AGRICULTURE AND IRRIGATION
PESTS OF CROPS
Boll Worm.—Boll worms are of two types-(i) Spotted boll worm (earias fabia, S and E. insulana, B), (ii) Pink boll worm (Pectinophora gossypiella, S.) The adults of the former have pale white upper wings with a greenish band in the middle while the adults of the latter have the upper wings completely greenish. The caterpillars of both the species, however, are brownish white and have a dark head and pro thoracic shield.
They have a number of black and brown spots on the body. The fully fed larvae measure about 19.05 mm. (3/4") in length. The other boll worms are pink in colour with brown heads.
(ii) Pink boll worm-
Marks of identification.- -The moth is about 12.7 mm. (½") across wings and is dark brown in colour. The first segment of the antenna has 4 to 6 stiff hair and the palps are long and curved upwards. Caterpillars when full grown measure 19.05 mm. (3/4") long and are pink in colour with a brown head.
Host plants.-Cotton, Bhendi, Ambadi and other malvaceous plants.
Nature of damage.-In the case of spotted boll worms, the caterpillars bore into the growing shoots of the plants in the initial stage of the crop. Later on when the flower buds appear the larvae bore into them and then enter in the bolls by making holes which are plugged with excreta. The infested buds and bolls open prematurely.
The caterpillars of the pink boll worm on the other hand never attack the shoots. They feed inside the bolls and make them drop down. The pest is more harmful to American cotton varieties, than to the Indian ones. As the caterpillars bore the bolls, the entry holes get closed and it becomes difficult to spot out the affected bolls until such bolls drop down.
Life History.-Eggs are laid singly on leaves, flower buds, bracts, bolls etc. They hatch within 4 to 6 days. Larval period in case of spotted boll worms is 9 to 16 days depending upon the climatic conditions. The pupation takes place inside the silken cocoons, outside the bolls in which stage it remains for 8 to 14 days. The total period of a life cycle is about 22 to 35 days. The pest is active from July to November.
In case of pink boll worms, the caterpillars on hatching feed on developing flowers, seed or lint. The larval period usually is about 3 to 4 weeks but some of them remain dormant in the seeds for a pretty long time for the perpetuation of the species. Pupation generally takes place inside the bolls or in the soil in silken cocoons from which moth emerges after about 10 days. The pest is active from July to December while the winter season is passed in the larval stage.
The controlling measures of the pest include—
(i) Removal and destruction of stubbles to check carryover of the pests to the next season;
(ii) Destruction of all the malvaceous plants growing in off season which serve as alternate hosts for the pest;
(iii) Fumigation of seed before sowing with carbon-di-sulphide @ 2 ozs. per 0.425 cu. metres (15 cu. feet) or heating seed at 145°F. to destroy the hibernating pink boll worm larvae;
(iv) Quick removal and destruction of the affected plant parts in the early stage of the pest incidence;
(v) Six dustings with 10 per cent. DDT+ 2 per cent lindane + 40 per cent, sulphur mixture or with 1 per cent endrin dust; and
(vi) Six sprayings at fortnightly intervals with 1 ox. of 20 per cent. E. C. endrin in 4/6 gallons of water strating from a month prior to flowering.
Red cotton bug-(Dysdercus Cingulatus, (Fabr.)
Marks' of intentification.-The adult is about half an inch long. It is bright red with eyes, scutellum and antenna coloured black. They have a series of white transverse bands on the ventral side of their abdomen. The nymphs resemble the adults in colour but are wingless.
The adults and nymphs suck plant sap and greatly impair the vitality of the plant. They also feed on the seeds and lower their oil content. Due to the excreta of these insects, the lint is spoilt.
Life history.-The female lays rounded bright yellow eggs in a mass on the soil near the plant. The eggs hatch in six to seven days. The nymphs, which are bright red, pass through six instars in 30 to 35 days before reaching the adult stage. The total period of their life cycle is about six to eight weeks, but in winter the pest hibernates in the adult stage. The pest is active from October to February.
The adults and nymphs can be collected in large numbers by shaking them in a tray containing little kerosene oil added to ordinary water. In case the pest becomes serious, which rarely happens, the crop may be treated with 5 per cent BHC.
Jassids (Empoaca Devasthans, Dist.)
