Control of Rice Insect Pests

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? • 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.

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 • 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 • Primary • Secondary • Examples of Cultural Control Practices • Adoption scale

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. Basics Advantages vs. Disadvantages of Cultural Control

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 • 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 • 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 • 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 • 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 • 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 • 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 • 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 • 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 • 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 • 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? 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 • 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 • 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

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

Single Field Cultural Control Practices How would Nitrogen effect . . . Nn = Nt + B – D + I - E • 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 • 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 • Rice treated with high N attracts more pests

Single Field Cultural Control Practices FERTILIZER AND EMIGRATION • 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 • 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 out-compete rice at high N

Single Field Cultural Control Practices THE KNOWN: Balance is important! • 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 • 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 • 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

Single Field Cultural Control Practices THE UNKNOWN • 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 • cultivars • soil types • Predict the consequences of intensified rice production on crop losses due to pests.

Single Field Cultural Control Practices DESIRED OUTPUTS • 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 • 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)

Control of Rice Insect Pests