AGRICULTURE AND IRRIGATION
A brief account of various pests of crops in the district is given in the following paragraphs. The damage done by the different pests cannot be estimated precisely, as it depends upon the severity of infestation in a particular year. The remedial measures suggested against different pests described below are such as may be adopted by the cultivators at minimum cost:-
Of cotton: Boll-worm, a pest of cotton, is of two-three types, viz., spotted boll-worm, pink boll-worm and heliothis sp.
Spotted boll-worm (Earias fabia S. E. insulna B): The caterpillars of this boll-worm are brownish white and have a dark head and prothoracic shield. They have a number of black and brown spots on the body and hence they are called spotted boll-worm. The full-fed larva measures about ½ inch in length. Eggs are laid down on leaves, flowers, buds, bracts, bolls, etc. They hatch within four to six days.
Larval period of spotted boll-worm is nine to sixteen days depending upon the climatic conditions. Pupation takes place inside the silken cocoons, outside the bolls. In this stage it remains for eight to fourteen days. The total period of life cycle of this boll-worm is about 22 to 35 days. The pest is active from July to November.
The caterpillars of the spotted boll-worm bore into the growing shoots of the plants in the initial stage of the crop. Later on when flower-buds appear, the larvae bore into them and enter in the bolls by making holes which are plugged by them with excreta. The infested buds and bolls are shed but if they remain on the plant, bolls open prematurely, as a result of which lint of inferior quality is produced. Such lint naturally fetches low price in the market.
Pink boll-worm (Pectinophora gossypiella S.) : The moth of this boll-worm is about ½ inch across wings and is dark brown in colour. The full-grown caterpillars of this boll-worm are pink in colour with brown head. The caterpillars on hatching, feed on developing flowers, seed or lint. The larval period usually is about three to four 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 ten days. The pest is active from July to December.
Unlike the spotted boll-worms, the caterpillars of the pink boll-worms never attack the shoots but feed inside the bolls and make them to drop down. The pest is more harmful to American cotton varieties than to Indian ones. As the caterpillars bore the bolls, the entrance holes get closed and it becomes difficult to spot out the affected bolls until they drop down or open prematurely.
Besides cotton, the host plants of the spotted boll-worms and pink boll-worms are bhendi, ambadi and other malvaceous plants.
Heliothis sp.: The moths of this pest are light yellowish brown with a wing expanse of 1.5 inches. The fore-wings are pale brown with some black dots and 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. Female of heliothis lays spherical greenish yellow eggs on tender parts of the plant. The eggs hatch in about six to seven days and newly hatched larvae start feeding on leaves and growing shoots. In case of severe infestation, they also bore and feed on bolls. Their larval period lasts for about two weeks and then full-grown larvae descend into the soil where they pupate in earthen cocoons. Their pupal period is from one to four weeks.
The newly-hatched larvae of heliothis initially feed on the leaves
and enter into the growing shoot and this internal feeding causes the drying of the growing shoots. In case of heavy infestation, the caterpillars also feed on the bolls which results into heavy damages to the cotton crop. Besides cotton the host plants of this pest are gram, tomato, tobacco, safflower, peas, etc.
The following are the measures of controlling the above-described three pests. Boll-worms, being internal feeders, are extremely difficult to control. In order to keep their incidence under check, therefore, both preventive and curative measures are necessary.
Preventive measures: They include removal and destruction of cotton stalks, shedding bolls and other plant debris after the last picking and to avoid growing of bhendi and malvaceous crops during off-season which serve as alternate hosts of the pest. Fumigation of seed with carbon-disulphide at one ounce per 15 cubic feet space or heating the seed to 145° F. to kill the hibernating larvae of pink boll-worms could also be practised with advantage. For uprooting the cotton stalks, plant pullers devised by the Department of Agriculture in the State sector can be used.
