AGRICULTURE AND IRRIGATION

PESTS

PESTS. Of Jowar.

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 ½" to ¼" in length. The moths are straw-coloured with forewings pale yellowish grey having minute dots on the apical margin and white hind wings.

 The caterpillars bore inside the stems causing thereby the drying of the central shoots called 'dead hearts'. Due to this stems and leaves turn red. The extent of damage is about 4 to 5 per cent.

Being an internal feeder, only preventive measures as given below are found practicable and economic: (1) The affected plants should be pulled out along with the caterpillars inside and destroyed promptly, (2) After harvest of the crop stubbles should be collected and burnt to destroy the hibernating larvae. (3) The fodder to be fed to cattle should be cut into small pieces and fed.

Army worms (cirphis unipuncta):

Full-grown caterpillars are 1" to 1½" long, smooth, stout-bodied, dull greenish coloured with broad light-coloured strips 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.

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 pest is active from June to November. Kharif crops suffer more from it than rabi crops. It is observed that when a long dry spell follows a good start of the monsoon, the pest assumes epidemic: form.

The pest can be controlled by adopting the following 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 pupae. Insecticidal measures have been found very effective. Five per cent BHC or endrin dust, if properly dusted at the rate of 30 lbs. per acre, successfully, controls the pest. Dusting done in the evening, especially if there is less 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 1 lb. in 25 gallons of water. About 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 evening, will also control the pest, for crops like nachani, if it does not rain, and if the soil is dry.

Hoppers and aphids (Peregrinus maidis, Ashm and Rhopalo-siphum maidis, F):

Delphacids (Peregrinus maidis, Ashm and Aphids (Rhopalo-siphum maidis. F.) and responsible for causing the sugary secretion on jowar 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 are 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. Ultimately the growing shoot of the plant is damaged and further growth is checked, The problem of sugary disease is still under investigation; how- ever, spraying with 0.02 per cent diazinon, thiometon, endrin or dusting with 5-10 per cent BHC dust @ 20 lbs. per acre help in reducing; the intensity of infestation of these pests. PESTS. Of Wheat.

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 the affected plants. The moths are small and are straw-coloured. Their forewings have a marginal dark line and the hind wings are white.

The caterpillar bores inside the stem thus causing the drying of the central shoots then 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 on. Drying of the plant often leads to reddening of stems and leaves.

Being internal feeders, only preventive measures are found practicable and economic. In the early stage of infestation, the stems of plants showing dead hearts should be pulled out along with the caterpillars and they should be destroyed promptly. After the harvest of the crop, the stubbles should be collected and burnt so as to destroy the hibernating larvae. After harvesting the crop, wheat stalks which are used as fodder should be stored in the form of cut fodder.

Gram pod borer (Heliothis armigera obsolata) :

Of Gram.

The caterpillars are greenish with darker broken grey lines along the sides of the body. They are 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.

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 1 lb. of 50 per cent water dispersible DDT powder in 25 gallons of water. About 60 to 80 gallons on a young crop and 100 gallons on a grown up crop are generally required.

Of Groundnut.

Aphids: They are small, black soft-bodied insects found on the lower side of leaves. 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 in Khandesh it frequently takes the form of an epidemic. The control measures are the same as those for aphids on safflower; 10 per cent BHC dust also gives some relief. The swarming caterpillar (spodoptera mauritia, Boisd):

PESTS. Of Paddy.

The full-grown caterpillars measure 1¼" to 1½" long, dark  greenish with slight yellow tinge. They can readily be distinguished from other caterpillars by the presence of white  longitudinal dorsal stripes along the length of their body. Their  heads are dark.

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 flooded.

Preventive measures include protection of seed beds by deep trenching with steep sides and hand collection of egg masses and their destruction. The caterpillars during the day-time bide under clods, so 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 20 to 30 lbs. per acre. The dusting if done in the evening will give better control as the caterpillars come out to feed at night. Where rains are frequent, spraying BHC water dispersible powder by diluting, 5 lbs. of 50 per cent BHC in 100 gallons of water can be tried. 60 to 100 gallons of spray per acre should be used for effective control.

The Rice Case Worms (Nymphulia Depunctalis Guen.):

The full-grown caterpillars are greenish white, ½" long and semi-aquatic and generally feeding on foliage inside tubular cases formed of pieces of paddy leaves. The caterpillars cut the paddy leaves into short lengths, construct tubular cases and remain inside them while feeding.