The adult is wedgeshaped, about 2 mm. long and pale green in colour. The front wings have a black spot on their posterior parts. The nymphs are wingless and are found in large numbers on the lower surfaces of the leaves. They walk diagonally in relation to their body.
Host Plants.-Cotton, bhendi, brinjal, potato and hollyhock.
Nature of damage.-Both the nymphs and adults suck the ceil sap from the leaves as a result of which the leaf margin funis yellowish and in ease of excessive infestation etiolation and drying up of leaves followed by stunted growth are seen.
Life history.-About 30 eggs are laid at a time by the adult female in the tissue of the leaf vein. The eggs hatch in 4 to 11 days. The nymphal stage remains from 7 to 21 days during which the nymphs moult five times. The entire life cycle is completed in two to Sour weeks. The pest is particularly active during the monsoon season.
Five per cent DDT dust mixed with an equal quantity of sulphur at the rate of 6.804 to 9.072 kg. (15 to 20 lb.) per acre is known to be effective. However, the use of DDT alone should be discouraged, as many times it leads to excessive increase in aphid or mite population. DDT and sulphur mixture should not be used for Indian or Asiatic cotton, as sulphur scorches these varieties severely. 0.2 per
cent spray of DDT 50 per cent (w/d) and sulphur (w/d) is very effective against jassids. 4 ozs. or 2 ozs. of endrin per acre or 0.01 per cent to 0.02 per cent parathion arc also effective against this pest.
Aphids (aphis gossypii, Glower)
The adult is oblong 1mm. long and dark yellowish green in colour. It is mostly found in the wingless stage.
The nymphs and adults suck the cell sap from the leaves due to which the loaves turn yellowish and dry.
Life history.- The alate and apterous forms reproduce partheno-genetically and viviparously. A single apterous female gives rise to
8 to 22 young ones per day, called nymphs. They pass through four moults before reaching the adult stage. The duration of their life cycle is 7 to 9 days.
The pest can be effectively controlled by spraying with nicotine sulphate at the rate of 0.453 kg. (1 lb.) in 363.677 litres (80 gallons) of water with 2.268 kg. (5 lb.) of soap. Spraying with pyrethrum extract in the proportion of one part in 1,000 parts of water also gives satisfactory results. Nearly 363.677 to 454.596 litres (80 to 100 gallons) of spray are required per acre. For control of aphids. DDT should not be used as it may not only not kill them but may also lead to their increase." BHC is somewhat effective but the kill obtained is less, than that with such compounds as nicotine sulphate and pyrethrum extract and may be used if others are not available. It is relatively cheaper. 2 ozs. of endrin per acre or 0.01 per cent to 0.02 per cent parathion is also effective against cotton aphids.
Mealy bugs (Ferrisiana Virgata, CKLL.)
The adult female is pale yellow in colour and its body is covered with white meal and glossy threads. Its average length is 2.6 to 3 mm. Newly hatched nymphs are light yellow in colour. Male is rarely winged. Adults and nymphs are seen congregating on the lower surface of the leaves and shoots of cotton plants.
Both the adults and nymphs suck the juice of the leaves and lender shoots, with the result that the plant gives a stunted and whitish appearance. The feeding also causes curling and chlorosis.
Alternate host plants.-Cashew, cocoa, azaleas, jute, lantana aculeata, soyabean, avocado, cettee. pepper, eroton, acalypha, ferm, colocasia, gladiolus, eranthemum and tuberose.
Life history.-The female reproduces parthenogenetically. The eggs hatch in about 19.29 minutes. A female undergoes 3 nymph instars, while a male has 4 nymphal instars. Total nymphal period lasts for about 18-19 days and the total life cycle from egg to the oviposition lasts for 42-56 days. The pest is active from June to October.
Spraying with 1 per cent fish oil rosin soap, 0.03 per cent diazinon or parathion and 0.10 per cent malathion helps in reducing the pest infestation.
Mites (Eriophes Gossypii, Bank)—
Marks of identification.-Eggs are creamy, spherical and semi-translucent and the larva is flesh coloured with three pairs of legs. It undergoes 3 moults before reaching the adult stage. Adults are minute with an oval body and four pairs of legs. They arc usually found on the lower surface of leaves.
