Rice

Insect Management

Brown plant hopper (BPH) Nilaparvata lugens Stal

The brown planthopper became a threat to rice production throughout South and South-East Asia in the early 1970s. BPH was first recorded in India in 1968 in West Bengal and BPH epidemics have occurred in Tamilnadu every few years viz., 1973-1974 at Madurai, 1975 at Coimbatore, 1983 at South Arcot District and in 1987 at Thanjavur district.

• Several factors have been cited to contribute to the outbreaks of BPH. The major factors are: Widespread planting of modern high yielding susceptible varieties
• Increased use of nitrogen containing fertilizers
• Increased use of insecticides
• Rapid expansion of irrigation systems
• Inadequate weed control
• Prevalence of biotypes
• Low relative humidity may be suitable for BPH population growth when there is adequate irrigation water. When the supplies of water is limited, a high relative humidity is favourable.
• Very high rainfall seems to increase the mortality of the first and second instar nymphs.
• On the other hand, it is believed that fairly high temperature and low rainfall condition are related to outbreak.

Damage

The brown planthopper damages the plant through the removal of the plant sap and as a vector of plant viruses viz., grassy stunt, ragged student and wilted stunt. The hoppers infest the plant at all stages of growth.

• As a result of feeding by the nymphs and adults, plants turn yellow and dry up rapidly. At early infestation round yellow patches appear which turn brown due to drying up of plants. This condition is called hopper burn.

Seasonal occurrence

• The hoppers remain active throughout the year.
• The population peaks in September and October and also during the later part of the cropping season. N. lugens occurs in overlapping generations.

Life history

• The nymphs and the adults both brachypterous and macropterous are brown coloured. Adults mate on the day of emergence and the female start laying eggs from the day following mating.
• Brachypterous females usually lay more eggs than macropterous forms.
• The eggs are thrust into mid-region of leaf-sheath.
• Eggs are covered with dome-shaped egg plug secreted by the female.
• Eggs hatch in about 6-9 days.
• The newly hatched nymph is cottony white and turns purple brown within an hour.
• The nymphs take 16 to 18 days to reach adulthood.

Alternate host

Leersia hexcandra

Natural enemies

• BPH is normally kept under biological control by diverse communities of natural enemies. Cyrtorhinnus lividipennis, Lycosa pseudoannulata, Microvelia douglasi atrolineata, Paederus fuscipes (Predators), Oligosita yasumatsu, Anagrus spp., Pseudogonatophus spp. (Parasitoids) and Metarhizium anisopliae var. anisopliae (Pathogen) are the important and most commonly occurring natural enemies of the BPH.

Sampling

Brown Plant Hopper (BPH), and Green Leaf Hopper (GLH)

• Sweep with an insect net 25 times over the seedlings in the nursery meant for one acre and assess the adult population.
• Nymphs of BPH and GLH are to be assessed in 100 seedlings selected from 5 places with 20 seedlings each.
• In the main field, tap vigorously 4 hills selected at random in each microplot and count the insects that have fallen on the water surface and assess the population per hill/tiller.

Management

• Avoid excessive use of nitrogen
• Control irrigation by intermittent draining
• Drain the water before use of insecticides and direct the spray towards the base of the plants.
• Apply any one of the following insecticides if BPH is present at the rate of 1 hopper/tiller in the absence of wolf spider and 2 hoppers per tiller when wolf spider at 1/hill.
• Monocrotophos 36 EC1250 ml
• Phosalone 35 EC 1500 ml
• Carbaryl 10% dust 25 kg/ha
• Methyl demeton 25 EC 1000 ml/ha
• Acephate 75 SP 625 g/ha
• Chlorpyriphos 20 EC 1250 ml/ha
• Carbofuran 3 G 17.5 kg/ha
• Dichlorvos 76 WSC 350 ml/ha
• Neem seed kernel extract 5% 25 kg
• Neem oil 3% 15 lit
• Iluppai oil 6% 30 lit
• Set up light traps or yellow pan traps during day time.

Rice caseworm Nymphula depunctalis (Guenee)

Case worm is an important pest of irrigated and rainfed wetland rice. The pest occurs in low populations, but sporadic increase in population results in intense defoliation of plants.