Curative measures: They consist of mechanical and chemical measures. Six sprayings with 0.03 per cent to 004 per cent endrin + sulphur (1: 1) or 0.2 per cent carbaryl + sulphur mixture and also 450 c.cs. to 600 c.cs. of 20 percent endrin E. C.+0.450 kg. or 0.600 kg. of wettable sulphur in 300 litres of water or one kg. of 50 per cent carbaryl + 1 kg. of wettable sulphur in 300 litres of water at fortnightly intervals starting from eight to ten weeks after sowing are most effective in reducing the pest incidence on irrigated cotton. In case of un-irrigated cotton three dustings with 10 per cent carbaryl at 15 days' interval starting from eight weeks after sowing are found quite useful.
Red cotton bug (Dysdercus cingulatus Fabr.): It is another minor pest of cotton. Like cotton it also affects bhendi, Deccan hemp (ambadi) and hollyhock.
The adult is about ½ inch long, with bright red colour and with eyes, secutellum and antenna coloured black. A series of white transverse bands are present on the ventral side of their abdomen. The nymphs resemble the adults in colour but are wingless. The adults and nymphs suck plant's sap and greatly impair the vitality of the plant. Besides, they also feed on the seeds and lower their oil-content. Lint is soiled by the excreta of these insects. The infested seeds become useless for sowing. The female lays rounded bright yellow eggs in. a mass on the soil near the plant. These hatch in about six to seven days. Nymphs, which are bright red, pass through six instars in 30 to 35 days before reaching the adult stage. The period of life-cycle
is about six to eight weeks, but during winter the pest hibernates in the adult stage. The pest is active from October to February.
For controlling the pest the adults and nymphs are collected in large number by shaking in a tray containing kerosene, soil and water. It is also controlled by dusting the crop thoroughly with a mixture of 10 per cent BHC + 10 per cent D.D.T.
Jassids: Jassids (Empoasca devastens, 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. Nymphs are wingless and arc found in large numbers on the lower surfaces of leaves. They walk diagonally. About thirty eggs are laid at a time by the adult female in the tissue of the leaf vein and are hatched in four to eleven days. The nymphal stage remains from seven to 21 days during which the nymphs moult five times. The period of life-cycle is from two to four weeks. The pest is particularly active during the monsoon season. Like cotton, it also affects bhendi, brinjal, potato and hollyhock.
Nymphs and adults suck the cell sap from leaves as a result of which the leaf margins turn yellowish. In case of excessive infestation reddening and drying up of leaves is followed by stunted growth.
The pest could be controlled by the use of 5 per cent D.D.T. dust at 8 to 10 kg. per acre in case of Asiatic cotton varieties while in case of American cotton varieties 5 per cent. D.D.T. + sulphur dust mixture was recommended in the past. But in recent years treatment with 0.02 per cent endrin + sulphur (1:1) and 300 c.cs. of 20 per cent endrin E. C. in 300 litres of water or 0.300 kg. of wettable sulphur has been used to advantage. Phosphamidon, methyl demeton, thiometon. dimethoate, parathion and diazinon at 0.02 per cent concentration has also been found to be promising against this pest.
Aphids. Aphids (Aphis gossypii, Glover) is another pest of cotton. The adult is about one mm. long and dark yellowish green in colour. It has two projections called cornicles on the dorsal side of the abdomen and mostly found in the wingless stage. A single apterous female gives birth to 8 to 22 young ones per day. They pass through four moults before reaching the adult stage. The period of their life-cycle is seven to nine days. Besides cotton, bhendi, potato, chillis. brinjal and water-melon are the host plants of this pest.
The nymphs and adults suck the cell sap from leaves due to which the leaves turn yellowish and dry. This pest can be controlled by the following measures:-
(1) Spraying with nicotine sulphate at the rate of one lb. in eighty gallons of water with five lb. of soap is quite effective.
(2) Spraying with pyrsthrum extract in the proportion of one
part in 1,000 parts of water also gives satisfactory results. Nearly 80 to 100 gallons of spray are required per acre in each case.