The nymphs and adults usually feed on the lower surface of the leaves. As a result they become silvery white and ultimately dry up. In case of severe infestation complete defoliation of plants is caused.
Host Plants.-It is a polyphagous species. However, castor, bhendi and cotton are the important host plants.
Life history.-The female lays about 10-100 eggs singly on leaves which hatch in 4-7 days. Nymphal stage lasts for 6-10 days. Total life cycle is completed in 3-4 weeks. Generally the adults live for 10-30 days.
Control measures.-(1) Spraying of 0.05 per cent aramite, 0.03 per cent dichlorobenzilic acid (akar) and 0.02 per cent parathion and 0.2 per cent sulphur effectively controls the pest.
Jowar stem borer (Chilo Zonellus, Swinh)—
The caterpillars are dirty white with many spots on the body and with a brown head. The full grown caterpillar measures about 12.7 to 19.05 mm. (½" to
¾") in length. The moths are straw coloured with forewings pale yellowish grey having minute dots on the apical margin and white hind wings.
Nature of damage.-The caterpillars bore inside the stems causing thereby the drying of the central shoots called "Dead Hearts" due to which reddening of stems and leaves takes place. The extent of damage is about 4 to 5 per cent.
Life history.-Creamy white eggs are laid on the leaves in clusters which hatch in six days. Young caterpillars bore into the stems and remain there for three to four weeks, after which the full grown caterpillars pupate in situ. The pupal period is 7 to 10 days and the total period of the life cycle is 5 to 6 weeks. The pest hibernates as a larvae in stubbles. The period of activity is from June to November. There are about four generations in a year. Summer jowar is frequently found heavily infested by this pest.
Being an internal feeder only preventive measures are found practicable and economic.
(i) The affected plants should be pulled out along with the caterpillars inside and destroyed promptly.
(ii) After the harvest the crop stubbles should be collected and burnt to destroy the hibernating larvae.
(iii) The fodder to be fed to cattle should be cut into small pieces and fed.
Army worms (cirphis unipuncta)—
Marks of identification.-Full grown caterpillars are 25.4 to 38.1 mm. (1" to 1½") long, smooth, stout-bodied, dull greenish coloured with broad light coloured stripes running along its length on either side of the body. They are found in the central whorl of plants, or may remain under stubbles around the plants under soil. Moths are of two types. One is brownish red with prominent spots on the anterior margin of the wings. The hind wings are pale in the middle with dark borders. The other is dusky brown with a dark median line and less prominent spots on the apical margin of the wings. A pest called swarming caterpillar which is a little darker and with longitudinal bands is also known to infest jowar. Their habits and the control measures for them are identical.
The caterpillars feed on leaves mostly at night, while during the day they remain hidden in the whorl or in the clods underground. They migrate from one field to another when their food is exhausted and hence the pest is called " army worms ".
Life history.-Round, greenish-white eggs are laid on central leaves in two parallel rows in batches which hatch in a week. Caterpillars feed on leaves from the margin inwards and hide in the central whorl of the plant. In bad cases of attack, they completely defoliate the plants as they have the habit of feeding together. Their larval period is from 21 to 28 days. Full grown caterpillars descend on the ground for pupation. Their pupal period lasts from 8 to 10 days. The total period of their life cycle is five to six weeks. The pest is active from June to November. Kharif crops suffer more from it than rabi for this reason. There may be a number of generations during a season, after which the insects hibernate in the pupal stage in the soil. The pest does not become abundant every year and it is observed that when a long dry spell follows a good start of monsoon, the pest assumes epidemic form. It shows a tendency to subside if heavy showers occur thereafter.
Control measures.-(1) Collection of egg masses and their destruction. (2) If the attack is localised caterpillars may be collected and destroyed. (3) After the harvest of the crop, the infested fields should be ploughed to expose the pupae. Insecticidal measures have been found very effective. 5 per cent BHC. or endrin dust, if properly dusted at the rate of 13.608 kg. (30 lb.) per acre, successfully
controls the pest. Dusting done in the evenings when there is no strong breeze is more effective as the pest is a night feeder. If water is easily available, 50 per cent BHC wettable powder may be used as a spray after diluting 0.453 kg. (1 lb.) in 113.649 litres (25 gallons) of water. About 363-677 to 454.596 litres (80 to 100 gallons) of spray per acre are needed to control the pest satisfactorily, depending on the size of the crop. 5 per cent BHC poison bait,' when broadcast in the ("veiling, will also control the pest, in case of small-size crops like nuchani if it does not rain, and if the soil is dry.