Damage symptom

 

• Damage is caused by larvae cutting off leaf tips for making characteristic leaf cases and by the removal of the green tissue.
• Defoliation occurs in rice plants before the maximum tillering stage.
• Plants that have been recently transplanted are preferred but larvae may infest the nursery.
• Larvae scrape the tissue leaving only the upper epidermis.
• Removal of leaf tissue present a ladder-like appearance.
• Attacked plants often become stunted.

Seasonal occurrence

Populations peak in May-June and November-December.

Life history

• Moths are nocturnal in habit and are attracted to light.
• They are delicate, white with fuscous marks and black specks on the wings.
• Mating takes place during night and each female lays about 60 eggs and may die 2-3 days after oviposition.
• The eggs are laid on the undersurface of the leaves floating in water.
• Larvae are transparent green in colour with light brownish orange heads.
• The first instar larva starts feeding on the green tissues by scrapping the leaf surface.
• It then moves to the leaf tips and cuts slit on the margin at a point 2-3cm below the tip and makes a fold.
• Then the larva makes another cut about 1cm below the first and rolls the margin with silk to form a tubular case.
• The inside of the case is lined with silk to hold a thin film of water which is essential for both respiration and preventing desiccation of larvae.
• A new case is constructed after every moult.
• Feeding is reduced under dry conditions and the presence of water droplets on the leaves is helpful for larval feeding. The larval stage lasts for 15-30 days.
• Pupation takes place inside the larval case with both the ends closed and attached to the stem just above the water level.
• The adult moth emerges in 4-7 days.

Alternate hosts

• Borachiaria mutica
• Cynodon dactylon
• Cyperus spp.
• Echinochloa colona

Case worm sampling

• Count the total number of leaves and affected leaves in 20 hills and work out the percentage.

Management

Mix 250 ml of kerosene to the standing water, dislodge the cases by passing a rope and drain water, collect the cases and destroy and spray Monocrotophos 36 WSC 40 ml or Quinalphos 25 EC 80 ml per tank.

Rice earhead bug : Leptocorisa acuta

• The rice earhead bug is found in all rice environments, but are more prevalent in rainfed wetland or upland rice.
• In India, on an average 3 to 10 per cent grains are damaged due to its infestation.

Damage symptom

• The intensity and type of damage by rice bugs depend on the stage of the crop, population density and ecological conditions.
• Both nymphs and adults are destructive.
• Nymphs prefer grains at milky stage for feeding.
• This inhibits kernel development either through mechanical injury at feeding or infection of toxin in addition to removal of milky sap panicles in heavily infested remain erect.
• Infested fields can often be detected even from a distance as they emit typical rice bug adour.

Seasonal occurrence

• The maximum pest population occurs during September.
• The bugs react favourably to high humidity and frequent drizzles.

Life history

• The mating generally occurs in the morning hours and the female lays about 250-300 eggs in two to three straight rows along the midrib on the upper surface of the leaf blade.
• The incubation is about a week.
• The nymphs on hatching feed voraciously and gregariously until the fourth instar.
• Feeding on flower heads continues throughout the day and does not cease even after the sunlight intensity is less.
• The nymphs take 25-30 days to reach adulthood.

Alternate hosts

More than 65 plans have been recorded as alternate host. Commonly seen on Echinochloa spp.

Sampling

Count the total number of earhead bugs in each microplot and arrive at the number per square metre.

Management

• When the bugs present at the rate of 5 bugs/100 earheads at flowering and 16 bugs/100 earheads at milky stage to grain maturity, dust any one of the following at 25 kg/ha twice, the first during flowering and second a week later:
  • Quinalphos 1.5% D
  • Carbaryl 10% D
  • Fenitrothion 2% D
  • Malathion5% D (or)
• Spray any one of the following twice as above:
  • Monocrotophos 36 WSC 500 ml/ha
  • Fenthion 100 EC 500 ml/ha
  • Fenitrohtion 50 EC 1000 ml/ha
  • Malathion 50 EC 500 ml/ha
• Botanical powder formulations viz., NSK, Notchi leaf powder extract, Ipomoea leaf powder and Prosopis leaf powder are effective in reducing the earhead bug population.
• Ecofriendly management of rice bug / earhead bug is done by dusting of Acorus calamus ACK 10D @ 25 kg/ha. It significantly reduce the earhead bug population with a benefit cost ratio of 12.6. The dust formulation is found to be cheaper and the raw materials are available in the market. It consists of Acorus calamus rhizome powder (1 part) and fly ash (9 parts). The cost TNAU ACK 10D works out to only Rs.6/kg.