(3) Endrin two ounces to four ounces or parathion 0.01 per cent to 0.02 per cent per acre also proves effective against cotton aphids.
(4) Insecticides like thiometon, phosphamidon, endrin, sulphur, diazinon or menazon at 0.02 per cent, dimethoate at 0.03 per cent or malathion at 0.05 per cent concentration have also been quite effective for controlling this pest.
Mites: Mites (Eriophes grossypii, Bank) is also one of the
important pests of cotton. Like cotton, bhendi and castor are the important hosts of this pest. The larvae is flesh-coloured with three pairs of legs. It undergoes three moults before becoming adult. Adults are minute-size creatures with an oval body and have four pairs of legs. They are usually found on the lower surface of leaves. Female lays about 10 to 100 eggs singly on leaves which hatch in four to seven days. The eggs are creamy, spherical and serai-translucent. Nymphal stage lasts for six to ten days. The period of life-cycle of this pest is three to four weeks. On an average the adults live from ten to thirty days.
The nymphs and adults usually feed on the lower surface of leaves, as a result of which they become silvery white and ultimately dry. In ease of severe infestation complete defoliation of plants is caused. This pest can be controlled by spraying with 0.05 per cent aramite, 0.03 per cent dischlorobenzilate (akar), 0.02 per cent parathion or 0.2 per cent sulphur.
Of jowar: Jowar stem borer (Chilo zonellus, Swinh) is one of the major pests of jowar. The caterpillars are dirty white with many spots on the body and with a brown head. The full-grown caterpillar measures about i inch to ¾ inch in length. The moths are straw-coloured with fore-wings pale yellowish grey having minute dots on the apical margin and white hind-wings. Creamy white eggs are laid on the leaves in clusters which hatch in six days. Young caterpillars bore into the stems and they remain there for three to four weeks, after which the full-grown caterpillars pupate inside the stems. The pupal period is seven to ten days and the total period of the life-cycle is five to six weeks. The pest hibernates as 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. Besides jowar, maize and grasses are also the host plants of this pest.
Caterpillars bore inside the stems causing thereby drying of the central shoots called "Dead Hearts" due to which reddening of stems takes place. This pest being an internal feeder, only preventive
and mechanical measures are found practical and economic. They are as under:-
(i) The affected plant should be pulled out along with the
caterpillars inside and destroyed promptly.
(ii) After harvest of 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 stored.
Jowar stem fly (Atherigona indica) is another pest of jowar. Its maggots are legless, tapering anteriorly and are found feeding inside the stems of young plants. The adults are similar to house-flies but are very much smaller in size and on their dorsal side, there are a few dark spots. Females lay the eggs on stems or tender seedlings and they hatch in two to three days. The maggots bore into the stems of young plants and feed inside the stem for about a week. Full-grown maggots pupate inside the infested stems of plants. The pupal period lasts for about a week. The pest is occasionally serious in the early stages of the crop. All the millets are the host of this pest. The maggots bore inside the stem and cause dead hearts and are generally more common in very young crops.
As the pest is an internal feeder, mechanical methods, though laborious, have been found to be more useful which consist of (i) removing the affected seedlings and destroying the larvae and (ii) increasing seed rate to make up for the loss. For hybrid varieties which are more susceptible to the attack of the pest, the following chemical control measures have been also effective-:-
(i) Soil application of 10 per cent phorate granules at the rate
of 7 kg. per acre prior to sowing. The granules should not come
in close contact with the seeds and (ii) if phorate is not available,
4 sprays with 0.05 per cent endrin (2.5 ml. of endrin 20 per
cent E. C. in one litre of water) at ten days' interval starting from
seven days after germination.
