Learn about how to control pests of cereal crops!
1. Jowar Stem Borer:
Chilo Zonellus Swinh. (Lepidoptera- Pyralididae):
It is a major pest of maize and jowar. However with respect to maize it causes damage only to the young plants while all stages of jowar are severely attacked. The period of infestation comes from the middle of March and continue upto September with a peak during August. Normally the attack on the plants starts from the top with the caterpillars boring into the shoots at the upper end.
However, there are instances where the caterpillar enters the shoot from the side, punctures even stems as high as 8 cm. from the ground. In either case they ingest the sap from the plants and bring about its withering which ultimately results in the formation of dead hearts. The withered plants have reduced leaves and stem. An attack by this pest from the top end of the plant is indicated by the presence of numerous punctures on the leaves forming the whorl.
The adult insect is a yellowish brown moth 20-30 mm. across the wing with deep brown spots, long legs and two projecting pulps in front of the head which give the appearance of a beak. Sexual dimorphism is characteristically exhibited in this species. The hind wings of male have a smoke like or pale straw colour, while those of females are bright whitish. Further, the abdominal tip of males is smooth and bluntly pointed while those of females is broad and covered with a thick tuft of hairs. The adults are short lived.
Life History:
The female lays greenish or creamy white, flattened, oval about 0.8 mm. long eggs at night on the lower surface of the leaf near mid rib in two rows overlapping each other. The eggs are normally laid from April to May. Each row contains about 50-100 eggs which in course of time change their colour first to orange and then to yellow. Hatching occurs in about 7-10 days liberating young caterpillars.
These immediately feed on leaves, on which they have hatched and then gradually penetrate into the leaf at the mid rib region to start their journey towards the main stem for the principal attack. Often their course from the leaf to the stem is interspersed with small punctures on the leaf for the purpose of ventilation. Thus they reach the shoots tunnelling and boring their way from the leaf. Soon the main stem looses its strength and becomes a dead heart.
The caterpillar thus draws its nourishment from the shoots and become fully matured in about 3-4 weeks. At this stage it prepares itself for pupation. It immediately makes an exit hole in the shoot and undergoes pupation within the infested stem in a chamber specially lined with thread like secretion. The pupal period lasts from 7-10 days.
The pupae are shining brown in colour and possess six spines arranged in two rows at the tip of the abdomen. At the end of pupal period fresh moth emerges through the exit hole. The entire life cycle lasts for about 5-6 weeks. Generally there are two broods in a year.
Control:
Many precautionary measures such as thorough examination of field before planting, removal of stubble trash and deadhearts from the plough field are employed. Besides these certain electrical devices such as attraction of moths by light traps are also adopted. Often biological control measures have been found to be successful. These include the introduction of egg parasites such as Trichogramma minutum and Bracon chinensis. Spraying of 1.5 litres thiodan 35 EC or 2 kg (50% soluble) carbaryl in 1000 litres of water/ha. 15-20 days after sowing helps in controlling the pest.
2. Gundhi Bug:
Leptocorisa Varicornis Fabr. (Heteroptera- Coreidae):
It is a common pest of rice and is a major one. Both the nymphs and adults destroy the ripening grains of the plants usually during August to October, extracting their milky juice with the consequence that the ears turn white forming shrivelled grains and preventing their maturation. A serious attack results in the appearance of empty, dry, brown earheads on the plant. Yield losses of 10-40% are common and in severe infestations the entire crop may be destroyed. Plants such as those of jowar, maize, bajra, etc. form the secondary host of this insect.
The adult insect is slender, green or light brown in colour. It emits strong unpleasant aromatic odour and hence the name ‘Gundhi bug’. Both male and female individuals are identical in appearance except that the abdominal apex of the latter is more swollen than that of the former.
Life History:
The female deposits eggs in one to three rows on the leaves of the paddy plant, each row containing 5-20 eggs. The eggs are black, oval and flattened but concave from above. Each egg has a dark brown shell with a white spot indicating the point of rupture during hatching. The eggs are fixed to the leaves by a gummy substance. The eggs hatch into young, pale green nymphs in about 6-8 days.
These nymphs are devoid of wings but green in colour in the beginning but possess long legs and antennae. Slowly the wing also develops and the nymph moults 5-times with in a period of 17-27 days before attaining the adult condition. An important feature of the final moult is the transfer of functional odoriferous glands from the abdomen to the thorax and the formation of three tarsal joints.
When the plant is at a tender stage both nymphs and adults congregate in large number around ripening ears, tender shoots and leaves. The entire life cycle is completed in about 4-5 weeks and in a year there are generally 5 broods during the paddy season. Multiplication normally occurs from July to November, hibernation from December to February and their population on grasses from March to June.