Gall midge (Anaikomban) Orseolia oryza (Wood-Mason)

• The rice gall midge has been reported in India in 1880 first in Bihar and subsequently it spread to many rice growing states.
• The yield loss due to gall midge varies from 3 to 70 per cent and the damage in Tamilnadu alone accounts for 30 per cent.

The reasons for the outbreak include

• Early monsoon showers following dry spell
• Continuous cloudy weather associated with the intermittent rains
• High relative humidity
• Optimum temperature (28°C – 32°C)
• Late planting
• Spread of high yielding susceptible varieties
• Continuous cropping
• High N application
• Closer plant spacings

Damage symptom

• It attacks the crop in the nursery and after transplanting upto tillering. Maggots feed on the growing point of the plant transforming the leaf sheath into tubular gall.
• Affected plants become stunted with profuse tillering and they do not bear any panicles.
• The characteristic symptom of attack by rice gall midge is the production of tubular and leaf like gall which is commonly termed as ‘silver shoot’ or Anaikomban.

Seasonal occurrence

• Rice gall midge incidence varies significantly with the planting date.
• Early planted (July) rice varieties have lower infestations than the late planted ones (August).
• Crop planted in October suffers maximum damage.

Life history

• On an average, the female lays about 150 oval shaped eggs either singly or in groups on the ligules rarely on the leaves.
• The egg period is 7 days.
• The newly hatched maggots wriggle down the leaf blade and move between the leaf sheath and the stem until they reach the opening point of the apical or side but at a node.
• The larvae feed inside the developing bud and a hollow chamber ‘gall’ forms around the larva.
• Pupation takes place within the gall.
• The pupal period varies from 2 to 8 days.
• The entire life cycle is completed within 25 to 28 days.

Alternate hosts

In addition to its attack on weeds such as Brachiaria mutica, Cynodon dactylon, etc., it has also been reported on other wild rices.

Natural enemies

Ophionea spp., Nalais capsiformis and the parasitoids Platygaster oryza have been found suppressing the midge population.

Sampling

• Count the total number of tillers and affected tillers in 20 hills and work out the percentage.

 

ETL :

Gall midge

10% silver shoots

Management

• Release of Platygaster oryzae parasitised galls @ 1 per 10 M2 in the main field 10 days after transplanting gives effective control (or)
• Spray any one of the following / ha.
  • Fenthion 100 EC 500 ml.
  • Endosulfan 35 EC 1000 ml.
  • Fenitrothion 50 EC 1000 ml.
  • Phosalone 35 EC 1500 ml.
  • Quinalphos 25 EC 1000 ml.

Greenhorned caterpillar (Melanitis leda ismene)

• It is a minor pest of rice.
• The pest occurs in all rice environments but is more prevalent in rainfed areas.
• The adult is a large, dark brown butterfly with large brown spots on the upper surface of the forewings. Pearl-like eggs are laid in rows on rice leaves.
• The caterpillar feeds on the margins and tips of leaves and remove leaf tissue and veins.
• Damage is similar to that of grasshoppers and army worms.
• Pupation takes place on the rice leaf.

Management

• Release Trichogramma japonicum (egg parasitoid) on 30 and 37 DAT (twice) and T. chilonis on 37, 44 and 51 DAT (thrice) followed by three sprays of Monocrotophos 1000 ml/ha on 58, 65 and 72 DAT also reduce t
• Release of T. chilonis against leaf folder is effective at 5 cc/ha/release at weekly intervals. (or)
• Spray any one of the following / ha.
  • Fenthion 100 EC 500 ml.
  • Endosulfan 35 EC 1000ml.
  • Fenitrothion 50 EC 1000 ml.
  • Phosalone 35 EC 1500 ml.
  • Quinalphos 25 EC 1000 ml.

Green leafhoppers (GLH) Nephoteltix spp.

The green leafhopper assemblage in India comprises of Nephoteltix nigropictus, N. virescens, N. cincticeps, N. malayanus and N. modulatus. During 1984-86 there was a severe outbreak of tungro complex transmitted by GLH, resulting in very heavy crop loss throughout Tamilnadu. When the epidemic is severe, 100 per cent yield loss can occur.

Damage symptom

Green leafhopper cause either direct damage to the rice crop by sucking the sap and injecting toxic chemicals or indirectly by transmitting virus diseases such as dwarf, transitory yellowing, tungro, yellow dwarf and yellow-orange. Among the diseases transmitted by Nephotettix spp. tungro is the most destructive.