Hoppers and aphids (Peregrinus Maidis, ashn. and Rhopalosiphum Maidis, F.)-
Delphacids (Peregrinus maidis, Ashm.) and aphids (Rhopalosiphum maidis, F.) are responsible for causing the sugary secretion on jowar locally known as chikta. It is quite severe especially on rabi jowar.
Delphacids are wedgeshaped, greenish brown in colour with blackish spots on wings.
Aphids-Adult is oblong and dark brown in colour having two projections called cornicles on the dorsal side of the abdomen. It is mostly found in the wingless stage.
Sugary secretion is seen on the leaves of the plant and also in the whorl which checks growth and causes damage to the growing shoot.
The problem of "sugary disease" is still under investigation. However, spraying with 0.02 per cent diazinon, thiometon endrin or dusting with 5-10 per cent. BHC dust 9.072 kg. (20 lb.) per acre help in reducing the intensity of infestation of these pests.
Blister beetle (Zonabris Pustulata) -
Marks of identification.-The beetles are black with yellowish brown stripes across their wings and over an inch long and about half an inch thick. Its other species are smaller, about three-fourth of an inch long and thin, with a light brown or greenish blue colour. All of them have rather a soft body and their wings are also thinner than those of other beetles. The adult insect secretes an acid substance from its body and when crushed on the human body, it causes a blister.
The beetles feed on the pollen and petals of flowers and thus reduce the setting of grains.
Host plants.-Bajri, jowar, cucurbits and beans.
Life history.- Whitish eggs are laid in the soil in masses which hatch in about a fortnight. The larvae feed on eggs of grasshoppers laid in the soil. The beetles emerge from pupae and remain active from August to December. They eat pollen and thus affect the setting of grains in the earhead.
Control measures.-Preventive measures consist of collection of beetles by means of hand-net and their destruction. They are also attracted to light, so that light traps may be used. However, insecticidal measures yield more satisfactory results. 5 per cent. BHC dust is effective against this pest if dusted properly at the rate of 9.072 kg. (20 lbs.) per acre.
Gram pod. borer [Heliothis (Armigera) Obsolata]
Marks of identification.-The moths are stout, light yellowish brown, with a wing expanse of 38.1 m. (1½")- The forewings are pale brown with some black dots and the hind wings are lighter in colour with smoky dark margins. The caterpillars are greenish with darker broken grey lines along the sides of the body. They are 38.1 to 50.8mm. (1½" to 2") in length when full grown.
They feed on tender foliage and young pods. They make holes in the pods and eat the developing seeds by inserting the anterior half portion of their body inside the pods.
Host plants.-Gram, cotton, tomato, peas, tobacco, ganja, safflower, etc., are the principal hosts.
Life history.-Shining greenish yellow eggs, spherical in shape are laid singly on the tender parts of plants and they hatch in about 6 or 7 days. On hatching, the caterpillars start feeding on tender leaves-arid shoots and as they grow, they bore into the pods and eat the developing grains inside. They become full grown in 14 to 15 days and descend on the ground and pupate in earthen cocoons in the soil near the plants. Their pupal period lasts from one week to a month. The pest is active from November to March.
Control measures.-Preventive measures include hand-picking of caterpillars and their destruction in the early stages of attack. Thorough ploughing after harvesting the crop in order to expose pupae is also often resorted to. The pest can be controlled by 0.2 per cent DDT spray obtained by diluting 0.453 kg. (1 lb.) of 50 percent water dispersible DDT powder in 113.649 litres (25 gallons) of water. About 272.758 to 363.677 litres (60 to 80 gallons) on a young crop and 454.596 litres (100 gallons) on a grown up crop are generally required.
Tur plume moth (Exelustes Atomosa).-The full grown caterpillars are about 12.7 mm. (½") long, greenish brown in colour and are fringed with short hair and spines. They bore into green pods and feed on the developing seeds.