Control:
Besides many precautionary steps like extermination of wild grasses from the sowing fields etc. and certain mechanical (electrical) measures such as light trap arrangement for catching the insects, the general tendency has been to employ either biological control or chemical control. Biological control measures warrant the introduction of certain beetles like six spotted tiger beetle, Cicindela – sixpunctata or certain species of Pentatomid and Reduviid bugs which prey on the adults.
Control by chemical measures is through the application of insecticides. Dusting the crop with carbaryl (Sevin) 5% or malathion 5% dust @ 20 kg/ha in the morning hours or spraying the crop with 0.05% monocrotophos or 0.07% endosulfan is useful. Dusting is usually done on the earheads, especially when they are in the milky stage and the bugs appear in large numbers.
3. Rice Grasshopper:
Hieroglyphus Banian Fabr. (Orthoptera- Acrididae):
It is a serious though sporadic pest of eastern U.P., damage to the paddy is caused both by the young and adult stages of the insects which feed upon the leaves and soft ear grain of the plants. The insects also attack other plants like sugarcane, jowar and different types of grasses.
The adult is a green, dry grass coloured medium sized individual with long slender legs. The young nymphs are very much like the adults except that they are smaller in size and possess a brownish yellow colour and allied species of this genus H. nigrorepletus Bol. is a minor pest of jowar.
Life History:
The female lays yellow eggs resembling rice grains in clusters usually during October month. The eggs are closely packed in hard “cement” which forms a pod like cylindrical structure termed “egg pod”. Each pod containing 30-40 eggs is laid 5-8 cm. deep in the soil by inserting the abdomen. The eggs remain buried under soil during hibernation stage i.e. upto June.
The eggs hatch during the monsoon season into young nymphs which immediately starts feeding on nearby grasses and later on migrates to the main crops. These nymphs become full grown in about 8-10 weeks, during which period they moult 5-times (sometime 6 times) at an interval of 10-15 days each. The young nymphs known as hoppers resemble very much the adult except for the fact that these hoppers are devoid of wings.
The nymphal period on the whole extends from 10-12 weeks after which a fully developed adult is formed. The entire life cycle lasts for about 17 weeks. Generally there is one brood in a year which appears during the monsoon rain.
Control:
As in the case of other pests, certain measure of success is achieved by adopting physical methods such as hand collecting and destroying the hoppers, and arrangement of light traps etc. However, insecticidal treatment has been found to be very effective by dusting 12.5 kg. 10% carbaryl (sevin) dust/ha on the first appearance of the pest. The grasshoppers can also be controlled by spraying the infested crops with endosulfan 1250 ml or 875 ml methyl parathion 50 EC in about 1000 litres of water per hectare.
4. Paddy Gall Fly:
Pachydiplosis Oryzae (Wood-Mason) (Diptera- Cecidomyiidae):
The paddy gallfly is very small in size and has a wing span of less than 2mm. The fly has long slender legs and produces in the paddy plants long tubular galls of silvery appearance in the place of normal stems with earheads. Hence the crop attacked by this insect is said to be suffering from “silver-shoot” disease. Its distribution covers East and South Asia.
In India, it attacks the paddy crops with varying intensity in most of the paddy growing areas but its infestation is very serious in the coastal regions of the country on account of weather conditions. The larva of the fly is known as maggot and is very harmful. Feeding of the maggot produces gall which kills the growing shoots.
Life History:
The fly breeds on a number of wild grasses and it is attracted to the paddy crop at its tillering stage. The female fly which is pink in colour lays about 200-300 reddish elongated eggs about 0.5mm. in length generally on the lower surface of the basal portion of the leaf. The tiny larva hatching out within 3-5 days creeps down between the leaf-sheaths till it reaches the apical point of the central shoot or tiller, as the case may be, and there it enters the tissue and destroys the growing point.
As a result of which the normal growth stops and a small gall is produced. This gall gradually elongates and a long hollow shoot of silvery appearance emerges in the place, which in a normal plant is occupied by the stem bearing the earhead. Thus the earhead formation is totally prevented.
In the meantime, the larva becomes full grown in about 10 days and pupates inside the tubular gall. The pupal period lasts about 3-5 days and thereafter, the fly emerges out of the gall through a hole already made before the pupal stage. Thus, the whole life cycle is completed in about 3 weeks. The adult fly lives only for about 3-4 days and therefore just after emergence it starts a new generation. In favourable climatic conditions there are 6-8 generations in a year.