Seasonal occurrence

The leaf hoppers appear in August, peak during October-November and the population declines later due to low temperature.

Life history

• The pre-mating period ranges from one to two days.
• Eggs are laid in small slits made in soft parts of the plant.
• The number of eggs in a batch seldom exceeds 30.
• The incubation period is 6 to 12 days.
• The nymphal period lasts for 14-37 days.
• Rice plants at tillering and panicle initiation stage are more favourable for the rapid build-up of pest population.

Alternative hosts

• Cynodon dactylon
• Echinochloa crussagalli
• E. colona
• Leersia hexandra

Natural enemies

• It is noted that predators have greater impact on the leaf hopper populations. Lycosa pseudoannulata, Cyrtorhinnus lividipennis, Tetragnatha spp. and Oxyopes spp. are the important predators, while Tomosvaryella spp. and Pipunculus spp. have been important parasitoids of nymphal and adult leaf hoppers.
• Erymia delphacis and E. radicans have been found to infect the leafhoppers though their potential in the field is yet to be tested.

Sampling and control

• Take 25 net sweepings in the nursery area.
• If the population exceeds 60 for 25 sweepings or 20/M2 by actual counting, spray any one of the following insecticides.
  • Fenitrothion 50 EC – 80 ml
  • Fenthion 100 EC – 40 ml
  • Quinalphos 25 EC – 80 ml
  • Phosalone 35 EC – 120 ml
  • Endosulfan 35 EC – 80 ml
  • Monocrotophos 36 WSC – 40 ml (or)
• Maintain 2.5cm of water in the nursery and broadcast anyone of the following:
  • Carbofuran 3 G - 3.5 kg
  • Phorate 10 G- 1.0 kg
  • Quinalphos 5 G - 2.0 kg

Rice hispa : Dicladispa armigera (Oliver)

Rice hispa frequently causes extensive damage to rice crops.

Damage symptom

• Both adults and grubs feed on and damage rice plants. The adults scrape the upper surface of the leaf blade, often leaving only the lower epidermis.

The damaged areas appear as white streaks parallel to midrib. The tunneling of the grubs between the two epidermal layers results in irregular transluscent white patches. The affected parts of the leaf whither off.

Seasonal occurrence

The adults appear in February and the population increases till June or July. Beyond August the population declines.

Life history

• The adult is a small, blue-black beetle with a spiny body.
• The adult mates 3-4 days after emergence.
• The eggs are laid singly near the tip of the leaf blade, generally on the ventral surface, and are partially inserted beneath the epidermis and covered by a dark substance.
• As many as 55 eggs will be laid by single female. The egg period is 4 to 5 days.
• The hatching grubs mine into leaf blades between the epidermal layers and feed on green tissues.
• The larval and pupal period are 7 to 12 days and 4 to 5 days respectively.
• The adults live 15-20 days.

Alternate hosts

• Echinochloa spp.
• Digitaria spp.

Control Measures

Cultural:

• Grasses like Cynodon dactylon, Echinochloa colona, Echinochloa crussgalli etc., were found as alternative hosts.
• Hence field sanitation has to be adopted with timely weeding both in the field and on bunds.

Mechanical:

• Sweeping rice plants with winnows coated with sticky materials may help to some extent in suppressing adult population.
• A rope soaked in kerosene and held by two men can be brushed across the foliage to kill Hispa beetles.
• The degree of control however, with this method is minimal.
• Clipping of tops of seedlings prior to planting removes not only Stem borer eggs but also Hispa eggs.

Chemical Control:

• Spraying of Monocrotophos 1.6 ml or Chlorpyriphos 2 ml or Phosalone 2 ml or Carboryl 3 gms/litre of water.
• Ethophenprox EC @ 7.0 g a.i./ha or Fipronil; SC @ 50 gm a.i./ha or apply Carbofuron granules @ 0.75 kg a.i./ha.

Rice leaf folders

The rice leaf folder complex comprises of species of which seven species are present in India viz., Brachmia arotraea, Cnaphalocrocis medinalis, Marasmia exigua, M. patnalis Bradley, M. ruralis and M. trebiusalis. Of these, C. medinalis and M. patnalis have been identified as the dominant species.

