Control of Rice Insect Pests
G.C. Jahn & Islam Zahirul
Integrated Pest Management
Training Course
LECTURE CONTENT
Introduction
 Basics of Cultural Control
 Single Field Cultural Control Practices
 Community-wide Cultural Control Practices
 Examples of Cultural Options Against
Specific Insect Pests

Introduction
What is CULTURAL CONTROL?

The modification of management
practices so that the environment is less
favorable for pest
– invasion
– reproduction
– survival
– immigration
Introduction
Ecological Pest Management


“Cultural control” is referred to as “Ecological
Pest Management” (EPM) by some authors
(e.g. Speight et al. 1999)
This is because cultural control is a way of
changing the ecological factors that affect pest
numbers.
Introduction
Is there a difference between
EPM and Cultural Control?

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In practice, they are the same.
In theory, they are different ways of looking at
crop protection, i.e. . . .
EPM – looks for intervention points to
manipulate the ecosystem
Cultural control – looks at each aspect of crop
management and how it affects pests.
For our purposes the terms can be used interchangeably.
Introduction
Aims of EPM
In EPM the crop is managed to:
 Improve resistance of the crop to pests, by
optimizing plant health
 Enhance the proliferation and efficiency of
natural enemies
Introduction
Aims of Cultural Control
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To achieve reductions in pest numbers through
crop management.
Increase yield.
Improve grain and crop quality.
Improve seed viability (germination rates).
Decrease cost of pest management.
Reduce the negative impact of pest
management on the environment and health by
reducing reliance on pesticides.
Basics
Basics of Cultural Control


Advantages vs. Disadvantages
Types of cultural control
–
–
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Primary
Secondary
Examples of Cultural Control Practices
Adoption scale
Basics
Advantages vs. Disadvantages
of Cultural Control
Advantages:
 Inexpensive
 Slow development of
resistance (compared to
chemical control)
 Low environmental
impact
 Compatible with other
pest management
Disadvantages
 May suppress some
pests, but increase
others
 May require communitywide adoption
 Generally slower than
pesticides for controlling
outbreaks.
Basics
Types of Cultural Control

Primary Cultural Control
–

those practices adopted specifically to control insect
pests.
Secondary Cultural Control
–
those practices adopted for general crop health, but
which also prevent pest build up.
Basics
Examples of Primary
Cultural Control

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Draining a rice field to control caseworm.
Transplanting older seedling to prevent whorl
maggot damage
Increasing the seeding rate to compensate for
feeding by ants or birds
Adjusting the timing of planting or land
preparation to avoid certain pests (e.g. chafer
beetle, stem borer, rice root weevil)
Basics
Examples of Secondary
Cultural Control

