Insects are intimately related to man, and they play an important part in the transmission of disease. They institute a group of arthropods that have bilateral symmetrical bodies, jointed appendages, with hearts situated dorsally and nervous system vertically. Their bodies are with a tough skin called exoskeleton and are divided into three parts – namely head provided with two antennae, eyes and mouth; the thorax composed of three segments with three pair of legs and two pair of wings; and an abdomen composed of nine to eleven segments, the last two being modified into the external genitals. They have distinct sexes and are reproduced from eggs. They have visual organs in the form of compound and simple eyes. They are not provided with lungs. They breathe by means of special type of tubular organs called trachea, which communicates with the external air by lateral openings called spiracles.
II. Winged – Mosquito
These insects are frequently though not necessarily associated with dirt. They abound in unhygienic conditions and their entry into clean places may be entirely accidental.
Fleas – There are many different kinds of fleas and each has a preference for the kind of host, e.g. human, cat, dog, vermin, etc. Any of these hosts may introduce fleas into an establishment. Fleas bite their host causing annoyance; and in case of humans, large red itching spot appears on the skin. Flea born epidemics are plague, endemic, murine, and typhus.
These are wingless insects 2-3 mm long with laterally flattened, hard thoraxes and abdomen, and three pairs of legs. They are bright coloured and both male and female suck blood.
Life history - 8-12 eggs at a time – within 2-4 days (summer) and ½ week (winter) the eggs hatch and hairy larvae appears – develops into pupa in 2 weeks time by spinning a cocoon covered with dirt and dust, in which it pupates – in 2 weeks time develops into an adult flea.
Habits – They prefer darkness and are sensitive to light. In the absence of rats, when starved they bite men. They travel about 20-30 yards, and can jump up to 3 inches.
Spraying with insecticide is a suitable way of eradicating them.
Lice – They are small wingless ectoparasites with hard chitinous covering and having three pairs of legs, each provided with a single claw. They live entirely on mammalian blood. They have oval grayish bodies that become brownish when filled with blood.
Head lice, which live in the hair of the head, are probably the most common of all lice. They cause intense irritation and such blood. Their eggs called ‘nits’ are numerous and stick firmly on hair, and cannot be removed by brushing.
Diseases conveyed – There is no disease that can be directly attributed to lice, but they cause irritation and annoyance and loss of sleep.
Life history – A female lice within 48 hrs of assuming adult form, produces it’s eggs. It lays about 300 eggs during it’s lifetime. In seams of clothing the eggs may remain alive for 30 days. The male is about 3mm long and female 3.3mm. The larva emerges in 6-7 days, during which 3 molts occur and insects become adults. A lice takes 15 days period to complete it’s cycle from an egg to it’s development of adult stage.
Average life span of lice – 36 to 58 days.
Anti-lice measures include general cleanliness of body, hair, clothes and articles of the room.
Bedbugs – No insect is more difficult to eradicate from a building than a bed bug. The main difficulty is to get at it. Gammaxine, D.D.T or kerosene oil containing pyrethrum maybe sprayed for exterminating the bed bugs. Cyanic acid, if used for the purpose, gives very good results, but it’s use requires a great care on account of having poisonous effect on human beings. It must also be emphasized that if articles are removed from the room, they should be thoroughly inspected first.
A bed bug measures from 3-5 mm in length and 1.5 to 2.5 mm in width. It is dark brown, thin, compressed creatures, so it takes it’s way in narrow cracks. Both male and female bugs bite, which cause considerable irritation and may result in large red patches with swelling.
They prefer human blood and are able to survive sometimes many months without food. They are natural by habit and deposit their eggs in crevices and cracks of woodwork and behind wallpaper. The eggs are stuck ton these surfaces by cement like substance exuded by the bug and are therefore difficult to brush off.
Bedbugs cover considerable distances although they cannot fly. They also give off an unpleasant smell.
Life history – females lay 1-12 eggs at a time several times a year – hatch in 7-10 days – larvae molts soon after a blood meal – reaches the adult stage after 4 subsequent molts – in another 2 weeks becomes sexually mature. Lifecycle takes about 8-10 weeks to complete.