• Owing to high magnitude of yield loss due to leaf folders, research on the latter has been identified as the most important technological need in Tamilnadu.
• Large scale outbreaks of leaffolders have been recorded from the 1960s onwards.
• These outbreaks are attributed mostly to reduced abundance of natural enemies either as a consequence of extreme weather conditions or the indiscriminate use of broad spectrum pesticides Use of excess nitrogen and modern susceptible varieties have enhanced the menace due to leaf folders.

Damage symptom

• The damage is caused by the caterpillars which fold the leaf blades into tubular structures and feed on the green leaf tissues within these structures.
• Usually one larva is found within one fold.
• Larval feeding results in white, transparent streaks.
• The discolouration and folding of the leaves affect the vigour of the plants and reduce their photosynthetic ability.
• The damaged plants also pre-dispose the plants to fungal and bacterial infection.

Seasonal occurrence

The moths have been recorded year round and most abundant during the rainy season.

Life history

• The adult moths hide in the day on the other weed hosts and are active during night and early morning hours.
• Egg laying starts one to two days after mating.
• Flat, oval and whitish eggs are laid singly or in rows parallel to a midrib on both surfaces of the young leaves and rarely on the stem.
• The egg period varies from 3 to 6 days.
• On hatching, the larvae crawl to the base of the leaf and start feeding. Leaf folds are formed from the second instar onwards.
• The larval period lasts for 21-28 days.
• Pupation occurs within the leaf folds in transparent white cocoons.
• The pupal period is 7-8 days and adult longevity is 8-9 days.

Alternate hosts

Several alternate hosts have been reported for the rice leaf folders. Other than rice, they feed on cultivated crops such as barley, maize, sorghum, sugarcane and wheat.

Natural enemies

• The biological control for the leaf folders is yet to make a mark although more than a hundred natural enemies have been recorded for the same.
• The field cricket Metioche vittaticollis Stal and the sward-tailed cricket Anasxcipha longipennis have been recently identified as the major egg predators.
• Amongst the parasitoids Trichogramma spp., Cardiochiles philippinensis, Goniozus triangulifer and Brachymeria spp. are the important parasitoids.
• Insect pathogens Beauveria bassiana Viumellin, Zoopthra radicans and Fusarium pallidorsum are the commonly found leaf folder pathogens.

Sampling

Count the total number of leaves and affected leaves in 20 hills and work out the percentage.

Management

• When 10% leaves are damaged in the vegetative phase and 5.0% of flag leaf damage is noticed at flowering, spray any one of the following:
  • Fenitrothion 50 EC 1000 ml
  • Monocrotophos 36 WSC 1000 ml
  • Chlorpyriphos 20 EC 1250 ml
  • Phosalone 35 EC 1500 ml
  • Carbaryl 50 WP 1.0 kg
  • Quinalphos 25 EC 1000 ml
  • Fenthin 100 EC 500 ml
  • Dichlorvos 76 WSC 250 ml
  • Neem seed kernel extract 5% 25kg

Control Measures

Cultural

• Avoid close planting and application of more nitrogenous fertilizers, as close
• crop growth and heavy manuring are conducive for leaf folder activity.
• Sufficient quantities of Potassic fertilizers are to be applied to reduce infestation.
• Grow varieties with high silica content.

Mechanical

Pass a thorny brush or a rope across the crop in vegetative phase to unfold the leaves and to expose the larvae to insecticidal application.

Biological

Trichogramma japanicum and Copidosomopsis nacoleidae were recorded as important egg parasitoids. Trichomma cnaphalocrosis as larval parasite and Xanthopimpla flavolineata and Tetrastichus ayyari as pupal parasites were reported to suppress the pest.

Chemical Control

• Spraying of Monocrotophos, Chlorpyriphos, Quinalphos, or Phosalone @ 0.5 kg a.i./ha or apply Cartap WP @ 300 gms a.i./ha or Fipronil SC @ 50 gms a.i./ha or Cartap 4 G @ 1.0 kg a.i./ha. Since larvae feed by hiding in leaf folds the insecticide do not contact larvae. So care has to be taken to unfold the damaged leaves before spraying for effective control.
• But now a days need based application of Profenophos 50EC @ 1 lit/ha on ETL basis is broadly recommended for the management of leaf folder as it is comparatively safe to natural enemies.

Economic threshold level (ETL)

One damaged leaf/hill during planting to pre-tillering period 1 to 2 freshly damaged leaves/hill during mid-tillering to booting period.

