Control of Rice Insect Pests

1
Control of Rice Insect Pests

• G.C. Jahn Islam Zahirul

Integrated Pest Management Training Course
2
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

3
What is CULTURAL CONTROL?
Introduction

• The modification of management practices so that
  the environment is less favorable for pest
• invasion
• reproduction
• survival
• immigration

4
Ecological Pest Management
Introduction

• 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.

5
Is there a difference between EPM and Cultural
Control?
Introduction

• 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
  inter-changeably.

6
Aims of EPM
Introduction

• 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

7
Aims of Cultural Control
Introduction

• 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.

8
Basics of Cultural Control
Basics

• Advantages vs. Disadvantages
• Types of cultural control
• Primary
• Secondary
• Examples of Cultural Control Practices
• Adoption scale

9
Advantages vs. Disadvantages of Cultural Control
Basics

• 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 community-wide adoption
• Generally slower than pesticides for controlling
  outbreaks.

10
Types of Cultural Control
Basics

• 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.

11
Examples of Primary Cultural Control
Basics

• 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)

12
Examples of Secondary Cultural Control
Basics

• 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)

13
Examples of CULTURAL CONTROL PRACTICES
Basics

• Rotations, intercropping, mixed cropping,
  barrier, trap crops
• Tillage
• Mulches
• HPR
• Phytosanitation
• Water management
• Fertilizer management

14
Adoption Scale
Basics

• 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
• e.g. transplanting vs direct seeding for weed
  control
• Community-wide cultural practices
• e.g. crop rotation to break pest life cycle

15
Single Field Cultural Control Practices
Single Field Cultural Control Practices

• Overview
• Planting methods
• Seedling age
• Clipping
• Plant Density
• Crop cover using Azolla
• Water management
• Fertilizer management

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Overview of Single Field Cultural Control
Practices
Single Field Cultural Control Practices

• 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.

17
Planting Methods
Single Field Cultural Control Practices

• 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.

18
Seedling Age
Single Field Cultural Control Practices

• 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.

19
Plant Density
Single Field Cultural Control Practices

• 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.

20
Clipping
Single Field Cultural Control Practices

• 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.

21
Crop Cover - Azolla
Single Field Cultural Control Practices

• 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).

22
What is Azolla?
Single Field Cultural Control Practices
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.

23
Uses of Azolla
Single Field Cultural Control Practices

• Symbiotic nitrogen fixation, thus high N content
• Used for green manure in wetland rice in China,
  Vietnam, and Philippines
• Weed suppression in rice

24
Water Management
Single Field Cultural Control Practices

• Draining field 1-2 days suppresses
• 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

25
Fertilizer Management
Single Field Cultural Control Practices

• 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

26
Why do we need Integrated Pest and Nutrient
Management (IPNM)?
Single Field Cultural Control Practices

• Some nutrient management causes pest outbreaks
• Some pest management techniques degrade the soil
• IPNM could reduce pest problems and enhance soil
  fertility

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IPNM FOR A CHANGING RICE ECOSYSTEM
Single Field Cultural Control Practices

• 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

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EXAMPLES PEST MANAGEMENT THAT REDUCES SOIL
QUALITY
Single Field Cultural Control Practices

• Burning straw to control insects and diseases
• Plowing fallow land to hinder weeds and the
  insect pests they harbor
• Draining fields

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EXAMPLES PEST MANAGEMENT THAT IMPROVES SOIL
QUALITY
Single Field Cultural Control Practices

• Flooding fields to prevent infestations of thrips
  mole crickets or weeds
• Crop rotation with a legume
• Using fish and ducks to help regulate pests

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EXAMPLES OF PEST PROBLEMS CAUSED BY FERTILIZER
Single Field Cultural Control Practices

• Nitrogen (N) applications tend to increase
  populations of
• 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

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EXAMPLES OF USING FERTILIZER TO HELP MANAGE PESTS
Single Field Cultural Control Practices

• 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

32
FERTILIZER APPLICATIONS CAN
Single Field Cultural Control Practices

• 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. . .

33
FACTORS TO CONSIDER
Single Field Cultural Control Practices

• Fertilizer
• Composition
• Timing
• Amount
• Cultivar
• Hybrid
• New plant type
• Transgenic
• Duration

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How would Nitrogen effect . . .
Single Field Cultural Control Practices

• Nn Nt B D I - E
• Birth rate?
• Mortality?
• Immigration
• Emigration?

