Learn about the pests that damage rice.
1. Pink Stem Borer, Sesamia Inferens (Walker) (Lepidoptera: Noctuidae):
The pink stem borer is a polyphagous insect and is distributed throughout India and Pakistan. In some parts of the country, it is a minor pest of sugarcane whereas in others, it is common on ragi (Elusine coracana), and in still others on wheat. In northern India, iris recorded on rice, sugarcane, maize, sorghum and wheat, but its damage is significant on rice and maize only. The damage is caused by the caterpillars which are pinkish brown and have a smooth cylindrical body, measuring about 25 mm. The moths are straw-coloured and have a stout body.
Life-Cycle:
The pest breeds actively from March-April to November on rice and then migrates to the wheat crop. The moths are nocturnal and lay eggs on leaves or on the ground. The eggs hatch in 6-8 days and the young caterpillars bore into the epidermal layers of the leaf sheath. Later on, they bore into the stem as a result of which the growing shoot dries up producing dead-hearts.
When the attacked plants die, 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 6-7 weeks. There are 4-5 generations of the pest in a year.
Damage:
This pest is common during the dry pre-monsoon period. The attacked young plants show dead hearts and are killed altogether. The older plants are not killed, but they produce a few grains only.
2. Whitebacked Planthopper, Sogatella Furcifera (Horvath) (Hemiptera: Delphacidae):
In recent years, a number of leaf-and planthoppers have assumed pest proportions on the paddy crop in various parts of India. In all, 21 species have been identified and the white-backed planthopper is the most widespread of them all. In 1966, this insect was reported for the first time as a serious pest in the Punjab and other adjoining States of India.
The nymphs and the adults of S. furcifera are very active and they can easily jump from one leaf to another on a slight disturbance. The adult is a straw-coloured, wedge- shaped insect, with white back. The nymph is greyish-white and turns dark grey when it nears maturity.
Life-Cycle:
The planthoppers breed continually in southern parts of India where paddy crop is available throughout the year. In northern parts, the planthopper becomes active in May in the paddy nursery, from where it shifts to the transplanted crop. By August and September, the population becomes quite high. The adults lay eggs generally on the leaf sheath. The eggs hatch in 3.4-4.6 days.
The nymphs feed on leaves and are transformed into adults within 8.9-13.1 days. The life-cycle is completed in 12.3-17.7 days. The adult females live for about a week. There are several generations in a year. In northern parts of India, the planthoppers remain inactive in the winter and their population becomes noticeable only from May onwards on the paddy nursery.
Damage:
The nymphs and the adults suck cell-sap from the leaf surface and tend to congregate on the leaf-sheath at the base of the plant. The leaves of attacked plants turn yellow and later on rust red. These symptoms start from the leaf tips and spread to the rest of the plant. Numerous brownish spots also appear on the feeding sites. The attacked plants ultimately dry up without producing ears. The insect also excretes honeydew on which a sooty mould appears, imparting a smoky hue to the paddy fields.
3. Green Leafhoppers, Nephotstcix Nigropictus (Stal) and N.Virescens (Distant) (Hemiptera: Cicadeilidae):
The green leafhoppers are found in all the rice growing regions of India, although they assume pest proportions only during certain years in Madhya Pradesh, Andhra Pradesh, Orissa and West Bengal. These species are also known pests of rice in Japan, the Philippines, Formosa and Sri Lanka. Both the species of leafhoppers are greenish and are smaller and slanderer than S. furcifera. The nymphs and the adults suck sap from the leaves of plants, turning them yellow and ultimately brown.
Life-Cycle:
The females, after undergoing a pre-oviposition period of 6-9 days, lay eggs on the inner surface of the leaf-sheath in groups of 3-18. The eggs hatch in 3-5 days and the nymphal stage is completed in 12-21 days. The adults live for 7-22 days in summer. There are about six overlapping generations from March to November. The insect over-winters in the adult stage. The pest population is the maximum in July-August and decreases markedly after a heavy rain.
Damage:
As a result of attack by this pest, the plants lose vigour and turn yellow. N. virescens is also known vector of virus diseases, of which tungro is the most serious.