Flea beetle (Choetochnema indica) is the pest of jowar and some times causes serious damage to the crop. This pest is also a serious pest of sann-hemp. The beetles are black and small about 1/10 inch long, oblong and with the hind pair of legs thickened by means of which they are able to jump about. Some species may be brownish in colour. In the younger stages, the grubs are supposed to be root-feeders.
The beetles feed generally on the middle portion of the leaf-blade and not on the border as is the case with caterpillars and grasshoppers. When the flea beetle feeds on the leaf, it causes numerous small holes on its surface. This pest can be controlled by dusting
10 per cent BHC at the rate of 8 to 10 kg. per acre. Treatment with 0.05 per cent aldrin or 0.15 per cent malathion also proves to be effective.
Army worms (Cirphis unipuncta) is one of the serious pests of jowar. Like jowar, it also affects maize, bajri, paddy and other cereals. Pull-grown caterpillars are 1 inch to 1½ inches long, smooth bodied, full, 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 in soil. Moths are of two types. One is brownish red with prominent spots on the anterior margin of the wings, the hind-wings being pale in the middle with dark borders. The other type of moth 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. The period of life-cycle of this pest is about five to six weeks. This pest is active from June to November. Kharif crops suffer more from it than the rabi crops.
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". The following are the
control measures for this pest:-
(1) collection of eggs masses and their destruction;
(2) if the attack is localised, caterpillars may be collected by employing labour and destroyed;
(3) deep ploughing of the infested fields after the harvest of the crop to expose the hibernating pupae to the action of weathering agencies and birds,
(4) dusting with 10 kg. of 10 per cent BHC or spraying 0.2 per cent BHC(½ kg. of 50 per cent BHC W.P.) in 120 litres of water; and
(5) dusting with 5 per cent aldrin or 3 per cent heptachlor
at the rate of 10 kg. per acre.
Hoppers and aphids: Peregrinus maidis, Ashm and Rhopolosiphum maidis F. and Aphis sacchari, Zhent are also the pests of jowar. Like jowar they also affect maize, sugarcane and grasses.
Delphacids (Peregrinus maidis, Ashm.) and Aphids are responsible for causing the sugary secretion on jowar, the symptoms of which are locally known as ' Chikta '. It is quite severe especially on rabi jowar. Delphacids are wedge-shaped, greenish brown in colour with blackish spots on wings. Aphids adult is oblong and dark brown or yellowish 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. Ultimately the growing shoots of the plant are damaged and further growth is checked. Though the problem of "Sugary disease" is still under investigation, spraying with 0.02 per cent diazinon, thiometon, endrin or dusting with 5 to 10 per cent BHC dust at the rate of 20 lb. per acre helps in reducing the intensity of infestation of these pests.
Of bajri: Blister beetle (Zonabris pustulatu) is the important pest of bajri. Like bajri, it also affects jowar, cucurbits and beans. 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 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. When crushed on the human body, it causes a blister and hence its name blister beetle. Whitish eggs are laid in the soil in masses which hatch in about a fortnight. The larvae feed on eggs of grass-hoppers laid in the soil. Thus they are beneficial. They pass through many different stages, which are dissimilar in appearance. 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. Thus, the adult stage of this pest is the only damaging stage, while its larval stage is beneficial.
The beetles feed on the pollen and petals of flowers and thus reduce the setting of grains. This pest could be controlled by preventive measures. They 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 but they are not very effective. However, insecticidal measures are more satisfactory. 5 per cent BHC dust is effective against this pest if dusted properly at the rate of 20 lb. per acre.
Of wheat: Pink borer (Semamia inferans Wlk.) is the major pest of wheat. Like wheat it also affects maize and sugarcane. Caterpillar is flesh coloured, smooth with dark spots on the body. Each spot bears a hair. Full-grown caterpillar measures about 2.5 cm. in length. Moths are small, with straw coloured fore-wings with a marginal dark line and the hind-wings are white. Creamy white eggs are laid in clusters, inside the leaf sheath in rows of two or three. They hatch in four to nine days. The larvae have the migratory habit and become full-grown in three to four weeks. Pupation takes place inside the bored stem. The adults emerge out after five to twelve days. Total life-cycle is about six to seven weeks.