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Maintaining water in the field to prevent mole
crickets, ants and other soil pests.
Land preparation – e.g. plowing to prepare the
soil for planting while at the same time turning
over stubble that harbors stem borers.
Weeding
Fertilization – splitting nitrogen applications to
avoid build up of certain pests (e.g. brown
planthoppers, gall midge)
Basics
Examples of CULTURAL CONTROL
PRACTICES
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Rotations, intercropping, mixed cropping,
barrier, trap crops
Tillage
Mulches
HPR
Phytosanitation
Water management
Fertilizer management
Basics
Adoption Scale
Some cultural practices offer direct benefits to the
farmer if carried out at the farm level. However,
some others require community-wide action to
be effective.
 Single field cultural practices
–
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e.g. transplanting vs direct seeding for weed control
Community-wide cultural practices
–
e.g. crop rotation to break pest life cycle
Single Field Cultural
Control Practices
Single Field Cultural Control
Practices
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Overview
Planting methods
Seedling age
Clipping
Plant Density
Crop cover – using Azolla
Water management
Fertilizer management
Single Field Cultural
Control Practices
Overview of Single Field Cultural
Control Practices
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Works well when for pests that can be
excluded from the field e.g. flooding eliminates
dryland pests such as root aphids.
Works for avoiding pests in time.
Does not work well for reducing overall pest
populations of species that readily move
between fields such as adult rats or flying
insects.
Single Field Cultural
Control Practices
Planting Methods
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Transplanting into flooded fields suppresses
dry land adapted pests such as white grubs,
root aphids, termites, mole cricket, ants, and
others.
Seed beds are easier to protect from pests,
than entire fields, due to small area.
Delayed transplanting is may help avoid certain
insects (e.g. stem borer) or diseases.
Single Field Cultural
Control Practices
Seedling Age
Transplanting older seedlings:
 Reduces seedling time in the field.
 Reduces population buildup of pests that
prefer the vegetative stage.
 Reduces damage from caseworms and whorl
maggots
 Avoid one generation of stem borers,
leafhoppers, and brown planthoppers.
Single Field Cultural
Control Practices
Plant Density
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The effect of plant density on insect pest
abundance is varied and complex.
Dense plantings change crop growth,
development, and microclimate, which in turn
has an effect on pests and their natural
enemies.
Sparse planting encourages weeds and
indirectly has an effect on insect abundance.
Single Field Cultural
Control Practices
Clipping
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Clipping the tops of bundled tall seedlings
prevents lodging and removes stem borer and
hispa eggs, if present.
Not commonly used with modern rice varieties.
During the wet season, removal of the top third
of a standing crop at the vegetative stage can
remove leaf folders and stem borer egg
masses, hispa eggs and grubs, and thrips.
Single Field Cultural
Control Practices
Crop Cover - Azolla
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Covering the paddy
water surface with
Azolla (water fern)
reduces incidence
of whorl maggot.
Azolla cover also
assists predators
move from hill to hill
in search of prey
(e.g. planthoppers).
Single Field Cultural
Control Practices
What is Azolla?
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A. nilotica
Azolla is an aquatic fern (pteridophyte), that
floats on the water surface of flooded rice
fields, small ponds, and canals.
1-5 cm, except for A. nilotica of Africa which
reaches 15 cm.
Multiplies vegetatively and sexually.
Seven Azolla species are recognized
Distributed widely from temperate to tropical
regions.
Single Field Cultural
Control Practices
Uses of Azolla
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Symbiotic nitrogen
fixation, thus high N
content
Used for green manure
in wetland rice in China,
Vietnam, and Philippines
Weed suppression in
rice
Single Field Cultural
Control Practices
Water Management
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Draining field 1-2 days suppresses:
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Whorl maggots,
root feeding midges,
water weevils,
caseworms
Alternate draining and flooding for 5-7 days
helps control black bugs, planthoppers, gall
midge, hispa, and stem borers
Single Field Cultural
Control Practices
Fertilizer Management
IPNM = Integrated Pest & Nutrient Management
= Managing soil nutrients and pests in a
complementary fashion, i.e.
pest management has a
neutral or positive effect
on soil quality
 soil nutrient management
has a neutral or positive
effect on pest levels

Single Field Cultural
Control Practices
Why do we need Integrated Pest
and Nutrient Management (IPNM)?
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Some nutrient
management causes
pest outbreaks
Some pest management
techniques degrade the
soil
IPNM could reduce pest
problems and enhance
soil fertility
Single Field Cultural
Control Practices
IPNM FOR A CHANGING
RICE ECOSYSTEM
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New cultivars & GMOs
Increased amounts of fertilizer being
used
Interactions poorly understood,
therefore the potential for disaster (e.g.
outbreaks) - note pesticides
Current pest problems related to
fertilizer use may be exacerbated
Single Field Cultural
Control Practices
EXAMPLES: PEST MANAGEMENT
THAT REDUCES SOIL QUALITY
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Burning straw to
control insects and
diseases
Plowing fallow
land to hinder
weeds and the
insect pests they
harbor
Draining fields
Single Field Cultural
Control Practices
EXAMPLES: PEST MANAGEMENT
THAT IMPROVES SOIL QUALITY
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Flooding fields to prevent infestations of thrips
mole crickets or weeds
Crop rotation with a legume
Using fish and ducks to help regulate pests
Single Field Cultural
Control Practices
EXAMPLES OF PEST PROBLEMS
CAUSED BY FERTILIZER

Nitrogen (N) applications tend to increase
populations of:
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weeds
sheath blight
leafhoppers
gall midge
N applications lead to heavier stem borer
larvae, which presumably cause more damage
High N levels associated with pest outbreaks
Single Field Cultural
Control Practices
EXAMPLES OF USING FERTILIZER
TO HELP MANAGE PESTS
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N applications decrease thrips populations
Phosphorous (P) improves tolerance for root
pests
Potassium (K) tends to suppress pests
Silicon increases resistance to blast,
bacterial blight, planthoppers and stem
borers
Zinc reduces stem borer damage
Single Field Cultural
Control Practices
FERTILIZER APPLICATIONS CAN:
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Raise pest levels
Lower pest levels
Raise the levels of some pests and lower the
levels of others
Have no effect on pest levels
Depending on several factors. . .
Single Field Cultural
Control Practices
FACTORS TO CONSIDER
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Fertilizer
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Composition
Timing
Amount
Cultivar
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Hybrid
New plant type
Transgenic
Duration
Single Field Cultural
Control Practices
How would Nitrogen effect . . .
Nn = Nt + B – D + I - E
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Birth rate?
Mortality?
Immigration
Emigration?
Single Field Cultural
Control Practices
FERTILIZER AND
BIRTH RATE