4. White Rice Leafhopper, Cofana Spectra (Distant) (Hemiptera: Cicadeilidae):
The adults and nymphs of this insect have been reported as pests of rice and a number of other monocot plants including Leersia hexandra Sw., Triticum aestivum L., Zea mays L., Cyprus rotundus L., Saccharum officinarum L., Sorghum vulgareL., Sorghum halepense L., Cyperus tria L., and Cynodon dcictylon L.
This insect is widely distributed in the sub-tropical and tropical regions in South Asia. The adults are yellowish and have a rounded, rather swollen head and four black spots on the vertex. The adult measures 5.7-7.4 mm in length. The nymphs are paler in colour.
Life-Cycle:
The insect is active throughout the year. The adults, on emergence, take approximately 1.8-6.8 days before mating. The females lacerate the leaf sheath with the help of their ovipositor and lay greenish eggs in masses. There may be 5-17 eggs in a mass and the female deposits a total of 17 masses in her life time of 30-35 days.
The eggs hatch in 6-7 days and the nymphs, on emergence, first feed inside the leaf sheath and, later, they move on to the leaf blade. There are 5 nymphal instars which are completed in 18 days. In South India, this pest is particularly active from July to March and completes 12 generations in a year.
Damage:
Both the adults and nymphs suck cell sap and cause yellow discoloration of the leaves. When infestation is heavy, the leaves turn brown and the plants fail to produce ears. Even in moderate infestation, there is a significant reduction in the tillering of the plants.
5. Zigzag Leafhopper, Recilia Dorsalis (Motschulsky) (Hemiptera: Cicadellidae):
The adults and nymphs of this insect are important pests of paddy in many countries including Japan, Korea, the Philippines, Vietnam, Malaysia, Bangladesh, India and Sri Lanka. The adult is a whitish-grey hopper which has V-shaped and zig-zag brown lines on its forewings and measures 3.1-3.8 mm in length.
Life-Cycle:
In tropical areas of the world, this insect breeds throughout the year. The females lacerate the leaf surface with the help of their ovipositors and deposit eggs in the exposed leaf tissue. Sometimes, however, the eggs are also seen simply scattered on the leaf sheaths. The female has a life span of approximately 155 days, and during that period she lays upto 90 eggs.
The eggs hatch in six days and the nymphs, on emergence, feed on the leaf blades. There are 5 nymphal instars and this developmental stage is completed in 120 days. The entire life-cycle from egg to the adult stage is completed in 180 days. In temperate regions such as Southern Japan and Korea, this pest is known to pass winter in the egg stage.
Damage:
As a result of the insect’s feeding on cell sap, the mature leaves acquire an orange discoloration at the margins and become dry at the tips. As younger leaves grow they also show the same signs. The female hoppers are also known to be vectors of the virus disease ‘orange leaf’ and of the mycoplasma ‘yellow dwarf’.
6. Rice Blue Leafhopper, Typhlocyba Maculifrons (Motschulsky) (Hemiptera: Cicadellidae):
This leafhopper is primarily a pest of rice nurseries throughout India and South-east Asia. Apart from paddy, it also feeds on sorghum, ragi, maize, sugarcane and wild grasses. It is a small bluish insect having a yellowish vertex with a black patch and a black spot in the middle of the pronotum. The adult measures 1.9-2.5 mm in length.
Life-Cycle:
This insect is found practically throughout the year and is particularly noticed in the nurseries before the planting season. The females lacerate the surface of the leaf sheath or the upper midrib of the leaf blade and deposit eggs in batches of 2, 3 or 4.
A female lives for 45-50 days and, during that period; she lays an average of 48 eggs. The eggs hatch in 6-12 days and the young nymphs, on emergence, start feeding inside the leaf sheath. The nymphs moult five times and become mature in 11-20 days and the entire life cycle is completed in 19-32 days.
Damage:
Both nymphs and adults suck cell sap from the leaves which, in the early stages of attack, exhibit whitish, waxy lines. As the damage progresses, the leaves show symptoms of withering. If the pest is not controlled, the plants die and the entire nursery may be lost.
7. Yellow Stem Borer, Scirpophaga Incertulas (Walker) (Lepidoptera: Pyralidae):
The yellow stem borer is a specific pest of rice and is common throughout the Orient as one of the most destructive pests of this crop. The caterpillars alone are destructive and, when full-grown, they measure about 20 mm and are dirty white or greenish yellow, having brown head and pronotum.