Life history.-Minute eggs are laid singly on the tender shoots, leaves, flowers or pods which hatch in about 5 days. On hatching, the caterpillars first scrape the surface of pods and gradually cut holes and thrust their heads into pods and feed on seeds and become full grown in about four weeks time. They pupate on the pod surface or even in the burrows of infested pods. Their pupal period
lasts for two weeks. The pupae are also fringed with short hair and spines and are often liable to be mistaken for larvae. The total period of their life cycle is about seven weeks.
Preventive measures are the collection of caterpillars by shaking shoots and pods in small trays containing water mixed with kerosene and non-cultivation of leguminous crops in the same fields in successive years. The insecticidal measures given under the gram pod borer may be tried with advantage.
The swarming caterpillar (spodoptera mauritia, boisd).—Full grown caterpillars measure 31.75 to 38.1 mm. (1¼" to 1½") long, are dark greenish with slight yellow tinge. They can readily be distinguished from other caterpillars by the presence of white longitudinal dorsal stripes along their length of body.
Immediately on hatching, the caterpillars feed on grass or young paddy seedlings. They are active only at night, and during the day they hide in leaf sheaths or leaf whorls or in soil if it is not Hooded.
Life History.- Two hundred to three hundred eggs covered with greyish hair are laid in masses. They hatch in 7 to S days. The caterpillars on hatching start feeding on leaves mostly at night and become full grown in about two weeks. Then they pupate in earthen cells generally in soil. The period of their life cycle is 40 to 50 days. They have a habit of migrating and hence they ravish field after field in a short time. More than one generation is found in a season. The pest is known to multiply when there is a long break in rains after an initial good start.
Preventive measures include protection of seed beds by deep trenching with steep sides and hand collection of egg-masses and their destruction. The caterpillars hide during the day time under clods, and hence trapping them under planks or small bunches of dry grass may be tried. Dragging a rope across the field may be resorted to after flooding the affected fields so that caterpillars in the leaf sheaths and whorls drop into the water. After the harvest of the crop, the affected fields should be ploughed to expose the pupae.
The pest can also be successfully controlled by dusting 5 per cent. BHC at the rate of 9.072 to 9.68 kg. (20-30 lbs.) per acre. The dusting if done in the evening will yield better results as the caterpillars come out to feed at night. Where rains are frequent, spraying BHC water-dispersible powder by diluting, 2.268 kg. (5 lbs.) of 50 per cent. BHC in 454.596 liters (100 gallons) of water can be tried. 272.758 to 454.596 litres (60 to 100 gallons) of spray per acre should be used for effective control.
The Rice case worms- (nymphula depunctalis, Guen.)—
Marks of identification.-The moths are ½" in length with a wing expanse of 31.75 mm. (1¼"). They are delicate and white with pale brown and black markings. Full-grown caterpillars are greenish
white, 12.7 mm. (½") long and semi-aquatic and generally feed on foliage inside tubular cases formed of pieces of paddy leaves.
Host plants.-Paddy and some varieties of grasses.
Nature of damage-The caterpillars cut the paddy leaves into short lengths, construct tubular cases and remain inside while feeding.
Life history.-Tiny eggs are laid on the tender leaves. On hatching, the caterpillars cut the paddy leaves into short lengths, construct tubular cases and remain feeding inside the small rolls and there become full-grown. They pupate inside the tubular cases or roils. Their detailed life history has not yet been investigated.
Control measures.-Preventive measures include removal and destruction of the tubular cases along with the caterpillars. In the early stages of the crop before (lowering, rope-dragging may be tried to dislodge the caterpillars after flooding the infested field and putting into it a little crude oil.
Insecticides recommended for the blue beetle and hispa will also control the pest to some extent. But one part of pyrethrun extract in 600 parts of water or 0.375 per cent. DDT spray obtained by mixing 3.175 to 3.629 kg. (7 to 8 lb.) of.50 per cent, water dispersible powder in 454.596 litres (100 gallons) of water has shown better results.
The sugarcane stem-borer-(Chilotrea Infuscatellus, S)—
The adult moth is greyish brown or straw-coloured and measures about 38.1 mm. (1½") when its wings are spread out. The lower wings are greyish white and the palpi are pointed forward. The newly hatched larva is somewhat greyish in colour, having a dark head and a translucent body with spots and hair. The tiny spots develop into spines. A fully developed larva measures about 31.75 mm. (1¼") and is greyish white in colour. The body is often covered with dark marks, having tubercles and short seta on them.