Silver fish – They are wingless insects, silver gray in colour and about 1 cm long. The young closely resemble the adults and both are rounded in front and tapered towards the rear. Silver fish require a moist place in which to live. They leave their hiding places in search of food of cellulose nature. They feed on starchy food, paste in wallpaper and books, and may attack clothing made of cotton or rayon, especially if starched.
Gamaxine, D.D.T, pyrethrum maybe sprayed for exterminating silver fish.
Cockroaches – They are more likely to be found in the kitchen and restaurant than in accommodation areas, although cockroaches do not necessarily require human food; and will feed on whitewash, hair and books if no other food is available.
Hygienic storage and disposal of food and waste and the cleanliness of all areas where food is handled are important points in the prevention of infestation.
Cockroaches are difficult to eradicate but a residual insecticide, for e.g. chlardecome, may be used in cracks, crevices and holes; especially in brick or plasterwork through which warm pipes pass.
Mosquitoes – They are often referred to as ‘biting flies’ but they are in fact, piercing insects, for the jaws of the female are transferred into a needle like object with which to penetrate the skin, when a blood meal is required. The initial stages of their life viz. egg, larval and pupae stages are spent in water. The presence of water is therefore extremely necessary for their existence. The male mosquito lives rarely 1-3 weeks. The female may live up to 4 mths or more. Mosquitoes prefer dark to light colours. Provision of the blood meal is essential for the female mosquito before laying a batch of eggs.
Life cycle – The female lays100-250/500 eggs on the surface of water. In 2-3 days, the eggs hatch out and a small worm like larvae appears. These larvae feed on vegetables. The larvae cast its full size in 6-10 days, when it changes into a coma shaped creature called Pupa. In 2-3 days it splits up and an adult mosquito emerges.
Methods of prevention and control:
a) To do away with the conditions which render possible the breeding of mosquitoes.
b) To destroy the mosquito at some period of life.
c) To prevent the mosquitoes from biting man.
A. To do away with conditions which render possible the breeding of mosquitoes -
i. Proper drainage
ii. Proper water disposal
iii. No stagnant water
B. To destroy the mosquitoes at some period of life –
- Kerosene oil / diesel is sprayed on the surface of water once a week
- Pyrethrum extract: Pyrethrum extract 2%
- Pine oil
5. All the above are mixed in liquid soft soap and a concentrated stock solution is made. This is diluted 10 times with water and stirred thoroughly before spraying.
- Paris-green-aceto-arsenite copper is mixed with100 parts of fine road dust, scaled lime; saw dust, etc. and blown by machine or manually. It is effective in dense vegetation.
- D.D.T (dichloro diphenyl trichloro ethane) – This is a white crystalline powder. It is used as 5-10% oily solution by spraying, or in 10% concentration if used as dust. It is used in the following forms –
a. D.D.T aromax emulsion consisting of D.D.T, aromax, soap flakes and water. It is sprayed.
b. D.D.T kerosene oil
c. Pyrethrums extract 4%, D.D.T and kerosene oil. This is also sprayed.
d. D.D.T in aerosols. The aerosol contains.4% pyrethrum, 3% D.D.T, 5% cycle hexane, 5%sesame oil.
e. Gammaxene or benzene hexa chloride (B.H.C). This is gammaxene P520 (water dispersible powder) and water in suspension and is sprayed.
I. Prevention of breeding of flies – It aims at prompt removal and disposal of all refuse. All garbage, kitchen wastes and similar refuse should be placed in garbage receptacles. For destruction of eggs, larvae and pupae of flies, powdered borax can be applied in solution.
II. Protection of food from flies.
III. Destruction of adult flies
a) By flytraps
b) Poisonous baits maybe used. 2% formalin solution with sugar and milk maybe used. Or sodium arsenate solution maybe used.
c) Spraying D.D.T, pyrethrum in kerosene, giolderin, chlordane or B.H.C will readily kill flies.
Carpet beetles – These are 2-4mm long like small mottled brown, gray and cream ladybirds. Adults are often seen from April – June, seeking places to lay their eggs. The larvae are most active in October before they hibernate. The adult beetle feds on pollen and nectar of flowers, but lays it’s nest in old nests of birds, fabrics and accumulated fluff in buildings. The larvae that hatch from eggs do the damage by feeding on feathers, fur, hair, wool or articles made from those substances. Carpet beetles are now the major hostile pests and do more damage than moths.