The adults have a wing expanse of 25-45 mm and are yellowish white with orange yellow front wings. The female moth is bigger than the male and has a centrally situated black spot on each of the forewings. The females have a prominent tuft of brownish yellow silken hair at the tip of their abdomen.
Life-Cycle:
In the northern regions of India, this pest is active from April to October and hibernates from November to March as a full-grown larva in rice stubble. The pupation starts sometimes in March and the emergence of moths begin in April. The moths become active after dusk when they mate and lay about 120-150 eggs on the underside of the leaves in 2-5 clusters of 60-100 eggs each.
The eggs are covered with yellowish brown hair of the female tuft. The eggs are oval, flattened, pearly white at the time these are laid, but turn black before hatching. They hatch in 6-7 days and the tiny black-headed caterpillars soon bore into the stem from the growing points downwards.
When a tiller is killed, the caterpillar inside migrates to another tiller of the same or of a different plant. The larva grows in 6 stages and is full-fed in 16-27 days. It then constructs an emergence hole which is always located above the water level and pupates inside the attacked plant. Within 9-12 days, it emerges as a moth.
The life cycle is completed in 31-46 days. There are 3 broods in Bengal, 2 in Orissa and 5 in Andhra Pradesh and Tamil Nadu where it is active throughout the year. In the Punjab, there are 4-5 generations noticed from April to October and the caterpillars of the last brood make silken hibernacula in the stubble inside which they hibernate for the winter.
Several egg parasitoids have been found to be quite effective, viz. Telenomus dignoides Nixon (Scelionidae) was observed to parasitize as high as 70.8 per cent eggs at Ludhiana, Telenomus rowani (Gahan) 67 per cent in October and Tetrastichus schoenobii Ferriere (Eulophidae) 75 per cent in May at Coimbatore. Inundative releases of exotic Trichogramma japonicum Ashmead at 50,000 ha-1 during egg laying period of rice stem borer reduced borer damage and increased crop yield.
An allied species, Scirpophaga innotata (Walker), the white stem borer, is also present in most of the paddy growing areas in India. The life-cycle and damage of this species is almost similar to S. incertulas.
Damage:
Damage due to stem borer is much higher in southern States where the pest multiplies throughout the year and shifts from one crop to the next. In Northern India the pest has recently started appearing in serious proportions. Basmati varieties suffer heavy damage than coarse varieties.
The plants attacked in early stages produce ears devoid of grain and are known as the ‘white ears’. An average loss of 100-500 kg of paddy per hectare has been reported from Andhra Pradesh. In Orissa, the cumulative loss has been estimated at 44G per cent; with an increase of one per cent incidence of the pest at the early stage, the yield is reduced by 0.604 per cent.
Control:
(i) The removal and destruction of stubble at the time of the first ploughing after harvesting the crop decreases the carry-over to the next crop.
(ii) Ploughing and flooding the field is also effective in killing the larvae.
(iii) Since the eggs of stem borer are laid near the tip of leaf, clipping of tips of seedlings before transplanting can reduce the carry over of eggs to the field.
(iv) The fields showing more than 5 per cent deadhearts should be sprayed with 425 g of cartap hydrochloride 75SG or 150 ml of chlorantriniliprole 20SC or 875 ml triazophos 40EC or 1.4 litres of monocrotophos 36SL or 2.5 litres of chlorpyriphos 20EC or 37.5 g of fipronil 80WG in 250 litres of water per ha. Alternatively, apply 10 kg of chlorantriniliprole 0.4GR or 25 kg of cartap hydrochloride 4G or 15 kg of fipronil 0.3G or 10 kg of chlorpyriphos 10G or 7.5 kg of phorate 10G per ha in the standing water in the field. Same chemical should not be used repeatedly.
8. Pale-Headed Striped Borer, Chilo Suppressalis (Walker) (Lepidoptera: Pyralidae):
This insect is also known as the rice stem borer in Japan and Asiatic rice borer in some other countries. It is a serious pest in Japan, the Philippines, Southern Indonesia, Spain and China. It has also been recorded from Formosa, Korea, Malaysia, the Hawaii Islands, Northern Australia and India. In India, it is not an economic pest. Except for a few wild grasses, this borer is confined to the rice plant throughout its habitat. Injury to the plant is caused by caterpillars which tunnel through the stem and feed on the soft tissues.