Host plants.-In Maharashtra State, it is generally a pest of sugarcane only but in other states it has been observed on maize and bajri as well.
The pest is mainly injurious to young cane. The, caterpillars enter the plants from the side at ground level, by making holes in the stalk and may bore either downwards or upwards or both ways. Thus, the central shoots dry up, causing " dead hearts" which is a characteristic sign of the presence of the pest within the plants. A dead heart can easily be pulled out.
Life history.--Oval, scale like, whitish eggs are laid overlapping each other on the undersurface of leaves by the side of the midrib. The egg-stage lasts for 3 to 5 days. The newly hatched caterpillar enters the cane near the eye at ground level and later tunnels as far as the roots. Sometimes the borer is found to migrate from the roots
to other tillers. The larval stage lasts for about a month and before pupation, it bites a round hole into the cane above ground level which is covered by a silken membrane from where the moth can escape. The pupal stage lasts for about a week and the entire life cycle is completed in about a month and a half. There are about eight generations in a year.
The controlling measures of the pest include—
(1) Removal of affected plants having "dead hearts" right
from the ground level, ensuring that the larva or pupa has come
out in the portion removed and feeding the same to the cattle or
burying them deep in order to prevent further development. This
method has been tried with success.
(2) Early planting in November or December in the ease of plait cane and late planting in August or September in the ease of Adsali cane will help in minimising the infestation, as the pest is less active during these months.
(3) Trichorgamma parasites may be released at the rate of one lakh per acre in three instalments at an interval of a fortnight in the infested field. This has not given satisfactory control, but the cheapness of this method attracted much attention.
(4) Light earthing up of cane will prevent the emergence of the moth by closing the holes with mud.
The sugarcane top shoot-borer-(Scirpophaga Nivella F).—
Marks of identification.-The moth is creamy white in colour having a wing span of a little over an inch when spread out and with orange hair-like structures at the tip of the abdomen of the female. The first pair of the wings of certain males has single black spot on each wing. Fully developed caterpillars measure about 25.4 mm. to 38.1 mm. (1inch to 1½ inches) in length and are yellowish white in colour.
This is a very serious pest of sugarcane that breeds throughout the year and is capable of attacking cane at a later stage. The newly hatched caterpillar enters first the midrib of the leaf and bores downwards into the shoots from the top. As a result of such feeding, the central.shoot dries up in a characteristic way, which later results in giving off side shoots which form a bunchy top. The punctures on the leaves and the death of the central shoot and the bunchy top are the characteristic effects of this pest.
Life history.-Eggs are laid on the undersurface of leaves in groups consisting of.'35 to 40 eggs which are covered with brownish hair like structures and hence arc clearly visible. The newly hatched caterpillar, after remaining for some time on the leaves, enters the shoots through the midrib of the leaf. The caterpillar feeds as it travels downward. A fully developed larva measures 25.4 to 38.1 mm. (1 to 1½ inches) and before pupation, it prepares a silken membrane from which the moth can escape. The pupa is found
in the larval tunnel. The egg stage continues for 7 to 10 days from which the moth on emergence starts laving eggs within 2 to 1 days of its life time.
(1) Mechanical methods such as mass collection and destruction of egg-masses and removal of affected plants, harvesting the crop by digging out the stump, and light earthings during the early stages of the crop are the only effective measures known so far.
(2) Conservation of egg parasites with the help of special boxes can be tried. Chemical measures have not yet proved successful. However,
for effective control of the shoot borer in general, the following measures are recommended:
(i) The crop should be harvested by digging out the stump and not by cutting at ground level.
(ii) A large scale campaign to collect and destroy the egg-masses of the top shoot borer should be carried out.
(iii) Two light earthings should be given during the early stages of the crop.
The sugarcane-leaf-hopper or pyrilla (Pyrilla SP.) -
The adult pvrilla bug is a straw coloured insect, with two pairs of pointed wings folded roof shaped on the back and with its head extended like a beak which is quite readily visible. The voting nymphs that hatch out from the eggs are pale brown in colour, having a pair of long characteristic processes covered by wax. They are active and are found in large numbers on cane.
Host plants.-Its host plant is mainly sugarcane but adults are sometimes found in small numbers on jowar and maize.