Rice skipper: Pelopidas mathias

• Skipper is a minor pest of rice, with extensive distribution in rice growing regions especially in the upland rice.
• Damage is caused by larvae that defoliate the rice plants.
• The newly hatched larva feed on tender leaves.
• It is highly active from August to November.
• The adult moths are active during the morning hours and the eggs are laid on the upper surface of the leaves.
• Egg period 3-6 days. Larvae are pale green with red streak on either side of the head.
• The larval stage lasts for 13 to 26 days.
• Pupation takes place within silken web spun inside the leaf fold. The adult butterfly emerges in 7 to 12 days after pupation.

Management

• Release Trichogramma japonicum (egg parasitoid) on 30 and 37 DAT (twice) and T. chilonis on 37, 44 and 51 DAT (thrice) followed by three sprays of Monocrotophos 1000 ml/ha on 58, 65 and 72 DAT also reduce t
• Spray any one of the following/ha :
  • Fenthion 100 EC500 ml.
  • Endosulfan 35 EC 1000ml.
  • Fenitrothion 50 EC 1000 ml.
  • Phosalone 35 EC 1500 ml.
  • Quinalphos 25 EC 1000 ml.

Rice yellow stemborer : Scirpophage incertulas Walker

The yellow stemborer is the dominant and the most destructive stemborer species in India. It is a regular pest in almost all districts of Tamilnadu. The extent of crop loss varies from one to nineteen per cent in early-planted and 38-80 per cent in late planted rice crops.

Damage symptom

About a week after hatching, the larvae from the leaf sheaths bore into the stem and feed on the inner surface of the walls. Such feeding frequently results in severing of the apical parts of the plant from the base. When this kind of damage occurs during the vegetative phase of the plant, the central leaf whorl does not unfold, turns brownish, and dries-off although the lower leaves remain green and healthy. This condition is known as "dead heart" and the affected tillers dry out without bearing any panicle.

• If infestation occurs later, after panicle initiation, severing of the growing plant parts from the base results in drying of panicle which may not emerge at all, those that have already emerged do not produce grains.
• These later become very conspicuous in the fields as being empty, they remain straight and whitish.
• They are called "white heads".
• Although the stem borer damage becomes evident only as dead heart and white ears, significant damage / loss occur due to larval feeding which results in reduced plant vigour, few tillers and many unfilled grains.

Seasonal occurrence

• S. incertulas occurs year-round in South India. Generally rice plants in the vegetative stage and early heading stage receive more eggs than those rearing maturity.
• Plants receiving more nitrogenous fertilizers are preferred. The pest affects the crop in the nursery, vegetative and pre-earhead stage.
• Mostly, late sown thaladi, samba and summer (navarai) season crops are severely damaged.

Life-history

• The adult female moths are yellowish with a black spot in the centre of the forewings.
• Male moths are light brown with numerous small brown spots.
• The moths are nocturnal, positively phototrophic and strong fliers.
• The moths usually emerge between 7:00 and 9:00 p.m.
• The moths are mostly attracted to ultra violet and green flourescent lights.
• Light traps are presently used only for studying population fluctuations.
• They are capable of flying 5-10 miles but can cover long distances if carried by winds.
• Mating in most species generally occurs between 7:00 and 9:00 p.m.
• The eggs are laid near the tip of the leaf blade.
• The stem borers lay eggs in masses, usually containing 50 to 80 eggs and a single female is capable of laying 100 to 200 eggs.
• The optimum hatching temperature is between 24 to 29°C and requires 90-100 per cent relative humidity.
• The eggs hatch during the day time.
• The larvae are pale yellow with a brown head.
• The hatching larvae are negatively geotrophic and crawl upwards towards the tip of the plants where they stay only for a short period.
• Some suspend themselves with a silken thread, which they spin, and sway in the wind to land on other plants.
• Most of those remaining on the tip descend towards the base and crawl between the leaf sheath and stem.
• Under optimum conditions there are five to six larval instars, under adverse conditions as many as nine instars are recorded.
• The total larval period lasts for 20 to 30 days.
• The pupation takes place in stem, straw or stubbles.
• The fully-grown larvae, before pupating, cut exit holes in the internodes through which the emerging moths escape.
• The pupae are covered in whitish silken cocoon.
• The moths usually emerge after the monsoons.