N increases birth rate
( = fecundity) of many
phloem-feeding
insects (e.g.
planthoppers and
leafhoppers insects)
More babies!
Single Field Cultural
Control Practices
FERTILIZER AND DEATH RATE
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N tends to lower insect death rate ( = mortality)
N increases insect tolerance to stress,
therefore lowers mortality
Some parasitoids concentrate attacks on insect
hosts that feed on the leaves with the highest
N content
Single Field Cultural
Control Practices
FERTILIZER AND IMMIGRATION
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Rice treated with high N attracts more pests
Single Field Cultural
Control Practices
FERTILIZER AND EMIGRATION
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N tends to soften plant
tissue, making
penetration of the plant
easier.
Therefore insects
should tend to stay in a
field with high N.
. . .which should reduce
emigration.
Comfortable animals tend
to stay at home
Single Field Cultural
Control Practices
WHAT IS KNOWN?
Nitrogen & insects
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Increase insect tolerance to stress
Greater insect fecundity (e.g. sucking insects)
Increases insect feeding rate
More abundant, e.g. brown planthopper
Less abundant, e.g. thrips and whorl maggot
Rice attracts more pest
Promotes recovery from pest damage
Single Field Cultural
Control Practices
THE KNOWN: Weeds & Pathogens
Sheath blight - increased severity with
increased N
 Blast - use silica to increase resistance
 Low density of Echinochloa can outcompete rice at high N

Single Field Cultural
Control Practices
THE KNOWN:
Balance is important!
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Studies in India, China, Indonesia, the
Philippines, and Vietnam have found lower
pest incidence in fields with site-specific
nutrient management, compared to farmers’
practice
Why?
Farmers tend to apply unbalanced fertilizer
regimes
Single Field Cultural
Control Practices
THE KNOWN: N effects
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N increases number of eggs produced by
some insects, (i.e. increase birth rate)
High N can attract ovipositing insects (i.e.
increase immigration).
N augments plant growth rate, therefore
softer tissues and easier penetration
(reduces emigration).
Single Field Cultural
Control Practices
THE KNOWN: P effects

P (Phosphorus)
improves root
development,
therefore greater
tolerance to root
pests (e.g. root
weevil)
Single Field Cultural
Control Practices
THE KNOWN: Potassium (K) Effects
Lowers plant sugar
 Lowers amino acids
 Promotes thicker cell walls
 Increases silica uptake
 Therefore suppresses many pests

Single Field Cultural
Control Practices
APPLICATIONS
of IPNM knowledge to date
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Avoid fast pest build up by splitting
applications of N, with a basal
application for slow release.
Plow straw into soil to increase silica
uptake and reduce stem borer
Apply N to promote recovery
following a pest attack
Single Field Cultural
Control Practices
THE UNKNOWN
Quantifying the balance
between pest & yield increases
when fertilizer is used
 Multiple effects: Fertilizer
combinations on different soil
types, with multiple pests on
different cultivars
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Single Field Cultural
Control Practices
THE UNKNOWN
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How will pests respond to fertilizer on
new cultivars?
How do natural enemies respond to
fertilizer applications? (How do
fertilizers effect the rate of death of
pests?)
How do grain sucking insects respond
to fertilizer applications and does this
effect grain quality?
Single Field Cultural
Control Practices
OBJECTIVES OF IPNM RESEARCH

Understand processes involved
in how fertilizers effect crop
losses due to pests on different
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–
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cultivars
soil types
Predict the consequences of
intensified rice production on
crop losses due to pests.
Single Field Cultural
Control Practices
?
DESIRED OUTPUTS
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Identify situations where outbreaks are
likely to occur
Predict effectiveness of pest control
strategies and soil nutrient
management under different
circumstances
Integrate pest and nutrient
management strategies
Community-wide
cultural control
Community-wide Cultural
Control: Overview
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Eliminating or drastically reducing a pest
population by removing its habitat.
Preserving a high diversity of natural enemies
by maintaining habitats.
Can use indicator species for diversity of
natural enemies (e.g. dragonflies in rice).
Rely on taxonomy and phylogenetics to define
biodiversity (Douglas and Brunner 2002, May 1990)
Community-wide
cultural control
Indicator species