The young larvae hatching from the eggs bore into the stem causing the death of the central shoot commonly known as dead hearts. The caterpillars migrate from one plant to another injuring many plants in their life. As the pest is an internal feeder preventive measures like removal of dead-hearts and destruction of the larvae, removal of stubbles after the harvest of the crop and their destruction may help to minimise the pest infection.
Of gram: Gram pod borer (Heliothis armigera) is the major pest of gram. Besides gram, cotton, tomato, peas, tobacco, ganja. safflower, etc., are the principal hosts of this pest. The moths are stout, light yellowish brown, with a wing expanse of 3.7 cm. The fore-wings 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 3.7 cm. to 5 cm. in length when full-grown. Shining greenish yellow eggs. spherical in shape, are laid singly on the tender parts of plants and they hatch in about six to seven days. On hatching the caterpillars start feeding on tender leaves and shoots and as they grow, bore into the pods and eat the developing grains inside. They become full-grown in 14 to 15 days and descend to 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.
The caterpillars 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. This pest could be controlled by the hand-picking of the caterpillars during initial stages of attack which would help in reducing the future infestation. Ploughing the field after the harvest of crop would destroy the pupae. The pest can be effectively controlled by spraying the crop with 0.1% carbaryl or 0.6% isobenzan or 0.2% DDT or 0.03% aldrin or endrin or heptachlor or 0.12% phosphamidon at the rate of 250 litres per acre.
Of tur: Tur pod caterpillar (Exelastes atomosa) is the major pest of tur crop. Wal is also the host of this pest. The moths are slender, not more than 12 mm. long and are grey with long, narrow wings. The front wings arc divided into two parts and the hind-wings are cut into three parts and provided with a fringe-like border. The full-grown caterpillars are about 12 mm. long, greenish brown in colour and are fringed with short hair and spines. Minute eggs are laid singly on the tender shoots, leaves, flowers or pods and they hatch in about five 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.
The caterpillars bore into green pods and feed on the developing seeds. This pest could be controlled by preventive measures. They include collection of the infested pods and their destruction during early stages of attack and avoiding leguminous crops consequently in the same field. Spraying the crop with 0.2% DDT at 250 litres per acre or dusting with 1% telodrin or 1% endrin or 5% BHC or 3% heptachlor or 10% carbaryl or 4% malathion or 1.5% dieldrin or 5% DDT or 3% morphothion or 2% parathion at 9 kg. per acre have also proved effective.
Tur pod fly (Agromyza obtusa) is another pest of tur crop. Freshly-laid egg is white, broad and rounded at the posterior and narrowed anteriorly into a curved elongated hollow process. It measures 0.66
x 0.15 mm. Newly-hatched larvae is greywhite with dark brown mouth-parts. It measures 0.61x0.12 mm. A fine brownish stripe runs along the entire mid-dorsal line of body. Full-grown larvae are creamy white measuring 3.5 to 4 mm. in length and 1.25 to 1.5 mm. in breadth. Pupae measure 2.5 mm. X 1.25 mm. Adult flies are glossy black with pubescent eyes and strong legs with femur slightly thickened, proboscis brown at the apex, wings clear, veins brown, yellowish at their bases, halteres black abdomen broadly ovate. They measure 2.75 mm. in length. Copulation starts within 24 hours after emergence and egg-laying takes place soon after. Life of adult is short and oviposition is limited to three to four days. A female lays on an average 38 eggs with a maximum of 79. It avoids very young as well as mature pods for oviposition. It pierces her ovipositor in pericarp and deposits a single egg. When a pod is opened the eggs appear like needles projecting from the wall of the pod. Larval period is about six days at 26°C, but during winter it may be as much as 21 days. Pupal stage lasts for 8 days at 27°C and 30 days at 18°C. Thus it requires about 22 to 23 days to complete one generation.