The moth is 12 mm long, with pale-yellow wings of 26 mm expanse. The male moth is smaller than the female. The newly emerged caterpillar is about 1.2 mm long and has five grey-brown linear dorsal stripes on its body. When full-grown, it is 26 mm long and 2.5 mm wide, and has a yellowish brown head. The middle dorsal stripe is lighter than the two along each side.
Life-Cycle:
The insect passes through 1-4 generations, depending upon the climate of its habitat. In temperate regions of Japan, China and Korea, it has two broods and the full-grown larvae of the second brood remain dormant in the stubble during the winter.
A female lays about 300 eggs in masses of variable sizes on the leaf blades near the tip or on the leafsheath. The eggs hatch in 4-10 days, depending on the weather. The newly emerged larvae feed on the leafsheaths in groups. The 2nd and 3rd instar larvae disperse to the adjacent plants. They bore into the culm, through the nodes by the tenth day.
As the larvae grow and plants wither, they disperse gradually to the neighbouring plants. The larvae of the second generation bore into the stem through the stalk of the panicle and travel downwards until they reach the lowermost part of the stem. The larva of the first generation becomes full-grown in 33-50 days after emerging from the egg.
The mature larva pupates within the rice stalk either near the middle or in the basal internode. Pupation is completed in 5-10 days. The hibernating larvae remain in the stems or stubble when the crop is harvested. They resume development in the spring; their pupation being followed by the emergence of moths.
Damage:
The attacked leafsheaths first show transparent patches, and later turns yellow-brown and eventually dry up. The caterpillars, as a result of their feeding inside the stem around the nodes, weaken the stems which easily break. Seedlings which have been attacked at the base show dead-hearts, i.e. the drying up of the central shoot. Attacked plants bear white heads, indicating empty panicles or those with a few filled grains.
Two other allied species, namely, Chilo indicus (Kapur) and Chilo infuscatellus Snellen, have also been recorded infesting paddy in certain areas in India.
9. Dark-Headed Striped Borer, Chilo Polychrysus (Meyrick) (Lepidoptera: Pyralidae):
The dark-headed striped borer is distributed widely in India, Pakistan, Bangladesh, Myanmar, Malaysia, Indonesia, Thailand, Vietnam, Laos, Sabah and the Philippines. In India, it is also known as the Malayan borer and has been reported from Assam, West Bengal, Orissa, Tamil Nadu and Kerala. In addition to paddy, the larvae of this pest also attack maize, sugarcane and several species of grasses.
The yellowish white caterpillar has a black head capsule, a black thoracic plate and five longitudinal stripes on its body. It is 18-24 mm in length. The forewings of the male moth are brown ochreous with a cluster of dark spots covered with golden scales in the middle. The hind wings are white. In comparison, the wings of the females are paler with smaller metallic spots. The wing span of male is 16-25 mm and that of the female is 22-30 mm.
Life-Cycle:
The female moths lay flat scale-like eggs in rows, arranged in groups of 30-200, on the underside of leaves. Up to 488 eggs may be laid by a female moth during an oviposition period of 3 days. The eggs hatch in 4-7 days. The young caterpillar on emergence has the habits of a tissue borer and it tunnels within the leaf sheath, mid-rib or the stem. The larva moults 5 times within a period of 23-36 days.
It makes a tunnel in the stem, forming an exit hole at the upper end and then pupates inside. The yellowish brown pupa has distinct abdominal stripes and when fully formed, are 10 mm long and 2 mm wide. The adults emerge in 4-6 days and have a life span of 2-5 days. The total life-cycle is completed in 26-61 days and there are six generations in a year.
The parasitoid, Bracon albolineatus Cameron (Braconidae), attacks the larvae and the parasite, Tetrasticlius sp. (Eulophidae), feeds on pupae.
Damage:
The caterpillars bore into the central shoot for feeding. As many as 7 larvae have been noticed in a single shoot. Since the larva bores into the outer leaves and the leaf sheaths first, they are the first to die, followed by the inner whorl, and finally the entire plant from its core. When there is severe damage, the loss may go up to 60 per cent of the crop.