Indicator species – species whose presence,
theoretically, indicate a certain level of species
richness in a habitat (MacNally and Fleishman
2002, Noss 1990)
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Why use indicator species?
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–
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Complete species inventory is expensive
Species inventory is time consuming
Less expertise required
Community-wide
cultural control
Community-wide Cultural Control
Practices
Examples:
 Crop rotation
 Crop area
 Rice cropping frequency
 Plant maturity
 Planting time
 Synchronous planting / flowering
Community-wide
cultural control
Community-wide Cultural Control
Practices -- continued
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Trap crops
Flooding stubble
Tillage
Weed control
Harvest methods
Straw and stubble destruction
Ratooning
Examples of EPM for
specific insect pests
Rice caseworm - Nymphula depunctalis (Guenee),
Pyralidae, Lepidoptera.
EPM for rice caseworm
 Rice fields with wider hill spacing (30 x 20 cm) usually
suffers less damage from caseworm.
 Early planting may escape the peak caseworm moth
activity period.
 Draining of fields for 5-7 days kills caseworm larvae.
 Use of older seedlings reduces the duration of the
susceptible stage of the crop.
Nitrogen fertilizer use at optimal dosages and split
applications reduce the rice caseworm’s abundance.
Examples of EPM for
specific insect pests
Rice whorl maggot - Hydrellia philippina
Ferino, Ephyridae, Diptera.
EPM for rice whorl maggot
 Adult flies are more attracted to standing water.
Therefore, by draining the water at 3-4 days intervals
during the first 30 days after transplanting, egg lying is
reduced.
 Covering the water surface with Azolla and Salvinia
molesta prevents rice whorl maggot infestation.
 Direct-seeded rice is not as attractive to adults as a
transplanted rice crop is.
 Fields with higher plant density suffers less damage.
Close planting decreases oviposition and subsequent
damage.
Examples of EPM for
specific insect pests
Slender rice bug - Leptocorisa acuta (Thunberg),
Alydidae, Hemiptera
Rice bug EPM
 Simultaneous crop maturity in all fields in an area
dilutes rice bug damage.
 Staggered planting should be avoided.
 Rice maturing late in a few fields may suffer severe
damage because of the rice bug concentration.
Rice bugs are capable of surviving on other vegetation
during the off-season. Control of bugs on other
vegetation, especially in the off-season, can be
beneficial.
Summary
Nn = Nt + B – D + I – E
Cultural control aims to increase:


mortality
emigration
Cultural control aims to decrease:


natality & fecundity
immigration
CONCLUSIONS
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Cultural control is a prophylactic method of
control, i.e. used for preventing pest problems.
Cultural control is rarely use as a tactical
means of control
Cultural control should be considered the first
defense, around which other control options
are built.
ACKNOWLEDGEMENTS
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T. W. Mew
K. L. Heong
A. Barrion
L. Almazan
Elsa Rubia Sanchez
References
CABI (CAB International) 2001. Crop Protection
Compendium (2001 – edition) – CD or on-line version.
United Kingdom.
Dent, D. 1995. Integrated Pest Management. Chapman
& Hall, London, 356 pp.
Dent, D. 2000. Integrated Pest Management (2nd Ed.)
CABI Publishing, Wallingford, 410 pp.
References - continued
Douglas MR and Brunner PC. 2002. Biodiversity of
Central Alpine Coregonus (Salmoniformes): impact of
one-hundred years of management. Ecological
Applications 12(1):154-172.
IRRI and UQ. 2002. RiceIPM (version 1) - International
Rice Research Institute (Philippines) and The
University of Queensland (Australia), CD.
Litsinger JA., 1994. Cultural, mechanical, and physical
control of rice insects. Pp. 549-584 In: EA Heinrichs
(ed.) Biology and Management of Rice Insects.
International Rice Research Institute, Philippines,
779p.
References - continued
MacNally R and Fleishman E. 2002. Using “indicator”
species to model species richness: model development
and predictions. Ecological Applications 12(1):79-92.
May, RM. 1990. Taxonomy as destiny. Nature 347:129130.
Noss, RF. 1990. Indicators for monitoring biodiversity: a
hiearchical approach. Conservation Biology 4:355-364.
References - continued
Reissig WH, Heinrichs EA, Litsinger JA, Moody K,
Fiedler L, Mew TW and Barrion AT. 1986. Illustrated
guide to integrated pest management in rice in tropical
Asia. International Rice Research institute, Philippines,
411p.
Takahashi, F. 1964. Reproduction curve with two
equilibrium points: a consideration in fluctuation of
insect populations. Research in population Ecology
6:28-38.