Young larvae, after hatching from the eggs, enter soft seeds and teed on them. At first, the damage resembles that of leaf miners as their galleries run just under the epidermis of seed. Later they burrow deep down resulting in decaying of the grains which become unlit for either consumption or germination. As high as 80 per cent of the pods and 63 per cent of the grains may be damaged. In advance
cases of damage, the pods present a twisted appearance. This pest could be controlled by the removal of affected pods of first brood during winter which will help in reducing the population to a great extent. The crop may be treated with 0.2 per cent DDT or 0.02 per cent endrin spray at the rate of 300 litres per acre to kill the adult flies.
Tur pod bug (Clavigralla gibbosd) is the minor pest of tur crop. It also affects wal crop. The adult bugs are about 12 cm. long, are greenish brown in colour, have a spined pronotum and a femur swollen at the apical end. The eggs are laid in rows, on hatching, the nymphs start sucking the juice from pods and pass through five moults to reach the adult stage.
Both the nymphs and adults suck the sap from pods and cause the infested pods to shrivel. The pest, however, is rarely serious. This pest could be controlled by the preventive measures same as those in the case of the pod caterpillar. 5 per cent BHC powder, if dusted at the rate of 8 kg. per acre, may control the pest.
Of groundnut: Groundnut aphids (Aphis craccivora Koch.) is the important pest of groundnut. They are small, black soft-bodied insects found on the lower side of leaves. Both the winged and wingless forms reproduce viviparously and parthenogenetically. On an average a single apterous and alate female produces 54 and 47 young ones in 8 to 17 and 14 to 18 days respectively. The nymphal period lasts for three to eight days during which the nymphs undergo four moults.
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. This pest could be controlled by dusting the infested crop with 10 per cent BHC at 15 to 20 lb. per acre. It is necessary to mix equal quantity of sulphur which besides, preventing the incidence of mites, keeps ' Tikka' disease under check. Spraying the infested crop with any one of the following insecticides will protect the crop, viz., 0.05 per cent malathion, 0.02 per cent thiometon, 0.03 per cent formothion, 0.1 per cent carbaryl + sulphur.
Of sugarcane: Sugarcane stem borer (Chilotrcea infuscatellus S.) is the important pest of sugarcane. The adult moth is greyish brown or straw-coloured and measures about 1½ inches 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 transluscent body with spots and hair. The tiny spots develop into spines later. A fully-developed larvae measures about li inches and is greyish white in colour. The body is often covered with dark marks, having tubercles and short setae on
them. Oval, scale like, whitish eggs are laid overlapping each other on the under-surface of leaves by the side of the mid-rib. The egg-stage lasts for three to five 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 about a week and the entire life-cycle is completed in about a month and half. There are about eight generations in a year.
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 shoot dries 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.
Sugarcane top shoot borer (Scripophaga nivella, F.) is another pest of sugarcane. The moth is creamy white in colour having a wing span of a little over an inch when spread out and with orange hairlike structures at the tip of the abdomen of female. The first pair of the wings of certain males has a single black spot on each wing. Fully-developed caterpillars measure about 1 inch to 1½ inches in length and are yellowish white in colour. Eggs are laid on the under-surface of leaves in groups consisting of 35 to 40 eggs which are covered with brownish hair-like structures and hence are clearly visible. The newly-hatched caterpillar, after remaining for some time on the leaves, enters the shoots through the mid-rib of the leaf. The caterpillar feeds as it travels downward. A fully-developed larvae measures 1 inch to 1½ inches and before pupation, it prepares a silken membrane from which the moth can escape; the pupae is found in the larval tunnel. The egg-stage lasts for six to seven days, while the larval period continues for three to six weeks. The pupal stage continues for seven to ten days from which the moth on emergence starts laying eggs within two to four days of its life-time.