The life cycle takes about a year and the larvae can survive for several months without food.
Frequent vacuum cleaning of fluff and debris from storage cupboards, floorboards, carpets and upholstery is the main means of control. Insecticide maybe sprayed between floorboards, under carpets, under felts and in the crevices.
Wood burring beetles – The common furniture beetle lays about 20-60 eggs in cracks and crevices of unfurnished wood. On hatching, the grub eats it’s way through the wood and this tunneling causes weakening of the wood and may take form 2-3 yrs. Eventually the grub matures, bores towards the surface of the wood and changes into pupa. From this emerges the beetle which bites it’s way into the open air through an exit hole which is about.15 cm in size. The beetles have a very short life of 2-3 weeks.
If small piles of bore dust beneath the holes indicate presence of active worms in the wood and treatment is necessary.
Eggs are laid in unpolished wooden surfaces, so the use of shellac, varnish, lacquer or polish acts as a deterrent. To kill woodworm, the exit holes should be sprayed, brushed or injected several times with antokil, usprinol, pyrethrum, etc. There are other treatments such as blowing poisonous gases. A badly infested piece of wood is better burnt.
Moths – Clothes and house moths are of pale buff colour and are seen flying mainly between June and October. They rarely live longer than a month.
The female lays its eggs (approx. 200 at a time) in some dark warm place, on material that later the grubs (pupae) can eat. Once the eggs hatch, the grubs immediately feed on the material the move about. When fully grown they crowd into sheltered places and spin a cocoon around themselves and become chrysalis (pupae). They later emerge as moths and start another lifecycle. The entire lifecycle varies from 1 month to 2 yrs.
The materials that are attacked by moth (the grubs) are wool, fur, skin and feather. They are immune to rubber, man-made or vegetable fibers. While feeding on these materials, the grubs form small holes in the articles and damage occurs frequently during the storage, because of the warmth, darkness and lack of disturbance.
always advisable that articles to be stored should be clean, protected by moth
deterrent and inspected frequently. Calmly used moth deterrents are
naphthalene, camphor tablets,
Rats and mice – Rats and mice are more likely to be found in kitchens and dining rooms than in bedrooms. Scraps of food, candles, soaps, etc attract them. Hygienic storage; disposal of food of all kinds of waste; and cleanliness of all areas where food is handled are important to prevent an infestation.
Rat’s destruction: –
a) By poisonous baits – Baits consists of an inner base to which some poison is added. The common bases are flour, bread, sugar, etc. the most common poison used is barium carbonate. Other poisons are white arsenic, phosphorus, zincphosphide, alphanaphnyl thiourea, sodium fluro acetate (1080) and dicoumarine (warfarin).
b) By fumigation – This is a very effective method and should be carried out by a trained squad. Cyanogas ‘A’ dust or cymag is used. The other gases which are used are carbon monoxide, carbon dioxide, sulphur dioxide.
c) By trapping – Generally wire cage traps are used for the purpose. Trapped rats are transferred everyday to the collecting cage, which is taken to the disposal station where the rats are drowned by immersing the whole cage in a tub containing phenyl or water.
Wood Rot –
Dry Rot – This is the term used for the decay of timber by a fungus which grows and lives on wood; and reduces it finally to a dry crumbling state – hence the name dry rot. It starts in damp (more than 20% moisture) unventilated places and spreads by sending out thin root like strands that creep over brickwork to attack the surrounding wood. Once a fungus gets hold, it produces fruit bodies. The spheres are produced in enormous numbers and are so small that they move as reddish brown dust, which may be blown about easily, to great distances.
Dry rot can be recognized by its offensive, mouldy smell; by it’s friable condition and the ‘dead’ sound when the wood is hit with a hammer. When a rot occurs it is necessary to find the reason for the dampness of the wood.
Having ascertained and cured the cause of dampness, all rotten wood must be thrown out 20-30 cms beyond the infested area and burnt. All brickwork near the infested wood should be sterilized by the use of a blowlamp and when cool, treated with a preservative before repairing.