35
FERTILIZER AND BIRTH RATE
Single Field Cultural Control Practices

• N increases birth rate ( fecundity) of many
  phloem-feeding insects (e.g. planthoppers and
  leafhoppers insects)

More babies!
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FERTILIZER AND DEATH RATE
Single Field Cultural Control Practices

• 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

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FERTILIZER AND IMMIGRATION
Single Field Cultural Control Practices

• Rice treated with high N attracts more pests

38
FERTILIZER AND EMIGRATION
Single Field Cultural Control Practices

• 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
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WHAT IS KNOWN? Nitrogen insects
Single Field Cultural Control Practices

• 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

40
THE KNOWN Weeds Pathogens
Single Field Cultural Control Practices

• Sheath blight - increased severity with increased
  N
• Blast - use silica to increase resistance
• Low density of Echinochloa can out-compete rice
  at high N

41
THE KNOWN Balance is important!
Single Field Cultural Control Practices

• 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

42
THE KNOWN N effects
Single Field Cultural Control Practices

• 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).

43
THE KNOWN P effects
Single Field Cultural Control Practices

• P (Phosphorus) improves root development,
  therefore greater tolerance to root pests (e.g.
  root weevil)

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THE KNOWN Potassium (K) Effects
Single Field Cultural Control Practices

• Lowers plant sugar
• Lowers amino acids
• Promotes thicker cell walls
• Increases silica uptake
• Therefore suppresses many pests

45
APPLICATIONS of IPNM knowledge to date
Single Field Cultural Control Practices

• 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

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THE UNKNOWN
Single Field Cultural Control Practices

• 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

47
THE UNKNOWN
Single Field Cultural Control Practices

• 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?

48
OBJECTIVES OF IPNM RESEARCH
Single Field Cultural Control Practices

• Understand processes involved in how fertilizers
  effect crop losses due to pests on different
• cultivars
• soil types
• Predict the consequences of intensified rice
  production on crop losses due to pests.

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DESIRED OUTPUTS
Single Field Cultural Control Practices

• 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

50
Community-wide Cultural Control Overview
Community-wide cultural control

• 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)

51
Indicator species
Community-wide cultural control

• Indicator species species whose presence,
  theoretically, indicate a certain level of
  species richness in a habitat (MacNally and
  Fleishman 2002, Noss 1990)
• Why use indicator species?
• Complete species inventory is expensive
• Species inventory is time consuming
• Less expertise required

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Community-wide Cultural Control Practices
Community-wide cultural control

• Examples
• Crop rotation
• Crop area
• Rice cropping frequency
• Plant maturity
• Planting time
• Synchronous planting / flowering

53
Community-wide Cultural Control Practices --
continued
Community-wide cultural control

• Trap crops
• Flooding stubble
• Tillage
• Weed control
• Harvest methods
• Straw and stubble destruction
• Ratooning

54
EPM for rice caseworm
Examples of EPM for specific insect pests
Rice caseworm - Nymphula depunctalis (Guenee),
Pyralidae, Lepidoptera.

• Ÿ  Rice fields with wider hill spacing (30 x 20
  cm) usually suffers less damage from caseworm.
• Ÿ  Early planting may escape the peak caseworm
  moth activity period.
• Ÿ  Draining of fields for 5-7 days kills caseworm
  larvae.
• Ÿ  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 caseworms
  abundance.

55
EPM for rice whorl maggot
Examples of EPM for specific insect pests
Rice whorl maggot - Hydrellia philippina Ferino,
Ephyridae, Diptera.

• Ÿ  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.
• Ÿ  Covering the water surface with Azolla and
  Salvinia molesta prevents rice whorl maggot
  infestation.
• Ÿ  Direct-seeded rice is not as attractive to
  adults as a transplanted rice crop is.
• Ÿ  Fields with higher plant density suffers less
  damage.
• Close planting decreases oviposition and
  subsequent damage.

56
Rice bug EPM
Slender rice bug - Leptocorisa acuta (Thunberg),
Alydidae, Hemiptera
Examples of EPM for specific insect pests

• Ÿ   Simultaneous crop maturity in all fields in
  an area dilutes rice bug damage.
• Ÿ   Staggered planting should be avoided.
• Ÿ   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.

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Summary

• Nn Nt B D I E
• Cultural control aims to increase
• mortality
• emigration
• Cultural control aims to decrease
• natality fecundity
• immigration

58
CONCLUSIONS

• 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.

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ACKNOWLEDGEMENTS

• T. W. Mew
• K. L. Heong
• A. Barrion
• L. Almazan
• Elsa Rubia Sanchez

60
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.

61
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.
•  

62
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
  347129-130.
• Noss, RF. 1990. Indicators for monitoring
  biodiversity a hiearchical approach.
  Conservation Biology 4355-364.

63
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 628-38.