This is a very serious pest of sugarcane that breeds throughout the year and is capable of attacking cane at a latter stage. The newly-hatched caterpillar enters first the mid-rib 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. This pest could be controlled by the following measures:-
Borers, being internal feeders, are extremely difficult to control. Both preventive and curative measures are necessary to keep them under check. Since most of the borers occur together and the type of damage caused by them is more or less common, the measures for their control are also given together.
Mechanical and cultural methods of control such as collection and destruction of egg masses, removal of infested plants, early earthing up of canes, changing the planting time to November or December in the case of plant cane and in August or September for Adsali cane against stem borers, or planting of sets in deep trenches for top shoot borers have been found to be quite useful against these pests. Releasing of an egg parasite Trichogramma minutum Riley, at the rate of about one lakh per acre in three instalments at fortnightly intervals was also practised in the past but did not however yield satisfactory control of these borers.
Regarding chemical control measures soil application of heptachlor, dieldrin and aldrin dust at ½ kg. per acre is reported to have given good results. Spraying with 0.3 per cent D.D.T. three times on 4, 6 and 9 weeks old crop is reported to have given promising results. Spraying with 0.5 per cent D.D.T. is also recommended. Application of insecticides like 0.05 to 0.2 per cent endrin, 0.25 per cent BHC or 0.05 per cent toxaphene have been observed to be quite effective against the pests.
Sugarcane leaf hopper or pyrilla (Pyrilla sp.) is mainly a pest of sugarcane. But sometime the adults are found in small numbers on jowar and maize. The adult pyrilla bug is straw-coloured insect with two pairs of wings folded roof shaped on the back and with its head extended like a pointed beak which is quite readily visible. The young 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.
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 fifty to sixty days. Egg-laying continues from April to November and the period of its great activity is July and August.
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.
This pest could be controlled by mechanical and cultural methods such as collection and destruction of egg-masses, disposal of cane trash, bagging of adults in nets etc, which were recommended in the past for controlling the pest. Dusting the crop with 5 per cent BHC at the rate of 15 kg. and 20 kg. per acre in the pre and post-monsoon periods respectively, helps in checking the infestation. Spraying 0.12 to 0.25 per cent BHC or DDT at the rate of 300 litres per acre for young cane during the pre-monsoon period and over 400 litres during post-monsoon period gives considerable relief. Similarly application of 0.02 per cent endrin gives effective control of the pest. Application of 10 per cent toxaphene was also found to be equally effective.
Scale insects (Aspidiotus glomeratus, Green) is the pest of sugarcane as well as wild grasses. Adults are greyish black in colour, irregularly oval and slightly convex in shape. Females are flat and pyriform. The males are winged and smaller in size but arc rare. Freshly-hatched crawlers are tiny and light yellowish in colour. The pupal stage is noticed in males. Pupae resemble adults in colour and possess wing pads.
Females lay eggs beneath the shield-like scale covering for three to four days and deposit about 270 to 400 eggs. The newly-hatched crawlers remain together for sometime and then slowly begin to disperse and remain active for 12 to 36 hours during which they undergo one moulting. The crawler then loses its. original form and is covered over by a scale covering. The female remains fixed to the host plant throughout its life, while the male emerges out of pupae after 18 to 25 days. About nine generations are completed in a year. This pest could be controlled by the following measures:-
(1) Systematic stripping of cane leaves followed by spraying
0.2 per cent parathion is recommended. (2) Treatment with
0.04 per cent endrin, dieldrin and 0.15 per cent malathion has also
been found promising against the pest.
Both crawlers and adults suck the cell sap from the cane stalks; as a result the infested canes become shrivelled, the inter-nodes are shortened and the sucrose percentage of the juice is affected. In case of severe infestation the entire cane is covered with the pest forming thick encrustation on the stem which affects the value of the cane and ultimately the crop dries up completely.