Wet Rot – This is the name given to the fungus decay in timber in very damp situations. The fungus usually involved is the cellar fungus and it attack timber when it is wet. It requires considerably more moisture for development than dry rot fungus (approx. 40-50% of the dry weight of the wood).
The fungus causes the darkening of the wood, which breaks up into small rectangular pieces on drying. There is usually a thin skin of sound wood left on the surface of the timber, but rarely is there any evidence of fungus growth.
Since the fungus requires relatively wet timber, it’s eradication is much more simple than in case of dry rot. Growth can be checked at once if the timber is thoroughly dried and the source of moisture removed. Badly decayed wood should be cut out and replaced with a fungicide.
APPLICATION OF PESTICIDES
The application of pesticides must be closely monitored and controlled. Only those personnel properly trained in the storage, dilution, and application of pesticides and properly licensed by the appropriate state agency should be authorized to apply pesticides.
Types of Pesticides
Pesticides may be classified in a number of ways:
1. By their effectiveness against certain kinds of pests:
Insecticides versus insects
2. By how they are formulated and applied:
3. By the chemistry of the pesticide:
Chlorinated hydrocarbons (Chlordane)
Organic phosphates (Malathion)
Natural organic insecticides (Pyrethmun)
Effectiveness against a particular pest species, safety, clinical hazard to property, type of formulations available, equipment required, and cost of material must all be taken into account when choosing a pesticide for a particular job. Recommendations change with experience, the development of new materials, and new governmental regulations. However, there is a degree of stability, and most recommendations last over a period of years.
Chlordane is a chlorinated hydrocarbon. It is a wide-spectrum; long-residual insecticide widely used against household pests, terminates, and turf pests. It is regarded as moderately toxic; however, certain formulations commonly used for termite control have a high percentage of the active compound and should be regarded as quite hazardous to non-professionals. Preformulated 2 to 3 percent chlordane oil solutions are available to the nonprofessional for cockroach control. Generally, the nonprofessional lacks the equipment and knowledge to do a satisfactory job of controlling cockroaches.
Diazinon (spectracide) is an organophosphate type, broad-spectrum insecticide that has a rather long residual and is fairly toxic. It is widely used to control cockroaches, ticks, ants, silverfish, spiders, and many other household pests. Diazinon is formulated as a 50 percent wetable powder or 25 percent emulsion. If used by a nonprofessional, considerable care should be exercised and directions followed precisely.
DDVP (vapona, dichlorous) is an arganophosphate, volatile insecticide-acaricide which is used under special conditions. Although it is quite toxic, DDVP breaks down rapidly. It is used in cockroach control programs by professional pest control operators and is widely used against flies. It is formulated as a resin strip which is hung from the ceiling. In many cases, however, these resin strips are used in an ineffective manner. One or two strips cannot possibly protect a huge room that has a constant source of fresh air entering from outside.
Kelthane (dicofol) is a chlorinated hydrocarbon type miticide that is relatively safe when used according to directions. It is widely employed for the control of mites. It is available as a 35 percent wetable powder and is recommended for use by nonprofessionals.
Malathion is an organophosphate-type, broadspectrum insecticide that has a very low hazard threshold when use according to directions. Although only slightly toxic to man and othermammals, it is highly toxic to fish and birds. It is effective against the two-spotted spider mite.
Methoxychlor (marlate) is a chlorinated hydrocarbon type, slightly toxic insecticide that is being used as a replacement for DDT. Methoxychlor is not accumulated in human body fat and does not contaminate the environment as DDT. It is available as a 50 percent wetable powder and is commonly sold as marlate. It is safe for use by nonprofessionals.
DDT is a chlorinated hydrocarbon type, broad spectrum insecticide that is very stable and persistent. It is only moderately toxic to man. However, because of its cumulative and persistent qualities it is no longer widely used.
Dimethoate (eygon) is a moderately toxic, organophosphate type insecticide used for fly control. It is not recommended for use by nonprofessionals.
The environmental concern with insects (pests) is primarily preventive in nature. Clean-out and clean-up will probably do more to control insects in areas where they are not wanted than any other prevention that can be adopted.