Preventive measures include removal and destruction of the tubular cases along with the caterpillars. In the early stages of the crop before flowering, rope-dragging may be tried to dislodge the caterpillars after flooding the infested field and putting a little crude oil into it. Insecticides recommended for the blue beetle and hispa will also control the pest to some extent. But one part of pyrethrum extract in 600 parts of water or 0.375% DDT spray obtained by mixing 7 to 8 lbs. of 50% water dispersible powder in 100 gallons of water has shown better results.

Of chillis.

Thrips and mites: These pests suck the cell sap due to which the leaves get badly curled. It is locally known as churda murda disease. The extent of damages is about 25%.

0.2% BHC + sulphur (wettable) effectively controls the disease. 0.02% endrin+ wettable sulphur (1:1) or 0.02% diazinon or 0.025% dieldrine + sulphur (1:1) are also found to be equally effective. Spotted boll worm (Earias fabia, S. E. insulana, B.):

PESTS.Of Cotton.

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 prothoracic shield. They have a number of black and brown spots on the body. The full fed larvae measures about ¾" in length. The other boll worms are pink in colour and with brown heads.

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 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 band 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. 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: (1) Fumigation of seed before sowing with carbon-di-sulphide @ 2 ozs. per 15 cu. feet or heating the seed at 145° F. to destroy the hibernating pink boll worm larvae. (2) Six dustings with 10% DDT+ 2% lindane+ 40% sulphur mixture or with 1% endrin dust and (3) Six sprayings at fortnightly intervals with 1 oz. of 20% E. C. endrin in 4-6 gallons of water starting from a month prior to flowering. It is desirable to add an equal quantity of sulphur to avoid mite incidence.

Red cotton bug (Dysdercus singulatus. Fabr.):

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. The excreta of these insects soils the lint.

The pest can be controlled by collecting the adults and nymphs in large numbers by shaking them in a tray containing little kerosene added to ordinary water. In case the pest becomes serious, the crop may be treated with 5% BHC.

Jassids (Empoasca devastans, Dist.):

The adult is wedge-shaped 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 leaves. They walk diagonally in relation to their body.

Both the nymphs and adults suck the cell sap from the leaves as a result of which the leaf margin turns yellowish and in case of excessive infestation etiolation and drying up of leaves followed by stunted growth take place.

5% DDT dust mixed with an equal quantity of sulphur at the rate or 15 to 20 lbs. per acre effectively controls the pest. 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% spray of DDT 50% water dispersible and sulphur water dispersible is very effective against jassids. 4 ozs. or 2 ozs. of endrin per acre or 0.01% to 0.02% parathion also effectively control the pest.

Aphids (Aphis gossypii, Glover):

The adult is oblong about 1 mm. 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 leaves turn yellowish and dry.

The pest can be effectively controlled by spraying nicotine sulphate at the rate of 1 lb. in 80 gallons of water with 5 lbs. of soap. Spraying with pyrethrum 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. DDT should not be used for controlling the aphids. 2 ozs. to 4 ozs. of endrin per acre or 0.01% to 0.02% parathion are also effective against cotton aphids.

Mealy bugs (Ferrisiana virgata, CKLL.):

The adult female is pale yellow in colour and her body is covered with white meal and glossy threads. Her average length is 2.6 to 3 mms. Newly hatched nymphs are light yellow in colour. The male adult 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 tender shoots, with the result that the plant gives a stunted and whitish appearance. The feeding also causes curling and chlorosis.

Spraying with 1% fish oil rosin soap, 0.03% diazinon or parathion and 0.10% malathion helps in reducing the pest infestation.

Mites (Eriophes gossypii, Bank):

The adults are minute with an oval body and four pairs of legs. They are usually found on the lower surfaces of leaves.

The nymphs and adults usually feed on the lower surface of the leaves. In case of severe infestation complete defoliation of plants is caused. Spraying of 0.05 % aramite, 0.03 % dichloro-benzilic acid (akar) and 0.02% parathion and 0.02% sulphur effectively control the pest.

Tur plume moth (Exelustes atomosa) :

PESTS. Of Tur.

The full-grown caterpillars are about ½" long, greenish brown in colour and fringed with short hairs and spines. They bore into green pods and feed on the developing seeds.

Preventive measures are the collection of caterpillars by shaking shoots and pods in small trays containing kerosenised water and avoiding to take leguminous crops in the same fields in successive years. The insecticidal measures given under the gram pod borer can be tried with advantage.

Of Sesamum.

The pests of sesamum are the gall fly, the sphinx-caterpillar, and the pod-sucking bug. Gall fly (Aspondylia sesami Felt) pili : The adult is like a small delicaet mosquito. The maggots are found inside the young flowers. The irritation causes gall formation and interferes with the process of pod formation. The insecticidal measures are not yet worked out. Preventive measures such as clipping and destroying the infested buds can be followed.

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