The nymphs and adult bugs suck the sap of cane leaves from the lower surface, as a result of which the leaves lose turgidity, begin to wither and ultimately get dried up. The bugs secrete a honeydew like substance; that spreads on the leaves on which a black fungus develops. As a result of pyrilla damage, the sucrose content of the juice is reduced.
Life history.-Pale greenish-yellow eggs are laid in clusters of 2 to 4 or 10 to 60, generally on the under surface of leaves and between the detached leaf sheaths and the stem. The eggs are covered with white cottony, waxy filaments. They hatch out within a week into tiny hoppers that start sucking the sap of leaves. The nymphs become adult bugs within 50 to 60 days. Egg laying continues front April to November. The pest is active during July and August.
Control measures.-(1) Collection and destruction of egg-masses and crushing the egg-masses on the leaves is found to be a convenient method of control.
(2) Stripping off the lower leaves to remove the eggs laid in the leaf sheath was a method recommended for a long time. Now, however, insecticides are used.
(3) Dusting the crop with 5 per cent BHC at the rate of 13.608: to 18.144 kg. (30 to 40 lb.) and 22.630 to 27.216 kg. (50 to 60 lb.) per acre in the pre and post monsoon periods, respectively, destroys both the nymphs and the adults. This method is now widelv used.
(4) Spraying 0 12 to 0.25 per cent BHC or 0.25 per cent DDT at the rate of 136.379 to 227.298 litres (30 to 50 gallons) per acre for young cane during the premonsoon period and over 454.596 litres (100 gallons) during the post-monsoon period also gives considerable relief. The quantity to be used depends on growth of cane and enough quantity should be used so as to cover the entire crops.
Wheat stem-borer (Sesamia Inferens, Wlk)—
The full fed caterpillar is about one inch long, flesh coloured, smooth with a black head and dark spots on the body. Each dark spot bears a hair. They are found inside the stems of She affected plants. The moths are small and are straw coloured. Their iorcwings have a marginal dark line and the hind wings are white.
Host plants.-Maize in the dry weather and sometimes wheat in winter.
The caterpillar bores inside the stem thus causing the drying of the central shoots which are called "dead hearts'". While entering the shoot, the initial feeding of the caterpillar on the whorl gives rise to numerous holes on the leaves which develop later. Drying of the plant often leads to reddening of stems and leaves.
Life history.-Creamy white eggs are laid in clusters inside the leaf sheaths of the stems. The young caterpillars alter hatching enter the stem and gradually kill the central shoot of the plant, thus creating dead hearts. If the plants are grown up, the earheads are also liable to damage. The caterpillars grow about an inch long and pupate inside the stem. The total period from the egg stage to the adult stage is 6 to 7 weeks and this period may be prolonged in the cold weather.
Being internal feeders, only preventive measures are found practicable and economic:-
(1) In the early stage of infestation, the stems of plants showing dead hearts should be pulled out along with the caterpillars and destroyed promptly.
(2) After the harvest of the crop, the stubbles should be collected and burnt so as to destroy the hibernating larvae,
(3) After harvesting the crop, wheat stalks which are used as fodder should be stored in the form of cut fodder. The pieces of cut fodder should measure about half an inch to three fourths an inch. Chemical measures have not yet proved effective.
They arc small, black, soft bodied insects found on the lower side of leaves. They are generally inactive.
It is a very important pest as it reduces the vitality and yield of plants by sucking the sap and also acts as the vector of a serious virus disease commonly known as " rosette " of groundnut.
The pest is of sporadic occurrence in most parts of the State, but its Khandesh it frequently takes the form of an epidemic.
Life history -The life history of this pest is similar to that of saffower aphid, but the species become abundant in the kharif season.
The control measures are the same as those for aphids on safflower; 10 per cent
BHC dust also gives some relief.
Thrips and mites.-These pests suck the cell sap due to which the leaves get badly curled up. It is locally known as " churda murda" disease. The extent of damage is about 25 per cent and the pest is considered to be a major one.
Control measures.-0.2 per cent BHC+ sulphur (wettable) is found to be a very effective control. 0.02 per cent endrin
+ wet-table sulphur (1:1) or 0.2 per cent diazinon or 0.025 per cent dieldrin + sulphur (1: 1) is also found to be equally effective.