Control:
The paddy gall fly infestation can be prevented, by spraying the crop with a number of insecticides, some of them are- phosphamidon 0.05%, diazinon 0.05%, carbaryl 0.2%, dimethoate 0.02%, lindane 0.5%. The collection and destruction of “silver shoots” can also help, provided it is started early in the season and the galls are rouged out as soon as these are seen.
5. Paddy Stem Borer:
Tryporyza Incertulas (Walk.) (Lepidoptera- Pyralididae):
Unlike other lepidopterous larvae, this paddy stem borer is “highly monophagous” and no alternate host plant besides rice has been recorded so far. It is found in practically all the rice growing regions of India as well as many rice growing tracts of the world. The adult moths have the wing expanse of 25-40 mm. and the wings are ochreous yellow in colour.
In the female moth, there is a prominent black spot on each of the forewings while this spot is indistinct in males. The female moth is bigger than the male. The female moths have a tuft of brown-yellow hair at the tip of their abdomen. Regarding the harm done to the paddy plant, the whole seedling dies if the infestation comes early.
Later, as a result of feeding of the larva inside the stem, it turns yellow and produces the dead heart, and when the infestation occurs at a still later stage, the earheads become white and grain remains worthless.
Life History:
The eggs are laid in 2-6 batches and each batch has about 65-85 eggs, on the underside of the leaves and are covered by buff coloured hairs contributed by the anal tuft of the female moth. The first stage larvae hatching out from the egg masses in about 6-9 days, crawl about on the plant or hang down from the leaves by silken thread and bore into the stem and enter the tissue for the rest of their life as larvae and pupae. The larva passes through 4-6 instars and is full fed in about 15-30 days and attains the length of 2-2.5 cm.
The full grown larva has a smooth surface of yellowish green tinge. The head is orange yellow. Before pupation it cuts open another hole which is located above the water level in the field through which ultimately the moth comes out. After the pupal period is over which lasts about 8-12 days depending on weather, the moth emerges and marks the beginning of the next generation. The whole life cycle is completed in about 30-50 days. There are several overlapping generations in a year.
Control:
At the egg stage, collection and destruction of egg masses is very effective. The pest can also be controlled by spraying the crop with any one of these insecticides: methyl parathion 0.08%, phospha-midon 0.05%, diazinon 0.06%.
6. Paddy Leaf Miner:
Hispa Armigera Oliv. (Coleoptera: Hispidae):
The grubs are leaf miners. Also known as Rice Hispa. This is also a pest of paddy which has been found widely distributed in this country and abroad. The damage is caused by the grubs and adults both which feed on the green delicate parts of the paddy leaves. The adult beetles are blue-black in appearance, measuring about 5 mm in length and are recognized by numerous short spines on the body.
Life History:
Each female individual lays about 50 to 60 eggs inside the leaves. The tender parts of the leaves are preferred for laying the eggs. After about 5-days, yellowish grub emerges which feeds inside the leaf-mine for about 10 days. Pupation takes place inside the mine and adult emerges in about 4 to 6 days. There are several generations in a year.
Control:
For controlling this insect spraying of 0.5% of insecticides like methyl parathion, and phosphamidon was found useful. Spraying the crop with 0.05% monocrotophos, as well as 0.07% endosulfan at the time of severe infestation also controls the pest-population.
7. Swarming Caterpillar:
Spodoptera Mauritia Boisd. (Lepidoptera- Noctuidae):
Swarming caterpillar is a sporadic pest but is very serious indeed whenever it appears in large number. It is distributed in the entire costal region of India as well as in the Oriental and Australian regions. As the name indicates, in caterpillar stage this pest has a tendency to migrate from field to field in large swarm.
The swarm browses a field like cattle and when field is completely finished, the swarm marches on in regular army formation to the adjoining field. Thus a very heavy damage is caused by the caterpillars. The caterpillar is polyphagous, feeding on cultivated crops and wild grasses, but paddy is the most important crop in the coastal areas due to the weather conditions, hence, it turns out to be a very serious pest of paddy.
Life History:
The adult is a medium sized moth of grey brown colour with beautifully designed patchy forewings which have a wavy border pattern on the fringe. The hind wings are practically white. The moth measures about 15-20 mm. in length and about 38-40 mm. across the wings. These moths lay eggs on the underside of the leaves in large masses, each containing up to several hundred eggs and about 1000 eggs are laid by a single female in her life time.
They are covered with buff coloured hairs from the female’s body. The eggs hatch in about 7 days or so depending on the prevailing temperature. The young larvae immediately begin to feed on nearest available plant. The larval stage lasts about 20-28 days. The first stage larva is extremely small which gradually grows through several moults into a full grown larva of about 3-4 cm. in length.