Alternate hosts

S. incertulas is regarded as monophagous with exclusive host specificity to rice. However, some recent studies have shown that wild rice Oryza rufipogon, O. nivara, O. latifolia and O. glaberrima and a grass weed Leptochloa panicoides to be the potential alternate host.

Natural enemies

The natural enemy wealth for the yellow stemborer is enormous. Nearly 100 parasitoids, predominantly egg parasitoids have been reported. Parasitism by Trichogramma spp., Tetrastichus spp. and Telenomus spp. are widely reported for stem borers.

ETL: Stemborer 2 egg masses/M2 or 10% dead hearts

Stem borer sampling

Dead hearts

Count the total number of tillers and affected tillers in 20 hills and work out the percentage.

White ears

Count the total number of white ears and healthy ears in 20 hills and work out the percentage.

Stem borer and leaf folder management

• Release Trichogramma japonicum (egg parasitoid) on 30 and 37 DAT (twice) and T. chilonis on 37, 44 and 51 DAT (thrice) followed by three sprays of Monocrotophos 1000 ml/ha on 58, 65 and 72 DAT also reduce the damage.
• The sprayings are based on ETL. Release of Trichogramma japonicum against stem borer is effective at 5 cc/ha/release at weekly intervals.
• Release of T. chilonis against leaf folder is effective at 5 cc/ha/release at weekly intervals. (or)
• Spray any one of the following/ha. :
  • Fenthion 100 EC500 ml.
  • Endosulfan 35 EC 1000ml.
  • Fenitrothion 50 EC 1000 ml.
  • Phosalone 35 EC 1500 ml.
  • Quinalphos 25 EC 1000 ml.

Rice swarming caterpillar Spodoptera mauritia Hub.

The rice swarming caterpillar S. mauritia is a sporadic pest which occasionally causes serious loss to rice crops.

Damage and symptom

• The swarming caterpillars cause severe damage to rice plants in nursery beds.
• They appear suddenly in masses and move like an army from field to field so that the seedbeds or direct-seeded fields look as if grazed by cattle.

Seasonal occurrence

This insect is essentially a seedling pest and rarely infests crop more than 6-7 weeks after transplanting.

Life history

• The adult insect is a greyish-black moth with a white blotch on its forewings.
• The moth is nocturnal and is not attracted to light.
• The moths mate 1-2 days after emergence and eggs are laid in batches on the lower surface of rice and are covered with greyish hairs.
• The egg incubation ranges from 5 to 9 days.
• Newly hatched larvae are active and scrape green matter from leaf tips and rest within rolled edges of young leaves.
• The larvae undergo five instars in an average of 22 days.
• Pupation takes place within earthern cells, and it lasts for 10-14 days.

Alternate hosts

The insect is polyphagous and infests various graminaceous crops and weeds.

Management (Nursery)

Army worm:

Drain water from the nursery and spray chlorpyriphos 20 EC 80 ml or Endosulfan 35 EC 80 ml during late evening.

Rice Thrips: Stenchaetothrips biformis (Bagnall)

The rice thrips is a sporadic pest of rice infesting mostly young plants.

Damage symptom

• The nymphs and adults have rasping mouth parts that lacerate the green tissues of leaves.
• They have only one mandible that is used to puncture the leaf tissue.
• Young plants, usually 1 to 2 weeks of transplanting are the most affected.
• Damage becomes evident as fine yellowish line or silvery streak on the leaves which later curl from the margin towards the midrib.
• The lower leaves are often killed.
• In severe infestations, the plants become stunted and wither.

Seasonal occurrence

When delayed monsoons occur or during low rainfall during June-July severe outbreaks of thrips have often been reported.

Life history

• The adult thrips are minute elongate insects.
• They can be either winged or apterous. Adults are day flying insects and are not attracted to light.
• Adult thrips live for about 20 days.
• The eggs are reniform and are inserted singly in tissues of the youngest leaves on the side facing the stem.
• A female lays about 25 eggs in its life time.
• Eggs hatch after 3 days.
• The newly hatched nymphs are almost transparent but turn yellowish white at first moult.
• There are 3 larval instars which lasts for 6 to 8 days.
• The pre-pupae are usually seen in groups.
• Pupation takes place inside rolled leaves.
• Pre-pupal and pupal stages together lasts for 3-4 days.

