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Rice Plant- and Leaf Hoppers

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Damage by several insect ... These bugs produce typical dirty smell in ... thrips damage can be differentiated from that of stem borer damage in the sense that ... – PowerPoint PPT presentation

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Title: Rice Plant- and Leaf Hoppers


1
Identification, symptoms and nature of damage of
Gundhi bug, Thrips and Armyworm
2
Introduction
  • Rice (Oryza sativa L.) is the staple food crop
    of humid and sub-humid Asia, cultivated in 112
    countries covering every continent and is
    consumed by 2500 million people in the developing
    countries. Rice is grown on an area of 44.3
    million hectares in different agro-climatic
    regions of the country with a production of 89.09
    million tonnes. However, Indias productivity is
    much lower than neighbouring countries.
  • Damage by several insect pests is one of the
    major factors responsible for lower rice yields.
    Intensive cultivation of rice has aggravated the
    problems of various biotic constraints like
    insects, diseases, and weeds.

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3
  • Rice gundhi bug, thrips and armyworm are
    important pests of rice and inflict heavy yield
    losses during certain years. Their effective
    management thus becomes essential to ensure good
    harvest to the farmers.

Pest problem being discussed with farmer
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1. Gundhi bug (Leptocorisa acuta)
  • Identification
  • Gundhi bug adults are slender yellowish green
    bugs with long antennae and legs.
  • Nymphs resemble adults except for presence of
    wings. These bugs produce typical dirty smell in
    the field and hence this pest is known as gundhi
    bug. The smell helps in detecting presence of
    this pest in the field.

Gundhi bug adult
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5
Nature of Damage
  • Female lays several dark brownish eggs in long
    rows on underside the leaves.

Gundhi bug eggs
  • Both nymphs and adults suck juice from developing
    grains during milky stage of the crop.
  • The affected grains remain chaffy and black spot
    develops on them due to fungal infection at the
    point of puncture. Under severe infestation
    several empty grains can be found in affected
    panicles.

Gundhi bug Nymph
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6
Staggered planting intensifies its incidence in
an area as bugs get grains in milky stage for
longer period of time and they migrate from field
to field.
  • Sawan grass (Echinochloa) weed is its alternate
    host plant and it should be destroyed in order to
    reduce incidence of this pest.
  • Economic threshold level
  • 1 bug/hill

Echinochloa (Sawan grass) Alternate host plant of
gundhi bug
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7
2. Thrips (Stenctenchaetothrips biformis)
Identification
  • Thrips are minute thin black-brown insects which
    jump on disturbance. These can be found by
    removing the leaf sheath at its junction with
    stem.

Rice thrips- adult Courtesy agritech.tnau.ac.in
  • Both nymphs and adults damage the crop during
    seedling stage in the nursery as well in the main
    field.
  • They suck sap from leaves resulting in yellowish
    streaks on them. Later, the leaves curl
    longitudinally from margins inwards leading to
    sharply pointed leaf tips resembling needles.

Rice thrips-Nymph Courtesy agritech.tnau.ac.in
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  • Infestation at panicle stage causes unfilled
    grains or spikelet sterility. Sometimes, complete
    panicle remain chaffy and are confused with
    white-ear damage of the stem borer.
  • However, thrips damage can be differentiated from
    that of stem borer damage in the sense that while
    white-ears can be easily pulled out but panicles
    affected by thrips can not be removed with that
    ease. Besides, panicles damaged by thrips have
    some black spot at their puncture points.

Silvery streaks on rice leaves caused by thrips
Courtesy agritech.tnau .ac.in
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3. Armyworm (Mythimna separata)
Identification
  • The armyworm, also called climbing cutworm or
    ear-cutting caterpillar, was named so because of
    larvaes habit of appearing in army-like enormous
    numbers.
  • Adults are dirty brown stout moths and larvae are
    also brownish in colour.

Armyworm adult
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Nature of Damage
  • Only larvae damage the crop. Though sporadic in
    occurrence, this pest may cause heavy losses
    during sudden outbreaks.
  • Larvae are nocturnal in nature and hide in loose
    soil, under trash, in stubbles and in whorls
    during day time. During night they become active
    and feed on foliage.

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  • When high populations occur, army of swarming
    larvae march in the field and feed voraciously
    on leaves.
  • Absence of standing water in the field
    facilitates their migration. Severely attacked
    field gives a grazed appearance. The larvae cut
    the ear-heads in addition to damaging the
    foliage.
  • Economic threshold level (ETL)
  • 1 larva/hill

Armyworm larva
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12
Let us sum up
  • Gundhi bugs produce typical foul smell in the
    field and hence this pest is known as gundhi
    bug.
  • Both nymphs and adults of gundhi bug suck juice
    from developing grains during milky stage of the
    crop.
  • Echinochloa weed is alternate host plant of
    gundhi bug and it should be destroyed in order to
    reduce incidence of this pest.
  • Both nymphs and adults of thrips suck sap from
    leaves causing yellowish streaks on them. Later,
    the leaves curl longitudinally from margins
    inwards leading to sharply pointed leaf tips
    resembling needles.

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  • Panicles damaged by thrips have black spots at
    their puncture points.
  • The armyworm, also called climbing cutworm or
    ear-cutting caterpillar, is named so because of
    larvaes habit of appearing in army-like enormous
    numbers.
  • Absence of standing water in the field
    facilitates migration of armyworms. Severely
    attacked field gives a grazed appearance.

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