of chain.
1.3.4 BIOLOGICAL INSECTICIDES
Recent efforts to reduce bread spectrum toxins added to environment have brought biological insecticides back to vogue. An example is the development and increase in use of Bacillus thuringieness, a bacterial disease of Lepidopterans and some other insects. It is used as a lavicide against a wide variety of caterpillars. Because it has little effect on other organism. It is considered more environmentally friendly than synthetic insecticides. The toxin forms. Baccillus Thuringiensis. Baccillus Thuringiensis. Toxin has been incorporated directly into plants through the use of genetic engineering.
1.3.5 TOXIC EFFECT OF REPELLENT
Some insecticide kill or harm other creatures in addition to those they are intended to kill. For example, birds may be poisoned when they eat food that was freshly sprayed with insecticides or when they mistakes insecticides granules on the ground for food and eat them.
Sprayed insecticides may drift the area to which it is applied into wildlife areas, especially when sprayed aerially.
DDT can be a threat to health or the environment when used under wrong conditions. It causes progressively higher concentration in the body of the animal farther up the food chain.
Biological parameters were used to evaluate the toxic effect of different brands of mosquito coil smoke in experimental rats. The smoke from the coil produced significant increase (P<0.05) in the level of total protein, total albumen, bilirubin and blood/urea nitrogen when animals were exposed to smoke for 14 days.
Similarly, the smoke from the coils also cause an elevation in the activities of aspirate amino transference and alanine amino transference. Although the smoke from the coil did not produce lesions in hearts, lungs and liver examined, the increase in liver enzyme activities could be due to early liver damage.
Epidemiological studies have shown that long-term exposure to mosquito coil smoke can induce asthma and persistent wheeze in children. These studies also shows that one burning mosquito coil produces the same amount of particulate mass (diameter up to 2.5nm) as 75-137 burning cigarette would, and the coil can be as high as that released from 51 burning cigarettes.
1.4 MOSQUITO COIL
Mosquito coil is a mosquito repelling incense usually shaped into a spiral and typically made from a dried paste of pyrethrum powder. Mosquito coils are widely used as mosquito repellants. The major active ingredients of mosquito coilsare purethrins accounting for about 0.3 – 0.4% of the coil mass. When a mosquito coil is burnt, the insecticides evaporates (pyrethrin, PAH, aldehyde, etc) with smoke, which prevent the mosquito from entering the room and harm those already in the room. The remaining components of mosquito coils include filters, binders, dyes and other additives capable of burning well without flame. He components generates large amunt of submicrometer particles and gaseous pollutants such as acenephthene, paranthrene, etc.
Mosquito coils are often used overnight in sleeping quarters where continous exposures may occur. Chronic exposure to coil smokes occur during rainy periods because mosquitoes are found to be more active in the environment due to collection of water and increase in green plants.
1.4.1 HOW MOSQUITO COILS WORK
Mosquito coils are burned on specially designed stands placed inside more attractive looking mosquito coils holders which contain holes to let the smoke out. The holders can usually be hung up or laid flat. Each mosquito coil slowly burns for around 8 hours, during which time repelling active ingredients such as pyrethoids or pyrethrum disperse with the smoke. The combination of ingredients in the smoke coil either prevents mosquitoes from entering the surrounding area, encourages them to leave the area if they have not already done so, or knocks the insect down and kills the.
1.4.2 HOW TO USE MOSQUITO COILS
Mosquito coils are particularly useful for protection against mosquitoes when sitting outside at night. They can be placed on a table so people can congregate around them. It helps to stay in the vicinity of the smoke given off, but this may be difficult if the smoke is carried away by the wind. A good tip is to place a mosquito coil down on the ground by people’s ankle and feet, as this is an area mosquitoes seem to bite frequently.
Again, the less wind there is, the more likely the mosquito coil smoke will have a chance to be effective. Mosquito coils are generally meant for use outdoors, but if they have to be used indoors, it is wise to make sure rooms are well ventilated. Packs of multiple mosquito coils are available with a coil stand included.
1.4.3 ADVANTAGES OF USING A MOSQUITO COIL
Mosquito coils nowadays burn without flame for up to eight hours of continuous repelling action. In quantitative tests, they provide about 80% protection. Mosquito coils are also cheep and need no special equipment to use it in other than just lighting it up. They are portable and fit into normal household practices of lighting candles or incense.
1.4.4 DISADVANTAGES OF USING MOSQUITO COILS
There are several hazards that we know to be caused by mosquito coils. In 1999, sparks from mosquito coils ignited a fire that swept through a three-story dormitory building at a summer camp, 23 persons including 19 children died in the blaze in South Korea.
The long-term exposure calls for concerns on the potential toxicological effects of smoke on humans.
1.4.5 ACTIVE INGREDIENTS IN MOSQUITO COIL
The active ingredients found in mosquito coils can be some of the following;
o PYRETHRUM (Natural, powdered material from a kind of chrysanthernum plant, performing moderated)
o PYRETHRINS (Extract of insecticidal chemicals in pyrethrum)
o ALLETHRIN Some times d-trans-alletrin)
(The first synthetic pyrethrin)
o ESOBIOTHRIN (a form of allethrin)
o DIBUTYL HYDROXYL TOLUENE (BHT) (an optional additive to prevent pyrethroid from oxidizing during burning).
o PIPERONYL BUTOXIDE (PBO) (an optional additive to improve the effectiveness of pyrethroid)
o N-(2-ethylexyl)-bicyclo-(2,2,1)hept-5-ene-2,3-dicarboximide (MGK 264) (an optional additive, to improve effectiveness of a pyrethroid).
1.5 CITRUS SINENSIS/ORANGE PLANT
The orange plant is a hybrid of ancient cultivated origin, possibly between Pomelo (citrus maxima) and tangerine (citrus reticulate). It is small flavouring tree growing to about 10m tall with evergreen leaves, which are arranged alternatively, of ovate shape with crenulate margins and 4-10cm long. The orange fruit is a hesperidium, a type of berry.
Orange originated in southeast Asia. The fruit of Citrus sinensis is called sweet orange to distinguish it from citrus aurantium, the bitter orange. The name is thought to ultimately derived from the sanskirt, for the orange tree, with its final form developing languages. In a number of languages.
In a number of language,it is known as a “Chinese apple” (e.g Dutch Sinaasappel, “China’s apple”.).
Orange can be found in almost all parts of Nigeria.
SPECIES OF CESTRUM &n
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