Alternate hosts

• Echinochloa colona
• E. crussgalli
• Cyperus iria
• C. rotundus

Thrips management

Nursery

• Pass a wet table tennis bat (painted with white paint) over the foliage in 12 places in the nursery.
• If thrips population exceeds 60 numbers in 12 passes or if rolling of ½ area of first and 2nd leaves in 10 per cent of seedlings first noticed, apply one of the following insecticides.
• 25 ml.
• Monocrotophos 36 WSC40 ml.
• Endosulfan 35 EC80 ml.

Mainfield

• ETL as in the nursery.
• Monocrotophos 36 WSC500 ml.
• Endosulfan 35 EC1000 ml.

Black bugs: Scotinophora lurida (Burm.)

• The whitebacked planthopper (WBPH) has emerged as a major pest of rice in the recent years destroying sizeable proportions of the crop.
• This occurs in both upland and wetland rice environments.

Damage symptoms:

• Both nymphs and adults suck the sap primarily at the base of the rice plants which leads to yellowing of the lower leaves, reduced vigour and stunting of plants. Severely attacked seedlings do not grow; are stunted, wilted and die.
• If the infestation is at the panicle initiation stage, the number of grains and panicle length decreases.
• But when attacked later, during maturation period, grains do not fill fully and ripening is delayed.

Seasonal occurrence

• The macropterous males and females immigrate into rice fields during late June and July.
• At this time, the hoppers show distinct ovipositional preference for rice plants.
• During summer, the number of brachypterous adults increase.
• The pest population declines in rice field in late August.
• Then there is a shift in ovipositional preference from rice to grass.
• During October-November, the adults emerging on grasses start laying diapaused eggs which hatch by the middle of April.
• Nymphs prefer weeds for feeding.
• The adult hoppers which develop from these nymphs infests the rice fields in June-July and the cycle repeats.

Life history

• The adults are positively phototrophic.
• The forewings are uniformly subhyaline with dark veins.
• There is a prominent white band between the juncture of the wings.
• There is a conspicuous black dot at the middle of posterior margin of each forewing which meet when the forewings come together.
• The pre-oviposition period ranges from 3 to 5 days.
• Eggs are laid in longitudinal rows within the leaf midribs.
• On an average the female hopper lays 164 eggs, the egg plug is longer and more pointed.
• The eggs hatch in about 6 days.
• Nymphs are white to dark grey or black in colour.
• They reach adulthood in 12 to 17 days passing through five instars.

Alternate hosts

Millets, maize and other grasses.

Management

Spray monocrotophos 750ml/ha for effective control of WBPH.

Rice Whorl Maggot: Hydrellia philippina Ferino

• In South India, it caused 20 to 30 per cent yield loss on the first crop during April to September in 1970s.
• The possible reason for the reported yield loss may be due to the inability of the plants to fully recover from the whorl maggot damage.

Damage symptom

The maggots feed on unopened leaves nibbling the inner margins. Conspicuous linear feeding lesions are visible when the leaf opens. Infested plants are stunted. Can cause damage to boot leaf and developing panicle.

Seasonal occurrence

• The autumn rice (April to Mid-July) is the most affected crop, with the peak infestation in the first week of July.
• Adult flies have high preference for high moisture.
• Under natural conditions, environments such as ponds, streams, lakes and irrigated rice fields provide a favourable ecological niche for the breeding of flies.

Life history

The adult females lay about 100 eggs on either side of the leaves. Flies prefer the basal half of the leaf. The maggots emerge after 2-6 days.

• The larvae move down the leaf in to the whorl on a film of dew and feed within the developing whorls.
• The larvae feed on mesophyll tissues and the larval period ranges from 8 to 17 days.
• Pupation takes place within the leaf sheaths and the pupal period is 5-9 days.
• The peak emergence of adult flies is from 7:00 to 10:00 a.m.

Alternate hosts

The whorl maggots survive on weeds such as Cynodon dactylon, Echinochloa colona, E. crussgalli etc.

Sampling

Count the total number of leaves and affected leaves in 20 hills and work out the percentage.

ETL : Whorl maggot : 25% damaged leaves

Control measures

Chemical

• Apply Phorate 10 G @ 10 kg / ha or Carbofuran 3 G @ 25 kg / ha or spray Fenitrothion 50 EC at 0.1 % (2 ml/lit).
• Apply Carbofuran granules @ 0.75 kg a.i./ha or Fipronil granules @ 75 g a.i./ha.

Economic threshold level (ETL)

20 % damaged hills upto 30 days after planting.