The colour pattern of the larvae consists of longitudinal stripes which in the beginning have a mixture of green and yellow with a reddish stripe along the side and which later on are mostly of yellowish brown hue. Pupation take place in the soil. The pupal stage lasts from 10-12 days after which the moths of the next generation appear and give rise to a new brood. Both the moths and caterpillars are nocturnal. There are varying numbers of generations in the different regions of the country.
Control:
For preventing the damage caused by the swarming caterpillar, the collection and destruction of the large egg masses, is very useful. Regarding chemical control, stomach poisons or a contact + stomach poison is very effective. Dusting the crop with sevin 10% or spraying 0.04% endosulfan or 0.2% carbaryl is also very effective.
8. Pink Borer:
Sesamia Inferens Walk. (Lepidoptera- Noctuidae):
The pink borer is a polyphagous insect and is distributed throughout India. It is a serious pest of maize and rice. Its larvae are pinkish-brown in colour which bore down the stem making long tunnels throughout the whole length. The central shoot is completely destroyed and dead hearts are formed. It feeds on wheat, barley, paddy, sugarcane, jowar etc.
Life History:
The pest breeds actively from March-April to November on rice and then migrates to the wheat crop. The moths are nocturnal and lay 150 eggs on leaves or on the ground. The eggs hatch in about 6-8 days and the young caterpillars bore in to the epidermal layers of the leaf sheaths. Later on, they bore into the stem as a result of which the growing shoots dries up producing dead hearts.
When the attacked plants dry the larvae move on to adjoining plants, they are full fed in 3-4 weeks and pupate inside the stem or in between the stem and leaves. The pupal stage lasts about a week and the life cycle is completed in about 6-7 weeks. There are 4-5 generations of the pest in a year.
Control:
Spraying methyl parathion 0.08%, phosphamidon 0.05% or diazinon 0.06% is effective in checking the infestation of this insect.
9. Armyworm:
Mythimna Separata Walk. (Lepidoptera- Noctuidae):
It is a pest of wheat, maize, jowar, bajra, sugarcane etc. The caterpillars are voracious, eating entire leaves and the whole plant, usually during nights and migrate from one filed to another field.
Life History:
Eggs are laid either singly or in clusters of about 100, inside the rolled leaves or between the leaf sheath and stems. They are sub-spherical, greenish white, turning yellow and take about 4-13 days or more to hatch, which depends on the climatic conditions. Older caterpillars are gregarious and have voracious appetites.
The caterpillars vary considerably in colour, from green to pink but have four distinct longitudinal black stripes and reach a mature size of 35-40 mm. after about 14-22 days in spring or 80-100 days in winter. The pupa is dark brown in colour 15-19 mm. in length.
Pupation takes place 4-5 cm. deep in the soil. Pupal stage is completed in about 7-22 or even more days. The length of pupal stage depends on temperature. The adults are reddish or grey moths with a central pale spot in each forewing. Wing span is from 35-50 mm. The whole life cycle takes about 25-64 days (31 days on an average) with 5 generations per year.
Control:
Cultural methods such as ploughing, stubble burning, flooding of the infested fields, removal of grass and alternative host plants from around the fields, all help to reduce the pest population. Dusting methyl parathion and other contact insecticides are very effective. Spraying the crop with 0.05% monocrotophos or 0.07% endosulfan at the time of heavy infestation reduces the pest population.
10. White Grub:
Holotrichia Consanguinea (Blanch.) (Coleoptera- Melolonthidae):
The grub feeds on the fibrous roots of maize, sorghum, brinjal, sugarcane etc. and is found in the upper layer of the soil about 5-10 cm. The full grown grub measures about 35 mm. long, is white in colour with brown head. The beetles are dull brown and about 18 mm. in length. While the grubs feed on roots, the adult beetle feeds on the plant leaves. It has also been reported as a major or minor pest of certain fibre crops, like many other insects, hence, considered as a pest of several crops and is polyphagous.
Life History:
The adult beetles lay eggs singly upto a depth of 10 cm. which hatch in about 7-10 days. The development completes in about 10 weeks. After the monsoon the grubs pupate in the soil. The pupal stage lasts for about 15 days. The beetles remain in soil at a depth of 10-20 cm. and come out only at night for feeding. The adults remain in soil and undergo diapause for about 8 months. They remain active only in rainy season i.e. June/October. There is only one generation in a year.
Control:
The white grubs can be checked by applying 10% carbaryl (Sevin) dust @ 12.5 kg/ha in the field. The soil can be treated with phorate granules, and quinalphos to control this pest. It may be pointed out that a number of pests of cereals like stemborers, aphids, hairy caterpillars, grass hoppers, and earhead bugs etc. can be controlled by using diazinon 5% or endosulfan 4% granules @ 20-25 kg/ha.