1. INSECT PESTS OF RICE
R. Regmi
Assistant professor
Department of entomology
2. INSECT PEST OF RICE
• Rice (Oryza sativa L.) is the most important staple
food crop of the world
• More than 60 % of worlds population depend on
it for food.
• It is major crop of Nepal accounting 55% of total
national cereal production.
• It is cultivated in 1,420,570 ha with production of
4,504,503 mt ton.
• Insect pests are responsible for average 25-30%
loss in Nepal
14. 1. Brown Plant hopper, Nilaparavata
lugens (Homoptera: Delphacidae)
• It is most destructive pest.
• Both nymph and adult feed on paddy,
sugarcane and grasses by sucking cell
sap.
• The brownish adults with brown eyes are
3.5 – 4.5 mm in length.
• Their legs are light brown and the tarsal
claw are black.
• The wings are hyaline with brown
marking and dark vein.
• The nymphs are brownish black in colour
and have grayish blue eyes.
15. Life cycle of BPH
• The adult remain most active from 10 to 32 degree C.
• The females start laying eggs within 3-10 days of their
emergence & deposit eggs in masses, by lacerating the
parenchymal tissue.
• The number of eggs per mass varies from 2 to 11 and female
lays on an average 124 egg masses.
• The eggs are somewhat dark and cylindrical having two distinct
spots.
• The incubation period ranges between 4 to 8 days.
• The nymphs on emergence start feeding on young leaves and
after moulting 5 times, they become adults in 2-3 weeks.
• The life cycle is completed in 18-24 days during June-October,
38-44 days during November – January and 18-35 days during
February -April.
16. Damage
• Both nymph and adults cause damage by sucking cell sap
from the leaves which turn yellow.
• A heavy infestation produce symptoms of “ hopper burn”
i.e. leaves become dry and brown after insect feeding and
patches of burned plants are often lodged.
• It has been noticed that even at low infestation the tillering
is adversely affected and there diminished vigor and
decreases in plant height.
• Under the favorable condition of high humidity, optimum
temperature, high nitrogen application and no wind the
population increases very rapidly.
• The insect is known to transmit the grassy stunt virus
disease of rice.
18. Management
• Avoid closer spacing of planting
• Alternate drying and wetting the fields during peak
infestation and draining out the standing water from the
field 2-3 times.
• Alleys 30 cm wide after every 3 meters of rice planting
provide proper aeration to the crop which ultimately
restricts the multiplication of the pest.
• Grow resistant varieties IR26, IR36, IR56, IR56, IR64, & IR72
• Spray at economic threshold 5-10 insects per hill, 100 ml
imidachloroprid or 625 g of Carbaryl 50WP or 2.0 lit of
Quinalphos 25EC in 250 liter of water and repeat if hopper
population is persist
19. 2. Yellow Rice Stem Borer, Scirpophaga
incertulas (Lepidoptera: Pyralidae)
• The yellow stem borer is a specific pest of rice.
• The caterpillar alone are destructive, when full grown,
they measure about 20mm and are dirty white or
greenish yellow having brown head and pronotum.
• The adult have a wing span 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 forewing.
• The female have prominent tuft of brownish yellow
silken hair at the tip of their abdomen.
20. Life cycle of YSB
The moth becomes active after dusk when they mate and lay
about 120- 150 eggs on underside of the leaves in 2-5 cluster
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 times these
are laid, but turns black before hatching.
They hatch in 6-7 days and the tiny black headed caterpillar
soon bore into the stem from the growing point downward.
When a tiller is killed, the caterpillar inside migrates to
another tiller of the same or of 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 emerge as a moth.
The life cycle is completed in 31-46 days.
21. Damage of YSB
• The larval feeding damage may cause death of
the central leaf whorl at the vegetative stage,
which is known as dead heart.
• Damage at the reproductive stage causes ear
devoid of grain, which is known as white
head.
23. Management of YSB:
• The removal and destruction of stubble at the time of
the first ploughing after harvesting the crop.
• Ploughing and flooding the field is also effective in
killing the larvae
• Clipping of tips of seedling before transplanting can
reduce the carryover of eggs to the field.
• Use trichocard with 50,000-1,00,000 Trichogramma
per ha after 3-4 weeks
• The field showing more than 5% dead hearts should
be sprayed 25kg of Cartap hydrochloride 4G or 15 kg of
Fipronil 0.3 G per ha in standing water in the field.
24. 3. Rice ear- head bug, Leptocorisa oratorius/ L.
acuta (Hemiptera: Alydidae)
• The adult of Leptocorisa oratorius is green, light brown or
mixed yellow in color.
• The adult are slender and about 20mm long.
• Males and female are 13-14mm and 16-19mm long
respectively.
• The head is triangular.
• The antennae consist of four segments.
• They have long legs.
• The abdomen of both male and female is constricted slightly
in the middle.
• The abdomen of females is somehow inflated(magnified).
• There are stink gland on either side of the abdomen that emit
foul odour, hence called stink bug or Gandhi bug.
• The grown up nymph are very similar to the adult in color and
size, but they are wingless.
25. Life cycle of REHB:
• The rice earhead bug breeds all the year round
• Generally most active from August to November.
• The female lay 250-300 eggs at night in 2-3 straight row consisting of
20-30 round yellow eggs along the midrib on the upper surface of the
leaf blade.
• The eggs are 2 mm long disc shaped or dorsally flat and elliptical, with
a slightly granulated and shiny surface.
• The egg hatch within 6-7 days and the nymph grow to maturity over
six instars within 2-3 weeks.
• The first instar nymph is very small 2 mm long and pale green which
turns into deep green during the following instar.
• The adult bug live for 33-35 days.
• Breeding also take place during winter though at slower rate.
26. Damage of REHB
• The pest is essentially diurnal with highest activities
in the morning and in the evening, seeking shelter
during hoter parts of day.
• Many generation are completed in a year.
• Adult and nymph both suck the sap of developing
rice grains at the milking stage and cause
considerable yield loss.
• Sucking of the grain sap causes empty or partially
filled and chaffy grains and enhances subsequent
fungal and bacterial infection.
27. Management:
• The population can be suppressed by killing the bug by using light
traps.
• Collection of adult bug using net
• Destroy weed to remove alternate host
• Keep on hanging the cattle urine soaked gunny bags or cow dung
wrapped cloth in the field to attract the bug.
• Synchronize rice planting to maintain simultaneous crop maturity in
the field in an area for equal distribution of bugs in all fields
• Conserve predator of rice bug like tiger beetle, Cicindela sexpunctata
by using chemical pesticide judiciously.
• Spray after at least 10 bug per 100 panicles with pesticide like
carbaryl (Carbaryl 5% dust@25kg/ha)
• Spray Fenvalerate 20 EC 0.5ml/liter of water
28. 4. Rice Hispa, Dicladispa armigera
(Coleoptera: Chrysomelidae)
• The adult is a small bluish black
beetle
• Measuring 5mm in length and is
recognized by numerous short
spines on the body, which give it a
characteristics appearance.
• The legless creamy white larvae
are not easily seen because they
are concealed inside the leaves
tissue.
29. Life cycle RH
• This pest breeds actively from May to October and
hibernates during winter probably in the adult stage.
• In May, the beetle starts laying eggs on nursery plants.
• The eggs are embedded in the leaf tissue towards the tip.
• On hatching the young grubs feed as leaf miner, between the
upper and lower epidermis.
• The attacked leaves turn membranous showing
characteristics blisters or blotches.
• Later on, the attacked leaves wither and die.
• When the larva are full grown, they pupate inside and finally
emerge as black beetle.
30. Damage:
Larvae cause damaged like leafminer.
The adults also feed on green matter and
produce parallel whitish streaks on the leaves.
The damage starts in nurseries and spread to
the rice fields.
31. Management:
• Clipping the infested leaf tip during transplanting
• Nursery bed is flooded and damaged beetles
flooded in water.
• Spray start at economic threshold level(1 adult
per hill).
• Spay 2-5 liter Chlorpyriphos 20EC or 2. 0 lit of
Quinalphos 25 EC in 250 liter of water per ha and
repeat spray after 2 weeks if attack continue.
32. 5. Rice Grass hopper, Hieroglyphus banian/
H. nigrorepletus(Orthoptera: Acrididae)
• Various species of grasshopper are widely distributed in
Nepal.
• They are polyphagous and feed on leaves of rice, maize,
millets, sugarcane, grasses etc.
• The adult are 40-50 mm long and are shining greenish yellow,
having 3 black lines running across the pronotum.
• Nymph are yellowish with many reddish brown spot in the
early stages but become greenish as they grow older.
33. Life cycle GH
• Hieroglyphus spp.have one generation in a year and pass the
winter & dry part of summer in egg stage.
• The eggs are found in the soil and they hatch in June or in
early July, a few days after the first shower of the monsoon.
• On emergence, the nymphs start feeding actively and
complete their development in seven stages within 3 weeks.
• The adult are seen feeding voraciously during August and
September.
• When they are 2 month old, they mate.
• The female starts laying eggs by inserting her abdomen in
the soil.
• The egg are laid 5-8 cm deep in pod, each containing 30-40
eggs.
34. Damage GH
• Both adult and Nymph cause damage causing
defoliating.
35. Management:
• Fish cum Rice farming
• Larva of the banded blister beetle (Mylabris
phalerata) attack the eggs of the rice
grasshopper.
• Trimming the bund and field sanitation
reduces the grasshopper population.
• Spray chlorpyriphos 2.5 lit Chlorpyriphos 20EC
in 250 liter of water per ha.
